Toxicity of Lead on Different Rice Genotypes

To attempt to understand the differences between rice genotypes in lead (Pb) tolerance, pot soil experiments were conducted with two rice genotypes at different soil Pb levels, i.e. 0 (the control), 800, 2000 mg kg^-1. The results showed that the soil Pb concentration of 800 mg kg^-1 is moderately toxic to rice, with 10%-30% decreases in plant biomasses. The soil Pb concentration of 2000 mg kg^-1 is a soil Pb level that will severely inhibit rice growth, with 20%-50% decreases in plant biomasses and significant reductions in grain yields (P<;0.01). The genotype Indica was generally more sensitive to soil Pb stress than the genotype Japonica, especially at earlier growth stages (such as at tillering stage), and in grain yield. The reducing rates of dry weights under soil Pb stress were generally in the order: root > shoot > grain, so rice root is more sensitive to soil Pb stress than shoot and grain. The toxicity of Pb on rice growth lessened as plant aged, so some adaptations and growth compensations to soil Pb stress may occur in rice plants along with plant growth and development.