Interactions of Ca2+ and NaCI stress on the ion relations and intracellular ph of Sorghum bicolor root tips: An in vivo 31P-NMR study

Timothy D. Colmer, Teresa W.M. Fan

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

In vivo 31P-NMR measurements showed that supplemental Ca2+ (5.0 mM CaSO4) decreased the magnitude of the NaCl-induced reduction of the pH gradient across the tonoplast (δpHtonoplast) in Sorghum bicolor root tips exposed to 200 mM NaCl. The reduced (δpHtonoplast) in root tips exposed to 200 mM NaCI was primarily due to vacuolar alkalization rather than cytoplasmic acidification. Maintenance of the (δpHtonoplast) may be Important for salinity tolerance since the trans-tonoplast H+ electrochemical gradient is the putative driving force for Na+ transport from the cytoplasm into the vacuole via a Na+/H+ antiport. Supplemental Ca2+ also reduced net Na accumulation, and maintained the levels of K, cytoplasmic P1 vacuolar P1 glucose-6-P, and total P in root tips exposed to 200 mM NaCl. The decreases in these solutes in root tips supplied with 0.5 mM CaSO4 under NaCl stress were probably due to increased membrane permeability, as evidenced by the release of P to the incubation solution. The eftect of supplemental Ca2+ on the (δpHtonoplast) may be related to the reduced net influx of Na+, which in turn could (i) lower tonoplast Na+/H+ antiport activity, and/or (ii) reduce Na+ inhibition of the tonoplast H+PP, ase, as suggested by some investigators. These findings are consistent with the hypothesis that supplemental Ca2+ helps maintain membrane function in root cells of NaCl-stressed non halophytes.

Original languageEnglish
Pages (from-to)1037-1044
Number of pages8
JournalJournal of Experimental Botany
Volume45
Issue number8
DOIs
StatePublished - Aug 1994

Keywords

  • 31P-NMR
  • Calcium
  • Intracellular pH
  • Salinity
  • Sorghum bicolor

ASJC Scopus subject areas

  • Physiology
  • Plant Science

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