The physiological response of the sweet cherry leaf to non-freezing low temperatures

Abstract

The effect of exposure of sweet cherry trees (Prunus avium L.) to non-freezing low temperature was investigated by measurements of chlorophyll fluorescence, gas exchange parameters and chlorophyll content in two experiments. In Experiment I, cultivars ‘Grace Star’ and ‘Schneiders’ were exposed to an average of 4.7 °C 21 and 27 days after full blooming (DAFB) and in Experiment II, cultivar ‘Grace Star’ to 2.2 °C 50 DAFB, for one, two or three consecutive nights. The aim of the present study was to evaluate the effect of low temperature exposure (LTE) on leaf physiology, recovery time and differences between cultivars in response to chilling stress. After the first, second and third LTE, a decrease in maximum and effective quantum yield of PS II (Fv/Fm and Fv′/Fm′), net photosynthesis (Pn), stomatal conductance (gs) and transpiration (E) was observed. Multiple LTE caused a greater physiological disturbance than single LTE. The recovery time after multiple LTE was prolonged. Trees with one and two LTE reached similar values to the controls within 24 and 48 h, respectively, while trees with three LTE did not reach within 48 h. The LTE in Experiment I showed no effect on Fv/Fm, while two LTE induced lower Pn, gs and E. After LTE, no differences between cultivars were found. The effect of chilling stress was more pronounced at lower temperatures and when the trees were chilled for several consecutive nights.