Effects Of High Cadmium Stress On Growth And Antioxidant Systems Of Leaves In Brassica Chinensis L.

Nowadays,cadmium-pollution in soil is one of the most serious environmental problems in the world which would cause certain negative impact to the growth and metabolism of plants, and at the same time it may cause serious human-body injuries. And it has the feature just like the cruciferous plant that can enrich cadmium. In this experiment, we took Qinggeng NO.1 as experimental materials. Here, we used high concentrations of cadmium stress treatments on pakchoi seedlings, then germination rate, biomass, content of photosynthate, level of reactive oxygen, antioxidant-enzyme activity and membrane lipid peroxidation should be measured to studyfon the effect of high concentration of cadmium stress treatments on activitis of antioxidant defense systems of pakchoi. The results are as follows:1. The germination rate, wet weight, dry weight, stem length and root length of pakchoi were inhibited with the concentration of cadmium increased it shows high concentrations of cadmium stress treatments inhibited the growth of pakchoi.2. Chlorophyll content in pakchoi leaf decreased with increasing Cd2+ concentrations and processing time. Soluble protein and soluble sugar content increased firstly and then decreased.3. Hydrogen peroxide (H2O2) content and superoxide radical (O2-) production rate was rise-decline-rise with the high concentrations of cadmium. MDA content increased gradually in the whole process, membrane lipid peroxidation increased with increasing the Cd2+, concentrations and processing time.4.Catalase (CAT) activity rise in the first stage, and then decreased, with high concentrations of cadmium in the process. Over time, APX was evidently inhibited at the concentration of cadmium was 120mg/L. GR activity was greatly inhibited in every concentrations over time. From the early stage of the stress treatment, MDAR activity showed a rising trend at each concentrations over time, but were lower than the control group.In conclusion, the results showed that in the early phase of high concentrations of cadmium treatments, Qinggeng N0.1 was increase in antioxidase activity and soluble sugar increased in Qinggeng NO.1 which showed tolerance to cadmium stress. However, with the prolongation of treatment time of cadmium stress, the levels of ROS of pakchoi leaves were up, the activities of antioxidant system of pakchoi leaves were down, photosynthetic yield declined, the level of membrane lipid peroxidation increased and the growth of plants were seriously restrained.