Rp. Beckett, SOME ASPECTS OF THE WATER RELATIONS OF THE LICHEN PARMOTREMA-TINCTORUM MEASURED USING THERMOCOUPLE PSYCHROMETRY, Lichenologist, 28, 1996, pp. 257-266
The thermocouple psychrometer was used to determine water potential, p
si, and its components in the lichen Parmotrema tinctorum. Data sugges
ted that using conventional pressure-volume curves to study the water
relations of lichens may give anomalous results, possibly because lich
ens may contain appreciable amounts of intercellular water. A way of c
orrecting pressure-volume curves to remove the effect of intercellular
water is discussed. Parmotrema tinctorum had a very low osmotic poten
tial at full turgor (c. - 2.5 MPa), and a low bulk modulus of elastici
ty (c. 2.1 MPa). As a result, P. tinctorum lost turgor only when the r
elative water content dropped below 0.47. Likely benefits of this for
the lichen are discussed. (C) 1996 The British Lichen Society.