Plants

22 pages, 2450 KiB

Open AccessEditor’s ChoiceReview

Valorization of Citrus Co-Products: Recovery of Bioactive Compounds and Application in Meat and Meat Products

by Gema Nieto, Juana Fernández-López, José A. Pérez-Álvarez, Rocío Peñalver, Gaspar Ros-Berruezo and Manuel Viuda-Martos

Plants 2021, 10(6), 1069; https://doi.org/10.3390/plants10061069 - 26 May 2021

Cited by 31 | Viewed by 9537

Abstract

Citrus fruits (orange, lemon, mandarin, and grapefruit) are one of the most extensively cultivated crops. Actually, fresh consumption far exceeds the demand and, subsequently, a great volume of the production is destined for the citrus-processing industries, which produce a huge quantity of co-products. [...] Read more.

Citrus fruits (orange, lemon, mandarin, and grapefruit) are one of the most extensively cultivated crops. Actually, fresh consumption far exceeds the demand and, subsequently, a great volume of the production is destined for the citrus-processing industries, which produce a huge quantity of co-products. These co-products, without proper treatment and disposal, might cause severe environmental problems. The co-products obtained from the citrus industry may be considered a very important source of high-added-value bioactive compounds that could be used in the pharmaceutical, cosmetic, and dietetic industries, and mainly in the food industry. Due to consumer demands, the food industry is exploring a new and economical source of bioactive compounds to develop novel foods with healthy properties. Thus, the aim of this review is to describe the possible benefits of citrus co-products as a source of bioactive compounds and their applications in the development of healthier meat and meat products. Full article

(This article belongs to the Special Issue Food Waste Valorization: Safety and Nutritional Aspect)

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26 pages, 8437 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Wetland Restoration with Hydrophytes: A Review

by Maria A. Rodrigo

Plants 2021, 10(6), 1035; https://doi.org/10.3390/plants10061035 - 21 May 2021

Cited by 21 | Viewed by 8910

Abstract

Restoration cases with hydrophytes (those which develop all their vital functions inside the water or very close to the water surface, e.g., flowering) are less abundant compared to those using emergent plants. Here, I synthesize the latest knowledge in wetland restoration based on [...] Read more.

Restoration cases with hydrophytes (those which develop all their vital functions inside the water or very close to the water surface, e.g., flowering) are less abundant compared to those using emergent plants. Here, I synthesize the latest knowledge in wetland restoration based on revegetation with hydrophytes and stress common challenges and potential solutions. The review mainly focusses on natural wetlands but also includes information about naturalized constructed wetlands, which nowadays are being used not only to improve water quality but also to increase biodiversity. Available publications, peer-reviewed and any public domain, from the last 20 years, were reviewed. Several countries developed pilot case-studies and field-scale projects with more or less success, the large-scale ones being less frequent. Using floating species is less generalized than submerged species. Sediment transfer is more adequate for temporary wetlands. Hydrophyte revegetation as a restoration tool could be improved by selecting suitable wetlands, increasing focus on species biology and ecology, choosing the suitable propagation and revegetation techniques (seeding, planting). The clear negative factors which prevent the revegetation success (herbivory, microalgae, filamentous green algae, water and sediment composition) have to be considered. Policy-making and wetland restoration practices must more effectively integrate the information already known, particularly under future climatic scenarios. Full article

(This article belongs to the Special Issue Macrophytes in Inland Waters: From Knowledge to Management)

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12 pages, 508 KiB

Open AccessEditor’s ChoiceArticle

Influence of Silver Nanoparticles on the Biological Indicators of Haplic Chernozem

by Sergey Kolesnikov, Natalia Tsepina, Tatiana Minnikova, Kamil Kazeev, Saglara Mandzhieva, Svetlana Sushkova, Tatiana Minkina, Mahmoud Mazarji, Rupesh Kumar Singh and Vishnu D. Rajput

Plants 2021, 10(5), 1022; https://doi.org/10.3390/plants10051022 - 20 May 2021

Cited by 25 | Viewed by 3716

Abstract

In recent years, silver nanoparticles (AgNPs) are increasingly used in various industries due to their antibacterial properties, which lead to an increase in pollution of the environment and soil ecosystems. However, the ecological effects of soil pollution by AgNPs were poorly studied than [...] Read more.

In recent years, silver nanoparticles (AgNPs) are increasingly used in various industries due to their antibacterial properties, which lead to an increase in pollution of the environment and soil ecosystems. However, the ecological effects of soil pollution by AgNPs were poorly studied than that with AgNPs of other metal-based NPs. The aim of this study is to assess the influence of AgNPs on the biological properties of Haplic Chernozem. Silver was introduced into the soil in the form of AgNPs with a concentration of 0.5; 1; 5; 10; 50, and 100 mg/kg in laboratory conditions. The influence of AgNPs on the biological properties of Haplic Chernozem was assessed 30 days after contamination. The degree of reduction in biological properties depends on the AgNPs concentration in the soil. This study showed that the sensitivity to contamination by AgNPs in the total number of bacteria and enzymatic activity was more than that in the abundance of bacteria of the genus Azotobacter. The integrated index of biological state (IIBS) of Haplic Chernozem was decreased by contamination with AgNPs. Silver nanoparticles in the concentration of 10 mg/kg caused a decrease in the indicator by 13% relative to the control. It also decreased IIBS by doses of 50 and 100 mg/kg by 22 and 27% relative to the control. All used biological indicators could be used for biomonitoring, biodiagnosis, bioindication, and regulation of ecological condition of soil contamination by AgNPs. Full article

(This article belongs to the Special Issue Applied Nano-Particles under Combined Stress on Plants)

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14 pages, 510 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Effects of Elevated CO₂ and Heat on Wheat Grain Quality

by Xizi Wang and Fulai Liu

Plants 2021, 10(5), 1027; https://doi.org/10.3390/plants10051027 - 20 May 2021

Cited by 42 | Viewed by 7470

Abstract

Wheat is one of the most important staple foods in temperate regions and is in increasing demand in urbanizing and industrializing countries such as China. Enhancing yield potential to meet the population explosion around the world and maintaining grain quality in wheat plants [...] Read more.

Wheat is one of the most important staple foods in temperate regions and is in increasing demand in urbanizing and industrializing countries such as China. Enhancing yield potential to meet the population explosion around the world and maintaining grain quality in wheat plants under climate change are crucial for food security and human nutrition. Global warming resulting from greenhouse effect has led to more frequent occurrence of extreme climatic events. Elevated atmospheric CO₂ concentration (eCO₂) along with rising temperature has a huge impact on ecosystems, agriculture and human health. There are numerous studies investigating the eCO₂ and heatwaves effects on wheat growth and productivity, and the mechanisms behind. This review outlines the state-of-the-art knowledge regarding the effects of eCO₂ and heat stress, individually and combined, on grain yield and grain quality in wheat crop. Strategies to enhance the resilience of wheat to future warmer and CO₂-enriched environment are discussed. Full article

(This article belongs to the Special Issue Crop Adaptation to Elevated CO₂ and Temperature)

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15 pages, 488 KiB

Open AccessEditor’s ChoiceArticle

Chemical Composition and New Biological Activities of Essential Oil and Hydrosol of Hypericum perforatum L. ssp. veronense (Schrank) H. Lindb

by Elma Vuko, Valerija Dunkić, Mirko Ruščić, Marija Nazlić, Nela Mandić, Barbara Soldo, Matilda Šprung and Željana Fredotović

Plants 2021, 10(5), 1014; https://doi.org/10.3390/plants10051014 - 19 May 2021

Cited by 26 | Viewed by 4328

Abstract

The chemical profile, antiproliferative, antioxidant and antiphytoviral activities of the species Hypericum perforatum ssp. veronense (Schrank) H. Lindb. (Clusiaceae) were investigated. Free volatiles were isolated and the chemical composition was determined in the lipophilic fraction (essential oil) and for the first time in [...] Read more.

The chemical profile, antiproliferative, antioxidant and antiphytoviral activities of the species Hypericum perforatum ssp. veronense (Schrank) H. Lindb. (Clusiaceae) were investigated. Free volatiles were isolated and the chemical composition was determined in the lipophilic fraction (essential oil) and for the first time in the water fraction (hydrosol). The aim is to provide phytochemical data for H. perforatum ssp. veronense useful for distinguishing ssp. veronense from ssp. angustifolium, as there are taxonomic disagreements between them and the composition of the secretory products may be helpful in this respect. In the essential oil, the most abundant compounds identified were α-pinene and n-nonane, while in the hydrosol, myrtenol, carvacrol and α-pinene were the most abundant. Overall, the class of monoterpenes and oxygenated monoterpenes dominated in the EO and hydrosol samples. The essential oil showed high antioxidant activity, in contrast to the antiproliferative activity, where the hydrosol showed exceptional activity against three cancer cell lines: Hela (cervical cancer cell line), HCT116 (human colon cancer cell line) and U2OS (human osteosarcoma cell line). Both the essential oil and hydrosol showed antiphytoviral activity against tobacco mosaic virus infection on the local host plants. This is the first report dealing with biological activities of hydrosol of H. perforatum ssp. veronense, and the obtained results suggest that this traditional medicinal plant is a valuable source of volatiles with promising antiproliferative, antioxidant and antiphytoviral activities. Full article

(This article belongs to the Special Issue Essential Oil Characterisation and Biological Activity of Extracts of Medical Plants from Europe)

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14 pages, 1482 KiB

Open AccessEditor’s ChoiceArticle

Metabolomic Analysis of Cannabinoid and Essential Oil Profiles in Different Hemp (Cannabis sativa L.) Phenotypes

by Marjeta Eržen, Iztok J. Košir, Miha Ocvirk, Samo Kreft and Andreja Čerenak

Plants 2021, 10(5), 966; https://doi.org/10.3390/plants10050966 - 12 May 2021

Cited by 25 | Viewed by 4759

Abstract

Hemp (Cannabis sativa L.) cannabinoids and terpenoids have therapeutic effects on human and animal health. Cannabis plants can often have a relatively high heterogeneity, which leads to different phenotypes that have different chemical profiles despite being from the same variety. Little information [...] Read more.

Hemp (Cannabis sativa L.) cannabinoids and terpenoids have therapeutic effects on human and animal health. Cannabis plants can often have a relatively high heterogeneity, which leads to different phenotypes that have different chemical profiles despite being from the same variety. Little information exists about cannabinoid and terpenoid profiles in different hemp phenotypes within the same variety. For this study, 11 phenotypes from three different varieties (“Carmagnola” selected (CS), “Tiborszallasi” (TS), and “Finola” selection (FS)) were analyzed. The components of essential oil (29) were analyzed using gas chromatography with flame ionization detection (GC/FID), and 10 different cannabinoids of each phenotype were determined using high-performance liquid chromatography (HPLC). Principal component analysis (PCA) and analysis of variance (ANOVA) showed that according to the components of essential oil, FS and TS plants were more uniform than CS plants, where there were great differences between CI and CII phenotypes. The content of cannabinoid CBD-A was the highest in all four FS phenotypes. By comparing cannabinoid profiles, FS was clearly separated from TS and CS, while these two varieties were not clearly distinguishable. Phenotypes TV and CI had the highest total content of Δ-9-THC, while all phenotypes of FS had the highest total content of CBD. The highest total content of CBG was determined in phenotype CI. Obtained results are useful for the development of new supplementary ingredients, for different pharmacy treatments, and for further breeding purposes. Full article

(This article belongs to the Special Issue Plant Analytical Chemistry)

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23 pages, 2271 KiB

Open AccessEditor’s ChoiceReview

Cryopreservation of Woody Crops: The Avocado Case

by Chris O’Brien, Jayeni Hiti-Bandaralage, Raquel Folgado, Alice Hayward, Sean Lahmeyer, Jim Folsom and Neena Mitter

Plants 2021, 10(5), 934; https://doi.org/10.3390/plants10050934 - 7 May 2021

Cited by 13 | Viewed by 6689

Abstract

Recent development and implementation of crop cryopreservation protocols has increased the capacity to maintain recalcitrant seeded germplasm collections via cryopreserved in vitro material. To preserve the greatest possible plant genetic resources globally for future food security and breeding programs, it is essential to [...] Read more.

