Stomatal resistance to water vapour exchange for com leavos In function of photosynthetically active radiation under field conditions.

Abstract

Diurnal changes of the stomatal resistance to water vapour diffusion in leaves were observed in three com (Zea mays L.) varieties: IAC-Maya, IAC-Maya Latente and Cargi11-601. The adaxial and abaxial stomatal resistance were measured separately with a steady-state porometer on adjacent portions of the leaf. The photosynthetically active radiation of lhe radiation flux density incident upon the leaf biade surface was also measured. At low soil moisture (matric potential of -0,4 MPa), a greater sensibijity for stomatal closing was observed for vas-iety IAC-Maya Latente, during periods of high evaporative demand. At high soil moisture (matric potential of -0,02 M Pa), the relationship between stomatal resistance and the photosynthetically active radiation of the radiation photons incident upon the adaxial leaf surface was a hyperbolic function. Also the sensibility of the abaxial stomatal resistance to the radiation flux density was higher than the adaxial stomatal resistance