Pathway and driving forces of selenite absorption in wheat leaf blades

Abstract

Selenium (Se) deficiency in the human diet is a widespread problem. Se biofortification of wheat crop by spraying foliage with selenite could effectively increase Se intake by enhancing the Se concentration in wheat grains. However, pathway and driving forces of selenite absorption in wheat leaf blades are not fully understood. In this study, the effects of selenite-applied concentration, selenite-exposed duration, stomatal inhibitors, respiratory inhibitors, and competitive anions on selenite absorption in wheat leaf blades were investigated. The results indicated that the selenite absorption rate increased linearly with increasing selenite concentrations, but it decreased greatly and reached a low level with treatment times of 4 h and longer. Stomatal inhibitors significantly inhibited selenite absorption. Respiratory inhibitors and inorganic phosphate (P<sub>i</sub>) strongly inhibited selenite absorption. Therefore, selenite passively enters wheat leaf blades via cuticle and stomata, and then enters mesophyll cells via P<sub>i</sub> transporters. Concentration gradients and selenite uptake by mesophyll cells provide continual driving forces for selenite absorption in leaf blades.