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Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change

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A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Response to Abiotic Stress and Climate Change".

Deadline for manuscript submissions: closed (20 February 2022) | Viewed by 39234

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Prof. Dr. Oscar Vicente

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Guest Editor

Institute for the Conservation and Improvement of Valencian Agrodiversity (COMAV), Universitat Politècnica de València, Camino de Vera 14, 46022 Valencia, Spain
Interests: climate change; plant biotechnology; plant reproduction; abiotic stress; plant stress physiology; halophytes; drought; salinity; stress tolerance; biostimulants
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Dr. Marius-Nicusor Grigore‬

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Faculty of Medicine and Biological Sciences, Stefan cel Mare University of Suceava, Suceava 720229, Romania
Interests: halophytes; halophytes anatomy and ecology; ecophysiology of halophytes; plant abiotic stress; conceptual and historical approach of halophytes
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Climate change represents a major challenge for agriculture and food security in the coming years. Soil salinity is, together with drought, one of the major causes of the reduction of crop yields worldwide, and climate change is contributing to the increasing loss of irrigated cropland due to secondary salinization, especially in arid and semiarid regions. The most promising strategy to address this problem should be based on the genetic improvement of crop salt tolerance. This, in turn, requires a deep understanding of the mechanisms underlying salt tolerance. Paradoxically, most studies on plant salt tolerance have been carried out using non-tolerant model species, such as Arabidopsis thaliana. Besides, even though tolerance is based on a series of conserved responses to salt stress – control of ion transport, osmolyte biosynthesis, and activation of antioxidant systems – the specific mechanisms of tolerance can vary widely in different species. Therefore, no single model will provide enough information.

All major crops are glycophytes, sensitive to relatively low levels of salt in the soil. The halophytes, on the contrary, are adapted to natural saline environments and are able to survive and complete their life cycle in habitats with soil salinity equivalent to 200 mM NaCl, or even higher, close to that of seawater. Halophytes are, therefore, ideal materials for basic studies of salt tolerance mechanisms in plants, at the physiological, biochemical, and molecular levels. Apart from being a source of knowledge, halophytes can also provide biotechnological tools – salt-tolerance genes and salt-induced promoters – for the genetic improvement of salt tolerance of conventional crops. Furthermore, some halophytes could represent the basis of a sustainable ‘saline agriculture’, being commercially grown in salinized land and irrigated with brackish or saline water. This Special Issue will cover all of the aforementioned basic and applied aspects of halophytes research, reflected in original research articles, reviews, mini-reviews, and opinion papers.

Prof. Dr. Óscar Vicente
Dr. Marius-Nicusor Grigore‬
Guest Editors

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Keywords

abiotic stress
antioxidant systems
climate change
ion transport
osmolyte accumulation
plant breeding
saline agriculture
salinity
salt stress responses
salt tolerance

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Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change II in Plants (6 articles)

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Editorial

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7 pages, 243 KiB

Open AccessEditorial

Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change

by Marius-Nicușor Grigore and Oscar Vicente

Plants 2023, 12(2), 221; https://doi.org/10.3390/plants12020221 - 04 Jan 2023

Cited by 13 | Viewed by 2112

Abstract

Halophytes, wild plants adapted to highly saline natural environments, represent extremely useful—and, at present, underutilised—experimental systems with which to investigate the mechanisms of salt tolerance in plants at the anatomical, physiological, biochemical and molecular levels. They can also provide biotechnological tools for the genetic improvement of salt tolerance in our conventional crops, such as salt tolerance genes or salt-induced promoters. Furthermore, halophytes may constitute the basis of sustainable ‘saline agriculture’ through commercial cultivation after some breeding to improve agronomic traits. All these issues are relevant in the present context of climate emergency, as soil salinity is—together with drought—the most critical environmental factor in reducing crop yield worldwide. In fact, climate change represents the most serious challenge for agricultural production and food security in the near future. Several of the topics mentioned above—mainly referring to basic studies on salt tolerance mechanisms—are addressed in the articles published within this Special Issue. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

Research

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21 pages, 4343 KiB

Open AccessArticle

Constitutive and Adaptive Traits of Environmental Stress Tolerance in the Threatened Halophyte Limonium angustebracteatum Erben (Plumbaginaceae)

by Ricardo Mir, Ignacio Romero, Sara González-Orenga, P. Pablo Ferrer-Gallego, Emilio Laguna, Monica Boscaiu, Lăcrămioara Oprică, Marius-Nicușor Grigore and Oscar Vicente

