Abstract: We investigated the influence of root agent and water stress on root elongation of wheat, and Cd uptake and translocation by wheat, in heterogeneous Cd-contaminated soil. We prepared heterogeneous Cd contaminated soils at three soil depths (06, 712 and 1318 cm) using rhizobox method. In a whole growth culture experiment, we studied the effect of root agent at three addition levels (0.1%, 0.2% and 0.4%), and the effect of three water stress treatments (60%, 50% and 40% MWHC (maximum water holding capacity)), on Cd uptake and translocation by wheat. The results indicated that root growth of wheat, compared with control, was enhanced by both treatments which significantly increased the total root length (cm) and root surface (cm2). In detail, the total root length in the subsoil (1318 cm depth) increased by 63.2%205.9% and 69.1%91.2% by root agent and water stress treatments, respectively. Root agent application promoted the wheat tillering numbers and increased the biomass of wheat grain by 5.6%50.3%. In terms of Cd uptake by wheat, the result showed that, except the 40% MWHC water stress treatment (WS3), Cd concentrations in shoots and grain of wheat were significantly decreased (P<0.05) by both treatments. Compared with control, the decreases ranged in 24.0%41.5% and 23.0%42.7%, respectively, with the best effect observed at the 0.4% additional level for root agent. The effect of different treatments on the Cd decrement in wheat grain followed the order of RA3≈RA2>WS2≈RA1≈WS1>WS3. Based on the above results, we concluded that root agent and water stress treatments can be recommended for remediation of field soils contaminated by heterogeneous heavy metals.

Key words: Cd-contaminated soil, root agent, water stress management, wheat, root elongation