Effect of phosphate and silicate on selenite uptake and phloem-mediated transport in tomato (Solanum lycopersicum L.)
2019
Wang, Mengke | Yang, Wenxiao | Zhou, Fei | Du, Zekun | Xue, Mingyue | Chen, Tao | Liang, Dongli
The ambiguous mechanism that selenite seems to be absorbed by roots via phosphorus (P) and silicon (Si) transporters signifies P and Si may affect selenite uptake. However, the role of P and Si in phloem-mediated selenium (Se) transport within plant tissue is unknown. Therefore, in this work, tomato (Solanum lycopersicum L.) seedlings were exposed to selenite under different hydroponic conditions firstly. And then, split-root experiments were conducted. Results showed that Se uptake decreased as external pH increased. At pH 8, more selenite in the form of SeO₃²⁻ was assimilated under P-deficient conditions than under P-normal conditions. Silicate inhibited Se uptake only at pH 3 (27.5% H₂SeO₃ +72.5% HSeO₃⁻). The results of split-root experiments showed that Se concentrations in seedlings increased under heterogeneously high P or Si. Selenium transport from shoots to roots immersed in solution without selenite was also enhanced. This study illustrated that the affinity of tomato roots to assimilate selenite species followed the order of H₂SeO₃ >HSeO₃⁻ >SeO₃²⁻. H₂SeO₃ was absorbed into roots via Si transporters, whereas HSeO₃⁻ and a portion of SeO₃²⁻ were absorbed via low- and high-affinity P transporters, respectively. In addition, heterogeneously high P or Si concentrations in environmental media could enhance phloem-mediated Se redistribution.
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