Recent development and implementation of crop cryopreservation protocols has increased the capacity to maintain recalcitrant seeded germplasm collections via cryopreserved in vitro material. To preserve the greatest possible plant genetic resources globally for future food security and breeding programs, it is essential to integrate in situ and ex situ conservation methods into a cohesive conservation plan. In vitro storage using tissue culture and cryopreservation techniques offers promising complementary tools that can be used to promote this approach. These techniques can be employed for crops difficult or impossible to maintain in seed banks for long-term conservation. This includes woody perennial plants, recalcitrant seed crops or crops with no seeds at all and vegetatively or clonally propagated crops where seeds are not true-to-type. Many of the world’s most important crops for food, nutrition and livelihoods, are vegetatively propagated or have recalcitrant seeds. This review will look at ex situ conservation, namely field repositories and in vitro storage for some of these economically important crops, focusing on conservation strategies for avocado. To date, cultivar-specific multiplication protocols have been established for maintaining multiple avocado cultivars in tissue culture. Cryopreservation of avocado somatic embryos and somatic embryogenesis have been successful. In addition, a shoot-tip cryopreservation protocol has been developed for cryo-storage and regeneration of true-to-type clonal avocado plants. Full article

(This article belongs to the Special Issue Plant Cryopreservation)

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30 pages, 460 KiB

Open AccessEditor’s ChoiceReview

Aqueous and Ethanolic Plant Extracts as Bio-Insecticides—Establishing a Bridge between Raw Scientific Data and Practical Reality

by Wilson R. Tavares, Maria do Carmo Barreto and Ana M. L. Seca

Plants 2021, 10(5), 920; https://doi.org/10.3390/plants10050920 - 4 May 2021

Cited by 27 | Viewed by 9410

Abstract

Global demand for food production is causing pressure to produce faster and bigger crop yields, leading to a rampant use of synthetical pesticides. To combat the nefarious consequences of its uses, a search for effective alternatives began in the last decades and is [...] Read more.

Global demand for food production is causing pressure to produce faster and bigger crop yields, leading to a rampant use of synthetical pesticides. To combat the nefarious consequences of its uses, a search for effective alternatives began in the last decades and is currently ongoing. Nature is seen as the main source of answers to crop protection problems, supported by several examples of plants/extracts used for this purpose in traditional agriculture. The literature reviewed allowed the identification of 95 plants whose extracts exhibit insecticide activity and can be used as bio-pesticides contributing to sustainable agriculture. The option for ethanol and/or water extracts is more environmentally friendly and resorts to easily accessible solvents, which can be reproduced by farmers themselves. This enables a bridge to be established between raw scientific data and a more practical reality. Azadirachta indica, Capsicum annuum, Nicotiana tabacum and Tagetes erecta are the most researched plants and have the potential to be viable options in the pest management approach. Azadirachta indica showed the most promising results and Brevicoryne brassicae was the most targeted pest species, being tested against the aqueous and/or ethanolic extracts of 23 different plants. Maceration using dried material (usually leaves) is the extraction method preferred by the majority of authors. Full article

(This article belongs to the Special Issue Botanical Insecticides 2020-2021)

18 pages, 2644 KiB

Open AccessEditor’s ChoiceReview

Photorespiration: The Futile Cycle?

by Xiaoxiao Shi and Arnold Bloom

Plants 2021, 10(5), 908; https://doi.org/10.3390/plants10050908 - 1 May 2021

Cited by 39 | Viewed by 9848

Abstract

Photorespiration, or C₂ photosynthesis, is generally considered a futile cycle that potentially decreases photosynthetic carbon fixation by more than 25%. Nonetheless, many essential processes, such as nitrogen assimilation, C₁ metabolism, and sulfur assimilation, depend on photorespiration. Most studies of photosynthetic and [...] Read more.

Photorespiration, or C₂ photosynthesis, is generally considered a futile cycle that potentially decreases photosynthetic carbon fixation by more than 25%. Nonetheless, many essential processes, such as nitrogen assimilation, C₁ metabolism, and sulfur assimilation, depend on photorespiration. Most studies of photosynthetic and photorespiratory reactions are conducted with magnesium as the sole metal cofactor despite many of the enzymes involved in these reactions readily associating with manganese. Indeed, when manganese is present, the energy efficiency of these reactions may improve. This review summarizes some commonly used methods to quantify photorespiration, outlines the influence of metal cofactors on photorespiratory enzymes, and discusses why photorespiration may not be as wasteful as previously believed. Full article

(This article belongs to the Special Issue Plant Photorespiration: A Key Process to Adapt to a Changing Environment)

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16 pages, 11087 KiB

Open AccessEditor’s ChoiceArticle

Antioxidant and Cytotoxic Activities of Usnea barbata (L.) F.H. Wigg. Dry Extracts in Different Solvents

by Violeta Popovici, Laura Bucur, Antoanela Popescu, Verginica Schröder, Teodor Costache, Dan Rambu, Iulia Elena Cucolea, Cerasela Elena Gîrd, Aureliana Caraiane, Daniela Gherghel, Gabriela Vochita and Victoria Badea

Plants 2021, 10(5), 909; https://doi.org/10.3390/plants10050909 - 1 May 2021

Cited by 22 | Viewed by 5524

Abstract

Lichens represent a significant source of antioxidants due to numerous metabolites that can reduce free radicals. Usnea barbata (L.) F.H. Wigg. has been recognized and used since ancient times for its therapeutic effects, some of which are based on its antioxidant properties. The [...] Read more.

Lichens represent a significant source of antioxidants due to numerous metabolites that can reduce free radicals. Usnea barbata (L.) F.H. Wigg. has been recognized and used since ancient times for its therapeutic effects, some of which are based on its antioxidant properties. The present study aims to analyze the phytochemical profile and to evaluate the antioxidant and cytotoxic potential of this lichen species. Five dry extracts of U. barbata (UBDE) in different solvents (acetone, ethyl acetate, ethanol, methanol, water) were prepared by refluxing at Soxhlet to achieve these proposed objectives and to identify which solvent is the most effective for the extraction. The usnic acid content (UAC) was quantified by ultra-high performance liquid chromatography (UHPLC). The total polyphenols content (TPC) and tannins content (TC) were evaluated by spectrophotometry, and the total polysaccharides (PSC) were extracted by a gravimetric method. The 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) free radical method was used to assess the antioxidant activity (AA) and the Brine Shrimp Lethality (BSL) assay was the biotest for cytotoxic activity evaluation. The ethyl acetate extract had the highest usnic acid content, and acetone extract had the highest content of total polyphenols and tannins. The most significant antioxidant effect was reported to methanol extract, and all the extracts proved high cytotoxicity. The water extract has the lowest cytotoxicity because usnic acid is slightly soluble in this solvent, and it was not found at UHPLC analysis. All extracts recorded a moderate correlation between the content of usnic acid, polyphenols, tannins, and AA; furthermore, it has been observed that the cytotoxicity varies inversely with the antioxidant effect. Full article

(This article belongs to the Special Issue Phenolic Composition and Antioxidant Activity of Plant Extracts)

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11 pages, 1481 KiB

Open AccessEditor’s ChoiceArticle

Tremellomycetes Yeasts in Kernel Ecological Niche: Early Indicators of Enhanced Competitiveness of Endophytic and Mycoparasitic Symbionts against Wheat Pathobiota

by Vladimir Vujanovic

Plants 2021, 10(5), 905; https://doi.org/10.3390/plants10050905 - 30 Apr 2021

Cited by 19 | Viewed by 3044

Abstract

Tremellomycetes rDNA sequences previously detected in wheat kernels by MiSeq were not reliably assigned to a genus or clade. From comparisons of ribosomal internal transcribed spacer region (ITS) and subsequent phylogenetic analyses, the following three basidiomycetous yeasts were resolved and identified: Vishniacozymavictoriae [...] Read more.

Tremellomycetes rDNA sequences previously detected in wheat kernels by MiSeq were not reliably assigned to a genus or clade. From comparisons of ribosomal internal transcribed spacer region (ITS) and subsequent phylogenetic analyses, the following three basidiomycetous yeasts were resolved and identified: Vishniacozymavictoriae, V. tephrensis, and an undescribed Vishniacozyma rDNA variant. The Vishniacozyma variant’s clade is evolutionarily close to, but phylogenetically distinct from, the V. carnescens clade. These three yeasts were discovered in wheat kernel samples from the Canadian prairies. Variations in relative Vishniacozyma species abundances coincided with altered wheat kernel weight, as well as host resistance to chemibiotrophic Tilletia (Common bunt—CB) and necrotrophic Fusarium (Fusarium head blight—FHB) pathogens. Wheat kernel weight was influenced by the coexistence of Vishniacozyma with endophytic plant growth-promoting and mycoparasitic biocontrol fungi that were acquired by plants. Kernels were coated with beneficial Penicillium endophyte and Sphaerodes mycoparasite, each of which had different influences on the wild yeast population. Its integral role in the kernel microbiome renders Vishniacozyma a measurable indicator of the microbiome–plant interaction. The ability of NGS technology to detect specific endophytic DNA variants and early changes in dynamics among symbionts within the kernel ecological niche enables the prediction of crop disease emergence, suggesting that advanced microbiological testing may be a potentially useful tool for both phytoprotection and more efficient wheat breeding programs. Full article

(This article belongs to the Special Issue Fungal Endophytes against Plant Pathogenic Fungi)

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18 pages, 3086 KiB

Open AccessEditor’s ChoiceArticle

Cold Plasma Affects Germination and Fungal Community Structure of Buckwheat Seeds

by Jure Mravlje, Marjana Regvar, Pia Starič, Miran Mozetič and Katarina Vogel-Mikuš

Plants 2021, 10(5), 851; https://doi.org/10.3390/plants10050851 - 23 Apr 2021

Cited by 29 | Viewed by 4690

Abstract

Crop seeds are frequently colonised by fungi from the field or storage places. Some fungi can cause plant diseases or produce mycotoxins, compromising the use of seeds as seeding material, food or feed. We have investigated the effects of cold plasma (CP) on [...] Read more.

Crop seeds are frequently colonised by fungi from the field or storage places. Some fungi can cause plant diseases or produce mycotoxins, compromising the use of seeds as seeding material, food or feed. We have investigated the effects of cold plasma (CP) on seed germination and diversity of seed-borne fungi in common and Tartary buckwheat. The seeds were treated with CP for 15, 30, 45, 60, 90, and 120 s in a low-pressure radiofrequency system using oxygen as the feed gas. The fungi from the seed surface and fungal endophytes were isolated using potato dextrose agar plates. After identification by molecular methods, the frequency and diversity of fungal strains were compared between CP treated and chemically surface-sterilised (30% of H₂O₂) seeds. CP treatments above 60 s negatively affected the germination of both buckwheat species. A significant reduction in fungal frequency and diversity was observed after 90 s and 120 s in common and Tartary buckwheat, respectively. The filamentous fungi of genera Alternaria and Epicoccum proved to be the most resistant to CP. The results of our study indicate that CP treatment used in our study may be applicable in postharvest and food production, but not for further seed sowing. Full article

(This article belongs to the Special Issue Breeding Buckwheat for Nutritional Quality)

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14 pages, 1467 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Salinity Stress Affects Photosynthesis, Malondialdehyde Formation, and Proline Content in Portulaca oleracea L.

by Helena Hnilickova, Kamil Kraus, Pavla Vachova and Frantisek Hnilicka

Plants 2021, 10(5), 845; https://doi.org/10.3390/plants10050845 - 22 Apr 2021

Cited by 147 | Viewed by 7734

Abstract

In this investigation, the effect of salt stress on Portulaca oleracea L. was monitored at salinity levels of 100 and 300 mM NaCl. At a concentration of 100 mM NaCl there was a decrease in stomatal conductance (gs) simultaneously with an increase in [...] Read more.

