期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：8
页码：4712-4716
DOI：10.1073/pnas.77.8.4712
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The concentrations of photochemical centers and of plastoquinone were measured in several kinds of photosynthetic membranes by optical difference spectroscopy. Photosystem I reaction centers were measured from the light-induced absorbance change at 700 nm (oxidation of the primary electron donor, P700). Photosystem II reaction centers were estimated from the light-induced absorbance change at 325 nm (reduction of the primary electron acceptor, Q). Spinach chloroplasts and membrane fractions obtained by French press treatment, mature and developing pea chloroplasts, and blue-green algal membranes were investigated. No loss of primary photochemical activity occurred during fractionation of the chloroplasts. The results indicated a large variability in the ratio of system II to system I reaction centers (from 0.43 to 3.3) in different photosynthetic membranes. Oxygen-evolving plants may change the ratio of their photosystems in response to environmental light conditions. The amount of photoreducible plastoquinone was also measured at 263 nm. In spinach chloroplasts, seven to eight plastoquinone molecules were found per reaction center of system II. Most of the plastoquinone pool was associated with the grana. However, the ratio of chemically determined plastoquinone to chlorophyll was similar in the grana and stroma thylakoids.
关键词：photoreaction ; electron transport ; spectrophotometry ; chloroplast function ; P700-chlorophyll
