Uptake and Distribution of Cadmium in Different Rice Cultivars

To attempt to understand the variations between rice cultivars in lead (Pb) uptake and distribution, pot soil experiments were conducted with two rice cultivars of different genotypes at different soil Pb levels. The results showed that Pb concentrations and accumulations in the plants of Shanyou 63 were generally higher than those of Wuyunjing 7 under all soil Pb levels, in all plant organs and at all plant growth stages. However, the magnitudes of the differences varied greatly with soil Pb levels, plant organs and plant growth stages. With regard to the differences between two rice cultivars in Pb concentrations at different stages, the magnitudes of the differences were the highest at maturity. Among soil Pb levels, the magnitudes of the differences were the highest under soil Pb treatments of 800 mg kg -1 . Concerning different parts of rice plants at maturity, the magnitudes of the differences were the highest in grains. Compared to the control, Pb distribution ratios of soil Pb treatments increased greatly in roots, but decreased significantly in shoots and grains. At maturity, Pb distribution ratios in roots of Shanyou 63 were obviously lower than those of Wuyunjing 7, but the ratios in shoots of Shanyou 63 were obviously higher than those of Wuyunjing 7. Under soil Pb treatments, the differences between two rice cultivars in Pb distributions ratios in grains were small. The results presented that Shanyou 63 (genotype indica) had higher abilities to absorb Pb from Pb-contaminated soil and transferred a larger proportion of Pb to the shoots than Wuyunjing 7 (genotype japonica). The results also indicate that Pb concentration in rice grain is governed mainly by plant Pb uptake and the transport of Pb from root to shoot, and may be a little by the transport of Pb from shoot to grain.