No evidence has proved that selenium (Se) is an essential micronutrient element for plants growth, but it is beneficial for human health at optimal dosages. Nevertheless, the attention has been largely paid to examine Se content in food stuffs because of Se deficiency in soil. Se fertilizers application to the soil is a beneficial measure to enhance Se content in crops, especially in the edible parts, and eventually achieved Se supplementation for human. As one of the elemental Se species, Se nanoparticles (SeNPs) have entered the field of version with the advantages of high biological activity and low toxicity compared with inorganic Se and organic Se. Unfortunately, little information is available on SeNPs uptake by plants.

Therefore, in this study, the effects of different particle sizes of SeNPs as well as different pH on the absorption of Se by wheat (Triticum aestivum L.) and rice (Oryza sativa L.) were investigated through hydroponics experiments in greenhouse. The results showed that SeNPs with different particle sizes had various characteristics for the absorption and transportation in different plants. SeNPs with 50 nm was more easily to be transferred from roots to shoots than SeNPs with larger sizes (i.e. 100 nm and 150 nm); and the transportation of Se was limited since the translocation factors were below 0.1 of all the treatments. In addition, Se absorption by plants was also affected by pH. Selenite [Se(IV)] was more easily absorbed by plants at lower pH, but SeNPs could be absorbed at an optimal pH and utilized efficiently by both of wheat and rice. Our research could provide some theoretical bases for using a new Se resource to enhance the Se content in agricultural products and increase the intake of Se by the populations.