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The regulations of calcium and DPC on germination and seedling growth in upland cotton(G.hirsutum L. cv Simian 3) under salt stress and their mechanisms were investigated. Results showed: Ca2?increased and maintained the activity of CAT, accelerated the transformation of substance in seeds, stimulated or promoted development of radicle,seed vigor,seedling emergence and improved quality of seedlings under salt stress. Salt tolerance of cotton was mainly due to salt compartmentation in body. Supplemental Ca2~ improved the ability of salt-rejection, increased the absorption and transportation of K?and Ca2~ to shoots, reduced the ratio of Na~/Ca2~ and Na?K?and maitain balance of ions in cotton body,decreased the leakage of cell electrolyties. Ca2~ increased the activities of SOD. POD and CAT, decreased content of O, and MDA in roots, decreased the damage of roots under salt stress, root/shoot ratio increased. Ca2?increased chlorophll content of leaves,enhanced photosynthesis, increased the accumulation of dry matter in cotton seedlings under salt stress. Ca2~ increased and maintained the activities of H? ATPase and H-~-PPase in plasma membrane and tonoplast vesicles isolated from the This is one of that Ca2~? young roots. major causes improved ion absorption and transportation, decreased Na~/Ca2~ and Na扞K~ ratio, maintained balanance of ions in body. Soaking seeds in range of appropriate concentrations of DPC enhanced root vigour effectively, promoted root development and raised root/shoot ratio under salt stress. Also decreased salt absorption, strengthened salt compartmentation, promoted the absorption and transportation of K?and Ca2~, maitained balance of ions in body, The optimum concentration of DPC for mitigating salt stress was 150mg U? Soaking seeds in 150mg L扗PC increased the activities of SOD and POD, decreased the content of MDA in leaves, decreased the leakage of leaves cell electrolyties, increased chlorophll content of leaves clearly, the accumulation of dry matter and growth rate in cotton seedlings increased markedly under salt stress.
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