INTRACELLULAR PH AND PROTON-TRANSPORT IN BARLEY ROOT-CELLS UNDER SALTSTRESS - IN-VIVO P-31-NMR STUDY

Salt stress-induced changes of intracellular pH and in levels of phosp horous compounds were monitored in intact root tips of barley seedling s (Hordeum vulgare cv. Akashinriki) by in vivo P-31-nuclear magnetic r esonance (NMR) spectroscopy, Vacuolar alkalization was observed after treatment with both 300 and 500 mM NaCl. Much of the observed apparent alkalization of the cytoplasm was eliminated when the effect of Na+ i ons on the titration curve was considered. Within 1 h after the initia tion of salt stress levels of glucose-6-phosphate and UDP-glucose decr eased markedly, and such decreases might lead directly or indirectly t o cell death. Simultaneous measurements of the external and intracellu lar pH revealed the promotion of external acidification and infernal a lkalization during salt stress. Possible mechanisms of Na+/H+ antiport at the tonoplast and the role of proton-pump in the plasma membrane a re discussed.