In this investigation, the effect of salt stress on Portulaca oleracea L. was monitored at salinity levels of 100 and 300 mM NaCl. At a concentration of 100 mM NaCl there was a decrease in stomatal conductance (gs) simultaneously with an increase in CO₂ assimilation (A) at the beginning of salt exposure (day 3). However, the leaf water potential (ψ_w), the substomatal concentration of CO₂ (Ci), the maximum quantum yield of photosystem II (Fv/Fm), and the proline and malondialdehyde (MDA) content remained unchanged. Exposure to 300 mM NaCl caused a decrease in gs from day 3 and a decrease in water potential, CO₂ assimilation, and Fv/Fm from day 9. There was a large increase in proline content and a significantly higher MDA concentration on days 6 and 9 of salt stress compared to the control group. After 22 days of exposure to 300 mM NaCl, there was a transition from the C4 cycle to crassulacean acid metabolism (CAM), manifested by a rapid increase in substomatal CO₂ concentration and negative CO₂ assimilation values. These results document the tolerance of P. oleracea to a lower level of salt stress and the possibility of its use in saline localities. Full article

(This article belongs to the Special Issue Salinity Stress in Plants and Molecular Responses)

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19 pages, 730 KiB

Open AccessEditor’s ChoiceReview

Culturable Yeasts as Biofertilizers and Biopesticides for a Sustainable Agriculture: A Comprehensive Review

by María Hernández-Fernández, Gustavo Cordero-Bueso, Marina Ruiz-Muñoz and Jesús M. Cantoral

Plants 2021, 10(5), 822; https://doi.org/10.3390/plants10050822 - 21 Apr 2021

Cited by 54 | Viewed by 16446

Abstract

The extensive use of synthetic fertilizers and pesticides has negative consequences in terms of soil microbial biodiversity and environmental contamination. Faced with this growing concern, a proposed alternative agricultural method is the use of microorganisms as biofertilizers. Many works have been focused on [...] Read more.

The extensive use of synthetic fertilizers and pesticides has negative consequences in terms of soil microbial biodiversity and environmental contamination. Faced with this growing concern, a proposed alternative agricultural method is the use of microorganisms as biofertilizers. Many works have been focused on bacteria, but the limited literature on yeasts and their potential ability to safely promote plant growth is gaining particular attention in recent years. Thus, the objective of this review is to highlight the application of yeasts as biological agents in different sectors of sustainable agricultural practices through direct or indirect mechanisms of action. Direct mechanisms include the ability of yeasts to provide soluble nutrients to plants, produce organic acids and phytohormones (indole-3-acetic acid). Indirect mechanisms involve the ability for yeasts to act as biocontrol agents through their high antifungal activity and lower insecticidal and herbicidal activity, and as soil bioremediating agents. They also act as protective agents against extreme environmental factors by activating defense mechanisms. It is evident that all the aspects that yeasts offer could be useful in the creation of quality biofertilizers and biopesticides. Hence, extensive research on yeasts could be promising and potentially provide an environmentally friendly solution to the increased crop production that will be required with a growing population. Full article

(This article belongs to the Special Issue Biostimulants as Growth Promoting and Stress Protecting Compounds)

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17 pages, 2816 KiB

Open AccessEditor’s ChoiceReview

Bioherbicidal Potential of the Essential Oils from Mediterranean Lamiaceae for Weed Control in Organic Farming

by Giuseppe De Mastro, Jihane El Mahdi and Claudia Ruta

Plants 2021, 10(4), 818; https://doi.org/10.3390/plants10040818 - 20 Apr 2021

Cited by 38 | Viewed by 5197

Abstract

In all farming systems, weeds are the most expensive pest to manage, accounting for 30% of potential losses. In organic farming, the problem may be further amplified by restrictions on herbicides, thus making weeds the main problem faced by organic farmers in the [...] Read more.

In all farming systems, weeds are the most expensive pest to manage, accounting for 30% of potential losses. In organic farming, the problem may be further amplified by restrictions on herbicides, thus making weeds the main problem faced by organic farmers in the field. In this sense, much research is focusing on the allelopathic potential of plants as an ecological weed control tool. Many plant species can release allelopathic compounds with high phytotoxicity that can be used in weed control. Species belonging to the Lamiaceae family have been studied widely for this purpose, and their essential oils (EOs) appear to be promising bioherbicides. However, there are still many challenges for their development. Considering these aspects, a review of the bioherbicidal effect of EOs from Mediterranean Lamiaceae could help identify the most effective ones and the challenges for their actual development. Full article

(This article belongs to the Special Issue Sustainable Weed Management)

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20 pages, 1993 KiB

Open AccessEditor’s ChoiceArticle

Effect of Different Ratios of Blue and Red LED Light on Brassicaceae Microgreens under a Controlled Environment

by Aušra Brazaitytė, Jurga Miliauskienė, Viktorija Vaštakaitė-Kairienė, Rūta Sutulienė, Kristina Laužikė, Pavelas Duchovskis and Stanisław Małek

Plants 2021, 10(4), 801; https://doi.org/10.3390/plants10040801 - 19 Apr 2021

Cited by 63 | Viewed by 8523

Abstract

The consumption of microgreens has increased due to their having higher levels of bioactive compounds and mineral nutrients than mature plants. The lighting conditions during the cultivation of microgreens, if optimally selected, can have a positive effect by further increasing their nutritional value. [...] Read more.

The consumption of microgreens has increased due to their having higher levels of bioactive compounds and mineral nutrients than mature plants. The lighting conditions during the cultivation of microgreens, if optimally selected, can have a positive effect by further increasing their nutritional value. Thus, our study aimed to determine the changes in mineral nutrients contents of Brassicaceae microgreens depending on different blue–red (B:R) light ratios in light-emitting diode (LED) lighting and to evaluate their growth and nutritional value according to different indexes. Experiments were performed in controlled environment growth chambers at IH LRCAF, 2020. Microgreens of mustard (Brassica juncea ‘Red Lace’) and kale (Brassica napus ‘Red Russian’) were grown hydroponically under different B:R light ratios: 0%B:100%R, 10%B:90%R, 25%B:75%R, 50%B:50%R, 75%B:25%R, and 100%B:0%R. A 220 μmol m⁻² s⁻¹ total photon flux density (TPFD), 18 h photoperiod, 21/17 ± 2 °C temperature and 60% ± 5% relative humidity in the growth chamber were maintained during cultivation. We observed that an increasing percentage of blue light in the LED illumination spectrum during growth was associated with reduced elongation in the microgreens of both species and had a positive effect on the accumulation of mostly macro- and micronutrients. However, different B:R light ratios indicate a species-dependent response to changes in growth parameters such as leaf area, fresh and dry mass, and optical leaf indexes such as for chlorophyll, flavonol, anthocyanin, and carotenoid reflectance. Full article

(This article belongs to the Special Issue Applications and Advances in Artificial Light for Horticulture and Crop Production)

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18 pages, 3131 KiB

Open AccessEditor’s ChoiceArticle

Breeding of High Cooking and Eating Quality in Rice by Marker-Assisted Backcrossing (MABc) Using KASP Markers

by Me-Sun Kim, Ju-Young Yang, Ju-Kyung Yu, Yi Lee, Yong-Jin Park, Kwon-Kyoo Kang and Yong-Gu Cho

Plants 2021, 10(4), 804; https://doi.org/10.3390/plants10040804 - 19 Apr 2021

Cited by 19 | Viewed by 4016

Abstract

The primary goals of rice breeding programs are grain quality and yield potential improvement. With the high demand for rice varieties of premium cooking and eating quality, we developed low-amylose content breeding lines crossed with Samgwang and Milkyqueen through the marker-assisted backcross (MABc) [...] Read more.

The primary goals of rice breeding programs are grain quality and yield potential improvement. With the high demand for rice varieties of premium cooking and eating quality, we developed low-amylose content breeding lines crossed with Samgwang and Milkyqueen through the marker-assisted backcross (MABc) breeding program. Trait markers of the SSIIIa gene referring to low-amylose content were identified through an SNP mapping activity, and the markers were applied to select favorable lines for a foreground selection. To rapidly recover the genetic background of Samgwang (recurrent parent genome, RPG), 386 genome-wide markers were used to select BC₁F₁ and BC₂F₁ individuals. Seven BC₂F₁ lines with targeted traits were selected, and the genetic background recovery range varied within 97.4–99.1% of RPG. The amylose content of the selected BC₂F₂ grains ranged from 12.4–16.8%. We demonstrated the MABc using a trait and genome-wide markers, allowing us to efficiently select lines of a target trait and reduce the breeding cycle effectively. In addition, the BC₂F₂ lines confirmed by molecular markers in this study can be utilized as parental lines for subsequent breeding programs of high-quality rice for cooking and eating. Full article

(This article belongs to the Special Issue Functional Analysis of Starch Metabolism in Plants)

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13 pages, 1908 KiB

Open AccessEditor’s ChoiceArticle

A Novel Protein Hydrolysate-Based Biostimulant Improves Tomato Performances under Drought Stress

by Silvana Francesca, Valerio Cirillo, Giampaolo Raimondi, Albino Maggio, Amalia Barone and Maria Manuela Rigano

Plants 2021, 10(4), 783; https://doi.org/10.3390/plants10040783 - 16 Apr 2021

Cited by 47 | Viewed by 5327

Abstract

Abiotic stresses adversely affect crop production causing yield reductions in important crops, including tomato (Solanum lycopersicum L.). Among the different abiotic stresses, drought is considered to be the most critical one, since limited water availability negatively impacts plant growth and development, especially [...] Read more.

Abiotic stresses adversely affect crop production causing yield reductions in important crops, including tomato (Solanum lycopersicum L.). Among the different abiotic stresses, drought is considered to be the most critical one, since limited water availability negatively impacts plant growth and development, especially in arid and semi-arid areas. The aim of this study was to understand how biostimulants may interact with critical physiological response mechanisms in tomato under limited water availability and to define strategies to improve tomato performances under drought stress. We investigated the physiological responses of the tomato genotype ‘E42’ grown in open fields under optimal conditions (100% irrigation) and limited water availability (50% irrigation) treated or not with a novel protein hydrolysate-based biostimulant (CycoFlow, Agriges, BN, Italy). Plants treated with the protein hydrolysate showed a better water status and pollen viability, which also resulted in higher yield under drought stress compared to untreated plants. The treatment with the biostimulant had also an effect on antioxidant contents and activity in leaves and fruits depending on the level of irrigation provided. Altogether, these results indicate that the application of protein hydrolysates on tomato improved plant performances under limited water availability and in different experimental fields. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International Electronic Conference on Plant Science)

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16 pages, 776 KiB

Open AccessEditor’s ChoiceReview

Cellular Phosphorylation Signaling and Gene Expression in Drought Stress Responses: ABA-Dependent and ABA-Independent Regulatory Systems

by Fumiyuki Soma, Fuminori Takahashi, Kazuko Yamaguchi-Shinozaki and Kazuo Shinozaki

Plants 2021, 10(4), 756; https://doi.org/10.3390/plants10040756 - 13 Apr 2021

Cited by 80 | Viewed by 11255

Abstract

Drought is a severe and complex abiotic stress that negatively affects plant growth and crop yields. Numerous genes with various functions are induced in response to drought stress to acquire drought stress tolerance. The phytohormone abscisic acid (ABA) accumulates mainly in the leaves [...] Read more.

Drought is a severe and complex abiotic stress that negatively affects plant growth and crop yields. Numerous genes with various functions are induced in response to drought stress to acquire drought stress tolerance. The phytohormone abscisic acid (ABA) accumulates mainly in the leaves in response to drought stress and then activates subclass III SNF1-related protein kinases 2 (SnRK2s), which are key phosphoregulators of ABA signaling. ABA mediates a wide variety of gene expression processes through stress-responsive transcription factors, including ABA-RESPONSIVE ELEMENT BINDING PROTEINS (AREBs)/ABRE-BINDING FACTORS (ABFs) and several other transcription factors. Seed plants have another type of SnRK2s, ABA-unresponsive subclass I SnRK2s, that mediates the stability of gene expression through the mRNA decay pathway and plant growth under drought stress in an ABA-independent manner. Recent research has elucidated the upstream regulators of SnRK2s, RAF-like protein kinases, involved in early responses to drought stress. ABA-independent transcriptional regulatory systems and ABA-responsive regulation function in drought-responsive gene expression. DEHYDRATION RESPONSIVE ELEMENT (DRE) is an important cis-acting element in ABA-independent transcription, whereas ABA-RESPONSIVE ELEMENT (ABRE) cis-acting element functions in ABA-responsive transcription. In this review article, we summarize recent advances in research on cellular and molecular drought stress responses and focus on phosphorylation signaling and transcription networks in Arabidopsis and crops. We also highlight gene networks of transcriptional regulation through two major regulatory pathways, ABA-dependent and ABA-independent pathways, that ABA-responsive subclass III SnRK2s and ABA-unresponsive subclass I SnRK2s mediate, respectively. We also discuss crosstalk in these regulatory systems under drought stress. Full article

(This article belongs to the Special Issue Plant Protein Kinases and Plant Stress Response)

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12 pages, 3646 KiB

Open AccessEditor’s ChoiceReview

β-Ionone: Its Occurrence and Biological Function and Metabolic Engineering

by Antonello Paparella, Liora Shaltiel-Harpaza and Mwafaq Ibdah

Plants 2021, 10(4), 754; https://doi.org/10.3390/plants10040754 - 12 Apr 2021

Cited by 73 | Viewed by 8162

Abstract

β-Ionone is a natural plant volatile compound, and it is the 9,10 and 9′,10′ cleavage product of β-carotene by the carotenoid cleavage dioxygenase. β-Ionone is widely distributed in flowers, fruits, and vegetables. β-Ionone and other apocarotenoids comprise flavors, aromas, pigments, growth regulators, and [...] Read more.

