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High salinity tolerance in the stl2 mutation of Ceratopteris richardii is associated with enhanced K + influx and loss
Author(s) -
WARNE T. R.,
HICKOK L. G.,
KINRAIDE T. B.,
VOGELIEN D. L.
Publication year - 1996
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1996.tb00223.x
Subject(s) - depolarization , chemistry , tetraethylammonium , wild type , tetraethylammonium chloride , membrane potential , sodium , biophysics , mutant , nuclear chemistry , potassium , biochemistry , biology , organic chemistry , gene
The roles of K + uptake and loss in the salinity response of the wild type and the salt‐tolerant mutant stl2 of Ceratopteris richardii were studied by measuring Rb + influx and loss and the effects of Na + , Mg 2+ , Ca 2+ and K + ‐transport inhibitors. In addition, electrophysiological responses were measured for both K + and Rb + and for the effects of Na + and NH 4 + on subsequent K + ‐induced depolarizations. stl2 had a 26–40% higher uptake rate for Rb + than the wild type at 0.5–10 mol m −3 RbCl. Similarly, membrane depolarizations induced by both RbCl and KCl were consistently greater in stl2 . In the presence of 0–180 mol m −3 NaCl, stl2 maintained a consistently greater Rb + influx than the wild type. stl2 retained a greater capacity for subsequent KCl‐induced depolarization following exposure to NaCl. Five mol m −3 Mg 2+ decreased Rb + uptake in stl2 ; however, additional Mg 2+ up to 40 mol m −3 did not affect Rb + uptake further. Ca 2+ supplementation resulted in a very minor decrease of Rb + uptake that was similar in the two genotypes. Tetraethylammonium chloride and CsCl gave similar inhibition of Rb + uptake in both genotypes, but NH 4 Cl gave substantially greater inhibition in the wild type than in stl2 . NH 4 Cl resulted in a greater membrane depolarization in the wild type and the capacity for subsequent depolarization by KCl was markedly reduced. stl2 exhibited a higher Independent loss of Rb + than the wild type, but, in the absence of external K + , loss of Rb + was equivalent in the two genotypes. Since constitutive K + contents are nearly identical, we conclude that high K + influx and loss exact a metabolic cost that is reflected in the inhibition of gametophytic growth. Growth inhibition can be alleviated by reduced supplemental K + or by treatments that slightly reduce K + influx, such as moderate concentrations of Na + or Mg 2+ . We propose that high throughput of K + allows maintenance of cytosolic K + under salt stress and that a high uptake rate for K + results in a reduced capacity for the entrance and accumulation of alternative cations such as Na + in the cytosol.