Screening of urease production and secretion by seven species of finnish lichens

Abstract

Several lichen species secrete enzymes when they are incubated under appropriate laboratory conditions. Enzyme secretion has sometimes been interpreted as a part of the ecophysiological relationships between lichens and their substrate. This hypothesis has been tested for both urease production and secretion by seven Arctic lichens. Those which grow on organic soils ( Cetraria nivalis and Stereocaulon paschale) as well as those that behave as epiphytes ( Nephroma arcticum and Peltigera aphthosa) secrete urease to a urea-containing medium. In contrast, Cladonia rangifera, growing on decayed wood, does not secrete this enzyme. Exceptionally, Cladonia stellaris, a terricolous species growing on a mineralized soil, secretes more urease activity than that retained in the thallus. A hypothesis concerning urease regulation is discussed.