Effects of drought stress on the water relations of sweet cherry trees

The present experiment aims to evaluate the effects of drought stress on sweet cherry water relations. Two irrigation treatments were applied: (i) a control treatment, in which irrigation was applied to maintain non-limiting soil water status; and (ii) a drought stress treatment, in which the trees were submitted to two drying periods until the midday stem water potential archived -1.6 MPa and -2.4 MPa in the first and second periods, respectively. The plant response was directly proportional to the intensity of water stress experienced during both drought periods. Thus, the depletion of soil matric potential values led to a decrease in stem water potential values and a stomatal regulation that contributed to a reduction in leaf cooling and a rise in canopy temperature. Thermal indices, the difference between the canopy and surrounding air temperatures and crop water stress index, proved to be useful water indicators for determining the tree water status under drought stress. Maximum daily shrinkage was the fastest plant water indicator to detect irrigation changes; however, it had the highest coefficient of variation. During the recovery cycles, all the water indicators studied returned to values similar to those of the control treatment.