Identification of four universal protochlorophyllide forms in dark-grown leaves by analyses of the 77 K fluorescence emission spectra

Abstract

Low-temperature (77 K) fluorescence emission spectra of dark-grown leaves from 12 different plant species were measured, corrected and analysed at different stages of development. The second and fourth derivative of the spectra indicated the peak positions of possible spectral bands, which were used for resolution of the fluorescence spectra into gaussian components. Based on the intensities of the gaussian components, statistical analyses were performed to determine a possible connection between the main peaks and their respective long-wavelength vibrational sublevels. Four universal protochloro-phyll(ide) forms were distinguished, with the main emission bands (half-bandwidths parentheses) at 633 (14.5), 645 (14.3), 657 (10.5) and 670 (20.1) nm respectively. Their vibrational sublevels were found at 693 (20.8), 710 (17.3), 726 (17.7) and 740 (21.0) nm respectively. The spectral characteristics of the different protochlorophyll(ide) forms are discussed in relation to their possible molecular structures and interactions with the surrounding membrane components.