Improving soil selenium availability as a strategy to promote selenium uptake by high-Se rice cultivar

Abstract The aim of this research was to investigate the mechanism of selenium (Se) utilization by roots between two rice genotypes. The plant Se concentration, root organic acidssecretion, soil Se fractions, soil pH, and infrared spectrum of soil were all determined through a root box experiment to clarify the differences in Se availability of rhizospheresoils between high- and low-Se rice cultivars. The results revealed that the grain Se concentration of the high-Se cultivarwas significantly higher than that of the low-Se cultivar. The concentration of available Se, e.g. water-soluble and exchangeable, in the rhizospheresoil of the high-Se rice cultivarwas dramatically higher than that of the low-Se rice cultivar, and the opposite result was observed in non- rhizospheresoil. The organic acidssecretion of the high-Se rice cultivarshowed a greater degree of reduction than that of the low-Se rice cultivarin response to the increase of Se application rates, while the infrared spectrum intensity of clay mineralin the rhizosphereof the high-Se rice cultivarexhibited a greater degree of increase than that of the low-Se rice cultivar. In addition, the pH of the rhizospheresoil of the high-Se rice cultivarwas significantly higher than that of the low-Se rice cultivarat 0 mg kg −1 Se treatment. The results demonstrated that the high-Se rice cultivarcould obtain more Se than the low-Se rice cultivarby mass flow, which is limited by the concentration of mobile Se in soil; The high-Se rice cultivarhad a greater ability to activate Se by increasing soil pHthan the low-Se rice cultivar; The secretion of organic acidscould activate Se by degrading clay minerals, while the high-Se rice cultivarmay have a greater ability to regulate the secretion of organic acids. The present study suggests the high-Se rice cultivarhas stronger ability to increase Se availability of rhizospheresoil than the low-Se rice cultivar.