Interannual carry-over effects of severe drought on field-grown young pear trees

Abstract

Perennial fruit trees will likely face a severe drought during their lifespan as climate change places pressure on irrigation resources. Our understanding of carry-over effects of seasonal drought on physiological performance is limited. This research assessed the physiological effects of soil water deficit on three-year-old field-grown pear trees of the combination ‘D'Anjou’/OHxF.87 and then also evaluated the carry-over effects of the drought the next season even when no water limitations were present. The first season trees under drought stress decreased their midday stem water potential to values below -3.0 MPa, and reduced stomatal conductance and root hydraulic conductance by 72 and 37 % respectively, compared to fully irrigated trees, which greatly penalized their vegetative growth and belowground expansion. Early leaf senescence was observed in stressed trees which at the end of the season had a total leaf area seven times smaller (0.06 m2) compared to trees with no water restrictions (0.44 m2). The next season, when both treatments were equally irrigated, there were no differences in the stem water potential, with values above -1.0 MPa. However, stomatal conductance for trees that were water limited the previous year remained lower by 32 % compared to those that were fully irrigated both seasons. Trees submitted to drought stress the previous season had smaller leaves with smaller stomata the next season. Moreover, carbon isotope composition in stems and leaves of those trees resulted affected highlighting the lasting effect of the previous season on tree water relations. Our results show that one season of severe drought stress can produce carry-over effects on the physiological and morphological responses of the trees the next season. Recovery from severe droughts can take many seasons even when water limitations do not persist.