Effect of fruiting on leaf gas exchange in olive (Olea europaea L.)

The effect on traits of photosynthesis and water relations of assimilate de mand was studied in olive tree that has strong alternate bearing. The diurn al and seasonal leaf gas exchanges, area dry mass, and saccharide and chlor ophyll (Chl) contents were measured by comparing shoots with fruit of "on-t rees" (heavy fruit load) with shoots without fruit on both "on-trees" and " off-trees" (light fruit load). In spite of large seasonal and diurnal diffe rences, leaf net photosynthetic rate (P-N), stomatal conductance (g(s)), su b-stomatal CO2 concentration (C-1), transpiration rate (E), and respiration rate (R-D) were not significantly influenced by fruit load or by the prese nce or absence of fruit on the shoot. An only exception was at the beginnin g of July when the one-year-old leaves on shoots with fruit had slightly hi gher P-N and E than leaves on shoots without fruit. water content, Chl and saccharide contents, and area dry mass of the leaf were not substantially i nfluenced by the presence/absence of fruit on the shoot or fruit load. Henc e the sink demand, associated with fruit growth, did not improve leaf photo synthetic efficiency in olive.