Calcium channels in higher plants

Calcium channels are involved principally in signal transduction. Their ope ning results in increased cytoplasmic Ca2+ concentration, and the spatial a nd temporal variations in this are thought to elicit specific physiological responses to diverse biotic and abiotic stimuli. Calcium-permeable channel s have been recorded in the plasma membrane, tonoplast, endoplasmic reticul um, chloroplast and nuclear membranes of plant cells. This article reviews their electrophysiological properties and discusses their physiological rol es. Emphasis is placed on the voltage-dependent and elicitor-activated Ca2 channels of the plasma membrane and the depolarisation-activated (SV), hyp erpolarisation-activated, IP3- and cADPR-dependent Ca2+ channels of the ton oplast. The closing of stomatal guard cells in the presence of abscisic aci d (ABA) is used to illustrate the co-ordination of Ca2+ channel activities during a physiological response. (C) 2000 Elsevier Science B.V. All rights reserved.