Stomatal responses of bean (Phaseolus vulgaris L.) leaves to changing irradiance, air humidity, and water potential of root medium

Stomatal responses of attached bean (Phaseolus vulgaris L.) leaves to chang ing spectral composition ("white" - WL, blue - BL, or red - RL radiation), air humidity (100 % or about 4 % RH), and water potential of the root mediu m (close to 0 or -1.2 MPa) were determined by air flow porometer. Opening o f stomata always increased under BL and decreased under RL. In response to decline in air humidity, leaf conductance showed transient increase before it reached lowered steady state. BL enhanced and RL. diminished this respon se.