Fluorescence emission spectra of desiccation-tolerant cryptogamic plants during a rehydration - desiccation cycle

UV-A induced fluorescence emission spectra of three desiccation-tolerant cryptogamic plant species were measured in the dry states, during rehydration and a subsequent dehydration period of 4 h. These cryptogamic species showed the blue-green fluorescence and the red chlorophyll fluorescence as had been described for higher plants. Moss leaves (Tortula ruralis), lacking an epidermis, exhibited only a weak blue-green fluorescence, whereas the thallus of the lichens Cladonia convoluta and Cladonia furcata showed a stronger blue-green fluorescence. The chlorophyll fluorescence ratio red/far-red (F-690/F-735) decreased when drying out, whereas the blue-green fluorescence and the fluorescence ratios blue/red (F-440/F-690) and blue/ far-red (F-440/F-735) increased by an order of magnitude. Ir is assumed that these changes are nor caused by a new formation and breakdown of blue-green fluorescing plant phenolics, but by altered optical properties of the leaves and thalli during desiccation.