Natural levels of saline elements in lichens: Determination of cellular fractions and their importance as saline tracers

Citation
R. Figueira et al., Natural levels of saline elements in lichens: Determination of cellular fractions and their importance as saline tracers, LICHENOLOGI, 31, 1999, pp. 183-196
Citations number
33
Categorie Soggetti
Plant Sciences
Journal title
LICHENOLOGIST
ISSN journal
00242829 → ACNP
Volume
31
Year of publication
1999
Part
2
Pages
183 - 196
Database
ISI
SICI code
0024-2829(199903)31:<183:NLOSEI>2.0.ZU;2-N
Abstract
Using a sequential elution procedure, the cellular location of Cl-, Na+, Mg 2+, K+ and Ca2+ was determined in the lichen Ramalina canariensis from the southwest coast of Portugal. After a dry deposition period, a logarithmic d ecease in the extracellular (surface and wall-bound) concentration of Cl-, Na+ and Mg2+ was observed with increasing distance from the coast. The impo rtance of each cellular fraction as an indication of the airborne salts was identified using factorial analysis methods, as was the relationship betwe en the extracellular and intracellular concentration of the saline elements . The factorial analysis showed that the most important elements for the bi omonitoring of airborne salinity were Cl-, Na+ and Mg2+. However, for the c ations, only the surface and wall-bound (for Na+) fractions seem to be rela ted to sea-salt deposition on the lichens. The intracellular fractions of t hese elements are relatively independent of the surface and wall-bound conc entrations, or reflect some non-linear processes induced by extreme extrace llular concentrations. Although they may represent a significant proportion of the total element concentration, intracellular element concentrations a re of little value in monitoring salt deposition, due to physiological cont rol by the organism. The use of rural analyses, without any fractional diff erentiation, can be a biased method for biomonitoring the accumulation of s alt spray by lichens, because it includes the intracellular fraction, which may be independent of the deposition taking place. The use of the differen t cellular fractions provides a more informative indication of the depositi on of atmospheric elements, while also giving information on any physiologi cal alterations induced by the specific environmental chemical factors, inc luding membrane damage. (C) 1999 The British Lichen Society.