Responses of plant water status to deficit irrigation and warming in young olive trees (Olea europaea)

Abstract

Changes in rainfall patterns and increases in average temperature are expected with climate change. Yet, little information is available as to how plant water status will respond to the combination of water deficit and increased air temperature in fruit trees species. The aim of this study was to evaluate the individual responses of deficit irrigation and warming and their combination on plant water status during the Spring in young olive trees. Two temperature and two irrigation levels were applied in open top chambers between August and December of 2018 and 2019 to 2-3 years-old trees grown in pots (cv. ´Arbequina´ in 2018; ´Coratina´ in 2019). The temperature levels were a near-ambient control and an elevated treatment that was 4 °C above the control, while the two irrigation levels were 100% and 50% of irrigation needs. Midday stem water potential (SWP), stomatal conductance and leaf temperature were measured periodically, and the difference between leaf and air temperature (ΔT) was calculated. The SWP generally decreased due to irrigation deficit and warming when applied individually. When both treatments were combined, an additive response was observed. In contrast, stomatal conductance was consistently decreased by deficit irrigation, but was often not affected by warming. Irrigation deficit did not affect ΔT, but it was significantly decreased by warming early in the season, which is indicative of greater evaporative leaf cooling at higher air temperature. The results emphasize the need for manipulative field experiments in studying the physiological responses to water availability and warming with global change.