Oxygen-dependent stomatal openings in Zea mays leaves. Effect of light and carbon dioxide.

The oxygen requirement for stomatal opening in maize plants (Zea mays L. hybrid INRA 508) was studied at different CO₂ concentrations and light intensities. In the absence of CO₂, stomatal opening always required O₂, but this requirement decreased with increasing light intensity. In darkness, the lowest O₂ partial pressure needed to obtain a weak stomatal movement was about 54 Pa. This value was lowered to ca 10 Pa in light (320 μmol m^-2 s^-1. On the other hand, in the absence of O₂, CO₂ enabled stomatal opening to occur in the light, presumably due to the evolved photosynthetic O₂. Thus, CO₂, which generally reduced stomatal aperture, could induce stomatal movement in anoxia and light. The effect of CO₂ on stomatal opening was closely dependent on O₂ concentration and light intensity. Stomatal aperture appeared CO₂-independent at an O₂ partial pressure which was dependent on light intensity and was about 25 Pa at 320 μmol m^-2 s^-1. The presence of a plasmalemma oxidase, in addition to mitochondrial oxidase, might explain the differences in the O₂ requirement at various light intensities. The possible involvement of such a system in relation to the effect of CO₂ is discussed. [ABSTRACT FROM AUTHOR]