FOLIAR RESPONSES OF OLIVE TREES (OLEA EUROPAEA L.) UNDER FIELD EXPOSURE TO ELEVATED CO2 CONCENTRATION

Five-year-old olive plants (cvs. Frantoio and Moraiolo) grown in large pots were exposed for seven months to ambient or high atmospheric CO2 concentration ([CO2]) in free-air CO2 enrichment facility. Exposure to elevated [CO2] enhanced net photosynthesis and decreased stomatal conductance, leading to greater water use efficiency. Stomatal density also decreased in elevated [CO2], while the ratio of intercellular to atmospheric [CO2] did not differ among leaves grown in ambient or enriched [CO2]. Cultivar differences in response to high [CO2] should be taken into account when planning future olive plantations in forecasted warmer and drier Mediterranean sites.