Rice genotype differences in nutrient status under excessive ferric‐iron conditions

Abstract

To investigate the relationship between rice genotypic variation in tolerance to iron (Fe) toxicity and nutrient element status, 10 rice genotypes with different growing performances under Fe toxicity were grown under normal culture solution and with excessive ferrous (Fe2+)‐Fe concentrations of 250 and 500 mg Fe2+ L‐1. A close relationship was obtained between the relative ratio of symptomatic leaf numbers to total leaf numbers (SLN/TLN) and a relative decrease in dry matter under Fe2+‐toxicity conditions. The genotypic variations in nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) uptake were evaluated by the relative decrease in the N, P, K, and Mg content in the plants. Remarkable genotypic variation in tolerance to excessive Fe2+ was observed. The results indicated that excessive Fe2+ reduced N, P, K, and Mg uptake. The nutrient element concentrations, however, were still higher above deficient criteria even in severely affected plants, suggesting that the retardation of growth may not be intirely due to the deficiency of these elements in plants at the seedling stage. Significant correlations were found between the genotypic variation and the decrease in N, P, K, and Mg uptake and in their tolerance to Fe2+ toxicity, which suggests that the ability to maintain higher nutrient element uptake under a Fe2+‐toxic condition contributes the tolerance to Fe2+ toxicity.