Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 69, Issue 7, Pages 1679-1692Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/erx460
Keywords
Apoplast; efflux; influx; Oryza sativa L.; cvs Pokkali and IR29; rice; salt stress; silicon; sodium accumulation; sodium transport; transpirational bypass flow
Categories
Funding
- Natural Sciences and Engineering Council of Canada (NSERC)
- Canadian Research Chair (CRC) program
- Ontario Graduate Scholarship (OGS) program
- University of Toronto
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Provision of silicon (Si) to roots of rice (Oryza sativa L.) can alleviate salt stress by blocking apoplastic, transpirational bypass flow of Na+ from root to shoot. However, little is known about how Si affects Na+ fluxes across cell membranes. Here, we measured radiotracer fluxes of Na-24(+), plasma membrane depolarization, tissue ion accumulation, and transpirational bypass flow, to examine the influence of Si on Na+ transport patterns in hydroponically grown, salt-sensitive (cv. IR29) and salt-tolerant (cv. Pokkali) rice. Si increased growth and lowered [Na+] in shoots of both cultivars, with minor effects in roots; neither root nor shoot [K+] were affected. In IR29, Si lowered shoot [Na+] via a large reduction in bypass flow, while in Pokkali, where bypass flow was small and not affected by Si, this was achieved mainly via a growth dilution of shoot Na+. Si had no effect on unidirectional 24Na(+) fluxes (influx and efflux), or on Na+-stimulated plasma-membrane depolarization, in either IR29 or Pokkali. We conclude that, while Si can reduce Na+ translocation via bypass flow in some (but not all) rice cultivars, it does not affect unidirectional Na+ transport or Na+ cycling in roots, either across root cell membranes or within the bulk root apoplast.
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