Control of water consumption by the olive tree

Abstract

Measurements of leaf water potential (psi) and stomatal conductance to H2O (g) were made in 26-year-old Manzanillo olive trees under irrigation and dry-farming conditions. On days of high water demand, the olive trees reduced water losses by closing the stomata, so preventing excessive water stress. The analysis of g values versus photosynthetically active radiation (IPAR) and vapour pressure deficit (VPD), showed that stomata were fully opened at relatively low IPARlevels, from about 500 μmol m-2 s-1. Also, g decreased with increasing VPD, for values of up to approximately 4 kPa. After plotting the relative extractable soil water (REW) values against their counterparts of pre-dawn leaf water potential (psipd), it was observed that psipd remained constant for values of REW higher than 0.4, with a mean value of -0.46 MPa.