Plants 2022, 11(9), 1137; https://doi.org/10.3390/plants11091137 - 22 Apr 2022

Cited by 4 | Viewed by 1972

Abstract

Limonium angustebracteatum is a halophyte endemic to the E and SE Iberian Peninsula with interest in conservation. Salt glands represent an important adaptive trait in recretohalophytes like this and other Limonium species, as they allow the excretion of excess salts, reducing the concentration of toxic ions in foliar tissues. This study included the analysis of the salt gland structure, composed of 12 cells, 4 secretory and 8 accessory. Several anatomical, physiological and biochemical responses to stress were also analysed in adult plants subjected to one month of water stress, complete lack of irrigation, and salt stress, by watering with aqueous solutions of 200, 400, 600 and 800 mM NaCl. Plant growth was inhibited by the severe water deficit and, to a lesser extent, by high NaCl concentrations. A variation in the anatomical structure of the leaves was detected under conditions of salt and water stress; plants from the salt stress treatment showed salt glands sunken between epidermal cells, bordered by very large epidermal cells, whereas in those from the water stress treatment, the epidermal cells were heterogeneous in shape and size. In both, the palisade structure of the leaves was altered. Salt excretion is usually accompanied by the accumulation of salts in the foliar tissue. This was also found in L. angustebracteatum, in which the concentration of all ions analysed was higher in the leaves than in the roots. The increase of K⁺ in the roots of plants subjected to water stress was also remarkable. The multivariate analysis indicated differences in water and salt stress responses, such as the accumulation of Na and Cl, or proline, but K⁺ homeostasis played a relevant role in the mechanism of tolerance to both stressful conditions. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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26 pages, 9430 KiB

Open AccessArticle

Recovery from Salinity and Drought Stress in the Perennial Sarcocornia fruticosa vs. the Annual Salicornia europaea and S. veneta

by Roberta Calone, Diana-Maria Mircea, Sara González-Orenga, Monica Boscaiu, Carla Lambertini, Lorenzo Barbanti and Oscar Vicente

Plants 2022, 11(8), 1058; https://doi.org/10.3390/plants11081058 - 13 Apr 2022

Cited by 15 | Viewed by 2947

Abstract

Current agricultural problems, such as the decline of freshwater and fertile land, foster saline agriculture development. Salicornia and Sarcocornia species, with a long history of human consumption, are ideal models for developing halophyte crops. A greenhouse experiment was set up to compare the response of the perennial Sarcocornia fruticosa and the two annual Salicornia europaea and S. veneta to 30 days of salt stress (watering with 700 mM NaCl) and water deficit (complete withholding of irrigation) separate treatments, followed by 15 days of recovery. The three species showed high tolerance to salt stress, based on the accumulation of ions (Na⁺, Cl⁻, Ca²⁺) in the shoots and the synthesis of organic osmolytes. These defence mechanisms were partly constitutive, as active ion transport to the shoots and high levels of glycine betaine were also observed in non-stressed plants. The three halophytes were sensitive to water stress, albeit S. fruticosa to a lesser extent. In fact, S. fruticosa showed a lower reduction in shoot fresh weight than S. europaea or S. veneta, no degradation of photosynthetic pigments, a significant increase in glycine betaine contents, and full recovery after the water stress treatment. The observed differences could be due to a better adaptation of S. fruticosa to a drier natural habitat, as compared to the two Salicornia species. However, a more gradual stress-induced senescence in the perennial S. fruticosa may contribute to greater drought tolerance in this species. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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21 pages, 5273 KiB

Open AccessFeature PaperArticle

Salicornia europaea L. Functional Traits Indicate Its Optimum Growth

by Stefany Cárdenas-Pérez, Ahmad Rajabi Dehnavi, Karol Leszczyński, Sandra Lubińska-Mielińska, Agnieszka Ludwiczak and Agnieszka Piernik

