Calcium Mediation of Cytokinin-Induced Cell Division

Abstract

An expt. on Funaria hygrometrica cultures using a vibrating microelectrode system indicated that (1) untreated caulonema cells have max. inward current at the nuclear region, (2) added cytokinin (benzyladenine) induces an increase in inward current along the length of target cells that subsequently shifts to distal ends of the cells (presumptive bud site), and (3) after establishment of the growth zone at the presumptive bud site, inward current falls. This current has a Ca2+ component, as demonstrated by the current falling to O after treatment with Gd3+ (Ca2+ uptake inhibitor). Detn. of the presumptive bud site is microfilament- and not microtubule-dependent. Free Ca2+ rises homogeneously within target cells immediately after cytokinin treatment, but after establishment of a bulging growth zone, free Ca2+ is spatially nonuniform (higher at the presumptive bud site) and decreases in cells of the developing bud. Apparently, an initial mode of action of cytokinin is the activation of plasma membrane ion channels that subsequently create a microdomain of high intracellular Ca2+ concn. at the presumptive bud site. [on SciFinder(R)]