The cytosolic Na+ : K+ ratio does not explain salinity‐induced growth impairment in barley: a dual‐tracer study using 42K+ and 24Na+
- 1 November 2006
- journal article
- Published by Wiley in Plant, Cell & Environment
- Vol. 29 (12), 2228-2237
- https://doi.org/10.1111/j.1365-3040.2006.01597.x
Abstract
It has long been believed that maintenance of low Na+ : K+ ratios in the cytosol of plant cells is critical to the plant's ability to tolerate salinity stress. Direct measurements of such ratios, however, have been few. Here we apply the non-invasive technique of compartmental analysis, using the short-lived radiotracers 42K+ and 22Na+, in intact seedlings of barley (Hordeum vulgare L.), to evaluate unidirectional plasma membrane fluxes and cytosolic concentrations of K+ and Na+ in root tissues, under eight nutritional conditions varying in levels of salinity and K+ supply. We show that Na+ : K+ ratios in the cytosol of root cells adjust significantly across the conditions tested, and that these ratios are poor predictors of the plant's growth response to salinity. Our study further demonstrates that Na+ is subject to rapid and futile cycling at the plasma membrane at all levels of Na+ supply, independently of external K+, while K+ influx is reduced by Na+, from a similar baseline, and to a similar extent, at both low and high K+ supply. We compare our results to those of other groups, and conclude that the maintenance of the cytosolic Na+ : K+ ratio is not central to plant survival under NaCl stress. We offer alternative explanations for sodium sensitivity in relation to the primary acquisition mechanisms of Na+ and K+.Keywords
This publication has 62 references indexed in Scilit:
- Rapid, Futile K+ Cycling and Pool-Size Dynamics Define Low-Affinity Potassium Transport in BarleyPlant Physiology, 2006
- Low unidirectional sodium influx into root cells restricts net sodium accumulation in Thellungiella halophila, a salt-tolerant relative of Arabidopsis thalianaJournal of Experimental Botany, 2006
- Genes and salt tolerance: bringing them togetherNew Phytologist, 2005
- High-affinity K+ uptake in pepper plantsJournal of Experimental Botany, 2005
- Cloning of Arabidopsis and barley cDNAs encoding HAK potassium transporters in root and shoot cellsPhysiologia Plantarum, 2000
- High-Affinity Potassium Transport in Barley Roots. Ammonium-Sensitive and -Insensitive PathwaysPlant Physiology, 2000
- The Role of Cytosolic Potassium and pH in the Growth of Barley RootsPlant Physiology, 1998
- Intracellular Compartmentation of Ions in Salt Adapted Tobacco CellsPlant Physiology, 1988
- Photosynthesis and Ion Content of Leaves and Isolated Chloroplasts of Salt-Stressed SpinachPlant Physiology, 1983
- Pump-leak sodium fluxes in low salt corn rootsThe Journal of Membrane Biology, 1982