Study On Physiological And Biochemical Characteristic Of Mangrove Plant Agiceras Corniculatum And Rhyzophora Stylosa Seedlings Under Cadmium Stress

This study selected the mangrove plants Agiceras corniculatum and Rhyzophora Stylosa seedlings as research subject.Designed a concentration of 0mmol·L^-1, 0.6mmol·L^-1, 6mmol·L^-1, 12mmol·L^-1,24mmol·L^-1and 30mmol·L^-1Cd stress on Agiceras corniculatum seedlings,and Designed a concentration of 0mmol·L^-1,0.1mmol·L^-1,5mmol·L^-1 ,10mmol·L^-1,15mmol·L^-1and 20mmol·L^-1Cd stress on Rhyzophora Stylosa seedlings.It was carried out to investigate the effect of cadmium on the membrane lipid peroxidation, chlorophyll content, protein content, antioxidant enzymes expression in mangrove plants Agiceras corniculatum and Rhyzophora Stylosa. The effects of Cd on the isoform of antioxidant enzymes in root and leaf of Agiceras corniculatum and Rhyzophora Stylosa seedlings were analyzed by means of PAGE. Above those on the two plants are also discussed. The major resultes are summerized as follows: 1.As Cd concentration increased from 0 to 6mmol·L^-1,the leaf net photosynthetic rate and transpiration rate of Agiceras corniculatum increased, When Cd concentration was higher than 6mmol·L^-1,those began to decrease.2. Under Lower concentrations of Cd treatment, Chlorophyll a, b and total chlorophyll content increased, while under higher concentrations of Cd, those decreased.3.The protein content of Agiceras corniculatum and Rhyzophora Stylosa seedlings decreased as Cd concentration increased . It is found that the protein content was negatively-related to Cd concentration.4. Both Agiceras corniculatum and Rhyzophora Stylosa seedlings were induced membrane lipid peroxidation by Cd, Lower concentrations of Cd stress could induce the protection of the seedlings, decrease the MDA and peroxide content in leaves, while higher concentrations of Cd stress could enhance lipid per oxidation, destroy protection ability and enhance MDA content in the seedlings.5. The effects of Cd on POD and SOD activities in root and leaf extracts of Agiceras corniculatum and Rhyzophora Stylosa seedlings were similar. The enzyme activites were stimulated in lower metal ion concentrations but were inhibited in higher concentrations. With different concentration of Cd treatment, POD activities in root of Agiceras corniculatum reached a significant level; As Cd concentration increased from 0.6 to 6mmol·L^-1, POD activities in leaf of Agiceras corniculatum are obviously different from each other;under 0.1～5 mmol·L^-1 Cd treatment,SOD activities in root and leaf of Rhyzophora Stylosa were significantly stimulated.6. The effects of Cd on the expression of POD isoenzyme in root and leaf extracts of Agiceras corniculatum seedlings were similar, the expression of POD isoenzyme was stimulated in lower Cd, the expression of SOD isoenzyme was Cu/Zn-SOD isoenzyme in leaf of Agiceras corniculatum, two CAT isoenzyme in root and leaf of Rhyzophora Stylosa seedlings were detected.7. The results showed that, in spite of no visible symptom in shape, the expression of antioxidant isoenzymes and protein changed, which could be detected by means ofelectrophoresis. Compared to the shape description and the determination of enzyme activities, the analysis of isoenzyme expression is more accurate and without delay to reflect the heavy metal pollution state and helps us a lot to monitor the mangrove ecosystem. Considering the sensitivity, we suggest that the analysis of POD isoenzyme could be used as a method for monitoring.