Figure 6.

Dominant mutations in ABI1 and particularly in ABI2 phosphatase cause partial impairment of CO₂-induced stomatal responses, whereas bicarbonate-induced activation of S-type anion channels is reduced in both abi1-1L and abi2-1L guard cell protoplasts. A, Time courses of stomatal conductances in response to stepwise change of CO₂ from 50 to 800 μL L^-1 in abi1-1L, abi2-1L and Ler plants (n = 6). B, Changes in stomatal conductance induced by each step of [CO₂]. C, D, E, Typical whole-cell recording without bicarbonate and F, G, H, with 11.5 mM free bicarbonate added to the pipette solution in the guard cell protoplasts of Ler wild type and abi1-1L and abi2-1L. Average steady-state current-voltage relationships for Ler (open circles, n = 6; filled circles, n = 7), abi1-1L (open circles, n = 6; filled circles, n = 7) and abi2-1L (open circles, n = 5; filled circles, n = 8) guard cell protoplasts are shown in I, J, and K, respectively.