Chlorophyll Fluorescence Signatures of Leaves during the Autumnal Chlorophyll Breakdown

Abstract

Summary The change of the in situ chlorophyll fluorescence spectra, the fluorescence induction kinetics (Kautsky effect: slow component) and the content of photosynthetic pigments were determined in green and yellowish-green leaves of wild vine ( Parthenocissus tricuspidata Veitchii ) during the autumnal senescence. Lower values for the ratio chlorophylls/carotenoids indicate a faster breakdown of chlorophylls than carotenoids. The intensity of the chlorophyll fluorescence of leaves rises with the decline of photosynthesis during increasing senescence and chlorophyll breakdown. The fluorescence intensity decreases again only in yellow leaves at a progressed stage of chlorophyll breakdown. The beginning decline of photosynthesis is visible in the variable fluorescence induction kinetics by a very low fluorescence decrease (fd) from the maximum (fmax) before changes in the pigment content are detectable. This is indicated by very low values of the fluorescence ratio Rfd. The chlorophyll fluorescence emission spectra of green Parthenocissus leaves exhibit two maxima near 690 and 735 nm. During the autumnal senescence the ratio of fluorescence at these wavelengths (ratio F 690/F 735) increases from values of ca. 1 to 8. The possibility of remote sensing of the decline of broadleaf vegetation via the changing chlorophyll fluorescence ratio F 690/F 735 is discussed.