Sejima Takehiro, Takagi Daisuke, Fukayama Hiroshi, Makino Amane, Miyake Chikahiro
Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, 657-8501 Japan.
Department of Agriculture, Graduate School of Agricultural Science, Tohoku University, Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981-8555 JapanCREST, JST, 7 Gobancho, Chiyoda-ku, Tokyo, 102-0076 Japan.
Plant Cell Physiol. 2014 Jun;55(6):1184-93. doi: 10.1093/pcp/pcu061. Epub 2014 May 3.
Under field conditions, the leaves of plants are exposed to fluctuating light, as observed in sunfleck. The duration and frequency of sunfleck, which is caused by the canopy being blown by the wind, are in the ranges from 0.2 to 50 s, and from 0.004 to 1 Hz, respectively. Furthermore, >60% of the sunfleck duration ranges from 0.2 to 0.8 s. In the present research, we analyzed the effects of repetitive illumination by short-pulse (SP) light of sunflower leaves on the photosynthetic electron flow. The duration of SP light was set in the range from 10 to 300 ms. We found that repetitive illumination with SP light did not induce the oxidation of P700 in PSI, and mainly inactivated PSI. Increases in the intensity, duration and frequency of SP light enhanced PSI photoinhibition. PSI photoinhibition required the presence of O2. The inactivation of PSI suppressed the net CO2 assimilation. On the other hand, the increase in the oxidized state of P700 suppressed PSI inactivation. That is, PSI with a reduced reaction center would produce reactive oxygen species (ROS) by SP light, leading to PSI photodamage. This mechanism probably explains the PSI photodamage induced by constant light.
在田间条件下，植物叶片会受到波动光照的影响，如光斑现象。光斑是由树冠被风吹动引起的，其持续时间和频率分别在0.2至50秒以及0.004至1赫兹范围内。此外，超过60%的光斑持续时间在0.2至0.8秒之间。在本研究中，我们分析了短脉冲（SP）光对向日葵叶片的重复照射对光合电子流的影响。SP光的持续时间设定在10至300毫秒范围内。我们发现，SP光的重复照射不会诱导光系统I（PSI）中P700的氧化，且主要使PSI失活。SP光强度、持续时间和频率的增加会增强PSI光抑制。PSI光抑制需要氧气的存在。PSI的失活抑制了净二氧化碳同化。另一方面，P700氧化态的增加抑制了PSI失活。也就是说，反应中心还原的PSI会通过SP光产生活性氧（ROS），导致PSI光损伤。这一机制可能解释了持续光照诱导的PSI光损伤。
