北京地区大叶黄杨春初返青过程的叶绿素荧光动力学研究

Characteristics of chlorophyll a fluorescence kinetics of Euonymus japonicus during early spring in Beijing region

该文利用调制式荧光仪与氧电极技术,研究北京地区大叶黄杨在春初返青过程中的荧光动力学及光合放氧的变化,探讨常绿阔叶植物在北方越冬过程中抵御逆境的适应机制,同时借助稳态荧光动力学曲线的变化揭示植物返青过程光暗反应的动态变化。结果表明:冬季大叶黄杨阳生叶与阴生叶的PSⅡ光化学效率、光合速率均很低;光合电子传递不通畅,低温强光双重胁迫导致阳生叶比阴生叶的电子链阻塞更严重;捕光天线系统遭遇破坏,这是植物减少过多激发能对PSⅡ反应中心破坏的一种光保护机制;PSⅡ保持较高的开放程度,借此减小激发能在供体侧积累对反应中心造成的伤害;同时非线性电子传递和天线系统之外的能量耗散是大叶黄杨越冬过程重要的光保护机制。初春随着温度的回升,捕光天线系统、光合电子链的活性、光合速率逐渐恢复。倒春寒发生时,大叶黄杨再次发生光抑制现象。

The kinetics of chlorophyll a fluorescence and photosynthesis oxygen evolution of Euonymus japonicus in early spring in Beijing region was examined using PAM2100 and OXYLAB. The goal of this study is to investigate the acclimation mechanism of evergreen broad-leaf plants against low temperature in winter in Beijing region. In addition, the dynamic changes between light reaction and carbon assimilation were also discussed. The results indicated that the photosynthetic rate of sun leaves and the photochemical rate of photosystem Ⅱ（PSⅡ） for shade leaves were very low in winter. Meanwhile, photosynthetic electron transport was blocked. Under the stress of low temperature and high light, photoinhabition of sun leaves was more serious than that of shade leaves. Excessive excitation energy was reduced due to the winter. PSⅡmaintained high opening degree damage of light-harvesting antenna to decrease the harm of excitation energy to the centre of PSⅡ Nonlinear electron transport and heat dissipation except for the antenna system were also important photoprotection ways for E. japonicus in winter. Consequently, activity of light-harvesting antenna system as well as that of photosynthetic chain and photosynthetic rate recovered gradually as air temperature rising in early spring. But photoinhabition would take place again when low temperature happened in late spring.