Key points are not available for this paper at this time.
S ummary The inhibition of stomatal opening in Commelina communis L. by abscisic acid (ABA) appears to be dependent on the availability of calcium ions. Incubation of epidermal strips in 10 −6 mol m −3 ABA had little effect in the absence of calcium, and a factorial experiment showed a highly significant calcium x ABA interaction. The effect of calcium appeared to be on the later stages of the opening process, and might have been the result of an inhibition of potassium uptake by the guard cells. There was no detectable effect of ABA when EGTA was used to chelate calcium from the apoplastic space. The data are consistent with the hypothesis that ABA increases the permeability of the plasma membranes of the guard cells to calcium. Calcium might then operate as a second messenger to regulate the ionic fluxes that determine guard cell turgor.
SILVA et al. (Thu,) studied this question.