Differences in the Behaviour of Adaxial and Abaxial Stomata of Amphistomatous Sunflower Leaves: Inherent or Environmental?

Experiments were carried out on sunflower, Helianthus annuus L., to determine whether the differences in behaviour between the abaxial and adaxial stomata of amphistomatous plants are inherent or due to leaf orientation. A single leaf enclosed in a cuvette was observed in normal and reverse orientation and the conductance of each surface was followed as Iight and humidity changed and the stem was severed. The differences in behaviour were found to be the result of leaf orientation rather than the result of inherent differences between adaxial and abaxial stomata.