[Nature of the long-wave fluorescence of photosystem I-enriched particles]

Abstract

Quantum efficient action spectra have been measured of longwave fluorescence of light chloroplast fragments at 20 and -196 degrees C. These spectra were measured as the functional dependence of fluorescence intensity on wave length of exciting light in 630--720 nm range being divided by absorption spectrum. Fluorescence intensity was measured in 8 and 4 nm spectral interval with centres at 730 and 755 nm at room and low temperatures respectively. Three maxima with centres at 650, 680 and 704 nm were revealed in the quantum efficient action spectra. It has been established that the last one resulted from self-absorption of chlorophyll aggregates with longwave fluorescence. It may be that the first maximum was due to high frequency component of multiplet, belonging to self-absorption of longwave chlorophyll aggregates. The shortwave shift of 704 nm maximum and the slight longwave one of 650 nm maximum were found in the quantum efficient action spectra of light chloroplast fragments treated with galactolipase. Good coincidence was revealed between absorption properties of longwave chlorophyll aggregates and those of Photosystem-1 centres, which were measured by other independent methods. It was concluded that longwave fluorescence of light chloroplast fragments belonged to Photosystem-1 centres.