Plants 2022, 11(8), 1051; https://doi.org/10.3390/plants11081051 - 12 Apr 2022

Cited by 17 | Viewed by 3562

Abstract

Salicornia europaea L. grows in areas periodically flooded by salty or brackish water. It has potential economic value, because it can be used as food, forage, or biofuel, and has potential in pharmaceuticals and cosmetics. Increasing interest in S. europaea is due to its extreme salt tolerance and well growth in marginal saline soils. However, the variation in its functional traits in response to environmental conditions is still poorly studied. There are still questions regarding the optimal level of salinity for different traits. Therefore, we worked to address the question if S. europaea traits from different scales are controlled by salinity level. Based on performed pot experiment, we found that almost all traits are salinity dependent but affected in different ways. We demonstrated that morphological, biomass, and anatomical properties indicate optimum growth between 200 and 400 mM NaCl and growth limitations at 0, 800, and 1000 mM NaCl. Moreover, we found the most affected traits which include photosynthetic pigments and protein content, plant surface area, peroxidase activity, and anatomic traits related to cell shape. Our results significantly expanded the knowledge about S. europaea functional traits variation in response to salinity, which can be important for discovering regulating processes and for possible future agricultural applications. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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20 pages, 7334 KiB

Open AccessArticle

Effect of Salinity on Growth, Ion Accumulation and Mineral Nutrition of Different Accessions of a Crop Wild Relative Legume Species, Trifolium fragiferum

by Astra Jēkabsone, Una Andersone-Ozola, Andis Karlsons, Māris Romanovs and Gederts Ievinsh

Plants 2022, 11(6), 797; https://doi.org/10.3390/plants11060797 - 17 Mar 2022

Cited by 21 | Viewed by 2704

Abstract

Crop wild relatives represent a valuable resource for the breeding of new crop varieties suitable for sustainable productivity in conditions of climate change. The aim of the present study was to assess salt tolerance of several wild accessions of T. fragiferum from habitats with different salinity levels in controlled conditions. Decrease of plant biomass and changes in partitioning between different organs was a characteristic response of plants with increasing substrate salinity, but these responses were genotype-specific. In several accessions, salinity stimulated reproductive development. The major differences in salinity responses between various T. fragiferum genotypes were at the level of dry biomass accumulation as well as water accumulation in plant tissues, resulting in relatively more similar effect on fresh mass. Na⁺ and Cl⁻ accumulation capacity were organ-specific, with leaf petioles accumulating more, followed by leaf blades and stolons. Responses of mineral nutrition clearly were both genotype- and organ-specific, but several elements showed a relatively general pattern, such as increase in Zn concentration in all plant parts, and decrease in Ca and Mg concentration. Alterations in mineralome possibly reflect a reprogramming of the metabolism to adapt to changes in growth, morphology and ion accumulation resulting from effect of NaCl. High intraspecies morphological and physiological variability in responses of T. fragiferum accessions to salinity allow to describe them as ecotypes. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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24 pages, 5058 KiB

Open AccessArticle

The Halophyte Species Solanum chilense Dun. Maintains Its Reproduction despite Sodium Accumulation in Its Floral Organs

by Servane Bigot, Paula Pongrac, Martin Šala, Johannes T. van Elteren, Juan-Pablo Martínez, Stanley Lutts and Muriel Quinet

Plants 2022, 11(5), 672; https://doi.org/10.3390/plants11050672 - 28 Feb 2022

Cited by 5 | Viewed by 2613

Abstract

Salinity is a growing global concern that affects the yield of crop species, including tomato (Solanum lycopersicum). Its wild relative Solanum chilense was reported to have halophyte properties. We compared salt resistance of both species during the reproductive phase, with a special focus on sodium localization in the flowers. Plants were exposed to NaCl from the seedling stage. Salinity decreased the number of inflorescences in both species but the number of flowers per inflorescence and sepal length only in S. lycopersicum. External salt supply decreased the stamen length in S. chilense, and it was associated with a decrease in pollen production and an increase in pollen viability. Although the fruit set was not affected by salinity, fruit weight and size decreased in S. lycopersicum. Concentrations and localization of Na, K, Mg, and Ca differed in reproductive structures of both species. Inflorescences and fruits of S. chilense accumulated more Na than S. lycopersicum. Sodium was mainly located in male floral organs of S. chilense but in non-reproductive floral organs in S. lycopersicum. The expression of Na transporter genes differed in flowers of both species. Overall, our results indicated that S. chilense was more salt-resistant than S. lycopersicum during the reproductive phase and that differences could be partly related to dissimilarities in element distribution and transport in flowers. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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17 pages, 2994 KiB

