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Abstract

An hypothesis is presented that provitamin D (dehydrocholesterol and/or ergosterol) can act as a UV-B receptor in plants and algae. We also propose that the proportions between provitamins D, previtamins D, and vitamins D (D2 and D3), after calibration, can be used to evaluate UV-B exposure of phytoplankton and terrestrial vegetation.Key words: Dehydrocholesterol, Ergosterol, Photoreceptor, Provitamin D, Ultraviolet, UV-B, Vitamin D IntroductionThere is an enormous literature on the medical aspects of vitamin D (see Feldman et al. 1997;Holick 1999). The present contribution presents a possible function of the provitamin/previtamin/vitamin D system in algae, plants and fungi, namely as an ultraviolet-B photoreceptor system. Our discussion is based mostly on literature data published by other workers. We will also discuss some own findings in a general way, while details will be published elsewhere. We shall start by introducing vitamin D and related compounds and their formation in various organisms.