FACTORS AFFECTING THE TOXICITY OF SEVERAL LICHEN ACIDS: EFFECT OF PH AND LICHEN ACID CONCENTRATION

摘要: The effect of pH 5-8 and lichen acid concentration gradients (2.7 x 10-3 2.7 1o-6 M) on the toxicity following acids: usnic, lecanoric, evernic, vulpinic, stictic, fumarprotocetraric, psoromic, atranorin, spores Funaria hygrometrica was tested. Percent germination sporeling growth were used as indicators toxicity. None acids significantly toxic, for either percent or at concentrations equal to below 10-5 M 7.0, but many which increased in values different from 7 may have been toxic lower if a assay. Lichen showed good correlation with parameter spore germination, growth, both. Some did not inhibit effective retarding vice versa. This observation is discussed relation changing fatty other lipid composition occurs. Two three O-methylated (evernic psoromic) among most inhibiting over all, these less than non-O-methylated acids. Stictic, also an acid, least inhibitor all both parameters, while vulpinic values. order relative different, depending they are tested measured. Thus, ecological sense, it difficult evaluate adaptive significance particular compound group compounds without knowing what factors influence those how vary organism's habitat. LICHENS produce number chemically diverse secondary products known acids, unique lichenized fungi. These can be found high 25% dry weight thallus more typically 5-10% weight. A single several majority depsides depsidones classes exist (Culberson, 1969). crystallized outer surface medullary hyphae mycobiont thallus. In this position readily available environment, well systematists who wish extract them simple quick manner. Aside their usefulness systematics, postulated natural roles. roles include biochemical weathering rock surfaces, acting sun-screens protect phycobiont 1 Received publication 20 December 1979; revision accepted 8 April 1980. We would like thank Drs. Page W. Morgan Robert S. Egan helpful suggestions during conduction experiments critical reading manuscript. Reprint requests should sent second author. intense radiation, allelopathic agents against plants animals (cf. review by Rundel, 1978). Many studies dealt potential shown retard gram-positive bacteria (Vartia, 1973), pathogenic decay fungi (Henningsson Lundstrom, 1970; Vartia, mycorrhizal-forming (Brown Mikola, 1974). Symbiont non-symbiont algae, vascular plants, retarded (Follmann, 1965; Follmann Villagran, Kinraide Ahmadjian, Huneck Schreiber, 1972; Lawrey, 1977). While assays conducted, differing reports emerged data. Where comparisons attempted, assay changed changed. Recently, Lawrey (1977) suggested that certain (0-methylated), considered evolutionarily advanced, greater hydroxylated counterparts. data bear out such hypothesis (with notable ex-