Effects Of Salt Stress On Physiological Characteristics Of Different Maturity Cotton Cultivars Seedling

In this experiment, different cotton cultivars were treated with0.3%stress to select the stronger salt resistance varieties. The differences of NaCl stress treatment on physiological characteristics, histological stain, cell ultrastructure were analysed and the salt stress resistance of cotton seedling was compared with the different cotton cultivars.As the followings, the main experimental results are summarized:(1)After3days under NaCl stress treatment, by comprehensive evaluation on physiological index including POD activity, SOD activity, O2-content, MDA content and relative conductivity with the leaves and roots of six cotton cultivars seeding, it was found that the comprehensive evaluation values of the mid-maturing varieties N177and N188were higher, the comprehensive evaluation values of cotton seedling leaves were0.63and0.77respectively; and the comprehensive evaluation values of cotton seedling roots were0.68and0.75respectively. The results showed that the mid-maturing varieties had the stronger resistance under NaCl stress.(2) The seeding roots histological stain was used to compare the injury degree of cell membrane with different cotton cultivars after3days under NaCl stress treatment, it was found that the mid-maturing variety N188was slightly stained, and other varieties were intensely stained. It showed that the mid-maturing variety N188had the stronger resistance under NaCl stress because it had the less cell death after salt stress.(3) Under the NaCl stress treatment, the various organelles of cotton seedling leaves and roots including the early-maturing varieties Zhong50, N52and the late-maturity varieties N203, K-1were seriously damaged. The chloroplasts were separated from the cytoplasm and their morphological structure were seriously damaged, mitochondrials degraded, nucleus disappeared and chromatin condensed in cotton seedling leaves. The mitochondrials were increased, nucleus disappeared and chromatin condensed in cotton seedling roots. But the mid-maturing varieties N177、N188were not damage seriously. There were no obvious changes about the morphological structure of chloroplasts. The mitochondrials and the cell walls maintained morphological structure integrity. This showed that the salt resistance of the mid-maturing varieties N177and N188was stronger.