Effects of cadmium on growth and photosynthetic activities in pakchoi and mustard

In this study, we determined the effects of different concentrations of soil cadmium (0-24 mg.kg(-1)) on growth and photosynthetic activities in leaves of pakchoi and mustard using pot experiments under greenhouse conditions. Both shoot and root weight decreased progressively with increasing Cd concentration for pakchoi and mustard. Negative linear relationships were observed between total Chlorophyll contents and Cd concentrations in soils in pakchoi (r(2)=-0.681, P < 0.01) and mustard (r(2)=-0.463, P < 0.05). In comparison to the controls (Cd=0 mg.kg(-1)), significant reductions of chlorophyll-a and chlorophyll-b were both observed at 24 mg Cd kg(-1)soil. The increase in cadmium concentration also caused a decline in the net rate of photosynthesis (P-n) and stomatal conductance (G(s)). At lower concentrations of Cd (e.g. 6 mg.kg(-1)), a retarded development was observed only in mustard. However, a significant decrease of G(s) for both plants was observed at concentrations above 12 mg Cd kg(-1) soil. From this study, we found the photosynthetic activity of pakchoi more sensitive to Cd stress than that of mustard.