Ameliorating Effect of Potassium on Iron Toxicity in Hybrid Rice

The effect of potassium (K) on ferrous iron (Fe2+) toxicity in hybrid rice (Oryza sativa L.) was investigated in this study. Plants were grown in nutrient solution with three K supplies (0.26, 0.51, and 1.02 mM) and five Fe2+ levels (0.09, 0.18, 0.36, 0.54, and 0.90 mM). Excessive Fe2+ greatly decreased root and shoot dry weights, root length, and shoot height of the hybrid rice, and this depression was obvious even at relatively low Fe2+ levels (above 0.18 mM). Excessive Fe2+ levels notably influenced morphological parameters and concentrations of K, phosphorus (P), and nitrogen (N) in the plants. High K supplies ameliorated the negative effects of higher Fe2+, as indicated by increases in biomass and nutrient contents. Proper K supply reduced translocation of Fe2+ from roots to shoots, especially to the upper leaves. Phosphorus, which is antagonistic to Fe2+, was significantly increased by K supply. Ameliorating effects of K may be attributed to the antagonistic effect of K on Fe absorption and translocation to shoots, especially to upper leaves, and to the improvement of plant nutritional status.