PT  - JOURNAL ARTICLE
AU  - Cramer, Grant R.
AU  - Läuchli, André
AU  - Polito, Vito S.
TI  - Displacement of Ca<sup>2+</sup> by Na<sup>+</sup> from the Plasmalemma of Root Cells
AID  - 10.1104/pp.79.1.207
DP  - 1985 Sep 01
TA  - Plant Physiology
PG  - 207--211
VI  - 79
IP  - 1
4099  - http://www.plantphysiol.org/content/79/1/207.short
4100  - http://www.plantphysiol.org/content/79/1/207.full
SO  - Plant Physiol.1985 Sep 01; 79
AB  - A microfluorometric assay using chlorotetracycline (CTC) as a probe for membrane-associated Ca2+ in intact cotton (Gossypium hirsutum L. cv Acala SJ-2) root hairs indicated displacement of Ca2+ by Na+ from membrane sites with increasing levels of NaCl (0 to 250 millimolar). K+(86Rb) efflux increased dramatically at high salinity. An increase in external Ca2+ concentration (10 millimolar) mitigated both responses. Other cations and mannitol, which did not affect Ca2+-CTC chelation properties, were found to have no effect on Ca2+-CTC fluorescence, indicating a Na+-specific effect. Reduction of Ca2+-CTC fluorescence by ethyleneglycol-bis-(β-aminoethyl ether) N,N′-tetraacetic acid, which does not cross membranes, provided an indication that reduction by Na+ of Ca2+-CTC fluorescence may be occurring primarily at the plasmalemma. The findings support prior proposals that Ca2+ protects membranes from adverse effects of Na+ thereby maintaining membrane integrity and minimizing leakage of cytosolic K+.