Читать книгу Physiology of Salt Stress in Plants - Группа авторов - Страница 40

During salt stress, plants have two options for their osmotic adjustments: de‐novo synthesis of organic osmolyte or the uptake of inorganic ions from the soil. Energetically, the former option is costly, whereas the latter option is economic by an order of magnitude to the plants (Munns et al. 2020; Shabala and Shabala 2011), but depends on the plants’ ability to establish an ionic homeostasis during salt stress. At the onset of salt stress, the relative concentration of Na⁺ in the soil is much higher than the K⁺ concentration. Thus, the plants are unable to accumulate the most favorable inorganic ion (K⁺) as an osmolyte. Contrary to the glycophytes, the halophytes adapted to use the Na⁺ as the cheap osmoticum to maintain cellular turgor pressure, cell elongation, and stomatal operation (Zhao et al. 2020). The halophytes achieved this ability by efficiently sequestering the Na⁺ and Cl⁻ to the vacuole and organic osmolyte only for the cytosol, which contributes only 10% of the cell volume and thus energetically cheaper to synthesize than the osmolyte for a whole cell (Zhao et al. 2020). Succulence is another necessary morphological adaptation of some of the halophytes from the Chenopodioideae, and Salicornioideae order (Flowers et al. 2015), however, the detailed mechanism of succulence development are not understood yet (Qi et al. 2009). The succulent cells in the halophytes provide them the ability to store the excess Na⁺ and K⁺ in those cells, higher H⁺‐ATPase activity, and nonenzymatic antioxidant activity in this tissue (Zeng et al. 2018; Zhao et al. 2020). Moreover, these succulent cells retain a constitutively lower number of open SV vacuolar channels and suppress the activity of FV in the vacuole.