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

The effect on traits of photosynthesis and water relations of assimilate demand was studied in olive tree that has strong alternate bearing. The diurnal and seasonal leaf gas exchanges, area dry mass, and saccharide and chlorophyll (Chl) contents were measured by comparing shoots with fruit of "on-trees" (heavy fruit load) with shoots without fruit on both "on-trees" and "off-trees" (light fruit load). In spite of large seasonal and diurnal differences, leaf net photosynthetic rate (P-N), stomatal conductance (g(s)), sub-stomatal CO2 concentration (C-1), transpiration rate (E), and respiration rate (R-D) were not significantly influenced by fruit load or by the presence or absence of fruit on the shoot. An only exception was at the beginning of July when the one-year-old leaves on shoots with fruit had slightly higher 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 influenced by the presence/absence of fruit on the shoot or fruit load. Hence the sink demand, associated with fruit growth, did not improve leaf photosynthetic efficiency in olive.