A SIMPLE APPROACH TO THE EVALUATION OF THE REABSORPTION OF CHLOROPHYLL FLUORESCENCE-SPECTRA IN INTACT LEAVES

A simple approach to the estimation of the effect of reabsorption on chlorophyll fluorescence spectra in intact leaves is reported. It permits one to calculate the chlorophyll fluorescence spectrum effectively emitted inside the leaf using the measured fluorescence spectrum and the total transmittance and reflectance of the leaf. Fluorescence spectra, excited by various laser wavelengths, were measured on leaves of an aurea mutant of tomato and its wild type which differ very much in chlorophyll content and chloroplast ultrastructure. Measured chlorophyll fluorescence spectra for the aurea mutant have higher values of the peak fluorescence ratio F685/F735 ratio of the two fluorescence bands than do the wild type. It is the result of a lower reabsorption effect which affects mainly the shorter-wavelength (685 nm) fluorescence band. The correction for reabsorption removes almost completely the differences between the fluorescence spectra of the two genotypes, confirming the validity of the model. Our work suggests that the evaluation of fluorescence reabsorption must be considered in the widely used methods of vegetation monitoring by chlorophyll fluorescence spectral measurements. It can improve the correlation between fluorescence properties and the physiological state of the plant.