Effect of selenium on uptake and translocation of arsenic in rice seedlings (Oryza sativa L.)

Arsenic (As) disrupts the biological functions of plants by inhibiting their developmental process. Selenium (Se) is a beneficial plant micronutrient when it is administered at the optimal doses. The present study investigated the possible mediatory role of selenite (Se(IV)) or selenate (Se(VI)) in arsenite (As(III)) or arsenate (As(V)) uptake by rice seedlings (Oryza sativa L.). Simultaneous exposure of rice seedlings to As(III) (5 mu M) and Se(IV) (5 mu M) increased the root As content after >= 30 h. The maximum increase in root As level (42.2%) was measured after 150 h. At the same time, the shoot As level decreased by 46.4% as the root-to-shoot As translocation rate declined. In contrast, Se(VI) supplementation caused the As content to decrease by 48.8% and 16.1% after 150 h in the roots and shoots, respectively. Nevertheless, when the As exposure duration was < 48 h, no significant differences in the shoot As levels were detected between treatments. The addition of Se(IV) to the As(V) solution applied to the rice seedlings did not significantly affect root As content but strongly decreased shoot As levels. Se (VI) supplementation had the opposite effect. Lower Se(IV) concentrations slightly increased root As content in seedlings treated with As(III) but strongly decreased shoot As content and the root-to-shoot translocation rate. At lower concentrations, Se(VI) addition significantly decreased both root and shoot As content after 7 d. On the other hand, the root-to-shoot translocation rate did not significantly decrease relative to that observed with the As(III) treatment alone. Our results indicate that Se(IV) could effectively mitigate As translocation from roots to shoots in rice.