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+.