β-Ionone is a natural plant volatile compound, and it is the 9,10 and 9′,10′ cleavage product of β-carotene by the carotenoid cleavage dioxygenase. β-Ionone is widely distributed in flowers, fruits, and vegetables. β-Ionone and other apocarotenoids comprise flavors, aromas, pigments, growth regulators, and defense compounds; serve as ecological cues; have roles as insect attractants or repellants, and have antibacterial and fungicidal properties. In recent years, β-ionone has also received increased attention from the biomedical community for its potential as an anticancer treatment and for other human health benefits. However, β-ionone is typically produced at relatively low levels in plants. Thus, expressing plant biosynthetic pathway genes in microbial hosts and engineering the metabolic pathway/host to increase metabolite production is an appealing alternative. In the present review, we discuss β-ionone occurrence, the biological activities of β-ionone, emphasizing insect attractant/repellant activities, and the current strategies and achievements used to reconstruct enzyme pathways in microorganisms in an effort to to attain higher amounts of the desired β-ionone. Full article

(This article belongs to the Collection Bioactive Compounds in Plants)

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22 pages, 7622 KiB

Open AccessEditor’s ChoiceReview

Natural Blues: Structure Meets Function in Anthocyanins

by Alan Houghton, Ingo Appelhagen and Cathie Martin

Plants 2021, 10(4), 726; https://doi.org/10.3390/plants10040726 - 8 Apr 2021

Cited by 74 | Viewed by 12018

Abstract

Choices of blue food colourants are extremely limited, with only two options in the USA, synthetic blue no. 1 and no. 2, and a third available in Europe, patent blue V. The food industry is investing heavily in finding naturally derived replacements, with [...] Read more.

Choices of blue food colourants are extremely limited, with only two options in the USA, synthetic blue no. 1 and no. 2, and a third available in Europe, patent blue V. The food industry is investing heavily in finding naturally derived replacements, with limited success to date. Here, we review the complex and multifold mechanisms whereby blue pigmentation by anthocyanins is achieved in nature. Our aim is to explain how structure determines the functionality of anthocyanin pigments, particularly their colour and their stability. Where possible, we describe the impact of progressive decorations on colour and stability, drawn from extensive but diverse physico-chemical studies. We also consider briefly how this understanding could be harnessed to develop blue food colourants on the basis of the understanding of how anthocyanins create blues in nature. Full article

(This article belongs to the Special Issue Plant Colours Omics and Biotechnological Advances)

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17 pages, 2171 KiB

Open AccessEditor’s ChoiceArticle

Laurus nobilis, Salvia sclarea and Salvia officinalis Essential Oils and Hydrolates: Evaluation of Liquid and Vapor Phase Chemical Composition and Biological Activities

by Elisa Ovidi, Valentina Laghezza Masci, Marta Zambelli, Antonio Tiezzi, Sara Vitalini and Stefania Garzoli

Plants 2021, 10(4), 707; https://doi.org/10.3390/plants10040707 - 6 Apr 2021

Cited by 39 | Viewed by 4527

Abstract

Laurus nobilis, Salvia officinalis and Salvia sclarea essential oils (EOs) and hydrolates (HYs) were investigated to define their chemical compositions and biological properties. Gas-chromatography/Mass-spectrometry (GC/MS) and Headspace-GC/MS (HS-GC/MS) techniques were used to characterize the liquid and vapor phase chemical composition of EOs [...] Read more.

Laurus nobilis, Salvia officinalis and Salvia sclarea essential oils (EOs) and hydrolates (HYs) were investigated to define their chemical compositions and biological properties. Gas-chromatography/Mass-spectrometry (GC/MS) and Headspace-GC/MS (HS-GC/MS) techniques were used to characterize the liquid and vapor phase chemical composition of EOs and HYs. 1,8-Cineole (42.2%, 33.5%) and α-pinene (16.7%, 39.0%) were the main compounds of L. nobilis EO; 1,8-cineole (30.3%, 48.4%) and camphor (17.1%, 8.7%) were for S. officinalis EO; linalyl acetate (62.6%, 30.1%) and linalool (11.1%, 28.9%) were for S. sclarea EO for the liquid and vapor phase, respectively. Chemical profile of HYs was characterized by 1,8-cineole (65.1%, 61.4%) as a main constituent of L. nobilis and S. officinalis HYs, while linalool (89.5%) was the main constituent of S. sclarea HY. The antioxidant activity of EOs and HYs was carried out by DPPH and ABTS assays and antimicrobial properties were also investigated by microdilution and the disc diffusion method for liquid and vapor phase against five different bacterial strains such as Escherichia coli ATCC 25922, Pseudomonas fluorescens ATCC 13525 and Acinetobacter bohemicus DSM 102855 among Gram-negative and Bacillus cereus ATCC 10876 and Kocuria marina DSM 16420 among Gram-positive. L. nobilis and S. officinalis EOs demonstrated considerable antibacterial activity, while S. sclarea EO proved to be less effective. Agar diffusion method and vapor phase test showed the EOs activity with the biggest halo inhibition diameters against A. bohemicus and B. cereus. A remarkably high antioxidant activity was determined for L. nobilis showing low EC₅₀ values and also for S. sclarea; good EO results were obtained in both of the used assays. S. officinalis EC₅₀ values were slightly higher to which corresponds to a lower antioxidant activity. Concerning the HYs, the EC₅₀ values for L. nobilis, S. officinalis and S. sclarea were remarkably high corresponding to an extremely low antioxidant activity, as also obtained by expressing the values in Trolox equivalent antioxidant capacity (TEAC). Full article

(This article belongs to the Special Issue Chemical Composition and Antimicrobial Activity of Essential Oils)

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14 pages, 2284 KiB

Open AccessEditor’s ChoiceArticle

Chitosan Nanoparticles Loaded with N-Acetyl Cysteine to Mitigate Ozone and Other Possible Oxidative Stresses in Durum Wheat

by Valentina Picchi, Serena Gobbi, Matteo Fattizzo, Mario Zefelippo and Franco Faoro

Plants 2021, 10(4), 691; https://doi.org/10.3390/plants10040691 - 2 Apr 2021

Cited by 31 | Viewed by 3185

Abstract

Modern durum wheat cultivars are more prone to ozone stress because of their high photosynthetic efficiency and leaf gas exchanges that cause a greater pollutant uptake. This, in turn, generates an increased reactive oxygen species (ROS) production that is a challenge to control [...] Read more.

Modern durum wheat cultivars are more prone to ozone stress because of their high photosynthetic efficiency and leaf gas exchanges that cause a greater pollutant uptake. This, in turn, generates an increased reactive oxygen species (ROS) production that is a challenge to control by the antioxidant system of the plant, therefore affecting final yield, with a reduction up to 25%. With the aim of mitigating oxidative stress in wheat, we used chitosan nanoparticles (CHT-NPs) either unloaded or loaded with the antioxidant compound N-acetyl cysteine (NAC), on plants grown either in a greenhouse or in an open field. NAC-loaded NPs were prepared by adding 0.5 mg/mL NAC to the CHT solution before ionotropic gelation with tripolyphosphate (TTP). Greenhouse experiments evidenced that CHT-NPs and CHT-NPs-NAC were able to increase the level of the leaf antioxidant pool, particularly ascorbic acid (AsA) content. However, the results of field trials, while confirming the increase in the AsA level, at least in the first phenological stages, were less conclusive. The presence of NAC did not appear to significantly affect the leaf antioxidant pool, although the grain yield was slightly higher in NAC-treated parcels. Furthermore, both NAC-loaded and -unloaded CHT-NPs partially reduced the symptom severity and increased the weight of 1000 seeds, thus showing a moderate mitigation of ozone injury. Full article

(This article belongs to the Special Issue Responses of Durum Wheat to Abiotic Stress)

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22 pages, 735 KiB

Open AccessEditor’s ChoiceReview

Plant Biostimulants from Cyanobacteria: An Emerging Strategy to Improve Yields and Sustainability in Agriculture

by Gaia Santini, Natascia Biondi, Liliana Rodolfi and Mario R. Tredici

Plants 2021, 10(4), 643; https://doi.org/10.3390/plants10040643 - 29 Mar 2021

Cited by 65 | Viewed by 7541

Abstract

Cyanobacteria can be considered a promising source for the development of new biostimulants as they are known to produce a variety of biologically active molecules that can positively affect plant growth, nutrient use efficiency, qualitative traits of the final product, and increase plant [...] Read more.

Cyanobacteria can be considered a promising source for the development of new biostimulants as they are known to produce a variety of biologically active molecules that can positively affect plant growth, nutrient use efficiency, qualitative traits of the final product, and increase plant tolerance to abiotic stresses. Moreover, the cultivation of cyanobacteria in controlled and confined systems, along with their metabolic plasticity, provides the possibility to improve and standardize composition and effects on plants of derived biostimulant extracts or hydrolysates, which is one of the most critical aspects in the production of commercial biostimulants. Faced with these opportunities, research on biostimulant properties of cyanobacteria has undergone a significant growth in recent years. However, research in this field is still scarce, especially as regards the number of investigated cyanobacterial species. Future research should focus on reducing the costs of cyanobacterial biomass production and plant treatment and on identifying the molecules that mediate the biostimulant effects in order to optimize their content and stability in the final product. Furthermore, the extension of agronomic trials to a wider number of plant species, different application doses, and environmental conditions would allow the development of tailored microbial biostimulants, thus facilitating the diffusion of these products among farmers. Full article

(This article belongs to the Special Issue Cyanobacteria and Microalgae Biotechnologies)

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28 pages, 1154 KiB

Open AccessEditor’s ChoiceReview

Metal and Metalloid Toxicity in Plants: An Overview on Molecular Aspects

by Paola I. Angulo-Bejarano, Jonathan Puente-Rivera and Rocío Cruz-Ortega

Plants 2021, 10(4), 635; https://doi.org/10.3390/plants10040635 - 27 Mar 2021

Cited by 176 | Viewed by 11614

Abstract

Worldwide, the effects of metal and metalloid toxicity are increasing, mainly due to anthropogenic causes. Soil contamination ranks among the most important factors, since it affects crop yield, and the metals/metalloids can enter the food chain and undergo biomagnification, having concomitant effects on [...] Read more.

Worldwide, the effects of metal and metalloid toxicity are increasing, mainly due to anthropogenic causes. Soil contamination ranks among the most important factors, since it affects crop yield, and the metals/metalloids can enter the food chain and undergo biomagnification, having concomitant effects on human health and alterations to the environment. Plants have developed complex mechanisms to overcome these biotic and abiotic stresses during evolution. Metals and metalloids exert several effects on plants generated by elements such as Zn, Cu, Al, Pb, Cd, and As, among others. The main strategies involve hyperaccumulation, tolerance, exclusion, and chelation with organic molecules. Recent studies in the omics era have increased knowledge on the plant genome and transcriptome plasticity to defend against these stimuli. The aim of the present review is to summarize relevant findings on the mechanisms by which plants take up, accumulate, transport, tolerate, and respond to this metal/metalloid stress. We also address some of the potential applications of biotechnology to improve plant tolerance or increase accumulation. Full article

(This article belongs to the Special Issue Heavy Metal Stress in Plants)

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26 pages, 1178 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Priming Strategies for Benefiting Plant Performance under Toxic Trace Metal Exposure

by Alina Wiszniewska

Plants 2021, 10(4), 623; https://doi.org/10.3390/plants10040623 - 25 Mar 2021

Cited by 35 | Viewed by 5088

Abstract

Combating environmental stress related to the presence of toxic elements is one of the most important challenges in plant production. The majority of plant species suffer from developmental abnormalities caused by an exposure to toxic concentrations of metals and metalloids, mainly Al, As, [...] Read more.

