ABSTRACT
Plant cells contain all the elements for a calcium-based signal transduction chain that can couple the stimulus of cytokinin to its physiological responses. This chapter focuses on evidence for Ca2+ as a second messenger and speculate on the events downstream from the message, that could link cytokinin to cell division. Since cytokinin can act as a mitotic stimulus, it must affect the cell cycle and the entry of cells from interphase into mitosis. Pan et al. showed that aluminum inhibits lateral branch formation on soybean shoots, which can be overcome by exogenous cytokinin applications to the shoot. The elongated target cells respond to cytokinin induction by a localized swelling at the distal end of target cells, then nuclear migration to that region 20 to 22 h after treatment, followed by initial cell formation. Calcium fluxes around quiescent and cytokinin-stimulatcd dividing caulonema cells of Funaria were measured using a Ca2+-selective vibrating microclectrode.
