Abstract

Yield and oil quality responses to different degrees of water stress have often reported for olive trees, but few studies have addressed how midday stem water potential (psi(stem)), stomatal conductance (g(s)), net assimilation (A(n)), and oil yield respond to rewatering after experiencing water deficit. The objective of this study was to evaluate the responses of psi(stem), g(s), and A(n) in olive leaves to rewatering after irrigation cut-off (ICO) periods during 2011/2012, 2012/2013, and 2013/2014 growing seasons. The drip-irrigated olive trees were located in the Pencahue Valley (Maule Region, Chile) and trained to a superintensive hedgerow system with a spacing of 1.5 m within rows x 5.0 m between rows. The experiment included a treatment irrigated to satisfy their water requirement based on a previous study (psi(stem) > - 2.5 MPa, T0) and two ICO treatments in a completely randomized design. For the ICO treatments, irrigation was cut-off from fruit set until reaching psi(stem) thresholds between - 3.0 and - 3.5 MPa for T1 and - 5.0 and - 5.5 MPa for T2. Once these thresholds were reached, the irrigation was restored to that of the T0 treatment level. In the T1 treatment, psi(stem), A(n), and g(s) were all fully recovered from moderate water stress, although the time needed for recovery varied between growing seasons. Except 2012/2013 season, the psi(stem) values were fully recovered 14 days from rewatering after severe water stress in the T2 treatment. A(n) and g(s) values were, however, 19-36% and 33-41%, respectively, less than those observed in T0 treatment after even 14 days of rewatering. Finally, the total oil yield per plant was significantly reduced in most study seasons after severe water stress (T2). These results suggest that the evolution of plant water status must be carefully monitored when water deficits are imposed in superintensive olive orchards to avoid unwanted delays in the recovery of photosynthesis and potential reductions in oil yields.