Читать книгу Physiology of Salt Stress in Plants - Группа авторов - Страница 13

Accumulation of excessive salt content in the soil causing direct and indirect adverse effects on flora and fauna is termed as salt stress (Shrivastava and Kumar 2015). The above situation can inhibit plant growth, and prolonged exposure may lead to a decrease. Higher saline level impacts the plants in various ways such as genotoxicity, alteration of metabolic processes, oxidative stress, water stress, ion toxicity, nutritional disorders, reduction of cell division and expansion, and membrane disorganization (Hasegawa et al. 2000; Munns 2002). The preliminary exposure to salt stress causes leaf surface area reduction. The immediate impacts include suppressed cell expansion and cell division and closure of stomata due to osmotic influence (Munns 2002; Flowers 2004). Furthermore, prolonged exposure imparts ionic stress leading to early senescence of mature leaves and thereby reducing the leaf surface area responsible for photosynthesis and plant growth.

The severity of salt stress is most predominant in the case of agricultural crops from a food security perspective; impacts include retarded seed germination, reduced biomass, and small yield. Higher abscisic acid (ABA) concentration results in the formation of specific genes through the plant defense mechanism which leads to counteracting its generation cause (Godoy et al. 1990; Lodeyro and Carrillo 2015). Generally, the acute level of salt toxicity causes instantaneous death in various species, whereas, in selected species, limited stress influences defense mechanisms mimicking halophytes. For instance, conversion of C₃ to CAM, amendment in epidermal bladder cell to withhold excessive NaCl enabling better survivability over the saline condition. Significant parts of the coastal irrigated areas face salination issues majorly due to the seawater intrusion. More than 45 M ha of cultivable land distributed among hundreds of countries covering more than 10% of the global land surface area have already been sacrificed due to saline irrigation. Additionally, approximately 1.5 M ha of fertile land becomes nonproductive every annum due to soil salinity (Munns and Tester 2008). Presently, about 1150 M ha of productive land are under induced stress, while80 M ha are only affected due to the anthropogenic activities (Rasool et al. 2013; Hossain 2019).