Combating environmental stress related to the presence of toxic elements is one of the most important challenges in plant production. The majority of plant species suffer from developmental abnormalities caused by an exposure to toxic concentrations of metals and metalloids, mainly Al, As, Cd, Cu, Hg, Ni, Pb, and Zn. However, defense mechanisms are activated with diverse intensity and efficiency. Enhancement of defense potential can be achieved though exogenously applied treatments, resulting in a higher capability of surviving and developing under stress and become, at least temporarily, tolerant to stress factors. In this review, I present several already recognized as well as novel methods of the priming process called priming, resulting in the so-called “primed state” of the plant organism. Primed plants have a higher capability of surviving and developing under stress, and become, at least temporarily, tolerant to stress factors. In this review, several already recognized as well as novel methods of priming plants towards tolerance to metallic stress are discussed, with attention paid to similarities in priming mechanisms activated by the most versatile priming agents. This knowledge could contribute to the development of priming mixtures to counteract negative effects of multi-metallic and multi-abiotic stresses. Presentation of mechanisms is complemented with information on the genes regulated by priming towards metallic stress tolerance. Novel compounds and techniques that can be exploited in priming experiments are also summarized. Full article

(This article belongs to the Special Issue Heavy Metal Stress in Plants)

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19 pages, 4206 KiB

Open AccessEditor’s ChoiceArticle

Impact of Germination on the Microstructural and Physicochemical Properties of Different Legume Types

by Denisa Atudorei, Silviu-Gabriel Stroe and Georgiana Gabriela Codină

Plants 2021, 10(3), 592; https://doi.org/10.3390/plants10030592 - 22 Mar 2021

Cited by 58 | Viewed by 6912

Abstract

The microstructural and physicochemical compositions of bean (Phaseolus vulgaris), lentil (Lens culinaris Merr.), soybean (Glycine max L.), chickpea (Cicer aretinium L.) and lupine (Lupinus albus) were investigated over 2 and 4 days of germination. Different [...] Read more.

The microstructural and physicochemical compositions of bean (Phaseolus vulgaris), lentil (Lens culinaris Merr.), soybean (Glycine max L.), chickpea (Cicer aretinium L.) and lupine (Lupinus albus) were investigated over 2 and 4 days of germination. Different changes were noticed during microscopic observations (Stereo Microscope, SEM) of the legume seeds subjected to germination, mostly related to the breakages of the seed structure. The germination caused the increase in protein content for bean, lentil, and chickpea and of ash content for lentil, soybean and chickpea. Germination increased the availability of sodium, magnesium, iron, zinc and also the acidity for all legume types. The content of fat decreased for lentil, chickpea, and lupine, whereas the content of carbohydrates and pH decreased for all legume types during the four-day germination period. Fourier transform infrared spectroscopic (FT-IR) spectra show that the compositions of germinated seeds were different from the control and varied depending on the type of legume. The multivariate analysis of the data shows close associations between chickpea, lentil, and bean and between lupine and soybean samples during the germination process. Significant negative correlations were obtained between carbohydrate contents and protein, fat and ash at the 0.01 level. Full article

(This article belongs to the Special Issue Quality Evaluation of Plant-Derived Foods)

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20 pages, 3168 KiB

Open AccessEditor’s ChoiceArticle

Ecological and Plant Community Implication on Essential Oils Composition in Useful Wild Officinal Species: A Pilot Case Study in Apulia (Italy)

by Enrico V. Perrino, Francesca Valerio, Ahmed Gannouchi, Antonio Trani and Giuseppe Mezzapesa

Plants 2021, 10(3), 574; https://doi.org/10.3390/plants10030574 - 18 Mar 2021

Cited by 54 | Viewed by 4405

Abstract

The study focused on the effects of ecology (plant communities and topographical data) on composition of essential oils (EOs) of some officinal wild plant species (Lamiales): Clinopodium suaveolens, Salvia fruticosa subsp. thomasii, Satureja montana subsp. montana, and Thymbra capitata, in different [...] Read more.

The study focused on the effects of ecology (plant communities and topographical data) on composition of essential oils (EOs) of some officinal wild plant species (Lamiales): Clinopodium suaveolens, Salvia fruticosa subsp. thomasii, Satureja montana subsp. montana, and Thymbra capitata, in different environments of Apulia (Italy). C. suaveolens and S. fruticosa subsp. thomasii are rare species of conservation interest, while S. montana subsp. montana and T. capitata, have a wide distribution and are used in traditional medicine or as spices. Results showed that the ecological context (phytosociological and ecological features) may influence the composition of EOs of the studied species. High differences in the compound composition have been found in S. montana subsp. montana, whereas minor effects were observed in C. suaveolens, S. fruticosa subsp. thomasii, and T. capitata accessions. The understanding of such aspects is necessary for providing optimal conditions to produce EOs rich in compounds known for their biological activities. The results are of great interest also for EOs producers and at the same time to improve our knowledge and valorize wild officinal plants. Full article

(This article belongs to the Section Plant Ecology)

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17 pages, 1193 KiB

Open AccessEditor’s ChoiceReview

Wild Plants Used as Herbs and Spices in Italy: An Ethnobotanical Review

by Riccardo Motti

Plants 2021, 10(3), 563; https://doi.org/10.3390/plants10030563 - 16 Mar 2021

Cited by 41 | Viewed by 5287

Abstract

Wild edible plants are an essential component of people’s diets in the Mediterranean basin. In Italy, ethnobotanical surveys have received increasing attention in the past two centuries, with some of these studies focusing on wild edible plants. In this regard, the literature in [...] Read more.

Wild edible plants are an essential component of people’s diets in the Mediterranean basin. In Italy, ethnobotanical surveys have received increasing attention in the past two centuries, with some of these studies focusing on wild edible plants. In this regard, the literature in Italy lacks the coverage of some major issues focusing on plants used as herbs and spices. I searched national journals for articles on the use of wild food plants in Italy, published from 1963 to 2020. Aims of the present review were to document plant lore regarding wild herbs and spices in Italy, identify the wild plants most frequently used as spices, analyze the distribution of wild herbs and spices used at a national scale, and finally, to describe the most common phytochemical compounds present in wild plant species. Based on the 34 studies reviewed, I documented 78 wild taxa as being used in Italy as herbs or spices. The studies I included in this systematic review demonstrate that wild species used as herbs and spices enrich Italian folk cuisine and can represent an important resource for profitable, integrated local small-scale activities. Full article

(This article belongs to the Collection Botany of Food Plants)

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17 pages, 2987 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of Drought Stress Effects on Traditional and Modern Apple Cultivars

by Ines Mihaljević, Marija Viljevac Vuletić, Domagoj Šimić, Vesna Tomaš, Daniela Horvat, Marko Josipović, Zvonimir Zdunić, Krunoslav Dugalić and Dominik Vuković

Plants 2021, 10(3), 561; https://doi.org/10.3390/plants10030561 - 16 Mar 2021

Cited by 46 | Viewed by 5177

Abstract

Genotype-dependent responses of apples to drought stress were evaluated between commercial and traditional apple cultivars. The results indicate different mechanisms of tolerance to investigated drought stress conditions. Chlorophyll fluorescence induction (OJIP) parameters, chlorophyll and carotenoid content, malondialdehyde (MDA), hydrogen peroxide (H₂O [...] Read more.

Genotype-dependent responses of apples to drought stress were evaluated between commercial and traditional apple cultivars. The results indicate different mechanisms of tolerance to investigated drought stress conditions. Chlorophyll fluorescence induction (OJIP) parameters, chlorophyll and carotenoid content, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), proline, phenols and leaf water content (WC) were measured. The traditional cultivar “Crvenka” confirmed the best tolerance to a drought stress condition, presenting higher photosynthetic efficiency, higher leaf water content, higher levels of chlorophyll content and lower lipid peroxidation with greater membrane stability. The commercial cultivar “Golden Delicious Reinders” showed decreased water content in leaves, increased lipid peroxidation levels and photoinhibition. Considering all results, the commercial cultivar “Golden Delicious Reinders” was adversely affected by drought, while traditional cultivars exhibited better tolerance to drought stress. Full article

(This article belongs to the Special Issue Physiology and Molecular Biology of Fruit Trees and Vines)

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18 pages, 18328 KiB

Open AccessEditor’s ChoiceArticle

Phenolic Compounds and Biological Activity of Selected Mentha Species

by Sanja Ćavar Zeljković, Jana Šišková, Karolína Komzáková, Nuria De Diego, Katarína Kaffková and Petr Tarkowski

Plants 2021, 10(3), 550; https://doi.org/10.3390/plants10030550 - 15 Mar 2021

Cited by 65 | Viewed by 7370

Abstract

Mentha species are widely used as food, medicine, spices, and flavoring agents. Thus, chemical composition is an important parameter for assessing the quality of mints. In general, the contents of menthol, menthone, eucalyptol, and limonene comprise one of the major parameters for assessing [...] Read more.

Mentha species are widely used as food, medicine, spices, and flavoring agents. Thus, chemical composition is an important parameter for assessing the quality of mints. In general, the contents of menthol, menthone, eucalyptol, and limonene comprise one of the major parameters for assessing the quality of commercially important mints. Building further on the phytochemical characterization of the quality of Mentha species, this work was focused on the composition of phenolic compounds in methanolic extracts. Thirteen Mentha species were grown under the same environmental conditions, and their methanolic extracts were subjected to the LC–MS/MS (liquid chromatography–tandem mass spectrometry) profiling of phenolics and the testing their biological activities, i.e., antioxidant and tyrosinase inhibition activities, which are important features for the cosmetic industry. The total phenolic content (TPC) ranged from 14.81 ± 1.09 mg GAE (gallic acid equivalents)/g for Mentha cervina to 58.93. ± 8.39 mg GAE/g for Mentha suaveolens. The antioxidant activity of examined Mentha related with the content of the phenolic compounds and ranged from 22.79 ± 1.85 to 106.04 ± 3.26 mg TE (Trolox equivalents)/g for M. cervina and Mentha x villosa, respectively. Additionally, Mentha pulegium (123.89 ± 5.64 mg KAE (kojic acid equivalents)/g) and Mentha x piperita (102.82 ± 15.16 mg KAE/g) showed a strong inhibition of the enzyme tyrosinase, which is related to skin hyperpigmentation. The most abundant compound in all samples was rosmarinic acid, ranging from 1363.38 ± 8323 to 2557.08 ± 64.21 μg/g. In general, the levels of phenolic acids in all examined mint extracts did not significantly differ. On the contrary, the levels of flavonoids varied within the species, especially in the case of hesperidin (from 0.73 ± 0.02 to 109. 39 ± 2.01 μg/g), luteolin (from 1.84 ± 0.11 to 31.03 ± 0.16 μg/g), and kaempferol (from 1.30 ± 0.17 to 33.68 ± 0.81 μg/g). Overall results indicated that all examined mints possess significant amounts of phenolic compounds that are responsible for antioxidant activity and, to some extent, for tyrosinase inhibition activity. Phenolics also proved to be adequate compounds, together with terpenoids, for the characterization of Mentha sp. Additionally, citrus-scented Mentha x villosa could be selected as a good candidate for the food and pharmaceutical industry, especially due its chemical composition and easy cultivation, even in winter continental conditions. Full article

(This article belongs to the Special Issue Plant Polyphenols—from Plants to Human Health)

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15 pages, 559 KiB

Open AccessEditor’s ChoiceArticle

Sustainable Processing of Floral Bio-Residues of Saffron (Crocus sativus L.) for Valuable Biorefinery Products

by Stefania Stelluti, Matteo Caser, Sonia Demasi and Valentina Scariot

Plants 2021, 10(3), 523; https://doi.org/10.3390/plants10030523 - 11 Mar 2021

Cited by 42 | Viewed by 3470

Abstract

Tepals constitute the most abundant bio-residues of saffron (Crocus sativus L.). As they are a natural source of polyphenols with antioxidant properties, they could be processed to generate valuable biorefinery products for applications in the pharmaceutical, cosmetic, and food industries, becoming a [...] Read more.

