Comparison of Cd Uptake and Partitioning in Plant Tissues by Two Hybrid Rice Grown in Two Contrasting Paddy Soils

Growing of hybrid rice cultivars are increasingly extended in South China for high rice production. However, much attention has been paid to the higher Cd uptake and grain accumulation by the hybrid rice than the conventional rice for the last 5 years. To understanding the possible mechanismfor the enhanced Cd uptake byhybrid rice cultivars, a pot experiments were conducted with two rice cultivars (a super hybrid rice and a common hybrid rice) on two different soils with and without Cd spiking (2.5 mg Cd·kg-1 soil) to soils. The uptake and partitioning ofCd by rice was determined with atomic adsorption spectroscopy(AAS) at different growth stages. The results showed that on the basis of total biomass construction , the most intense active Cd uptake for both hybrid rice cultivars happened at the heading stage. Compared to common hybrid rice cultivars, Cd uptake by super rice ones was much enhanced under Cd spiking. While super rice cultivars had a higher capacity to translocate and partition Cd to grains than the common rice under no Cd spiking. That is, under no Cd pollution, the Cd translocation and partitioning drive the grain Cd level by the rice cultivars. However, with spiked Cd, soil factor may become significant in controlling the Cd availability as super rice had Cd uptake in grains as several folds as common rice cultivars when grown in an acidic soil. This explained intense enhanced Cd uptake and accumulation in rice grains by hybrid rice cultivars grown in red soil region from South China as reported in previous studies.