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Annals of Botany 73: 493-500, 1994
© 1994 Annals of Botany Company
Texture and Hygroscopic Features of the Upper Surface of the Thallus in the Lichen Family Umbilicariaceae
Centro de Ciencias Medioambientales, CSIC, Serrano 115 dup, 28006 Madrid, Spain
The texture of the upper surface of the thallus and its relationship to certain aspects of water relations were studied in 20 lichen taxa of the family Umbilicariaceae. The anatomy and thickness of the upper cortex were studied by light microscopy of transverse sections and the texture of the upper surface of the thallus was observed by scanning electron microscopy. The hygroscopic features of the upper surface of the thallus were measured with 20 µl drops of a water-soluble ink. Both the maximum surface area covered by the absorbed drop and the time elapsed until its complete absorption were recorded. The degree of wettability was closely related to surface texture but not to cortical thickness. The lichens which possessed the most hygroscopic upper surface (in some cases more so than the filter paper) were those species which usually obtain water as vapour from the air, whereas those species dependent on the substrate for their water had a relatively impermeable upper surface.Copyright 1994, 1999 Academic Press
Umbilicariaceae, upper surface texture, hygroscopic features, water relations