Title

Sodium/Potassium Selectivity and Pleiotropy in stl2, a Highly Salt-tolerant Mutation of Ceratopteris richardii

Department

Ecology, Evolution, and Organismal Biology

Document Type

Article

Publication Date

8-1999

Abstract

The roles of Na+ and K+ (Rb+) uptake were further studied in a NaCl-tolerant strain of Ceratopteris richardii containing the stl2 mutation by direct comparison with the wild-type strain. In addition to Na+ tolerance, stl2 also confers tolerance to Mg2+ and sensitivity to K+. In addition to higher K+ (Rb+) uptake at concentrations commonly associated with low-affinity K+ transport, stl2 maintained higher uptake down to 0·1 mol m–3 Rb+. Up to a 25-fold excess of Na+ had little effect in either genotype on K+ (Rb+) uptake at low concentrations, i.e. 0·2 and 0·5 mol m–3 RbCl. Pretreatment with K+ (20 mol m–3) inhibited uptake of K+ (Rb+) in the wild type, whereas concurrent inclusion of K+ inhibited uptake of Rb+ more in stl2. In the absence of K+, Na+ uptake (0·01–60 mol m–3) was nearly identical in the wild type and stl2. K+ inhibited Na+ uptake more effectively in stl2 than the wild type, especially at 60 mol m–3 Na+. Greater inhibition of K+ uptake in stl2 occurred with MgCl2 or TEA (tetraethylammonium chloride) preincubation or with simultaneous inclusion of Al3+ (Al2SO4). The higher effective velocity of K+ uptake at a wide range of concentrations and the enhanced selectivity for K+ and against Na+ contribute to the preservation of higher cytosolic K+ and lower Na+ under salinity stress.

Journal

Plant, Cell & Environment

Journal ISSN

0140-7791

Volume

22

Issue

8

First Page

1027

Last Page

1034

Digital Object Identifier (DOI)

10.1046/j.1365-3040.1999.00465.x