Abstract
Highlights: • In the olive tree, a pattern of wood vessel enlargement with branch age is shown. • This pattern varies according to the aridity conditions of the main cultivation area. • Some varieties cannot adjust their sap conduction potential when aridity increases. • Results raise questions about selection of tolerant varieties to low water resources.Abstract: This study examines the impact of drought, and by extension potential water scarcity, on the potential of sap conduction in the olive tree, the emblematic fruit tree of the Mediterranean Basin. To understand adaptation of sap conduction potential of varieties concerning drought, we focus on wood anatomical traits in trees cultivated in the conservatory orchard of the 'Conservatoire Botanique National Méditerranéen' (Porquerolles, France) and others from their main cultivation area. Leveraging branch diameter as a key factor influencing anatomical traits, we model density of vessels (DVS) and lumen area of vessels in transverse section (LAV) variation based on branch diameter using regression analyses. Our results show that the pattern of increase in LAV cannot be considered to be dependent on the biogeography and evolutionary history of varieties. But, it is significantly linked to the aridity conditions of the main cultivation area of these varieties. In the perspective of a future drastic increase in aridity, results point to the potential incapacity of varieties from non-irrigated semi-arid zones, to produce vessels large enough to transport sap to the leafy parts of branches, and other varieties from the northern margins of olive distribution area, to modulate conduction in terms of efficiencysafety balance. While some varieties exhibit a robust or moderately plastic phenotype, showing negligible variations in conduction potential with changing aridity in growing conditions, these results concern about the sustainability and future viability of some varieties. More broadly, they raise questions about the olive cultivation sector's resilience in the face of intensifying water stress.