Plant water relations of leaves of pomegranate trees under different irrigation conditions

Adult pomegranate trees (Punica granatum (L.) cv. Mollar de Elche) were submitted to three irrigation treatments. Control (T0) plants were drip irrigated in order to guarantee non-limiting soil water conditions, T1 plants (deficit irrigation) were drip irrigated according to the criteria commonly used by the growers in the area and T2 plants were subjected to water withholding and recovery periods of 34 and 6 days, respectively, during the summer of 2009. The results indicated that pomegranate plants confront water stress by developing stress avoidance and stress tolerance mechanisms. From the time of deficit irrigation (T1) and water withholding (T2) began to be applied, leaf conductance decreased in order to control water loss via transpiration and to avoid leaf turgor loss (stress avoidance mechanism). Close to the end of the stress period, when maximum stress levels had developed, active osmotic adjustment was triggered, contributing to the maintenance of leaf turgor (stress tolerance mechanism). Other drought tolerance characteristics commonly seen in xeromorphic plants were also observed, such as high relative apoplastic water content (42–58%), which would contribute to the retention of water at low leaf water potentials.

► No information exists on mechanisms developed by pomegranate to confront drought.
► Irrigation criteria used by the growers in the area did not satisfy pomegranate water requirements
► Decreases in leaf conductance avoid leaf turgor loss (avoidance mechanism).
► Osmotic adjustment contributes to maintain leaf turgor (tolerance mechanism).
► High relative apoplastic water contribute to the retention of water under drought.