北京地区大叶黄杨越冬进程中光系统Ⅱ的行为特征

利用PAM2100调制式叶绿素荧光仪与氧电极技术,监测常绿阔叶植物大叶黄杨在北京地区越冬进程中光系统Ⅱ(PSⅡ)行为特征的转变。结果表明:随着越冬进程的推进,光合放氧速率和PSⅡ光化学效率相继降低,阳生叶降低的幅度均比阴生叶大。深冬,阳生叶的荧光诱导曲线的动力学变化完全消失,而阴生叶能保持一定的荧光动力学变化。同时,植物采取多种防御措施相互配合,保护PSⅡ反应中心:首先,初始荧光(Fo)与最大PSⅡ光化学效率(FV/Fm)同步降低,表明植物通过减小捕光天线系统的方式减少过多光能对PSⅡ反应中心的激发压;其次,光化学猝灭(qP)始终较高,表明PSⅡ通过保持较高的开放程度,减少激发能在PSⅡ供体侧的积累;最后,非线性电子传递与天线系统之外的热耗散是大叶黄杨越冬进程重要的光保护机制。

Study on characteristic of chlorophyll a fluorescence kinetics of overwintering Euonymus japonicus in Beijing

Chlorophyll a fluorescence kinetics and photosynthesis rate of overwintering Euonmymus japonicus in Beijing public gardens were investigated with PAM2100 and OXYLAB.The acclimation mechanism of Photosystem Ⅱ(PSⅡ) was discussed.With the onset of winter,both photochemichal rate of PSⅡ and photosynthetic rate decreased gradually,and the decrease of sun leaves were greater than that of shade leaves.In winter,kinetics of chlorophyll a fluorescence induction curves of sun leaves disappeared,while that of shade leaves still exists.On the other hand,several mechanisms combined to effectively protect the photosynthetic apparatus from photodamage in winter.Firstly,the fact that both minimal fluorescence(Fo) and max photochemical rate of PSⅡ(FV/Fm) decreased indicated that the plant reduced excitons of PSⅡ through cutting the size of light-harvesting antenna.Secondly,results of photochemical quench(qP) suggested that excitons of PSⅡ donor side could be absorbed by keeping open of PSⅡ.Furthermore,both nonlinear electron transport rate and energy dissipation other than antenna were important photoprotective ways for overwintering Euonmymus japonicus.