Physio-chemical mechanism of cadmium tolerance of Chinese cabbage (Brassica chinensis)

Thirteen cabbage (Brassica chinensis) cultivars were cultured hydroponically with 50μmol/L cadmium to analyze their physio-chemical response to Cd stress.The results show some degree of inhibition on growth and physio-chemical metabolism in cabbage due to Cd stress regardless of Cd accumulation in shoots.There is always Cd tolerance effect though it varies with cultivar type. Through analysis of Cd tolerance index(TI) among the 13 selected cabbage cultivars, correlation coefficient between TI-P(TI based on plant dry matter accumulation) and TI-S(TI based on shoot growth) is noted to be more significant than that between TI-P and TI-R(TI based on root growth), implying that TI-S is a more appropriate criterion than TI-R in morphological evaluation of cabbage Cd tolerance. Meanwhile, proline and malondialdchyde(MDA) contents, and AsA-POD and SOD activities in tested cabbage shoots increase variously under Cd stress. In particular, the increases of proline content and SOD activity(under Cd stress) are correlated positively with TI-S, implying their feasibility as physio-chemical indices in Cd tolerance analyses.