Open AccessArticle

Comparative Analysis of Root Na⁺ Relation under Salinity between Oryza sativa and Oryza coarctata

by Tetsuya Ishikawa, Lana Shabala, Meixue Zhou, Gayatri Venkataraman, Min Yu, Gothandapani Sellamuthu, Zhong-Hua Chen and Sergey Shabala

Plants 2022, 11(5), 656; https://doi.org/10.3390/plants11050656 - 28 Feb 2022

Cited by 7 | Viewed by 2170

Abstract

Na⁺ toxicity is one of the major physiological constraints imposed by salinity on plant performance. At the same time, Na⁺ uptake may be beneficial under some circumstances as an easily accessible inorganic ion that can be used for increasing solute concentrations and maintaining cell turgor. Two rice species, Oryza sativa (cultivated rice, salt-sensitive) and Oryza coarctata (wild rice, salt-tolerant), demonstrated different strategies in controlling Na⁺ uptake. Glasshouse experiments and gene expression analysis suggested that salt-treated wild rice quickly increased xylem Na⁺ loading for osmotic adjustment but maintained a non-toxic level of stable shoot Na⁺ concentration by increased activity of a high affinity K⁺ transporter HKT1;5 (essential for xylem Na⁺ unloading) and a Na⁺/H⁺ exchanger NHX (for sequestering Na⁺ and K⁺ into root vacuoles). Cultivated rice prevented Na⁺ uptake and transport to the shoot at the beginning of salt treatment but failed to maintain it in the long term. While electrophysiological assays revealed greater net Na⁺ uptake upon salt application in cultivated rice, O. sativa plants showed much stronger activation of the root plasma membrane Na⁺/H⁺ Salt Overly Sensitive 1 (SOS1) exchanger. Thus, it appears that wild rice limits passive Na⁺ entry into root cells while cultivated rice relies heavily on SOS1-mediating Na⁺ exclusion, with major penalties imposed by the existence of the “futile cycle” at the plasma membrane. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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22 pages, 3479 KiB

Open AccessArticle

Physiological Adaptation of Three Wild Halophytic Suaeda Species: Salt Tolerance Strategies and Metal Accumulation Capacity

by Farag Ibraheem, Ateeq Al-Zahrani and Ahmed Mosa

Plants 2022, 11(4), 537; https://doi.org/10.3390/plants11040537 - 17 Feb 2022

Cited by 14 | Viewed by 2911

Abstract

Understanding salt tolerance mechanisms in halophytes is critical for improving the world’s agriculture under climate change scenarios. Herein, the physiological and metabolic responses of Suaeda monoica, Suaeda vermiculata, and Suaeda schimperi against abiotic stress in their natural saline environment on the east coast of the Red Sea were investigated. The tested species are exposed to different levels of salinity along with elemental disorders, including deficiency in essential nutrients (N&P in particular) and/or elevated levels of potentially toxic elements. The tested species employed common and species-specific tolerance mechanisms that are driven by the level of salinity and the genetic constitution of Suaeda species. These mechanisms include: (i) utilization of inorganic elements as cheap osmotica (Na+ in particular), (ii) lowering C/N ratio (S. monoica and S. schimperi) that benefits growth priority, (iii) efficient utilization of low soil N (S. vermiculata) that ensures survival priority, (v) biosynthesis of betacyanin (S. schimperi and S. vermiculata) and (vi) downregulation of overall metabolism (S. vermiculata) to avoid oxidative stress. Based on their cellular metal accumulation, S. monoica is an efficient phytoextractor of Cr, Co, Cu, Ni, and Zn, whereas S. vermiculata is a hyper-accumulator of Hg and Pb. S. schimperi is an effective phytoextractor of Fe, Hg, and Cr. These results highlight the significance of Suaeda species as a promising model halophyte and as phytoremediators of their hostile environments. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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14 pages, 2136 KiB

