Plasma-membrane electrical responses to salt and osmotic gradients contradict radiotracer kinetics, and reveal Na -transport dynamics in rice (Oryza sativa L.)
Ahmed M Hamam, Devrim Coskun, Dev T Britto, Darren Plett, Herbert J Kronzucker
Planta | Springer | Published : 2019
A systematic analysis of NaCl-dependent, plasma-membrane depolarization (∆∆Ψ) in rice roots calls into question the current leading model of rapid membrane cycling of Na+ under salt stress. To investigate the character and mechanisms of Na+ influx into roots, Na+-dependent changes in plasma-membrane electrical potentials (∆∆Ψ) were measured in root cells of intact rice (Oryza sativa L., cv. Pokkali) seedlings. As external sodium concentrations ([Na+]ext) were increased in a step gradient from 0 to 100 mM, membrane potentials depolarized in a saturable manner, fitting a Michaelis–Menten model and contradicting the linear (non-saturating) models developed from radiotracer studies. Clear diffe..View full abstract
We thank M. Butler and R. Pasuta at McMaster Nuclear Reactor (Hamilton, Ontario, Canada) for supplying <SUP>24</SUP>Na<SUP>+</SUP> and <SUP>42</SUP>K<SUP>+</SUP>. We also thank Dr. D. Dubins at the University of Toronto Leslie Dan Faculty of Pharmacy for access to their osmometer. This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Ontario Graduate Student Scholarship (OGS), and the University of Toronto.