Rainfall intensifies fruit peel cracking in water stressed pomegranate trees

The purpose of the present study was to study the relationship between the leaf and fruit water relations of pomegranate plants at different water deficit levels during the end of the fruit growth and ripening phases. Moreover, special attention was paid to analysing whether the effect that rainfall has on peel cracking of pomegranate fruits growing in water deficit conditions is associated with changes in turgor within the fruit. For this, field-grown adult pomegranate trees (Punica granatum L) cv. Mollar de Elche were subjected to five irrigation treatments. During the growing season, control plants (treatment T0) were irrigated above crop water requirements. During the experimental period (DOY 247-283), T1, T2, T3, and T4 treatments were irrigated as T0 except for 6 (DOY 277-283), 15 (DOY268-283), 25 (DOY258-283) and 36 (DOY247-283) days before harvest (DOY 283), respectively, when irrigation was withheld. Rain fell on DOY 270 (3.5 mm), DOY 271 (84 mm) and DOY 272 (0.9 mm), totalling 88.4 mm. During the experiment, total ETo was 162 mm, and the total amount of water received was 128, 110, 86, 49 and 0 mm for T0, T1, T2, T3 and T4, respectively, without considering precipitation. The results indicated that during the end of fruit growth and ripening phases pomegranate fruit was clearly sensitive to water deficit. During these phenological periods water could enter the fruits via the phloem rather than via the xylem. Despite this, T3 and T4 plants reached much more severe water stress levels than those reported in the literature, although leaf turgor was maintained. However, in all treatments fruit turgor was lost as a consequence of water stress, which induced a reduced expansion of fruits. When rainfall affected previously water stressed pomegranate plants an asymmetric increase in fruit turgor pressure took place, because aril turgor increased to a much greater extent than peel turgor, the pressure of the arils on the peel favouring cracking (C) 2014 Elsevier B.V. All rights reserved.