ABSTRACT
The bryophytes are involved in many kinds of biological competition (Rice, 1979; 1984), such as bryophyte/bryophyte competition even between the plants of same species (self-incompatibility), bryophytes/ vascular plants, bryophytes /algae and especially due to their ecological similarity, bryophytes/ lichens (During and Van Tooren, 1990). Lichens produce numerous secondary metabolic compounds, among which lichen acids are produced in a large quantity. These can be found in high concentrations (25%) but generally they are 5-10% of thallus dry weight (Lawrey,1995; Gardner and Mueller, 1981). They accumulate as crystals on the external surface of medullary hyphae, hence, available immediately as toxic compounds in biological competition.
