Changes in Leaf Osmotic and Elastic Properties and Canopy Structure of Strawberries under Mild Water Stress

Abstract

Field-grown strawberry (Fragaria × annanasa Duch. cv. Chandler) plants were subjected to two irrigation regimes from Nov. 1989 to July 1990 to evaluate the physiological and morphological effects of mild water stress. Irrigation was applied when soil matric potential reached -10 and-70 kPa for the wet and dry treatments, respectively. During the spring, these regimes did not promote significant changes in plant water relations, transpiration rates, plant morphology, or canopy architecture. However, during the summer, after several stress cycles, significant differences between treatments were observed. Pressure-volume curves of dry-treatment plants indicated that leaf osmotic potentials, measured at full and zero turgor, decreased 0.2 to 0.4 MPa. This decrease in osmotic potential also was accompanied by a 50% increase in the modulus of elasticity for these water-stressed plants compared to well-watered plants. Dry-treatment plants also showed stress avoidance mechanisms in changes of whole-plant morphology and canopy architecture, from monolayer to polylayer leaf distribution and leaf orientation from south to north. Despite what would appear to be useful drought-resistance strategies, there was significantly lower fruit production by plants grown under the dry treatment.