Tepals constitute the most abundant bio-residues of saffron (Crocus sativus L.). As they are a natural source of polyphenols with antioxidant properties, they could be processed to generate valuable biorefinery products for applications in the pharmaceutical, cosmetic, and food industries, becoming a new source of income while reducing bio-waste. Proper storage of by-products is important in biorefining and dehydration is widely used in the herb sector, especially for highly perishable harvested flowers. This study aimed to deepen the phytochemical composition of dried saffron tepals and to investigate whether this was influenced by the extraction technique. In particular, the conventional maceration was compared with the Ultrasound Assisted Extraction (UAE), using different solvents (water and three methanol concentrations, i.e., 20%, 50%, and 80%). Compared to the spice, the dried saffron tepals showed a lower content of total phenolics (average value 1127.94 ± 32.34 mg GAE 100 g⁻¹ DW) and anthocyanins (up to 413.30 ± 137.16 mg G3G 100 g⁻¹ DW), but a higher antioxidant activity, which was measured through the FRAP, ABTS, and DPPH assays. The HPLC-DAD analysis detected some phenolic compounds (i.e., ferulic acid, isoquercitrin, and quercitrin) not previously found in fresh saffron tepals. Vitamin C, already discovered in the spice, was interestingly detected also in dried tepals. Regarding the extraction technique, in most cases, UAE with safer solvents (i.e., water or low percentage of methanol) showed results of phenolic compounds and vitamin C similar to maceration, allowing an improvement in extractions by halving the time. Thus, this study demonstrated that saffron tepals can be dried maintaining their quality and that green extractions can be adopted to obtain high yields of valuable antioxidant phytochemicals, meeting the requirement for a sustainable biorefining. Full article

(This article belongs to the Special Issue Isolation and Analysis of Characteristic Compounds from Herbal and Plant Extracts)

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14 pages, 9268 KiB

Open AccessEditor’s ChoiceArticle

Hormetic Responses of Photosystem II in Tomato to Botrytis cinerea

by Maria-Lavrentia Stamelou, Ilektra Sperdouli, Ioanna Pyrri, Ioannis-Dimosthenis S. Adamakis and Michael Moustakas

Plants 2021, 10(3), 521; https://doi.org/10.3390/plants10030521 - 10 Mar 2021

Cited by 32 | Viewed by 3348

Abstract

Botrytis cinerea, a fungal pathogen that causes gray mold, is damaging more than 200 plant species, and especially tomato. Photosystem II (PSII) responses in tomato (Solanum lycopersicum L.) leaves to Botrytis cinerea spore suspension application were evaluated by chlorophyll fluorescence imaging [...] Read more.

Botrytis cinerea, a fungal pathogen that causes gray mold, is damaging more than 200 plant species, and especially tomato. Photosystem II (PSII) responses in tomato (Solanum lycopersicum L.) leaves to Botrytis cinerea spore suspension application were evaluated by chlorophyll fluorescence imaging analysis. Hydrogen peroxide (H₂O₂) that was detected 30 min after Botrytis application with an increasing trend up to 240 min, is possibly convening tolerance against B. cinerea at short-time exposure, but when increasing at relative longer exposure, is becoming a damaging molecule. In accordance, an enhanced photosystem II (PSII) functionality was observed 30 min after application of B. cinerea, with a higher fraction of absorbed light energy to be directed to photochemistry (Φ_PSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in a significant decrease in the dissipated non-regulated energy (Φ_NO), indicating a possible decreased singlet oxygen (¹O₂) formation, thus specifying a modified reactive oxygen species (ROS) homeostasis. Therefore, 30 min after application of Botrytis spore suspension, before any visual symptoms appeared, defense response mechanisms were triggered, with PSII photochemistry to be adjusted by NPQ in a such way that PSII functionality to be enhanced, but being fully inhibited at the application spot and the adjacent area, after longer exposure (240 min). Hence, the response of tomato PSII to B. cinerea, indicates a hormetic temporal response in terms of “stress defense response” and “toxicity”, expanding the features of hormesis to biotic factors also. The enhanced PSII functionality 30 min after Botrytis application can possible be related with the need of an increased sugar production that is associated with a stronger plant defense potential through the induction of defense genes. Full article

(This article belongs to the Special Issue Photosynthetic Responses to Biotic and Abiotic Stress)

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18 pages, 1763 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of Chemical Composition and Antioxidant Activity of Essential Oils and Crude Extracts of Four Characteristic Zingiberaceae Herbs

by Milena Ivanović, Kaja Makoter and Maša Islamčević Razboršek

Plants 2021, 10(3), 501; https://doi.org/10.3390/plants10030501 - 8 Mar 2021

Cited by 43 | Viewed by 6081

Abstract

The ginger family (Zingiberaceae) includes plants that are known worldwide to have a distinctive smell and taste, which are often used as spices in the kitchen, but also in various industries (pharmaceutical, medical, and cosmetic) due to their proven biological activity. [...] Read more.

The ginger family (Zingiberaceae) includes plants that are known worldwide to have a distinctive smell and taste, which are often used as spices in the kitchen, but also in various industries (pharmaceutical, medical, and cosmetic) due to their proven biological activity. The aim of this study was to investigate and compare the chemical composition and antioxidant activity (AA) of essential oils (EOs) of four characteristic ginger species: Elettaria cardamomum L. Maton (cardamom), Curcuma Longa L. (turmeric), Zingiber Officinale Roscoe (ginger), and Alpinia Officinarum Hance (galangal). Furthermore, the total phenolic content (TPC) and AA of crude extracts obtained after using ultrasound-assisted extraction (UAE) and different extraction solvents (80% ethanol, 80% methanol and water) were evaluated. A total of 87 different chemical components were determined by GC-MS/MS in the EOs obtained after hydrodistillation, 14 of which were identified in varying amounts in all EOs. The major compounds found in cardamom, turmeric, ginger, and galangal were α-terpinyl acetate (40.70%), β-turmerone (25.77%), α-zingiberene (22.69%) and 1,8-cineol (42.71%), respectively. In general, 80% ethanol was found to be the most effective extracting solvent for the bioactivities of the investigated species from the Zingiberaceae family. Among the crude extracts, ethanolic extract of galangal showed the highest TPC value (63.01 ± 1.06 mg GA g⁻¹ DW), while the lowest TPC content was found in cardamom water extract (1.04 ± 0.29 mg GA g⁻¹ DW). The AA evaluated by two different assays (ferric-reducing antioxidant power-FRAP and the scavenging activity of the cationic ABTS radical) proved that galangal rhizome is the plant with the highest antioxidant potential. In addition, no statistical difference was found between the AA of turmeric and ginger extracts, while cardamom rhizome was again inferior. In contrast to the crude extracts, the EOs resulted in significantly lower ABTS and FRAP values, with turmeric EO showing the highest AA. Full article

(This article belongs to the Special Issue Plant Analytical Chemistry)

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31 pages, 3200 KiB

Open AccessEditor’s ChoiceArticle

Genetic Diversity and Pathogenicity of Botryosphaeriaceae Species Associated with Symptomatic Citrus Plants in Europe

by Jadson Diogo Pereira Bezerra, Pedro Wilhelm Crous, Dalia Aiello, Maria Lodovica Gullino, Giancarlo Polizzi and Vladimiro Guarnaccia

Plants 2021, 10(3), 492; https://doi.org/10.3390/plants10030492 - 5 Mar 2021

Cited by 39 | Viewed by 3959

Abstract

This study represents the first survey studying the occurrence, genetic diversity, and pathogenicity of Botryosphaeriaceae species associated with symptomatic citrus species in citrus-production areas in five European countries. Based on morphological features and phylogenetic analyses of internal transcribed spacer (ITS) of nuclear ribosomal [...] Read more.

This study represents the first survey studying the occurrence, genetic diversity, and pathogenicity of Botryosphaeriaceae species associated with symptomatic citrus species in citrus-production areas in five European countries. Based on morphological features and phylogenetic analyses of internal transcribed spacer (ITS) of nuclear ribosomal DNA (nrDNA), translation elongation factor 1-alpha (TEF1) and β-tubulin (TUB2) genes, nine species were identified as belonging to the genera Diplodia, Dothiorella, Lasiodiplodia, and Neofusicoccum. Isolates of Neofusicoccum parvum and Diplodia pseudoseriata were the most frequently detected, while Dothiorella viticola had the widest distribution, occurring in four of the five countries sampled. Representative isolates of the nine Botryosphaeriaceae species used in the pathogenicity tests caused similar symptoms to those observed in nature. Isolates assayed were all re-isolated, thereby fulfilling Koch’s postulates. Isolates of Diplodia pseudoseriata and Diplodia olivarum are recorded for the first time on citrus and all species found in our study, except N. parvum, are reported for the first time on citrus in Europe. Full article

(This article belongs to the Special Issue Citrus Fungal and Oomycete Diseases)

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13 pages, 1264 KiB

Open AccessEditor’s ChoiceArticle

DNA Modification Patterns within the Transposable Elements of the Fig (Ficus carica L.) Genome

by Gabriele Usai, Alberto Vangelisti, Samuel Simoni, Tommaso Giordani, Lucia Natali, Andrea Cavallini and Flavia Mascagni

Plants 2021, 10(3), 451; https://doi.org/10.3390/plants10030451 - 27 Feb 2021

Cited by 16 | Viewed by 2942

Abstract

Transposable element activity can be harmful to the host’s genome integrity, but it can also provide selective advantages. One strategy to cope with transposons is epigenetic control through DNA base modifications. We report the non-canonic DNA modification dynamics of fig (Ficus carica [...] Read more.

Transposable element activity can be harmful to the host’s genome integrity, but it can also provide selective advantages. One strategy to cope with transposons is epigenetic control through DNA base modifications. We report the non-canonic DNA modification dynamics of fig (Ficus carica L.) by exploiting high-quality genome reference and related N4-methylcytosine (4mC) and N6-methyladenine (6mA) data. Overall, 1.49% of transposon nucleotides showed either 4mC or 6mA modifications: the 4mC/6mA ratio was similar in Class I and Class II transposons, with a prevalence of 4mC, which is comparable to coding genes. Different percentages of 4mC or 6mA were observed among LTR-retrotransposon lineages and sub-lineages. Furthermore, both the Copia and Gypsy retroelements showed higher modification rates in the LTR and coding regions compared with their neighbour regions. Finally, the unconventional methylation of retrotransposons is unrelated to the number of close genes, suggesting that the 4mC and 6mA frequency in LTR-retrotransposons should not be related to transcriptional repression in the adjacency of the element. In conclusion, this study highlighted unconventional DNA modification patterns in fig transposable elements. Further investigations will focus on functional implications, in regards to how modified retroelements affect the expression of neighbouring genes, and whether these epigenetic markers can spread from repeats to genes, shaping the plant phenotype. Full article

(This article belongs to the Special Issue DNA Methylation in Plants)

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12 pages, 717 KiB

Open AccessEditor’s ChoiceReview

Plant Recovery after Metal Stress—A Review

by Jagna Chmielowska-Bąk and Joanna Deckert

Plants 2021, 10(3), 450; https://doi.org/10.3390/plants10030450 - 27 Feb 2021

Cited by 25 | Viewed by 5098

Abstract

Contamination of the environment with metals, their adverse impact on plant performance and transmission to the human food chain through crops and vegetables are important concerns worldwide. Although the literature on metal contamination, toxicity and plant response to this stress factor is quite [...] Read more.

Contamination of the environment with metals, their adverse impact on plant performance and transmission to the human food chain through crops and vegetables are important concerns worldwide. Although the literature on metal contamination, toxicity and plant response to this stress factor is quite abundant, there are very limited reports on the phenomenon of plant recovery after metal stress. The present article reviews available literature on the recovery process examined in various plant species, in response to several metals (Al, Cd, Cu, Ni, Pb, Zn), applied at different concentrations and treatment duration. The reviewed studies have been carried out in laboratory conditions. However, it should be highlighted that although metal stress is not as transient as most of other stress factors (e.g., drought, heat, chilling), metal concentration in the soil may still decrease due to, e.g., leaching to lower soil layers or uptake by organisms. Thus, in natural conditions, plants may be subjected to post-metal-stress conditions. The review also discusses the mechanism behind efficient recovery and the impact of post metal stress on future plant performance—possible acquisition of stress memory, adaptation to unfavorable conditions and cross-tolerance towards other stress factors. Full article

(This article belongs to the Special Issue Physiological and Molecular Mechanisms of Plant Response to Metal Stress)

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31 pages, 989 KiB

Open AccessEditor’s ChoicePerspective

Potassium Control of Plant Functions: Ecological and Agricultural Implications

by Jordi Sardans and Josep Peñuelas

Plants 2021, 10(2), 419; https://doi.org/10.3390/plants10020419 - 23 Feb 2021

Cited by 181 | Viewed by 12681

Abstract

Potassium, mostly as a cation (K⁺), together with calcium (Ca²⁺) are the most abundant inorganic chemicals in plant cellular media, but they are rarely discussed. K⁺ is not a component of molecular or macromolecular plant structures, thus it [...] Read more.

