Some Aspects of the Water Relations of Lichens from Habitats of Contrasting Water Status studied using Thermocouple Psychrometry

Thermocouple psychrometry was used to investigate the waterrelations of eight species of lichens from sites of contrastingwater status. Lichens from exposed, dry habitats had lower thallusK concentrations but lower osmotic potentials than plants frommesic sites. As a result, K contributed a much smaller proportionto osmotic potential in plants from dry sites, suggesting thatlow cytoplasmic K concentrations are important for desiccationtolerance. While containing less water at saturation, plantsfrom dry habitats had lower thallus elastic moduli and lowerapoplastic water fractions. They therefore lost turgor at lowerrelative water contents than plants from wetter sites. The significanceof these results for the water relations of lichens is discussed.Copyright1995, 1999 Academic Press Lichen, desiccation, stress, thermocouple psychrometry