Diffusive conductances of adaxial and abaxial epidermes: Response to photon flux density during development of water stress in primary bean leaves

Maximum diffusive conductance of abaxial epidermis of primary bean leaves was considerably higher than that of adaxial epidermis. While conductances of both epidermes responded parallel to a decrease in leaf water potential (they increased slightly, reached maxima and decreased to very low values), differences in their response to photon flux density were found. The conductance of abaxial epidermis increased rapidly over lower photon flux densities and gradually over higher photon flux densities, on the other hand the conductance of adaxial epidermis increased only gradually over the whole range. The observed parallel or different response of adaxial and abaxial epidermes to leaf water potential or photon flux density did not change with changes in experimental conditions.