Silicon uptake and translocation in low‐silica rice mutants investigated by isotope fractionation

Abstract

AbstractSilicon (Si) alleviates biotic and abiotic stress in plants and many studies have been conducted in Si uptake by the roots. However, there is limited information about Si translocation during grain filling and the Si transport pathways regulating plant Si uptake. In the present study, we performed a 2‐yr field trial on the wild‐type rice (Oryza sativa L.) varieties Oochikara and Taichung‐65 and their corresponding mutants lsi1 and lsi2. We used multi‐collector, inductively coupled plasma mass spectrometry to evaluate Si isotope fractionation by the Lsi1 and Lsi2 transporters. The qualitative isotope fractionation caused by Lsi1 and Lsi2 (δ30SiLsi1 and δ30SiLsi2) were −2.95 and −2.61‰, respectively, in 2016 and −1.35 and −1.67‰, respectively, in 2017, indicating that transporter Lsi1 and Lsi2 preferentially absorbed 28Si rather than 30Si. Moreover, there was net 28Si enrichment in the mutants, indicating that except for Lsi1 and Lsi2, other Si transport pathways belong to ion channels and electrogenic pumps occur in rice. The unexpected observed decrease in 30Si from the husk to the grain suggests xylem‐to‐phloem Si transfer during grain filling. Hence, Si isotope fractionation is a useful tool to investigate plant Si uptake and translocation.