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 acids secretion, 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 rhizosphere soils between high- and low-Se rice cultivars. The results revealed that the grain Se concentration of the high-Se cultivar was significantly higher than that of the low-Se cultivar. The concentration of available Se, e.g. water-soluble and exchangeable, in the rhizosphere soil of the high-Se rice cultivar was dramatically higher than that of the low-Se rice cultivar, and the opposite result was observed in non-rhizosphere soil. The organic acids secretion of the high-Se rice cultivar showed a greater degree of reduction than that of the low-Se rice cultivar in response to the increase of Se application rates, while the infrared spectrum intensity of clay mineral in the rhizosphere of the high-Se rice cultivar exhibited a greater degree of increase than that of the low-Se rice cultivar. In addition, the pH of the rhizosphere soil of the high-Se rice cultivar was significantly higher than that of the low-Se rice cultivar at 0 mg kg−1 Se treatment. The results demonstrated that the high-Se rice cultivar could obtain more Se than the low-Se rice cultivar by mass flow, which is limited by the concentration of mobile Se in soil; The high-Se rice cultivar had a greater ability to activate Se by increasing soil pH than the low-Se rice cultivar; The secretion of organic acids could activate Se by degrading clay minerals, while the high-Se rice cultivar may have a greater ability to regulate the secretion of organic acids. The present study suggests the high-Se rice cultivar has stronger ability to increase Se availability of rhizosphere soil than the low-Se rice cultivar.