TIME-RESOLVED SPECTRAL STUDIES OF BLUE-GREEN FLUORESCENCE OF LEAVES, MESOPHYLL AND CHLOROPLASTS OF SUGAR-BEET (BETA-VULGARIS L)

Synchrotron radiation and the time-correlated single-photon-counting t echnique were used to investigate the spectral and time-resolved chara cteristics of blue-green fluorescence of leaves, mesophyll and chlorop lasts. Four kinetic components were resolved. Decay-associated spectra and comparative analysis showed that the fluorescence of leaves, on b oth sides, was dominated by the fast (0.3 ns) and the medium (1 ns) ki netic components, comprising fluorophores emitting principally in the blue and present in the epidermal layer. In the mesophyll, these two f aster components have two maxima, in the blue and in the green part of the spectrum, with a shift of the blue maxima to longer wavelengths w hen compared to leaves. The slow component (3.5 ns) was green-related with a strong indication for the presence of flavins. The very slow co mponent (9 ns) has a maximal fractional intensity in mesophyll and was blue-related. The excitation and emission characteristics and the eff ect of anaerobic atmosphere on the fractional intensities of the slow and very slow component showed that they contain fluorescence of flavi n nucleotides and nicotinamide nucleotides, respectively. Time-resolve d measurements could be a means to extract the information on nucleoti de fluorescence from the overall leaf fluorescence, and therefore to e valuate changes in mesophyll redox sate.