Effects of Ca2+, K+ and cGMP on Na+ uptake in pepper plants

The effects of Ca-,(2+) K+ and cGNIP on Na+ influx in pepper plants (Capsicum annum L.) were studied. Calcium and K+ inhibited Na+ net uptake and had no effect on Na+ efflux. The inhibition of Na+ uptake by Ca2+ showed a K-i of 0.46 mM and micromolar concentrations of the membrane permeable cyclic nucleotide 8-bromo-cGMP inhibited Na+ uptake. These results suggest that transporters with low discrimination between K+ and Na+, sensitive to Ca2+ and to cyclic nucleotides, may constitute important pathways for Na+ influx. As suggested for other plant species, non-selective voltage-independent cation channels may mediate a large amount of Na+ influx into pepper plants. (C) 2003 Elsevier Ireland Ltd. All rights reserved.