Photosynthesis of Olive Leaves: Effect of Light Flux Density, Leaf Age, Temperature, Peltates, and H2O Vapor Pressure Deficit on Gas Exchange

Abstract

Clonal plants of four olive ( Olea europaea L.) cultivars that originated in cool, moderately hot, and hot climates were examined for their photosynthetic potentials. Within 3 to 4 weeks, plants had fully expanded leaves; by 3 months the apparent photosynthesis, A, increased to a maximum of 5.4 µmol CO 2 /m 2 per sec, while the water use efficiency (WUE) was 2.6 mmol CO 2 /mol H 2 O. The mean chloropohyll content was 0.564 mmol/chlorophyll (a + b)/m 2 . Mean assimilation rate was negatively correlated to leaf area. The values of A were three to four times less than those reported for apple and almond, whereas WUE was 22% greater. A values were proportional to stomatal conductance. Mesophyll resistance was higher than several C3 plants and the optimum temperature for photosynthesis varied among cultivars, seemingly according to the climate where they originated. Stomata opened and closed within 10 min in response to changes in humidity. Gas exchange properties were not affected by peltate removal.