Effect of phosphorus on iron toxicity: photosynthetic and antioxidant responses of rice cultivars

Abstract

Iron (Fe) toxicity is a problem that affects many rice areas in lowland environments. The aim of this study was to investigate, through photosynthetic and antioxidant responses, the effect of phosphorus (P) nutrition as a mitigator of iron (Fe) toxicity in rice cultivars. The experimental design used was in randomized blocks, with four replications Three rice cultivars (Br/Irga 409, Irga 424, and Irga 425) were exposed to two concentrations of Fe (2 and 200 mg L-1) combined with two concentrations of P (2.5 and 15 mg L-1) in a nutrient solution, for 60 days. The results show that the excess of Fe reduced the root dry matter of all cultivars, but only the cultivar Br/Irga 409 showed a decrease in the shoot dry matter. The antioxidant enzymatic activity was not efficient to attenuate the toxicity by Fe due to the higher lipid peroxidation and decrease in the net CO2 assimilation rate. The cultivar Irga 425 showed greater tolerance to conditions of toxicity by Fe when associated with the increase in P availability, with high photosynthetic responses and enzymatic activity (superoxide dismutase). The cultivar Br/Irga 409 showed greater sensitivity to toxicity by Fe compared to other cultivars.