Shoot hydraulic characteristics, plant water status and stomatal response in olive trees under different soil water conditions

Aims: To evaluate the impact of the amount and distribution of soil water on xylem anatomy and xylem hydraulics of current-year shoots, plant water status and stomatal conductance of mature 'Manzanilla' olive trees. Methods: Measurements of water potential, stomatal conductance, hydraulic conductivity, vulnerability to embolism, vessel diameter distribution and vessel density were made in trees under full irrigation with non-limiting soil water conditions, localized irrigation, and rain-fed conditions. Results: All trees showed lower stomatal conductance values in the afternoon than in the morning. The irrigated trees showed water potential values around -1.4 and -1.6 MPa whereas the rain-fed trees reached lower values. All trees showed similar specific hydraulic conductivity (K s) and loss of conductivity values during the morning. In the afternoon, K s of rain-fed trees tended to be lower than of irrigated trees. No differences in vulnerability to embolism, vessel-diameter distribution and vessel density were observed between treatments. Conclusions: A tight control of stomatal conductance was observed in olive which allowed irrigated trees to avoid critical water potential values and keep them in a safe range to avoid embolism. The applied water treatments did not influence the xylem anatomy and vulnerability to embolism of current-year shoots of mature olive trees.This project was funding both by the Spanish Ministry of Science and Innovation (research project AGL2006-04666/AGR) and the Austrian Science Fund (FWF) (project No. P20852-B16). J. M. Torres Ruiz held a doctoral fellowship from the Spanish Ministry of Science and Innovation (BES-2007-17149, MCINN).Peer Reviewe