镉对不同基因型小白菜根系生长特性的影响

采用水培试验，研究了镉（Cd）不同处理浓度对两种基因型小白菜（金夏王青梗菜和上海矮抗青）的生长及根系形态的影响。结果表明, 随着Cd 处理浓度的增加，两种基因型小白菜根系除直径无显著差异外，根系鲜重、长度、体积、表面积、根系活力均持续下降，且青梗菜的下降幅度显著高于矮抗青。随着镉处理浓度的增加，两种小白菜体内镉含量明显增加，与处理浓度呈显著正相关。当处理浓度大于Cd2+ 0.25 mg/L，矮抗青地上部与根系镉含量超过青梗菜。两种小白菜地上部分鲜重和光合速率均呈先升后降的趋势，其中青梗菜的临界值为Cd 2+ 0.1 mg/L时，而矮抗青的临界值为Cd2+ 0.25 mg/L时。镉浓度为Cd 2+ 1.0 mg/L时，二品种气孔导度均有显著下降，而蒸腾速率变化相对较小。根系较地上部分对镉更为敏感。两种小白菜对镉浓度的反应虽然总体趋势一致，但青梗菜根系的生物量、形态参数、活力及光合参数的下降幅度显著高于矮抗青，表明矮抗青比青梗菜具有较强的耐镉特性，与种子萌发时的敏感性一致。

Effects of Cd on growth characteristics of root systems of pakchoi 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.