The influence of pH and lichen metabolites (vulpinic acid and (+) usnic acid) on the growth of the lichen photobiont Trebouxia irregularis

The quantitative response to two lichen metabolites, vulpinic acid and (+) usnic acid, on biomass production by the photobiont Trebouxia irregularis, isolated from the lichen Cladina mitis, was determined experimentally. The presence of usnic acid resulted in inhibition of photobiont growth, and the effect depended on the pH of the culture medium. The concentration effect of usnic acid was observed. The application of vulpinic acid almost complet ely inhibited the growth of T. irregularis and no significant differences w ere found among samples at different medium pH values. (C) 1998 The British Lichen Society.