Potassium, mostly as a cation (K⁺), together with calcium (Ca²⁺) are the most abundant inorganic chemicals in plant cellular media, but they are rarely discussed. K⁺ is not a component of molecular or macromolecular plant structures, thus it is more difficult to link it to concrete metabolic pathways than nitrogen or phosphorus. Over the last two decades, many studies have reported on the role of K⁺ in several physiological functions, including controlling cellular growth and wood formation, xylem–phloem water content and movement, nutrient and metabolite transport, and stress responses. In this paper, we present an overview of contemporary findings associating K⁺ with various plant functions, emphasizing plant-mediated responses to environmental abiotic and biotic shifts and stresses by controlling transmembrane potentials and water, nutrient, and metabolite transport. These essential roles of K⁺ account for its high concentrations in the most active plant organs, such as leaves, and are consistent with the increasing number of ecological and agricultural studies that report K⁺ as a key element in the function and structure of terrestrial ecosystems, crop production, and global food security. We synthesized these roles from an integrated perspective, considering the metabolic and physiological functions of individual plants and their complex roles in terrestrial ecosystem functions and food security within the current context of ongoing global change. Thus, we provide a bridge between studies of K⁺ at the plant and ecological levels to ultimately claim that K⁺ should be considered at least at a level similar to N and P in terrestrial ecological studies. Full article

(This article belongs to the Section Plant Ecology)

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13 pages, 699 KiB

Open AccessEditor’s ChoiceReview

Recapitulation of the Function and Role of ROS Generated in Response to Heat Stress in Plants

by Emily Medina, Su-Hwa Kim, Miriam Yun and Won-Gyu Choi

Plants 2021, 10(2), 371; https://doi.org/10.3390/plants10020371 - 15 Feb 2021

Cited by 80 | Viewed by 9498

Abstract

In natural ecosystems, plants are constantly exposed to changes in their surroundings as they grow, caused by a lifestyle that requires them to live where their seeds fall. Thus, plants strive to adapt and respond to changes in their exposed environment that change [...] Read more.

In natural ecosystems, plants are constantly exposed to changes in their surroundings as they grow, caused by a lifestyle that requires them to live where their seeds fall. Thus, plants strive to adapt and respond to changes in their exposed environment that change every moment. Heat stress that naturally occurs when plants grow in the summer or a tropical area adversely affects plants’ growth and poses a risk to plant development. When plants are subjected to heat stress, they recognize heat stress and respond using highly complex intracellular signaling systems such as reactive oxygen species (ROS). ROS was previously considered a byproduct that impairs plant growth. However, in recent studies, ROS gained attention for its function as a signaling molecule when plants respond to environmental stresses such as heat stress. In particular, ROS, produced in response to heat stress in various plant cell compartments such as mitochondria and chloroplasts, plays a crucial role as a signaling molecule that promotes plant growth and triggers subsequent downstream reactions. Therefore, this review aims to address the latest research trends and understandings, focusing on the function and role of ROS in responding and adapting plants to heat stress. Full article

(This article belongs to the Special Issue Specificity of ROS and Redox Regulatory Systems)

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12 pages, 721 KiB

Open AccessEditor’s ChoiceReview

Downstream Signalling from Molecular Hydrogen

by John T. Hancock and Grace Russell

Plants 2021, 10(2), 367; https://doi.org/10.3390/plants10020367 - 14 Feb 2021

Cited by 23 | Viewed by 3988

Abstract

Molecular hydrogen (H₂) is now considered part of the suite of small molecules that can control cellular activity. As such, H₂ has been suggested to be used in the therapy of diseases in humans and in plant science to enhance [...] Read more.

Molecular hydrogen (H₂) is now considered part of the suite of small molecules that can control cellular activity. As such, H₂ has been suggested to be used in the therapy of diseases in humans and in plant science to enhance the growth and productivity of plants. Treatments of plants may involve the creation of hydrogen-rich water (HRW), which can then be applied to the foliage or roots systems of the plants. However, the molecular action of H₂ remains elusive. It has been suggested that the presence of H₂ may act as an antioxidant or on the antioxidant capacity of cells, perhaps through the scavenging of hydroxyl radicals. H₂ may act through influencing heme oxygenase activity or through the interaction with reactive nitrogen species. However, controversy exists around all the mechanisms suggested. Here, the downstream mechanisms in which H₂ may be involved are critically reviewed, with a particular emphasis on the H₂ mitigation of stress responses. Hopefully, this review will provide insight that may inform future research in this area. Full article

(This article belongs to the Special Issue Production and Role of Molecular Hydrogen in Plants)

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23 pages, 2206 KiB

Open AccessEditor’s ChoiceReview

A Beginner’s Guide to Osmoprotection by Biostimulants

by David Jiménez-Arias, Francisco J. García-Machado, Sarai Morales-Sierra, Ana L. García-García, Antonio J. Herrera, Francisco Valdés, Juan C. Luis and Andrés A. Borges

Plants 2021, 10(2), 363; https://doi.org/10.3390/plants10020363 - 13 Feb 2021

Cited by 22 | Viewed by 6462

Abstract

Water is indispensable for the life of any organism on Earth. Consequently, osmotic stress due to salinity and drought is the greatest threat to crop productivity. Ongoing climate change includes rising temperatures and less precipitation over large areas of the planet. This is [...] Read more.

Water is indispensable for the life of any organism on Earth. Consequently, osmotic stress due to salinity and drought is the greatest threat to crop productivity. Ongoing climate change includes rising temperatures and less precipitation over large areas of the planet. This is leading to increased vulnerability to the drought conditions that habitually threaten food security in many countries. Such a scenario poses a daunting challenge for scientists: the search for innovative solutions to save water and cultivate under water deficit. A search for formulations including biostimulants capable of improving tolerance to this stress is a promising specific approach. This review updates the most recent state of the art in the field. Full article

(This article belongs to the Special Issue Chemical Activators of the Natural Defences of the Plant)

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14 pages, 1987 KiB

Open AccessEditor’s ChoiceArticle

Foliar Application of Different Vegetal-Derived Protein Hydrolysates Distinctively Modulates Tomato Root Development and Metabolism

by Angela Valentina Ceccarelli, Begoña Miras-Moreno, Valentina Buffagni, Biancamaria Senizza, Youry Pii, Mariateresa Cardarelli, Youssef Rouphael, Giuseppe Colla and Luigi Lucini

Plants 2021, 10(2), 326; https://doi.org/10.3390/plants10020326 - 8 Feb 2021

Cited by 45 | Viewed by 5100

Abstract

Despite the scientific evidence supporting their biostimulant activity, the molecular mechanism(s) underlying the activity of protein hydrolysates (PHs) and the specificity among different products are still poorly explored. This work tested five different protein hydrolysates, produced from different plant sources using the same [...] Read more.

Despite the scientific evidence supporting their biostimulant activity, the molecular mechanism(s) underlying the activity of protein hydrolysates (PHs) and the specificity among different products are still poorly explored. This work tested five different protein hydrolysates, produced from different plant sources using the same enzymatic approach, for their ability to promote rooting in tomato cuttings following quick dipping. Provided that all the different PHs increased root length (45–93%) and some of them increased root number (37–56%), untargeted metabolomics followed by multivariate statistics and pathway analysis were used to unravel the molecular processes at the basis of the biostimulant activity. Distinct metabolomic signatures could be found in roots following the PHs treatments. In general, PHs shaped the phytohormone profile, modulating the complex interaction between cytokinins and auxins, an interplay playing a pivotal role in root development, and triggered a down accumulation of brassinosteroids. Concerning secondary metabolism, PHs induced the accumulation of aliphatic glucosinolates, alkaloids, and phenylpropanoids, potentially eliciting crop resilience to stress conditions. Here, we confirm that PHs may have a hormone-like activity, and that their application can modulate plant growth, likely interfering with signaling processes. Noteworthy, the heterogenicity of the botanical origin supported the distinctive and peculiar metabolomic responses we observed across the products tested. While supporting their biostimulant activity, these findings suggest that a generalized crop response to PHs cannot be defined and that specific effects are rather to be investigated. Full article

(This article belongs to the Special Issue Biostimulants as Growth Promoting and Stress Protecting Compounds)

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33 pages, 4287 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Silicon Cycling in Soils Revisited

by Jörg Schaller, Daniel Puppe, Danuta Kaczorek, Ruth Ellerbrock and Michael Sommer

Plants 2021, 10(2), 295; https://doi.org/10.3390/plants10020295 - 4 Feb 2021

Cited by 129 | Viewed by 8761

Abstract

Silicon (Si) speciation and availability in soils is highly important for ecosystem functioning, because Si is a beneficial element for plant growth. Si chemistry is highly complex compared to other elements in soils, because Si reaction rates are relatively slow and dependent on [...] Read more.

Silicon (Si) speciation and availability in soils is highly important for ecosystem functioning, because Si is a beneficial element for plant growth. Si chemistry is highly complex compared to other elements in soils, because Si reaction rates are relatively slow and dependent on Si species. Consequently, we review the occurrence of different Si species in soil solution and their changes by polymerization, depolymerization, and condensation in relation to important soil processes. We show that an argumentation based on thermodynamic endmembers of Si dependent processes, as currently done, is often difficult, because some reactions such as mineral crystallization require months to years (sometimes even centuries or millennia). Furthermore, we give an overview of Si reactions in soil solution and the predominance of certain solid compounds, which is a neglected but important parameter controlling the availability, reactivity, and function of Si in soils. We further discuss the drivers of soil Si cycling and how humans interfere with these processes. The soil Si cycle is of major importance for ecosystem functioning; therefore, a deeper understanding of drivers of Si cycling (e.g., predominant speciation), human disturbances and the implication for important soil properties (water storage, nutrient availability, and micro aggregate stability) is of fundamental relevance. Full article

(This article belongs to the Special Issue Silicon in the Soil-Plant Continuum)

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17 pages, 4048 KiB

Open AccessEditor’s ChoiceArticle

Can Foliar Pulverization with CaCl₂ and Ca(NO₃)₂ Trigger Ca Enrichment in Solanum tuberosum L. Tubers?

by Ana Rita F. Coelho, Fernando C. Lidon, Cláudia Campos Pessoa, Ana Coelho Marques, Inês Carmo Luís, João Caleiro, Manuela Simões, José Kullberg, Paulo Legoinha, Maria Brito, Mauro Guerra, Roberta G. Leitão, Carlos Galhano, Paula Scotti-Campos, José N. Semedo, Maria Manuela Silva, Isabel P. Pais, Maria J. Silva, Ana P. Rodrigues, Maria F. Pessoa, José C. Ramalho and Fernando H. Reboredo Show full author list Hide full author list

Plants 2021, 10(2), 245; https://doi.org/10.3390/plants10020245 - 27 Jan 2021

Cited by 25 | Viewed by 3070

Abstract

This study aimed to assess the efficiency of Ca enrichment in tubers of three genotypes of Solanum tuberosum L., through foliar spraying with CaCl₂ and Ca(NO₃)₂ solutions. In this context, soil heterogeneity of three potato-growing fields, as well as [...] Read more.

This study aimed to assess the efficiency of Ca enrichment in tubers of three genotypes of Solanum tuberosum L., through foliar spraying with CaCl₂ and Ca(NO₃)₂ solutions. In this context, soil heterogeneity of three potato-growing fields, as well as the implications of Ca accumulation among tissues and some quality parameters were assessed. Three potato varieties (Agria, Picasso and Rossi) were grown in three production fields and during the life cycle, four pulverizations with calcium chloride (3 and 6 kg ha⁻¹) or calcium nitrate (0.5, 2 and 4 kg ha⁻¹) were applied. For screening the potential phytotoxicity, using Agria as a test system, the potential synthesis of photoassimilates was determined, and it was found that after the 3rd Ca application, leaf gas exchanges were moderately (net photosynthesis), to strongly (stomatal conductance) affected, although without impact on Ca accumulation in tubers. At harvest, the average Ca biofortification index varied between 5–40%, 40–35% and 4.3–13% in Agria, Picasso and Rossi, respectively. Moreover, the equatorial region of the tubers in general showed that Ca accumulation prevailed in the epidermis and, in some cases, in inner areas of the potato tubers. Biofortified tubers with Ca also showed some significant changes in total soluble solids and colorimetric parameters. It is concluded that Ca enrichment of potato tubers through foliar spraying complemented the xylem mass flow of Ca from roots, through phloem redistribution. Both fertilizers showed similar efficiency, but Rossi revealed a lower index of Ca accumulation, eventually due to different metabolic characteristics. Although affected by Ca enrichment, potato tubers maintained a high quality for industrial processing. Full article

(This article belongs to the Special Issue Edible Plants)

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21 pages, 3023 KiB

Open AccessEditor’s ChoiceReview

The Ubiquitin Switch in Plant Stress Response

by Paymon Doroodian and Zhihua Hua

Plants 2021, 10(2), 246; https://doi.org/10.3390/plants10020246 - 27 Jan 2021

Cited by 38 | Viewed by 5059

Abstract

Ubiquitin is a 76 amino acid polypeptide common to all eukaryotic organisms. It functions as a post-translationally modifying mark covalently linked to a large cohort of yet poorly defined protein substrates. The resulting ubiquitylated proteins can rapidly change their activities, cellular localization, or [...] Read more.

