STOMATAL RESPONSES TO CHANGES IN VAPOR-PRESSURE DIFFERENCE BETWEEN LEAF AND AIR

We observed that stomata of Gossypium hirsutum, Glycine mar and Xanthi um strumarium respond to a change in vapour pressure difference betwee n leaf and air at ambient partial pressures of CO2 and below the CO2 c ompensation point. Our report is at variance with a recent report (J.A . Bunce 1997, Plant, Cell and Environment 20, pp, 131-135) that stomat al sensitivity of leaves to a change in vapour pressure difference bet ween leaf and air was eliminated when gas exchange measurements were m ade at near-zero carbon dioxide partial pressures (0-5 Pa).