Drought tolerance in cork oak is associated with low leaf stomatal and hydraulic conductances

To investigate the role of seeds origin in drought tolerance, the response to water deprivation of cork oak seedlings differing in climatic conditions at their geographical origin was compared. Gafour is the provenance from the driest site and Feija is the provenance from the wettest site. Net photosynthesis (An), stomatal conductance (gs) and leaf water potential were measured during dehydration. A delayed decrease in leaf water potential is observed after water withholding in Gafour as compared to Feija leaves. At the onset of dehydration, An and gs were higher in Feija. After withholding watering, Gafour leaves were able to maintain a higher An and gs than Feija leaves. Most likely, drought tolerance in Gafour leaves is associated to their lower gs under well-hydrated conditions. The stomatal density (Ds) and specific leaf area (SLA) were not different in well-watered leaves but, leaf hydraulic conductance was lower in Gafour leaves when compared to Feija leaves. Our results suggested that lower stomatal and hydraulic conductances of Gafour leaves could be involved in bringing about the better resistance to dehydration.