Water seareity is one of the main restrietions to aehieve food security for a growing population. Thus, new defieit irrigation strategies are being developed based on plant physiology but surprisingly, little is known on fruit physiology. The reeent results on the importanee on non-struetural earbohydrates (NSC) to faeilitate osmotie adjustment (Blum, 2017) and their differential transport depending on the water stress level (Gersony et al., 2020) eould be useful to explain the effeet of fruil loading on plant water relations but it has not been studied yet. The aim of this work is to study the effeet of the fruit presenee or absenee on the leaves water relations mediated by their effeet on leaf soluble sugar dynamies and thus, on leaf osmotie potential analyzing (i) the regulation of stomatal eonduetanee (gs), net photosynthesis (AN) and leafwater potential ('I'lcar) produeed by fruits and (ii) determine leaf osmotie potential (lt) and NSC dynamies depending on the presenee or absenee of fruits and water stress. The experiment was earried out between July and November 2018 on twelve olive trees. Six of them were well-watered (WW) trees and the rest were water-stressed (WS). In eaeh of these treatments, half had the presenee of fruits (+) and the other half had absenee of fruils (-) (n = 3). AN, gs, 'l'le,r, were measured weekly and lt and NSC eontent were measured in four speeifie moments in eaeh tree. The results showed that WW+ presented higher AN and gs values, lower leaf NSC and lt less negative than WW-, indieating that earbohydrates were being exported to the fruit. Assuming that fruits behave as a earbon sink organ, we also observe that WS+ presented more negative 'l'le,r values than WS-. This response would be modulated by the hydrie treatments, beeause the effeet of AN and gs was not as prominent in WS nor that of the hydrie potential in WW. In eonclusion, our results suggested that fruits can modulate leaf NSC and maintain the earbon and water relations under water stress.

This researeh was supported by Spanish Ministry of Seienee, Innovation and Universities (researeh projeet AGL2015-71585-R). A. Montero and A. Perez-Martin helped us with field measurements and osmotie potential analysis. A.P-A was the recipienl of a eontraet form FPI-CSIC program (Spain). We thank to Internacional Olivarera, S.A. U (Interoliva), for allowing us 10 make the experimenls at Sanabria orehard

2 páginas.- 2 referencias.- Poster presentado en el BP2021: XXIV Reunión de la Sociedad Española de Biología de Plantas y XVII Congreso Hispano-Luso de Biología de Plantas, 7 y 8 de julio de 2021. online

Peer reviewed