Open AccessArticle

Bioactive Compounds in Sarcocornia and Arthrocnemum, Two Wild Halophilic Genera from the Iberian Peninsula

by Irene Sánchez-Gavilán, Esteban Ramírez Chueca and Vicenta de la Fuente García

Plants 2021, 10(10), 2218; https://doi.org/10.3390/plants10102218 - 19 Oct 2021

Cited by 7 | Viewed by 2276

Abstract

(1) Background: this study describes bioactive compounds in the following halophytes: Sarcocornia (S. alpini, S. pruinosa, and S. perennis) and Arthrocnemum (A. macrostachyum). The material comes from: coastal marshes in Tinto River, Guadiana River, and some interior provinces from the Iberian Peninsula. (2) Methods: the techniques used were Folin–Ciocalteu, GC-MS, and ESI-MS/MS. (3) Results: Five phenolic acids were found in Sarcocornia: trans-cinnamic, salicylic, veratric, coumaric, and caffeic acids. In addition, in Arthronemum, ferulic acid was also detected. The obtained flavonoids were cyanidin-3-O-arabinoside, luteolin-7-glucoside, dihydroquercetin, and p-coumaroyl-glucoside. They also presented fatty acids, such as palmitic, linoleic, and oleic acids in Sarcocornia, while palmitic, linolenic, and stearic acids were the main fatty acids in A. macrostachyum. (4) Conclusions: the high diversity of the compounds identified confirms the relation between nutritional interest and salt tolerance in halophytes. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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20 pages, 4917 KiB

Open AccessArticle

Heavy Metal Pre-Conditioning History Modulates Spartina patens Physiological Tolerance along a Salinity Gradient

by João Carreiras, Jesús Alberto Pérez-Romero, Enrique Mateos-Naranjo, Susana Redondo-Gómez, Ana Rita Matos, Isabel Caçador and Bernardo Duarte

Plants 2021, 10(10), 2072; https://doi.org/10.3390/plants10102072 - 30 Sep 2021

Cited by 5 | Viewed by 1666

Abstract

Land salinization, resulting from the ongoing climate change phenomena, is having an increasing impact on coastal ecosystems like salt marshes. Although halophyte species can live and thrive in high salinities, they experience differences in their salt tolerance range, being this a determining factor in the plant distribution and frequency throughout marshes. Furthermore, intraspecific variation to NaCl response is observed in high-ranging halophyte species at a population level. The present study aims to determine if the environmental history, namely heavy metal pre-conditioning, can have a meaningful influence on salinity tolerance mechanisms of Spartina patens, a highly disperse grass invader in the Mediterranean marshes. For this purpose, individuals from pristine and heavy metal contaminated marsh populations were exposed to a high-ranging salinity gradient, and their intraspecific biophysical and biochemical feedbacks were analyzed. When comparing the tolerance mechanisms of both populations, S. patens from the contaminated marsh appeared to be more resilient and tolerant to salt stress, this was particularly present at the high salinities. Consequently, as the salinity increases in the environment, the heavy metal contaminated marsh may experience a more resilient and better adapted S. patens community. Therefore, the heavy metal pre-conditioning of salt mash populations appears to be able to create intraspecific physiological variations at the population level that can have a great influence on marsh plant distribution outcome. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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19 pages, 2301 KiB

Open AccessArticle

Plant Growth Regulators Application Enhance Tolerance to Salinity and Benefit the Halophyte Plantago coronopus in Saline Agriculture

by Milagros Bueno and María del Pilar Cordovilla

Plants 2021, 10(9), 1872; https://doi.org/10.3390/plants10091872 - 10 Sep 2021

Cited by 10 | Viewed by 2941

Abstract

Climate change, soil salinisation and desertification, intensive agriculture and the poor quality of irrigation water all create serious problems for the agriculture that supplies the world with food. Halophyte cultivation could constitute an alternative to glycophytic cultures and help resolve these issues. Plantago coronopus can be used in biosaline agriculture as it tolerates salt concentrations of 100 mM NaCl. To increase the salt tolerance of this plant, plant growth regulators such as polyamine spermidine, salicylic acid, gibberellins, cytokinins, and auxins were added in a hydroponic culture before the irrigation of NaCl (200 mM). In 45-day-old plants, dry weight, water content, osmolyte (sorbitol), antioxidants (phenols, flavonoids), polyamines (putrescine, spermidine, spermine (free, bound, and conjugated forms)) and ethylene were determined. In non-saline conditions, all plant regulators improved growth while in plants treated with salt, spermidine application was the most effective in improving growth, osmolyte accumulation (43%) and an increase of antioxidants (24%) in P. coronopus. The pretreatments that increase the sorbitol content, endogenous amines (bound spermine fraction), phenols and flavonoids may be the most effective in protecting to P. coronopus against stress and, therefore, could contribute to improving the tolerance to salinity and increase nutritional quality of P. coronopus. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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20 pages, 2463 KiB

