Fig. 1.

Humidity-, light- and low CO₂-induced increase in whole-plant stomatal conductance is reduced in Arabidopsis slac1 mutants. (Wild type, black circles; slac1-1, white circles; slac1-3, grey circles.) (a, b) Wild type, slac1-1, and slac1-3 plants were kept in low relative air humidity (17.9 ± 0.7%) for 120–180 min, thereafter humidity was abruptly increased to 47.3 ± 0.6% at time 0 as indicated in the upper panel. Error bars indicate ±SEM, n = 3. (c, d) Stomatal conductance patterns of wild type, slac1-1, and slac1-3 plants kept in darkness overnight (12 h) and then exposed to 130 μmol m^-2 s^-1 light as indicated in upper panel are shown. Error bars indicate ±SEM, n = 4. (e, f) To address low CO₂-induced stomatal opening of wild type, slac1-1, and slac1-3 plants were kept in 400 μmol mol^-1 of CO₂ and 20-25% relative air humidity until stomatal conductance values had stabilized (2-3 h), thereafter CO₂ concentration was decreased to 40 μmol mol^-1 at time 0 (±SEM, n = 4-8). Patterns of absolute (a, c, e) as well as relative stomatal conductance normalized to value at 0 time point (b, d, f) are shown.