Bustan, A., Gilat Research Center, Agricultural Research Organization, Negev, Israel, Desert Agro-Research Center, Ramat-Negev R and D D.N. Halutza, Israel
Dag, A., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Yermiyahu, U., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Erel, R., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Presnov, E., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Agam, N., Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Be'er Sheva, Israel
Kool, D., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Iwema, J., Gilat Research Center, Agricultural Research Organization, Negev, Israel, Soil Physics, Ecohydrology and Groundwater Management, Wageningen University, Wageningen, Netherlands, Department of Civil Engineering, University of Bristol, Bristol, United Kingdom
Zipori, I., Gilat Research Center, Agricultural Research Organization, Negev, Israel
Ben-Gal, A., Gilat Research Center, Agricultural Research Organization, Negev, Israel

We tested the hypothesis that whole-tree water consumption of olives (Olea europaea L.) is fruit load-dependent and investigated the driving physiological mechanisms. Fruit load was manipulated in mature olives grown in weighing-drainage lysimeters. Fruit was thinned or entirely removed from trees at three separate stages of growth: early, mid and late in the season. Tree-scale transpiration, calculated from lysimeter water balance, was found to be a function of fruit load, canopy size and weather conditions. Fruit removal caused an immediate decline in water consumption, measured as whole-plant transpiration normalized to tree size, which persisted until the end of the season. The later the execution of fruit removal, the greater was the response. The amount of water transpired by a fruit-loaded tree was found to be roughly 30% greater than that of an equivalent low- or nonyielding tree. The tree-scale response to fruit was reflected in stem water potential but was not mirrored in leaf-scale physiological measurements of stomatal conductance or photosynthesis. Trees with low or no fruit load had higher vegetative growth rates. However, no significant difference was observed in the overall aboveground dry biomass among groups, when fruit was included. This case, where carbon sources and sinks were both not limiting, suggests that the role of fruit on water consumption involves signaling and alterations in hydraulic properties of vascular tissues and tree organs. © 2016 The Author 2016.