| Abstract: | The effects of air temperature (To), leaf-air vapour pressuredifferences VPD) and water deficit on stomatal responses tochanging irradiance were studied in Phaseolus vulgaris L. Responseswere approximately sigmoidal, with rates of closure being fasterthan the rates of opening. The mean half-time for closure was5.4 min and for the opening 9.2 min. Under water deficit, bothstomatal opening and closing were faster than in well-wateredconditions. Stomata were more sensitive to VPD and water stressthan to To. The higher the VPD or To the more rapid was thestomatal response, except in stressed plants where there wasno significant effect of To. Under water stress, stomata weremore sensitive to water potential ( |
