Studies on the Localization and Spectral Characteristics of the Fluorescence Emission of Differently Pigmented Wheat Leaves

Abstract

AbstractIntensity, spectral characteristics and localization of the UV‐laser (337 nm) induced blue‐green and red fluorescence emission of green, etiolated and white primary leaves of wheat seedlings were studied in a combined fluorospectral and fluoromicroscopic investigation. The blue‐green fluorescence of the green leaf was characterized by a maximum near 450 nm (blue region) and a shoulder near 530 nm (green region), whereas the red chlorophyll fluorescence exhibited maxima in the near‐red (F690) and far‐red (F735). The etiolated leaf with some carotenoids and traces of chlorophyll a, in turn, showed a higher intensity of the blue‐green fluorescence with a shoulder in the green region and a strong red fluorescence peak near 684 to 690 nm, the far‐red chlorophyll fluorescence maximum (F735) was, however, absent. The norfluorazone‐treated white leaf, free of chlorophylls and carotenoids, only exhibited blue‐green fluorescence of a very high intensity. In green and etiolated leaves the blue‐green fluorescence primarily derived from the cell walls of the epidermis and the red fluorescence from the chlorophyll a of the mesophyll cells. In white leaves the blue‐green fluorescence emanated from all cell walls of epidermis, mesophyll and leaf vein bundles. The shape and intensity of the blue‐green and red fluorescence emission is determined by the reabsorption properties of chlorophylls and carotenoids in the mesophyll, thus giving rise to quite different values of the various fluorescence ratios F450/F690, F450/F530, F450/F735 and F690/F735 in green and etiolated leaves.