GRAPHIS ScnIPTA

Influence of air-drying and storage at -15 oC on cellular
distributions of cations in Cladonia portentosa
MARKO HYVANTNPN ANd PETER D. CRITTENDEN
Hyviirinen, M. & Crittenden, P. D. 2000: Influence of air-drying and storage
at - l5 oC on cellular distributions of cations in Cladonia portentosa. Graphis
Scripta I2: 9-l l. Stockholm. ISSN 0901-7593.
The impact of air-drylng and storage frozen on cellular distribution of potassium,
magnesium and calcium in the apices (top 5 mm) of the cushionforming
lichen Cladonia portentosa was investigated. Only small changes in
cellular distributions of cations were detected in lichen specimens stored at -
15 oC for six months compared to freshly collected ones. These results
indicate that large-scale pollution studies, based on changes in cellular distribution,
that tequire storing lichen rnaterial are methodologically feasible
provided that the sample size is kept high enough to counteract potential
moderate increases in variation.
Marko Hlrucirinen, Department of Biolog,t, University of Oulu, P.O. Box
3000, FIN-900 I 4, Oulu, Finland. e-mail: Marko.Hyvarinen@oulu.fi.
Peter D. Crittenden, School of Biological Sciences, University of Nottingham,
University Park, Nottingham NG7 2RD, UK.
The sequential elution technique developed by
Brown and co-workers (e.g. Brown & Wells
1988) has become a widely used laboratory
practice in studies on cellular cation distribution
and kinetics of cation uptake in cryptogams
(reviewed by Nieboer et al. 1978;
Brown & Beckett 1984; Brown 1991). Even
though this method has a great potential in
detecting air pollution induced changes in
cation distribution in lichens (see Hyviirinen
& Crittenden 1996) its applicability in large
scale studies is hindered by the prevailing
understanding that the lichen material should
be either fresh or stored moist for only up to
two weeks to avoid marked redistribution of
cations (e.g. Brown & Avalos 1993).
Materials and methods
In order to determine whether the sequential
elution technique can be applied to air-dried
and short-term frozen stored material two
separate batches of Cladonia portentosa were
collected from a heathland at Stiperstones,
Shrophsire, UK. Both collections, the first one
in early April and the second one in early
October were carried out during periods of
frequent rainfall when lichen cushions were
naturally moistened by rainwater. The first
batch was air-dried in room temperature,
sealed in polythene bags and stored at - 15 "C.
After 6 months this material was defrosted (in
polythene bags) at room temperature, rehydrated
overnight at 4 "C and 100 % relative
humidity (over water in a desiccator), sprayed
twice with deionized water to ensure full saturation
and then subjected, together with the
newly collected batch of lichens, to the
sequential elution procedure of Brown &
Wells (1988) with some modifications. Thallus
apices (top 5 mm, c. 200 mg fresh weight
per each specimen) were submerged for l0
min in 40 ml water (Wl) in order to remove