Studies on lichen-dominated systems. XVIII. Morphological control of evaporation in lichens

• Published in: Canadian Journal of Botany
• Main Authors: Larson, D. W., Kershaw, K. A.
• Format: Article in Journal/Newspaper
• Language: French
• Published: Canadian Science Publishing 1976
• Subjects: Arctic; Subarctic
• Online Access: http://dx.doi.org/10.1139/b76-220; http://www.nrcresearchpress.com/doi/pdf/10.1139/b76-220

The current belief that lichens are incapable of controlling their water relations is based largely on evidence collected from experiments testing for active metabolic controls only. In this study, controlled wind tunnel experiments designed to test for any passive morphological control of evaporation in four lichen species show that such mechanisms are important to the water relations of the plants and thus suggest that the observed morphological variability in lichens is of great ecological significance.Time-dependent and moisture-content-dependent changes in evaporation rate were examined using samples of lichen thalli from a number of different arctic and subarctic populations of Alectoria ochroleuca (Hoffm.) Massal., Alectoria nitidula (Th.Fr) Vain, Cetraria nivalis (L.) Ach., and Cladina alpestris (L.) Harm. The work has shown that the observed interspecific and intraspecific variability in evaporative resistance found in these plants is influenced by three separate morphological characteristics: variability in surface area to weight ratio; variability in thallus shape; and variability in the degree of clumping of thalli. When other aspects of the ecology and physiology of the test lichens were considered, it became clear that these lichens exhibited a potential to modify their morphological characteristics over long periods of time in such a way that greater photosynthetic productivity was assured.It was concluded that although the control of water relations in lichens is of a different nature from higher plants, the control is present nonetheless.