关键词: 银杏, 光系统Ⅱ, 发射光谱, 叶绿素荧光参数, JIP 测定

Abstract: 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 PSⅡ function declined were that the antenna pigment were destroyed and the receptor side of electron transfer of PSⅡ was impeded. The damaged extent of PSⅡ antenna pigments was directly proportional to net photosynthetic rate and chlorophyll content, but the center pigment structure of PSⅡ was damaged until November. With the aging of leaves, the number of PSⅡ reaction center continual decreased, in which the number of PSⅡ active reaction centers dropped 49%, but the PSⅡ reaction centers only dropped 27%. It showed that the active reaction centers were more ulnerable be damaged than the reaction centers. At the side of PSⅡ receptor, 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 PSⅡ function descent. In November, the structure of PSⅡ mostly been destroyed.

Key words: ginkgo, PSⅡ, emission spectra, chlorophyll fluorescence parameters, JIP-test