The Physiology of Abiotic Stress in Plants

Dear Colleagues,

Global change involves an undeniable reduction in the resources available to plants, and therefore the accentuation of abiotic stresses. Simultaneously, the increase in population determines the need to ensure greater quantities of food and other plant products that are useful to the growing population. The need to identify cropping systems with lower inputs increases the intensity of the abiotic stresses that plants must face. The use of innovative technical means, such as biostimulants, could be a solution, but often only the possible positive results of their use are analyzed, without delving into what the mechanisms of action may be. A powerful means by which to understand the response of plants and, therefore, to try to reduce the impact of abiotic stresses is the analysis of plant physiology. These are often non-destructive investigations that have the merit of providing precise indications of the mechanisms of action. The purpose of this Special Issue is to analyze the physiology of abiotic stresses in plants to define the response mechanisms of action and which strategies plants can implement to overcome suboptimal conditions that increasingly reduce them more frequently and with greater intensity.

Prof. Dr. Daniela Romano
Guest Editor

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• gas exchange
• chlorophyll fluorescence
• oxidative stress
• signal transduction
• technical means
• biostimulants

Title: Garlic under drought and salt stress and verification of AsPIP1-3 gene function
Authors: Hanyu Wei1,#; Rong Zhou1,2; Yunhe Bai1; Min Liu1; Fangling Jiang1,*; Zhen Wu1,*
Affiliation: 1 College of Horticulture, Nanjing Agricultural University, Nanjing 210095, China 2 Department of Food Science, Aarhus University, Agro Food Park 48, DK-8200, Aarhus N, Denmark
Abstract: In order to screen candidate aquaporin genes involved in resisting osmotic stress , this study used 'Er Shuizao' garlic as test material, subjected it to drought and salt stress treatments, analyzed the physiological responses of garlic under drought and salt stress, and used qRT-PCR technology was used to study the expression levels and changing trends of aquaporin genes under drought and salt stress, and to screen aquaporin genes with stress resistance. The results showed that the relative water content and chlorophyll content of leaves decreased, the O2- production rate increased, and H 2 O 2 accumulated. The activities of SOD, POD and CAT showed a trend of first increasing and then decreasing; the content of soluble sugar and proline increased to maintain cell osmotic balance; the content of MDA and relative conductivity continued to increase. Most aquaporin genes showed a trend of first increasing and then decreasing under drought and salt stress. AsPIP1-3 responded to drought and salt stress and up-regulated expression. The relative expression was the highest on the 6th day of stress, and was related to antioxidant enzyme activity and osmotic regulation. The material change trends are consistent, indicating that AsPIP1-3 plays a role in resisting garlic osmotic stress. Using 'Er Shuizao' garlic as the test material, the AsPIP1-3 gene sequence was cloned, a subcellular localization vector and a gene overexpression vector were constructed, and the gene was positioned, observed and analyzed through laser confocal and Agrobacterium-mediated transgenic methods. Functional verification under drought stress. The results showed that aquaporin AsPIP1-3 was located on the cell membrane, which was consistent with the predicted results of subcellular localization. Under drought stress, the germination rate and root length of transgenic Arabidopsis were significantly different from those of the wild type. After Arabidopsis thaliana was transplanted and subjected to drought treatment, the ROS accumulation of transgenic Arabidopsis was reduced, the antioxidant enzyme activity was significantly higher than that of the wild type, the relative conductivity and MDA content were significantly reduced, and the proline content was increased. Transcription level analysis of genes related to drought stress response showed that the transcription levels of AtRD22, AtP5CS, AtABF3 and AtLEA genes were significantly increased. Overexpression of AsPIP1-3 genes improved the drought tolerance of transgenic plants. Research shows that AsPIP1-3 proteins function on the cell membrane, and transgenic Arabidopsis exhibits stronger drought tolerance.

