中文摘要：

以自然生长条件下银杏叶片为材料,测定叶片衰老过程中净光合速率,叶绿素含量,类囊体膜室温荧光发射光谱和叶绿素荧光参数的变化。结果表明：光系统Ⅱ（PSⅡ）功能的衰退与叶片衰老程度是一致的,PSⅡ功能衰退是由于天线色素被破坏和受体侧电子传递受阻造成的。PSⅡ天线色素受破坏程度与净光合速率和叶绿素含量变化显著正相关,而PSⅡ中心色素结构一直到11月才受到较大的影响;随着叶片衰老加剧,PSⅡ反应中心数不断减少,其中活性反应中心数骤降49%,大于反应中心27%的降幅,这表明有活性的反应中心更容易受破坏;叶片衰老过程中PSⅡ受体侧QA被还原的速率、次数和还原需要的能量都不断增加,此时用于推动QA下游电子传递的能量越来越少;快速叶绿素荧光诱导动力学曲线表明电子传递链受阻导致了PSⅡ功能下降,PSⅡ主体结构瓦解于11月。

英文摘要：

Use natural growth ginkgo leaves as experimental materials,the net photosynthetic rate,the chlorophyll content,the fluorescence emission spectra of thylakoids membranes at room temperature and the chlorophyll fluorescence parameters were measured.The results showed that photosystemⅡ（PSⅡ）function declined the same as leaf senescence.The reasons of PSⅡfunction declined were that the antenna pigment were destroyed and the receptor side of electron transfer of PSⅡwas impeded.The damaged extent of PSⅡ antenna pigments was directly proportional to net photosynthetic rate and chlorophyll content,but the center pigment structure of PSⅡwas damaged until November.With the aging of leaves,the number of PSⅡ reaction center continual decreased,in which the number of PSⅡactive reaction centers dropped 49%,but the PSⅡreaction centers only dropped 27%.It showed that the active reaction centers were more vulnerable be damaged than the reaction centers.At the side of PSⅡreceptor,the rate,the frequency and the energy needing of QA reduction continual increase.At the same time,less energy was used for electron transfer of QA downstream.Changes of chlorophyll fluorescence transient showed that the impeded electron transport chain led to PSⅡfunction descent.In November,the structure of PSⅡmostly been destroyed.