LIGHT EXPOSURE AND THE COMPOSITION OF LIPOPHILOUS CAROTENOIDS IN CYANOBACTERIAL LICHENS

Lipophilous carotenoids together with chlorophyll a were extracted in acetone from 1) a variety of cyanobacterial lichens stemming from habi tats with strongly different light exposure, ranging from the Judean D esert, Israel, to a shaded forest floor in Germany, 2) Peltigera praet extata collected from a deciduous forest in the vicinity of Wurzburg a t bimonthly intervals during an entire year, and 3) Peltigera species which in a short term experiment (five days) had been exposed to alter ed light conditions with respect to those they had grown under. Pigmen t determination by high performance liquid chromatography (HPLC) showe d no clear trend in the concentrations of zeaxanthin (and echinenone) under different incident light intensities. In contrast, canthaxathin contents increased and the concentrations of chlorophyll a and beta-ca rotene decreased with enhanced light exposure of the lichens. This was observed for all three types of investigation and indicates that the ratio of canthaxanthin to beta-carotene in a cyano-bacterial lichen is strongly influenced by the light environment it has recently grown in .