中文摘要：

为了探讨植物叶片对UV-B辐射增强的响应机制,采用叶绿素荧光测定技术,分别测定在人工模拟低剂量UV-B（2.4μW/cm~2）辐射条件下乌拉尔甘草叶片的叶绿素荧光诱导动力曲线、初始荧光（F_0）、最大荧光（F_m）、光合机构比活性参数（ABS/RC、TR_o/RC和ET_o/RC）和性能指数等变化规律。结果表明：（1）低剂量UV-B辐射未引起甘草叶片O-J-I-P叶绿素荧光诱导曲线中的相数发生改变,UV-B辐射对PSⅡ的影响主要发生在其受体侧,而非供体侧;（2）低剂量UV-B辐射引起了甘草叶片光合系统F_v/F_m以及F_m、F_0的明显变化,同时也影响了光合机构的开放程度和电子从Q_A向Q_B传递效率,从而影响了光转化效率;相应性能指数（PI_（abs）和PI_（total））的改变亦验证了此结果。研究认为,低剂量UV-B辐射抑制乌拉尔甘草叶片光合系统Ⅱ受体侧Q_A至PQ之间的电子传递效率,从而影响了Q_A之后的光化学反应及非光化学反应。

英文摘要：

To investigate the response of photosynthetic apparatus to UV-B radiation,we investigated the changes of chlorophyll fluorescence parameters under artificial simulated low UV-B radiation treatment（2.4μW/cm~2）,that including Chl a fluorescence transients induced dynamic curve,F_0,F_m,the parameters of PSⅡreaction center activity（ABS/RC,TR_o/RCand ET_o/RC）and performance index（PI）in leaves of Glycyrrhiza uralensis,by using the pocket PEA.The results suggested that：（1）UV-B mainly influenced the acceptor side of PSⅡ system rather than its donor side because of the O-J-I-P chlorophyll fluorescence induction curves didn＇t change by low level UV-B radiation.（2）The results of F_0,F_mand F_v/F_mindicated that UV-B radiation inhibited the openness of reaction center and blocked the transporting of electron from Q_Ato Q_B,and that was confirmed by the decreasing of PI_（abs）and PI_（total）.Thus,low level UV-B radiation influences photochemical or non-photochemical reaction beyond Q_Aas result of reduced electron transportation efficiency from Q_Ato PQ.