Open AccessArticle

Responses to Salinity in Four Plantago Species from Tunisia

by Hela Belhaj Ltaeif, Anis Sakhraoui, Sara González-Orenga, Anbu Landa Faz, Monica Boscaiu, Oscar Vicente and Slim Rouz

Plants 2021, 10(7), 1392; https://doi.org/10.3390/plants10071392 - 07 Jul 2021

Cited by 13 | Viewed by 3483

Abstract

The genus Plantago is particularly interesting for studying the mechanisms of salt tolerance in plants, as it includes both halophytes and glycophytes, as well as species adapted to xeric environments. In this study, the salt stress responses of two halophytes, P. crassifolia and P. coronopus, were compared with those of two glycophytes, P. ovata and P. afra. Plants obtained by seed germination of the four species, collected in different regions of Tunisia, were subjected to increasing salinity treatments for one month under greenhouse conditions. Morphological traits and biochemical parameters, such as ion accumulation and the leaf contents of photosynthetic pigments, osmolytes, oxidative stress markers and antioxidant metabolites, were measured after the treatments. Salt-induced growth inhibition was more pronounced in P. afra, and only plants subjected to the lowest applied NaCl concentration (200 mM) survived until the end of the treatments. The biochemical responses were different in the two groups of plants; the halophytes accumulated higher Na⁺ and proline concentrations, whereas MDA levels in their leaves decreased, indicating a lower level of oxidative stress. Overall, the results showed that P. coronopus and P. crassifolia are the most tolerant to salt stress, and P. afra is the most susceptible of the four species. Plantago ovata is also quite resistant, apparently by using specific mechanisms of tolerance that are more efficient than in the halophytes, such as a less pronounced inhibition of photosynthesis, the accumulation of higher levels of Cl⁻ ions in the leaves, or the activation of K⁺ uptake and transport to the aerial part under high salinity conditions. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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21 pages, 5617 KiB

Open AccessArticle

Differential Salt Tolerance Strategies in Three Halophytes from the Same Ecological Habitat: Augmentation of Antioxidant Enzymes and Compounds

by AbdEl-Mageed F. M. Ghanem, Elsayed Mohamed, Ahmed M. M. A. Kasem and Abbas A. El-Ghamery

Plants 2021, 10(6), 1100; https://doi.org/10.3390/plants10061100 - 30 May 2021

Cited by 45 | Viewed by 3632

Abstract

Understanding the salt tolerance mechanism in obligate halophytes provides valuable information for conservation and re-habitation of saline areas. Here, we investigated the responses of three obligate halophytes namely Arthrocnemum macrostachyum, Sarcocornia fruticosa and Salicornia europaea to salt stress (0, 100, 200, 400 and 600 mM NaCl) during their vegetative growth with regard to biomass, ions contents (Na⁺, K⁺ and Ca²⁺), chlorophyll contents, carotenoids, phenolic compounds, flavonoids, and superoxide dismutase, peroxidase and esterase activities. S. europaea showed the lowest biomass, root K⁺ content, Chl a/b ratio, and carotenoids under salinity. This reduction of biomass is concomitant with the increase in proline contents and peroxidase activity. On the other hand, the promotion of growth under low salinity and maintenance under high salinity (200 and 400 Mm NaCl) in A. Macrostachyum and S. fruticosa are accompanied by an increase in Chl a/b ratio, carotenoids, phenolics contents, and esterase activity. Proline content was decreased under high salinity (400 and 600 mM NaCl) in both species compared to S. europaea, while peroxidase showed the lowest activity in both plants under all salt levels except under 600 mM NaCl in Arthrocnemum macrostachyum compared to S. europaea. These results suggest two differential strategies; (1) the salt tolerance is due to activation of antioxidant enzymes and biosynthesis of proline in S. europaea, (2) the salt tolerance in A. macrostachyum, S. fruticosa are due to rearrangement of chlorophyll ratio and biosynthesis of antioxidant compounds (carotenoids, phenolics and flavonoids) which their cost seem to need less energy than activation of antioxidant enzymes. The differential behavior in halophytes of the same habitat confirms that the tolerance mechanism in halophytes is species-specific which provides new insight about the restoration strategy of saline areas. Full article

(This article belongs to the Special Issue Wild Halophytes: Tools for Understanding Salt Tolerance Mechanisms of Plants and for Adapting Agriculture to Climate Change)

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