盐胁迫下水稻叶绿体中Na+、Cl-积累导致叶片净光合速率下降

研究了0-200mmol/L的NaCl胁迫下耐盐性不同的水稻品种Pokkali(耐盐）和Peta(盐敏感）根系，叶片和叶绿体中Na^ ,K^ 和Cl^-含量的变化及其与叶片光合作用的关系。结果表明：随着NaCl胁迫时间和浓度的增加，供试2个品种在根，叶片和叶绿体中Na^ ,Cl^－含量增加，K^ 含量下降。耐盐品种体内Na^ ,Cl^－含量增加或K^ 含量减少的幅度小于盐敏感品种。在200mmol/L的NaCl胁迫下盐敏感品种根，叶片和叶绿体中的Na^ /K^ 分别是耐盐品种的208％，308％和297％。与Na^ 相比，耐盐品种根系对K^ 吸收和向叶片运输的选择性（SK，Na)较强。但在经过0，100和200mmol/L的NaCl处理后2个品种叶绿体中的Na^ /K^ 均高于叶片（SK，Na均小于1）。盐胁迫下水稻叶绿体中Na^ ,Cl^-含量和Na^ /K^ 与叶片净光合速度呈极显著负相关。

Na+ and Cl- Accumulation in Chloroplasts Results in a Decrease in Net Photosynthetic Rate in Rice Leaves Under Salt Stress

Changes in Na , K and Cl- contents in the roots, leaves and chloroplasts and the relations of them to photosynthesis in rice cultivars Pokkali (salt-tolerant) and Peta (salt-sensitive) under 0-200 mmol/L NaCl stress were studied. The results showed that Na and Cl- contents increased and K content decreased with increasing external NaCl concentration and duration of treatment in roots (Fig.1), leaves (Fig.2) and chloroplasts (Fig.3) of two rice cultivars with different salt tolerance. The extent of the increase in Na and Cl- contents or decrease in K content was lower in salt-tolerant cultivar than in salt-sensitive one. Na /K ratio in the roots, leaves and chloroplasts of salt-sensitive cultivar was 208%,308% and 297% that of salt-tolerant one under salt stress. The selectivity of K absorption in the roots and transportation to leaves was stronger compared to Na (Table 1). Na /K ratio in chloroplasts was also higher than that in the leaves (S K,Na was also lower than 1) in two rice cultivars under 0, 100,and 200 mmol/L NaCl stress. Na and Cl- contents and Na /K ratio in the chloroplasts were most significantly negatively correlated with net photosynthetic rate of leaves in two rice cultivars under salt stress (Table 2).