Fig. 4.

Decrease of intracellular Ca²⁺ concentration rapidly restores K⁺_in channel activity and cameleon Ca²⁺ reporter analyses indicates slightly elevated cytosolic Ca²⁺ in Arabidopsis slac1 mutant guard cells. (a) Whole-cell recordings of K⁺_in currents with <10 nM free [Ca²⁺]_cyt in the pipette solution in slac1-1 and in wild type guard cells. (b) Average steady state current–voltage relationships for guard cells, as recorded in (a). (c) Baseline cytosolic Ca²⁺-dependent ratiometric fluorescence levels in wild type (n = 35) and slac1-1 (n = 39) guard cells transformed with yellow cameleon 3.6; *, P < 0.001. Error bars indicate ±SEM.