Abstract
One-year-old olive (Olea europaea L) cuttings of two cultivars (Frantoio and Moraiolo) were exposed for five months to ambient (360 ± 16μmol mol1) or elevated (560 ± 52 μmol mol1) CO2concentration in a free-air CO2enrichment facility. Current-year leaves were used for gas exchangemeasurements, chlorophyll and nutrient determinations. Stomata! density wasmeasured on frozen hydrated current-year leaves by low temperature scanningelectron microscopy. Above-ground dry mass (stem and leaves) and leaf areawere determined, and leaf mass ratio and specific leaf area calculated. Resultsshowed that exposure to elevated CO2enhanced rates of net photosynthesis anddecreased stomatal conductance, leading to higher water use efficiency; this wasnot translated in increased growth rates (particularly in the cultivar Frantoio, which showed reductions in above-ground plant dry mass compared with thecultivar Moraiolo). Chlorophyll concentrations (chlorophyll content per unitleaf area) decreased only in Frantoio leaves of plants grown in elevated CO2Stomatal density and leaf nutrients did not differ between treatments andcultivars. Some adjustment to elevated CO2was observed for the cultivarFrantoio, which showed strong reductions in leaf area, thus counterbalancingincreased photosynthetic rates per unit leaf area (but also decreased stem drymass). The decrease in total leaf dry mass in response to elevated CO2wasaccompanied by a decrease in the fraction of aerial plant dry mass belonging toleaves (elevated CO2changed dry mass allocation by decreasing leaf mass ratio), suggesting that canopy-level adjustment in carbon assimilation may occur inboth cultivars. © 2002 Taylor & Francis Group, LLC.