Figure 2.

Guard cell whole vacuole currents elicited by cADPR. (A) Whole vacuole currents from Vicia faba guard cell vacuole in the absence of cADPR in symmetric 200 mM KCl and other conditions as shown. (B and C) Currents from the same vacuole respectively in the presence of 100 nM cADPR on the cytosolic (bath) side of the membrane and then 20 min after onset of bath perfusion with cADPR-free solution. (D) I–V relationship for whole vacuole instantaneous currents before (○) and after (•) addition of 100 nM cADPR, conditions as in A and B. (E) Difference relationship for cADPR-induced currents, with conditions as in D (■) or with the addition of 20 mM CaCl₂ (a_Ca = 4.9 mM) to the pipette solution (□). The I–V difference relationship for controls carried out with 100 nM noncyclic ADPR is also shown (▵). In D and E all data are replicates from 7 vacuoles. (F) Instantaneous currents induced by 100 nM cADPR (as in E, ■) at +100 mV (○) and −100 mV (•) over a range of [Ca²⁺]_cyt concentrations. Each point is the mean ± SEM of n = 7 or 8.