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 (F v /F m and F v ′/F m ′), 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 F v /F m , 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.

中文翻译：

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甜樱桃叶对非冷冻低温的生理反应

通过两个实验中叶绿素荧光、气体交换参数和叶绿素含量的测量，研究了甜樱桃树（Prunus avium L.）暴露于非冷冻低温下的影响。在实验 I 中，栽培品种 'Grace Star' 和 'Schneiders' 在盛开后 21 天和 27 天（DAFB）暴露于平均 4.7 °C 的环境中，而在实验 II 中，栽培品种 'Grace Star' 暴露于 2.2 °C 50 DAFB，对于连续一晚、两晚或三晚。本研究的目的是评估低温暴露 (LTE) 对叶片生理、恢复时间和不同品种对冷胁迫响应的差异的影响。在第一次、第二次和第三次 LTE 之后，PS II（F v /F m 和 F v '/F m '）的最大和有效量子产率下降，净光合作用（Pn），观察到气孔导度 (gs) 和蒸腾作用 (E)。多个 LTE 比单个 LTE 引起更大的生理干扰。多次LTE后恢复时间延长。具有 1 个和 2 个 LTE 的树分别在 24 和 48 小时内达到与对照相似的值，而具有三个 LTE 的树在 48 小时内没有达到。实验一中的 LTE 对 F v /F m 没有影响，而两个 LTE 导致较低的 Pn、gs 和 E。在 LTE 之后，没有发现品种之间的差异。低温胁迫的影响在较低的温度下和连续数夜对树木进行冷冻时更为明显。分别，而具有三个 LTE 的树在 48 小时内没有到达。实验一中的 LTE 对 F v /F m 没有影响，而两个 LTE 导致较低的 Pn、gs 和 E。在 LTE 之后，没有发现品种之间的差异。低温胁迫的影响在较低的温度下和连续数夜对树木进行冷冻时更为明显。分别，而具有三个 LTE 的树在 48 小时内没有到达。实验一中的 LTE 对 F v /F m 没有影响，而两个 LTE 导致较低的 Pn、gs 和 E。在 LTE 之后，没有发现品种之间的差异。低温胁迫的影响在较低的温度下和连续数夜对树木进行冷冻时更为明显。