Selenium Speciation and Distribution in the Rhizosphere and Selenium Uptake of two Rice (Oryza sativa) Genotypes

This study was conducted to expound rhizosphere effects on chemical behavior of selenium (Se). The selenium-enriched and non-selenium-enriched rice (Xiushui 48 and Bing 9652) were studied by pot experiment. After 0.5 mg Se kg(-1) was added, the rice was grown in the root box until ripening stage, and effects of interspecific root interactions of the two rice cultivars on Se chemical forms in different rhizosphere areas were evaluated using a sequential extraction procedure. Rhizosphere effect of different rice cultivars causes different chemical behaviors on selenium. The soluble Se content in rhizosphere soil and near rhizosphere soil of the two rice cultivars was significantly higher in tillering stage than ripening stage. The soluble Se content in rhizosphere soil and near rhizosphere soil of Xiushui 48 was higher than that of Bing 9652 in tillering and ripening stage. There were no significant differences in exchangeable Se content in rhizosphere of different rice cultivars between different distances from root chamber at the tillering stage of rice. However, in the ripening stage of rice, near-rhizosphere region of Xiushui 48 had higher microbial biomass than that of Bing 9652, and accordingly higher exchangeable Se content. At the tillering stage, there was no significant difference in organic matter-sulfide-bound and elemental (organic) Se in 5 mm within the rhizosphere. However, at the ripening stage, organic Se of Xiushui 48 root zone reduced by 5.7-11.4% in average compared to Bing 9652 in 5 mm within the rhizosphere. It indicated that organic Se with lower bioavailability in high-Se rice cultivar (Xiushui 48) root zone was converted to exchangeable Se with high bioavailability. Unlike low-Se rice cultivar (Bing 9652), Xiushui 48 had a lower root Se concentration and strong ability to transport Se to the grain. (c) 2018 Friends Science Publishers