ИСТИНА

The intensity and shape of the fluorescence spectra of plant leaves are able to provide the information about functional activity of the photosynthetic apparatus and general physiological condition of the plant. These spectra typically contain two broad maximum at 680-690 nm and 720-740 nm. The intensity of the fluorescence bands influenced by factors such as the chlorophyll content, the photosynthetic activity, the leaf’s optical properties. The fluorescence spectra of the leaves of beans Vicia faba L. (variety "Black Russian") were investigated under different light conditions of plants cultivation. Fluorescence spectra were measured using a spectrofluorometer Solar CM 2203. The leaf separated from a stem was placed in a holder and illuminated with blue light (450 nm) within 70 seconds to standardize the experimental conditions. Thereafter, the sample was kept in the dark for 5 minutes and then the same light was turned on and fluorescence spectra were recorded. The registration of the spectrum was about 60 seconds. Induction fluorescence changes (fluorescence quenching) manifested itself as decrease of intensity at 685 nm (F685) and 740 nm (F740) during the transition from initial to stationary fluorescence spectrum. In addition increase of ratio F740/F685 probably associated with the redistribution of excitation energy in favor of the photosystem I was observed. While reducing light intensity of cultivation plants relative quenching of fluorescence was decreased and at very low intensities was practically absent. This indicates a gradual decrease of the photosynthetic activity per chlorophyll with lowering illumination of plants. This technique of fluorescence spectra registration allows to use several indicators characterizing the functional activity of the photosynthetic apparatus of plants.