Title: Abiotic stress attenuation and improving water use efficiency with silicon
Authors: Jonas Pereira de Souza Junior1; Davie M. Kadyampakeni1; Milton Garcia Costa2; Kamilla Silva Oliveira3; Renato de Mello Prado2
Affiliation: 1 University of Florida, Institute of Food and Agriculture Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL33850, USA. 2 São Paulo State University, Scholl of Veterinarian and Agronomy Science, Via de Acesso Paulo Donato Castellane s/n, Jaboticabal, 14800-000, Brazil. 3 School of Plant, Environmental, and Soil Sciences, Lousiana State University Agricultural Center, 104 M.B. Sturgis Hall, Baton Rouge, LA. 70803-2110, United States of America.
Abstract: Silicon (Si) is increasingly recognized for its role in enhancing plant resilience to abiotic stresses, thereby improving water use efficiency (WUE). The growing challenges posed by global warming and climate change, such as drought, salinity, and temperature extremes, underscore the importance of beneficial effects of Si for sustainable agriculture. This review explores the mechanisms of Si in enhancing WUE, including stomatal regulation, root water uptake, and cellular water retention. Silicon modulates plant hormones like abscisic acid (ABA), strengthens cell walls, and enhances antioxidant defenses, reducing water loss and oxidative damage. Silicon is also known to improve root architecture and influence aquaporin gene expression, thus optimizing water uptake. Advances in omics technologies provide insights into regulatory networks of Si, essential for developing Si-based strategies to enhance WUE and crop resilience. Practical applications of Si in agriculture, including various sources and methods, are discussed, emphasizing economic and environmental benefits. As climate change exacerbates abiotic stresses, the role of Si in promoting sustainable water management and agricultural sustainability becomes crucial. This review highlights the multifaceted role of Si in plant water relations, underscoring its potential to mitigate the deleterious impacts of abiotic stresses and support sustainable development goals. Future research directions and applications of Si in agriculture are proposed to improve crop productivity and resilience.

Title: Comparative analysis of photosynthetic performance in local and commercial tomato cultivars using OJIP fluorescence transients under drought stress and recovery
Authors: Peco, J.D.1,2; Centeno, A.2; Moratiel, R.2; Moreno, M.M.1; Villena, J.1; Pérez–López, D. 2*
Affiliation: 1– Dpto. Producción Vegetal, ETSIA–Universidad de Castilla–La Mancha, Ronda de Calatrava, 13003 Ciudad Real, Spain. 2– Dpto. Producción Agraria, CEIGRAM–Universidad Politécnica de Madrid, Av. Puerta de Hierro, 2, 28040 Madrid, Spain.
Abstract: Tomato (Solanum lycopersicum L.) is a vital crop in semi-arid regions, particularly within the greenhouses of southeastern Spain, where water scarcity poses a significant challenge to production. Understanding tomato plants' responses to water stress is crucial for improving irrigation efficiency and ensuring sustainable agriculture. This study evaluates the drought tolerance of six tomato cultivars (three local and three commercial) through a comparative analysis of photosynthetic performance using OJIP fluorescence transients. Additionally, measurements of stem water potential, chlorophyll content, and photosynthetic parameters were conducted to assess physiological responses to two brief periods of water stress (WS1) and one extended period of water stress (WS2), followed by rehydration. Our findings indicate diverse photosynthetic activity responses to water stress across the studied cultivars. These variations could not be attributed solely to their origin (local or commercial). On the other hand, the OJIP fluorescence transient analysis revealed significant differences in the impact on the photosynthetic machinery among the cultivars. Specifically, the intermediate rehydration in WS1 positively influenced the photosynthetic machinery, whereas WS2 plants were more adversely affected by prolonged stress. Although the variations in drought responses were not consistently linked to the cultivars' origins, notable differences in drought resistance were observed among individual cultivars using OJIP fluorescence transient analysis. These results highlight the potential of certain local varieties in breeding programs aimed at enhancing drought tolerance. The study underscores the importance of evaluating a wide range of cultivars to identify those with superior drought resilience. This research provides valuable insights into the physiological mechanisms underlying drought tolerance in tomatoes, contributing to the development of more resilient cultivars that can better withstand water scarcity.