Effects Of Zinc On The Growth And Antioxidative System In Brassica Chinensis L. Under Cadmium Stress

This study was carried out to investigate the effects of cadmium on the growth and antioxidative system, and the influences of zinc on the growth and antioxidative enzymes under cadmium stress in Brassica chinensis L. The major results were summarezed as follows:1) Effects of different concentrations of cadmium on growth and antioxidative system in Brassica chinensis L: The growth and chlorophyll content were enhanced by low concentrations of Cd (below 0.1 mg L-1), whereas the growth was seriously inhibited by 10 mg L-1 Cd. SOD activity decreased with increasing Cd concentration in growth medium. The activities of GPOD and CAT increased at the treatment of 0.01 and 0.1 mg L-1, but decreased dramatically at 10 mg L-1 treatment. Cd increased the activities of APX, DHAR and GR. AsA and GSH contents increased at 10 mg L-1 Cd level.2) Effects of zinc on growth and absorbtion of Cd in different type of Brassica chinensis L. Two varieties of Brassica chinensis L. (Hu and You) were grown in nutrient solution containing Cd 5 rng L-1'+Zn 0.1 mg L-1, Cd 5 mg L-1+Zn 1 mg L-1, Cd 5 mg L-1+Zn 10 mg L-1 to investigate the effects of zinc on the growth and absorption of cadmium. The results showed that 5 mg L-1 Cd decreased the freshweight and dry weight of both shoot and root, increased the content of H2O2 and MDA in both of cultivars. This indicated that Cd affected the growth of Brassica chinensis L, but this effect was zinc concentration and cultivar dependent. The concentration of Cd in shoot of Hu increased with the increasing of zinc concentrations in culture solution, however, adition zinc to culture solution had no significant effect on the shoot Cd concentration of You.3) Effects of zinc on antioxidant enzymes in Brassica chinensis L, under cadmium stress: Brassica chinensis L. were grown in nutrient solution containing 5 mg L-1 Cd(Cd5), Cd5+Znl, Cd5+ZnlO to study the effects of zinc on the growth and antioxidant enzymes. 5 mg L-1 Cd decreased the content of H2O2 and the activities of SOD, CAT, DHAR, APX and GR, but the activity of GPOD was increased. The treatment of Cd5+Znl decreased the activities of SOD, POD, CAT, DHAR and GR, and increased the content of H2O2. Under the Cd5+ZnlO treatment, the activities of SOD, CAT declined continuously, but the activity of GPOD recovered to the normal level. There are no distinct changes in DHAR activity. The activities of APX and GR increased along with the decline of H2O2.