Complete Fluorescence Emission Spectra Determined During the Induction Kinetic Using a Diode-Array Detector

Abstract

By using a diode-array detector it has become possible for the first time to measure with one leaf sample complete fluorescence emission spectra during the fast rise and the slow decline of the Kautsky induction kinetic. Thus fast spectral changes in the millisecond range can be detected. Changes in pigment-protein complexes during the first seconds of illumination of an etiolated leaf can be measured at room temperature. During the Kautsky induction kinetic of photosynthetically active green leaves, the maxima of the emission spectrum does not change. However, compared to the long wavelength signal at the maximum at about 735 nm, the short wavelength signal at the maximum at about 690 nm in general increases faster during the fast rise and decreases faster during the slow decline. This is demonstrated for greening and fully green maize leaves. The spectral changes can be expressed by the ratio between the fluorescence signals at the two emission maxima (F690/F735) calculated from the stored spectra taken during the fast rise and the slow decrease of the induction kinetic. The general validity of this ratio change during the Kautsky kinetic is demonstrated for leaves of a variety of different plant species each with a high and a low chlorophyll content.