Light-induced changes of fluorescence and absorbance in spinach chloroplasts at −40 °C

摘要: 1. 1. Spinach chloroplasts were stored in the dark for at least 1 h, rapidly cooled to −40 °C, and illuminated with continuous light or short saturating flashes. In agreement measurements of Joliot Joliot, that had been preilluminated one two flashes just before cooling showed a less efficient increase yield chlorophyll fluorescence upon illumination °C than dark-adapted chloroplasts. The effect disappeared below −150 but reappeared again warming °C. Little was seen room temperature presence 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), added after preillumination. 2. 2. Light-induced absorbance difference spectra region 500–560 nm indicated participation components, socalled 518-nm change (P518) C-550. After preillumination 518 smaller, almost no C-550 observed. four flashes, bands clearly visible again. 3. 3. same type flash pattern minimum second maximum fourth flash. 100 μM hydroxylamine, response low high sixth flash, which confirmed hypothesis related so-called S-state electron transport pathway from water Photosystem 2. 4. 4. kinetics light-induced changes each wavelength, and, apart size deflection, they independent preillumination. Flash experiments one-quantum reaction. This also true chloroplasts, several needed approximately saturate yield. 5. 5. results are discussed terms mechanism involving donors acceptors System 2 photosynthesis.