Tartachnyk Iryna I, Blanke Michael M
INRES-Horticulture, University of Bonn, Auf dem Hügel 6, D-53121 Bonn, Germany.
J Plant Physiol. 2008 Nov 28;165(17):1847-52. doi: 10.1016/j.jplph.2007.11.011.
The objective of this work was to examine immediate physiological plant responses to hail and subsequent recovery in terms of evapotranspiration, leaf temperature and primary photochemical processes using apple as a model crop. Thermal emission pictures were taken in darkness to avoid interference from stomatal movements; temperature gradients were identified in concentric rings around sites of hail injury, with a distinct drop in temperature of up to 2.3 degrees C in the center immediately after the induced hail injury. This was due to enhanced evapotranspiration from the injured tissue. Six to twelve minutes after hail injury, the initial decrease in leaf temperature partially reversed. Chlorophyll fluorescence kinetics of light-adapted leaves showed a dramatic decrease in effective photosynthetic electron transport rate (ETR), from 20.5 to 9.0 micromol electron m(-2)s(-1) within 5 min from hail injury, and a rapid recovery to 14.1 micromol electron m(-2)s(-1) within the next 5 min. After 7h, ETR partially recovered to 17.4 micromol electron m(-2)s(-1). An initial drop in non-photochemical efficiency (NPQ) from 1.07 to 0.90 units within 5 min after hail injury was followed by a sharp increase to 1.67 units after another 5 min. During the next hour, NPQ gradually decreased to the initial level. This indicates increased thermal dissipation in photosystem II (PS II) as a protective mechanism against incident excessive energy in the leaves with closed stomata for 1h after hail injury. In contrast to the fluorescence kinetics of light-adapted leaves, maximum quantum yield Fv/Fm of PSII in the dark-adapted state remained unchanged at 0.79-0.81 relative units for the first 5 min after hail injury. Thereafter, Fv/Fm slowly declined to 0.75 within 1h, and to a trough of 0.73 at 3h. Seven hours after hail injury, Fv/Fm values were at 0.76, indicating partial recovery of PS II efficiency. The discrepancy in the dynamics of ETR and Fv/Fm responses may be explained by the formation of alternative electron sinks such as reactive oxygen species, particularly superoxides, which withdraw electrons from the photosynthetic transport, resulting in apparently higher values of calculated ETR.
这项工作的目的是以苹果作为模式作物，从蒸散、叶片温度和初级光化学过程方面研究植物对冰雹的即时生理反应以及随后的恢复情况。在黑暗中拍摄热发射图像以避免气孔运动的干扰；在冰雹损伤部位周围的同心环中识别出温度梯度，在人工诱导冰雹损伤后，中心部位的温度立即明显下降，降幅高达2.3摄氏度。这是由于受损组织的蒸散增强所致。冰雹损伤后6至12分钟，叶片温度的初始下降部分逆转。光适应叶片的叶绿素荧光动力学显示，有效光合电子传递速率（ETR）急剧下降，从冰雹损伤后5分钟内的20.5微摩尔电子每平方米秒降至9.0微摩尔电子每平方米秒，并在接下来的5分钟内迅速恢复至14.1微摩尔电子每平方米秒。7小时后，ETR部分恢复至17.4微摩尔电子每平方米秒。冰雹损伤后5分钟内，非光化学效率（NPQ）从1.07单位初始下降至0.90单位，随后在又一个5分钟后急剧增加至1.67单位。在接下来的一小时内，NPQ逐渐降至初始水平。这表明在冰雹损伤后1小时内，气孔关闭的叶片中，作为一种保护机制，光系统II（PS II）中的热耗散增加，以抵御入射的过多能量。与光适应叶片的荧光动力学相反，暗适应状态下PSII的最大量子产率Fv/Fm在冰雹损伤后的前5分钟保持不变，为0.79 - 0.81相对单位。此后，Fv/Fm在1小时内缓慢降至0.75，并在3小时降至0.73的低谷。冰雹损伤7小时后，Fv/Fm值为0.76，表明PS II效率部分恢复。ETR和Fv/Fm反应动力学的差异可能是由于形成了替代电子汇，如活性氧物种，特别是超氧化物，它们从光合运输中提取电子，导致计算出的ETR值明显更高。
