Tetrazolium reduction as an indicator of environmental stress in lichens and isolated bionts

A rapid and inexpensive quantitative method was developed for evaluating the physiological condition of intact lichens and cultured symbionts. Formation of the colored product triphenyl formazan (TPF), which is produced after reduction of triphenyltetrazolium chloride (TTC), was used as an indication of dehydrogenase activity. Low pH, exposure to copper, supplemental UV and temperature extremes significantly reduced the capacity of cultured lichens and bionts to produce formazan, suggesting each of these treatments may produce physiological damage. It is projected that this method may also be suitable for monitoring impact of various environmental stresses on field-collected lichens.