Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Shijiazhuang, 050021, People's Republic of China.
Dr. M. Ajmal Khan Institute of Sustainable Halophyte Utilization, University of Karachi, Karachi, 75270, Pakistan.
J Plant Res. 2021 Jul;134(4):779-796. doi: 10.1007/s10265-021-01285-5. Epub 2021 Mar 25.
Ion secretion facilitates recretohalophytes to tolerate saline and drought conditions but its relative contribution to the survival of many species remains poorly understood. Tamarix chinensis has high potential for restoration of saline deteriorated lands. The water management and high salt tolerance of the plant have highlighted the need to determine the strategies that govern these mechanisms. Here we report the selectivity of this halophyte to transport, utilize, and secrete different cations and anions under various NaCl (0, 100, 200 and 400 mM) concentrations. Plant growth, photosynthesis and antioxidant defense responses were also determined to relate them with the function of ion secretion. Results reflected two different sets of strategies adopted by plants to survive low and high salinities. Exposure to highly saline conditions caused reduction in photosynthesis due to stomatal and biochemical limitations. The decreased content of photosynthetic pigments exposed plants to excessive light energy that accelerated production of ROS (i.e., hydrogen peroxide HO) and caused damage to cellular membranes. The increased activities of anti-oxidative enzymes (superoxide-dismutase, catalase, ascorbate-peroxidase, and glutathione-reductase) were insufficient to detoxify HO. In contrast, plants treated with low salinity did not face stomatal limitations while the photosynthetic pigments increased. As no damage to membranes was detected, the increased content of HO was postulated for its messenger role. The assimilation of essential nutrients was affected due to increased content of toxic ions (Na and Cl) in the growing medium and within the plants. However, the ability to regulate K facilitated plants to improve water use efficiency under hyper-osmotic environment. The removal of toxic ions from the photosynthesizing tissues demands high energy, which was evident in the compromised growth of plants. This study offers a window to physiological mechanisms, e.g., potassium retention that ensure salt secretion as a beneficial strategy for prolonged survival of T. chinensis.
离子分泌有助于泌盐植物耐受盐和干旱条件，但许多物种的生存对其相对贡献仍知之甚少。柽柳具有恢复盐渍化土地的巨大潜力。该植物的水分管理和高耐盐性凸显了确定控制这些机制的策略的必要性。在这里，我们报告了这种盐生植物在不同 NaCl（0、100、200 和 400 mM）浓度下对不同阳离子和阴离子的运输、利用和分泌的选择性。还确定了植物生长、光合作用和抗氧化防御反应，以将它们与离子分泌的功能相关联。结果反映了植物在低和高盐度下生存所采用的两套不同策略。暴露在高盐条件下会由于气孔和生化限制而导致光合作用减少。光合色素含量的降低使植物暴露在过量的光能下，加速了 ROS（即过氧化氢 HO）的产生，并导致细胞膜受损。抗氧化酶（超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶和谷胱甘肽还原酶）的活性增加不足以清除 HO。相比之下，在处理低盐时，植物不会面临气孔限制，而光合色素增加。由于没有检测到膜的损伤，HO 的增加被认为是其信使作用。由于生长介质中和植物内有毒离子（Na 和 Cl）含量增加，必需营养物质的同化受到影响。然而，钾的调节能力有助于植物在高渗环境下提高水利用效率。从光合组织中去除有毒离子需要大量能量，这在植物生长受损中表现明显。这项研究提供了一个了解生理机制的窗口，例如钾的保留，这确保了盐分泌作为延长柽柳生存的有益策略。