Ubiquitin is a 76 amino acid polypeptide common to all eukaryotic organisms. It functions as a post-translationally modifying mark covalently linked to a large cohort of yet poorly defined protein substrates. The resulting ubiquitylated proteins can rapidly change their activities, cellular localization, or turnover through the 26S proteasome if they are no longer needed or are abnormal. Such a selective modification is essential to many signal transduction pathways particularly in those related to stress responses by rapidly enhancing or quenching output. Hence, this modification system, the so-called ubiquitin-26S proteasome system (UPS), has caught the attention in the plant research community over the last two decades for its roles in plant abiotic and biotic stress responses. Through direct or indirect mediation of plant hormones, the UPS selectively degrades key components in stress signaling to either negatively or positively regulate plant response to a given stimulus. As a result, a tightly regulated signaling network has become of much interest over the years. The ever-increasing changes of the global climate require both the development of new crops to cope with rapid changing environment and new knowledge to survey the dynamics of ecosystem. This review examines how the ubiquitin can switch and tune plant stress response and poses potential avenues to further explore this system. Full article

(This article belongs to the Special Issue Role of the Ubiquitin System in Plant Stress Responses)

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42 pages, 3447 KiB

Open AccessEditor’s ChoiceReview

Global Plant Virus Disease Pandemics and Epidemics

by Roger A. C. Jones

Plants 2021, 10(2), 233; https://doi.org/10.3390/plants10020233 - 25 Jan 2021

Cited by 189 | Viewed by 22240

Abstract

The world’s staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. This situation is becoming increasingly serious because of the human population’s growing food requirements [...] Read more.

The world’s staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. This situation is becoming increasingly serious because of the human population’s growing food requirements and increasing difficulties in managing virus diseases effectively arising from global warming. This review provides historical and recent information about virus disease pandemics and major epidemics that originated within different world regions, spread to other continents, and now have very wide distributions. Because they threaten food security, all are cause for considerable concern for humanity. The pandemic disease examples described are six (maize lethal necrosis, rice tungro, sweet potato virus, banana bunchy top, citrus tristeza, plum pox). The major epidemic disease examples described are seven (wheat yellow dwarf, wheat streak mosaic, potato tuber necrotic ringspot, faba bean necrotic yellows, pepino mosaic, tomato brown rugose fruit, and cucumber green mottle mosaic). Most examples involve long-distance virus dispersal, albeit inadvertent, by international trade in seed or planting material. With every example, the factors responsible for its development, geographical distribution and global importance are explained. Finally, an overall explanation is given of how to manage global virus disease pandemics and epidemics effectively. Full article

(This article belongs to the Special Issue Plant Virus Epidemiology)

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16 pages, 5968 KiB

Open AccessEditor’s ChoiceArticle

Effect of Three Nanoparticles (Se, Si and Cu) on the Bioactive Compounds of Bell Pepper Fruits under Saline Stress

by Yolanda González-García, Claribel Cárdenas-Álvarez, Gregorio Cadenas-Pliego, Adalberto Benavides-Mendoza, Marcelino Cabrera-de-la-Fuente, Alberto Sandoval-Rangel, Jesús Valdés-Reyna and Antonio Juárez-Maldonado

Plants 2021, 10(2), 217; https://doi.org/10.3390/plants10020217 - 23 Jan 2021

Cited by 61 | Viewed by 5019

Abstract

The bell pepper is a vegetable with high antioxidant content, and its consumption is important because it can reduce the risk of certain diseases in humans. Plants can be affected by different types of stress, whether biotic or abiotic. Among the abiotic factors, [...] Read more.

The bell pepper is a vegetable with high antioxidant content, and its consumption is important because it can reduce the risk of certain diseases in humans. Plants can be affected by different types of stress, whether biotic or abiotic. Among the abiotic factors, there is saline stress that affects the metabolism and physiology of plants, which causes damage, decreasing productivity and quality of fruits. The objective of this work was to evaluate the application of selenium, silicon and copper nanoparticles and saline stress on the bioactive compounds of bell pepper fruits. The bell pepper plants were exposed to saline stress (25 mM NaCl and 50 mM) in the nutrient solution throughout the crop cycle. The nanoparticles were applied drenching solution of these to substrate (Se NPs 10 and 50 mg L⁻¹, Si NPs 200 and 1000 mg L⁻¹, Cu NPs 100 and 500 mg L⁻¹). The results show that saline stress reduces chlorophylls, lycopene, and β-carotene in leaves; but increased the activity of some enzymes (e.g., glutathione peroxidase and phenylalanine ammonia lyase, and glutathione). In fruits, saline stress decreased flavonoids and glutathione. The nanoparticles increased chlorophylls, lycopene and glutathione peroxidase activity in the leaves; and ascorbate peroxidase, glutathione peroxidase, catalase and phenylalanine ammonia lyase activity, and also phenols, flavonoids, glutathione, β-carotene, yellow carotenoids in fruits. The application of nanoparticles to bell pepper plants under saline stress is efficient to increase the content of bioactive compounds in fruits. Full article

(This article belongs to the Special Issue Nanotechnology Advances in Plant Science and Biotechnology)

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27 pages, 2802 KiB

Open AccessEditor’s ChoiceReview

Bryo-Activities: A Review on How Bryophytes Are Contributing to the Arsenal of Natural Bioactive Compounds against Fungi

by Mauro Commisso, Francesco Guarino, Laura Marchi, Antonella Muto, Amalia Piro and Francesca Degola

Plants 2021, 10(2), 203; https://doi.org/10.3390/plants10020203 - 21 Jan 2021

Cited by 43 | Viewed by 10159

Abstract

Usually regarded as less evolved than their more recently diverged vascular sisters, which currently dominate vegetation landscape, bryophytes seem having nothing to envy to the defensive arsenal of other plants, since they had acquired a suite of chemical traits that allowed them to [...] Read more.

Usually regarded as less evolved than their more recently diverged vascular sisters, which currently dominate vegetation landscape, bryophytes seem having nothing to envy to the defensive arsenal of other plants, since they had acquired a suite of chemical traits that allowed them to adapt and persist on land. In fact, these closest modern relatives of the ancestors to the earliest terrestrial plants proved to be marvelous chemists, as they traditionally were a popular remedy among tribal people all over the world, that exploit their pharmacological properties to cure the most different diseases. The phytochemistry of bryophytes exhibits a stunning assortment of biologically active compounds such as lipids, proteins, steroids, organic acids, alcohols, aliphatic and aromatic compounds, polyphenols, terpenoids, acetogenins and phenylquinones, thus it is not surprising that substances obtained from various species belonging to such ancestral plants are widely employed as antitumor, antipyretic, insecticidal and antimicrobial. This review explores in particular the antifungal potential of the three Bryophyta divisions—mosses (Musci), hornworts (Anthocerotae) and liverworts (Hepaticae)—to be used as a sources of interesting bioactive constituents for both pharmaceutical and agricultural areas, providing an updated overview of the latest relevant insights. Full article

(This article belongs to the Special Issue Fungal Model Systems: What Can They Tell Us about the Biological Activity of Plant Extracts and Natural Compounds?)

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25 pages, 3104 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Zinc Enrichment in Two Contrasting Genotypes of Triticum aestivum L. Grains: Interactions between Edaphic Conditions and Foliar Fertilizers

by Inês Carmo Luís, Fernando C. Lidon, Cláudia Campos Pessoa, Ana Coelho Marques, Ana Rita F. Coelho, Manuela Simões, Manuel Patanita, José Dôres, José C. Ramalho, Maria Manuela Silva, Ana Sofia Almeida, Isabel P. Pais, Maria Fernanda Pessoa, Fernando Henrique Reboredo, Paulo Legoinha, Mauro Guerra, Roberta G. Leitão and Paula Scotti Campos

Plants 2021, 10(2), 204; https://doi.org/10.3390/plants10020204 - 21 Jan 2021

Cited by 22 | Viewed by 2920

Abstract

This study aimed to assess the implications of Zn enrichment in wheat grains as a function of contrasting genotypes, edaphic conditions and foliar fertilizers. Triticum aestivum L. varieties Roxo and Paiva were grown in four production fields, and sprayed with ZnSO₄ (0, [...] Read more.

This study aimed to assess the implications of Zn enrichment in wheat grains as a function of contrasting genotypes, edaphic conditions and foliar fertilizers. Triticum aestivum L. varieties Roxo and Paiva were grown in four production fields, and sprayed with ZnSO₄ (0, 16.20 and 36.40 kg/ha) Zn-EDTA (0, 6.30 and 12.60 kg/ha) and Tecnifol Zinc (0, 3.90 and 7.80 kg/ha). The heterogeneous edaphic conditions of the wheat fields were chemically characterized, it being found that soil properties determine different Zn accumulation in the grains of both genotypes. Foliar spraying enhanced to different extents Zn content in the grains of both genotypes, but the average of enrichment indexes varied among the wheat fields. Zinc mostly accumulated in the embryo and vascular bundle and to a lesser extent in the endosperm. Grain yield and test weight sprayed by ZnSO₄ gave the highest values in both genotypes, but the opposite was found for Zn-EDTA. Considering the color parameters, lightness and red–green transitions were found to be a conjunction of genotype characteristics, fertilization types and edaphic conditions prevailing in each field. It is concluded that the index of Zn enrichment in wheat grains is a docket of edaphic conditions, genotype and type of fertilization. Full article

(This article belongs to the Collection Plant Nutrition Biofortification)

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19 pages, 1119 KiB

Open AccessEditor’s ChoiceReview

Abiotic Stress in Crop Species: Improving Tolerance by Applying Plant Metabolites

by Francisca Godoy, Karina Olivos-Hernández, Claudia Stange and Michael Handford

Plants 2021, 10(2), 186; https://doi.org/10.3390/plants10020186 - 20 Jan 2021

Cited by 144 | Viewed by 20562

Abstract

Reductions in crop yields brought about by abiotic stress are expected to increase as climate change, and other factors, generate harsher environmental conditions in regions traditionally used for cultivation. Although breeding and genetically modified and edited organisms have generated many varieties with greater [...] Read more.

Reductions in crop yields brought about by abiotic stress are expected to increase as climate change, and other factors, generate harsher environmental conditions in regions traditionally used for cultivation. Although breeding and genetically modified and edited organisms have generated many varieties with greater abiotic stress tolerance, their practical use depends on lengthy processes, such as biological cycles and legal aspects. On the other hand, a non-genetic approach to improve crop yield in stress conditions involves the exogenous application of natural compounds, including plant metabolites. In this review, we examine the recent literature related to the application of different natural primary (proline, l-tryptophan, glutathione, and citric acid) and secondary (polyols, ascorbic acid, lipoic acid, glycine betaine, α-tocopherol, and melatonin) plant metabolites in improving tolerance to abiotic stress. We focus on drought, saline, heavy metal, and temperature as environmental parameters that are forecast to become more extreme or frequent as the climate continues to alter. The benefits of such applications are often evaluated by measuring their effects on metabolic, biochemical, and morphological parameters in a variety of crop plants, which usually result in improved yields when applied in greenhouse conditions or in the field. As this strategy has proven to be an effective way to raise plant tolerance to abiotic stress, we also discuss the prospect of its widespread implementation in the short term. Full article

(This article belongs to the Special Issue Plant Metabolites and Regulation under Environmental Stress)

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