环境地球化学国家重点实验室知识库

The herbicidal effects of harmaline extracted from Peganum harmala seed on cell growth and photosynthesis of green algae Chlorella pyrenoidosa were investigated using chlorophyll a fluorescence and thermoluminescence techniques. Exposure to harmaline inhibited cell growth, pigments contents and oxygen evolution of C. pyrenoidosa. Oxygen evolution was more sensitive to harmaline toxicity than cell growth or the whole photosystem II (PSII) activity, maybe it was the first target site of harmaline. The JIPtest parameters showed that harmaline inhibited the donor side of PSII. Harmaline decreased photochemical efficiency and electron transport flow of PSII but increased the energy dissipation. The charge recombination was also affected by harmaline. Amplitude of the fast phase decreased and the slow phase increased at the highest level of harmaline. Electron transfer from QA to QB was inhibited and backward electron transport flow from QA to oxygen evolution complex was enhanced at 10 lg mL1 harmaline. Exposure to 10 lg mL1 harmaline caused appearance of C band in thermoluminescence. Exposure to 5 lg mL1 harmaline inhibited the formation of proton gradient. The highest concentration of harmaline treatment inhibited S3QB charge recombination but promoted formation of QA YD + charge pairs. P. harmala harmaline may be a promising herbicide because of its inhibition of cell growth, pigments synthesis, oxygen evolution and PSII activities.