The UV-light (337 nm) induced complete fluorescence-emission spectra of sun and shade leaves of the beech were measured between 400 to 800 nm and during the autumnal chlorophyll breakdown. The fluorescence-emission spectra are characterized by maxima in the blue region at 450 nm (blue fluorescence BF), near 530 nm (green fluorescence GF) and the two red chlorophyll fluorescence maxima near 690 and 735 nm. Lower leaf sides exhibit a higher BF, GF and red chlorophyll fluorescence (RF) emission than the upper leaf sides. The differences and changes in the fluorescence ratios BF/GF and BF/RF as well as in the chlorophyll fluorescence ratio F690/F735 between sun and shade leaves and during autumnal chlorophyll breakdown are presented. It is assumed that BF and GF emission emanate from at least two different blue-green-fluorescing substances and sites in the leaf. The possible nature of blue fluorescence-emitting plant substances is discussed.
