Cultivar variation in morphological response of peanut roots to cadmium stress and its relation to cadmium accumulation.

This study aimed to test the hypothesis that root morphology may play a crucial role in the variation in Cd accumulation among peanut (Arachis hypogaea L.) cultivars. The biomass, Cd accumulation and root morphology of five peanut cultivars were determined under 2 and 20μM CdCl2 in a hydroponic experiment. Excess Cd considerably decreased the root lengths (RL), surface area (SA), specific root length (SRL) and number of root tips, but increased the root diameters (RD). Cd-induced decreases in RL and SA were significant in the 0-0.2 and 0.2-0.4mm diameter classes. Peanut cultivars differ in Cd accumulation and root morphological parameters. A positive correlation was observed between RL and Cd amount in shoots. RD negatively correlated to Cd concentrations in roots and shoots. Positive correlations were also found between RL vs. shoot Cd concentration, SA vs. Cd amount in shoots, SRL vs. root Cd concentration, SRL vs. shoot Cd concentration, and SRL vs. Cd amount in shoots. The fine roots play a crucial role in determining Cd accumulation in peanut plants. Cultivars with more fine roots in their root system (i.e. Haihua 1 and Zhenghong 3) have high capability of Cd accumulation.