Effects of Cd on growth characteristics of root systems of Chinese white cabbages with different genotypes

Plant growth and root morphological response of two cultivars of Brassica chinensis L. (Jinxiawang qinggengcai and Shanghai aikangqing) to cadmium (Cd) were investigated using hydroponic experiments. The results show that fresh root weight, specific root length, specific root volume, specific root surface area and root vigor for both genotypes are significantly decreased with the increase of Cd concentrations, and the decreased ranges of Jinxiawang qinggengcai are greater than those of Shanghai aikangqing, while average root diameters are not changed. Cd concentrations in both genotypes are significantly increased with the increase of Cd concentrations in the solution, and Cd concentrations of shoot and root of Shanghai aikangqing are much greater than those of Jinxiawang qinggengcai when Cd concentrations in the solution are larger than 0.25mg/L. Fresh shoot weight and photosynthetic rate of both genotypes are increased firstly and then decreased with the increase of Cd concentrations, and reach to the maximium values at 0.1 mg/L and 0.25 mg/L for Jinxiawang qinggengcai and Shanghai aikangqing, respectively. Stomata conductances(Gs) for both genotypes are significantly decreased at Cd 1.0 mg/L, and the decreased range of transpiration rate(Tr) are small. Root is more sensitive to Cd than that of shoot. The decreased ranges of root biomass, root morphological parameters, root vigor and photosynthetic parameters of Jinxiawang qinggengcai under the Cd treatments are much greater than those of Shanghai aikangqing. These results indicate that Shanghai aikangqing has higher ability to tolerate high Cd stress than Jinxiawang qinggengcai’s.