| Pot experiments were conducted to test the effects of chilling stress on several physiological indexes such as growth, photosynthesis, active oxygen and nitrogen metabolisms of chamaecrista rotundifolia CPI86134. In this paper, we explored the harm and the mechanism of chilling stress to chamaecrista rotundifolia CPI 86134 and its protective practice to avoid the cold harm.1.Effects of chilling stress on several physiological metabolisms of chamaecrista rotundifoliaChilling stress significantly inhibited the growth of chamaecrista rotundifolia. The length and weight of shoot and root, root/shoot ratio were all decreased to compare with the contrast. The root activity decreased with the root/shoot indicated that chilling stress had great effect on inhibiting the growth of root.Chilling stress had markly effects on leaf microstructure and ultrastructure of chamaecrista rotundifolia, The chloroplast suffering from chilling stress were distinguished by a reduction in the amount of grana, grana lamellae and stroma lamellae when compared with the chloroplast of normal plant. It was also found that the membrane of the chloroplast and mitochondria ruptured, even disappeared under chilling stress. It also been found that ridge of mitochondria vanished and changed into vesiculation. The shape of the mitochondria were destroyed severely and hard to be recognized.Chilling stress severely decreased the chlorophyll (chl) and carotenoid contents in leaves of chamaecrista rotundifolia with intensifying the cold condition and lasting the time. The total content of chlorophyll (chl) under 15℃ ,10℃ ,5℃ treatments decreased 3.84%, 22.40%, 32.00% respectively to compare with the contrast of 25 . Significant difference was found between 5℃ and 25℃ . The content of carotenoid decreased 3.36%, 14.99%, 21.70% as well. At 5℃ chilling stress, the total content of chlorophyll(chl) in the treating time from 24h to 120h reduced 23.34%,24.76%,26.80%,30.11% and 32.00%. The difference between the treatments of lasting chilling stress time and the contrast were all significant. In the same condition, the content of carotenoid reduced 13.14%, 14.71%, 17.29%, 19.28% and 21.70%, they were all significantly different from the contrast. Futhermore, chilling stress significantly increased the content of soluble sugar, and the lower temperature, the more content of soluble sugar was found.Chilling stress increased the amount of total soluble protein in leaves of chamaecrista rotundifolia. The content of free amino acids and soluble protein were all greatly increased with the intensifying the cold condition. The content of free amino acids under 15℃ ,10℃ ,5℃ chilling stress increased 26.51%, 128.11% and 324.43% respectively to compare with the contrast of 25℃.Chilling stress significantly increased the leakage of electrolyte, the contents of malondialdehyde (MDA) and H2O2 as well as the net rate of (V generation in leaves of chamaecrista rotundifolia. The activities of superoxide dismutase and ascorbate peroxidase increased in chilling stress leaves as compared with normal contrast. These results indicated that chilling stress caused membrane lipid peroxidation and destroyed the completeness of plasma membrane . The change of the activities of superoxide dismutase and ascorbate peroxidase were the adaptive reactions to active oxygen stress in chilling stress on chamaecrista rotundifolia.On 0 chilling stress which designed as the ultra-low temperature in this experiment, the leakage of electrolyte and HA as well as the net rate of ·O2- generation in leaves of chamaecrista rotundifolia all significantly increased. At the same time, the activities of superoxide dismutase increased. 2. Control practices to protect chamaecrista rotundifolia from chilling stressThe cultural experiment results showed that the two treatments with the wateringconcentration of 0.25 and 0.5mmol/L CaCl2 and the spraying concentration of 100 150mg/L ABA both effectively increased the chlorophyll (chl) and carotenoid... |
PDF Full Text Request