THE EFFECT OF IRRADIATING ADAXIAL OR ABAXIAL SIDE ON PHOTOSYNTHESIS OF ROSE LEAVES

In many cropping systems most of the light irradiates the adaxial side of leaves. However, in cropping systems with intra canopy lighting a reasonable fraction of light may irradiate even the abaxial side of the leaves. The aim of this study was to investigate the effect of irradiating the abaxial leaf side compared to irradiating the adaxial side, in rose plants grown in glasshouse with the bending technique. The instantaneous effects on the optical properties and the light response of photosynthesis were analysed in intact leaves. Results demonstrated that the rate of net photosynthesis was higher when leaves were lighted from the adaxial side compared to the abaxial side. This was the consequence of both a higher light absorption and higher quantum yield (photosynthesis per unit absorbed light) in adaxial-lighted leaves.