Lichen biology

Mark Hovenden mark_hov at antdiv.gov.au
Tue Aug 3 21:59:01 EST 1993


Following in the vane of these...

>In article <1993Jul23.022139.20420 at cujo.curtin.edu.au>, Stanley George Kailis <NKAILISS at cc.curtin.edu.au> says:
>>
>>Research findings on growth of lichens (fungi, algae, cyanobacteria) in
>>space ( Space like conditions). Is anyone conducting research of this
>>type.
>>
>>Stanley G Kailis, Curtin University, Box U1987 GPO Perth, Australia. Fax
>>+619 3512109.
>
>I work with Dr. Elfie Stocker of the Institut of Plant Physiology of Salzburg (Austria) about lichen.
>I study species of genera Cladonia in culture. I am interesting to know what you do.
>
>Zorer Roberto, Institut of Plant Physiology, Hellbrunnerstrasse 34, A-5020 SALZBURG Austria
>e-mail: zorer at dsb835.edvz.sbg.ac.at   or   zorer at cribi1.bio.unipd.it

I am working for the Australian Antarctic Division as a Plant
Ecophysiologist and have spent much of the last few years in
Antarctica.

The research I have been doing concerns the major macrolichen species
in the Windmill Islands region of Antarctica.  The three major
aspects of my research involve aspects of lichen microdistribution
with photosynthesis - hydration - light relations and, separately,
lichen microdistribution and nutrient relations, as well as seasonal
changes in lichen nutrient relations and nutrient requirements.

Is there anybody else on this net involved in this type of research
or anything even vaguely familiar.  Dave Thomas I know is working on
some bizarre space-like things and S.G. Kailas seems to be interested
in them.  Much of my work, and that of my cohorts, is involved in the
effects of year-round low temperatures on the growth and survival of
lichens.  I have added two abstracts of papers which I will be
presenting at a conference in Perth, Western Australia, in late
September.  Perhaps you'll be there Stanley George Kailas?

I would like to correspond with any others *interested* in this work
even if you're not actually *working* in this field.

All the best,

Mark

Field photosynthetic activity of lichens in the Windmill Islands
oasis, Wilkes Land,  continental Antarctica

M.J Hovenden, A.E. Jackson and R.D. Seppelt.
Australian Antarctic Division, Channel Hwy, Kingston, TAS 7050

The chlorophyll fluorescence of three lichen species [Umbilicaria
decussata  (Vill.) Zahlbr., Pseudephebe minuscula  (Nyl. ex Arnold)
Brodo & Hawksw. and Usnea sphacelata R.Br.] was monitored in the
vicinity of Casey Station, Wilkes Land, continental Antarctica using
a PAM-2000 modulated fluorescence system.  Photochemical quantum
yield, thallus water content and microclimatic variables were studied
when lichens were in equilibrium with the atmosphere as well as when
moistened by snow showers.  Lichens were photosynthetically active
only when moistened by snow fall or by run-off from snow melt.  The
levels of photosynthetic activity in the field for all species were
influenced by microenvironmental conditions and patterns in response
were site and species specific.  Highest levels of photosynthetic
activity occurred in the evening after snowfall when thalli were
moist and exposed to moderate light levels and near-zero
temperatures.  Photosynthetic activity was reduced by cold as well as
warm, bright conditions.  Highest thallus water contents occurred
during the middle of the day after substantial falls of snow.  P.
minuscula maintained highest thallus water contents at all sites and
appears to have a high water compensation point.  Umbilicaria
decussata studied in the laboratory did not become photosynthetically
active even when exposed to a humid atmosphere for 51 hours and, when
dehydrating after artificial wetting, showed an optimum thallus water
content for photosynthesis of c. 90% dry weight and a thallus water
compensation point of about 35% dry weight.  In the field U.
decussata did not become active except when moistened by snow.  Usnea
sphacelata exposed to the atmosphere had a low thallus water content
(c. 30%) which was not related to RH.  The results indicate that the
lichens are photosynthetically inactive for most of the summer period
and are totally reliant on snow as a water supply.  This is important
when modelling carbon gain and growth rates of continental Antarctic
lichens.


Effects of a rapid unseasonal rewetting episode on mineral location
in antarctic lichens.

Rodney.D. Seppelt and Mark J. Hovenden
Australian Antarctic Division, Channel Hwy, Kingston TAS 7050
Australia

Throughout the midwinter months the vegetation of the Windmill
Islands region of continental Antarctica is exposed to extremely low
ambient temperatures, almost total darkness and low relative humidity
and free water is scarce.  On 16 June 1992 an unusual weather pattern
caused ambient temperatures to climb above zero and to remain so for
some 60 hours melting nearly all of the accumulated snow.  Toward the
end of 18 June heavy rainfall occurred.  The subsequent low
temperatures caused the large amount of free water to freeze.  The
local vegetation was therefore frozen when saturated, a highly
unusual event, and many lichens were totally encased in ice, being
completely inundated at the time of freezing.  It may be expected
that such conditions would stress the lichens and probably result in
cell membrane damage.

Samples from the two dominant species of macrolichens in the area
[Usnea sphacelata R.Br. andUmbilicaria decussata (Vill.) Zahlbr.]
were collected from three sites on a hill on Clark Peninsula in the
Windmill Islands region of continental Antarctica before and after
the rewetting event.  A sequential elution procedure using deionised
water followed by 20mM NiCl and finally acid digestion of lichen
tissues was used to assess membrane integrity by studying the
location of Na, K, Mg and Ca.

The results show that there was no significant change in the level of
Na, K, Ca or Mg from before to after the rewetting event in either
species at any site.  The rewetting and freezing of lichen thalli in
the middle of winter had no effect on membrane integrity and did not
change the distribution or total content of any of the mineral
elements analysed.



Mark J. Hovenden        	       	    	Ph:     	002 323441
Land Based Biology      	       	     FAX:    	002 323351
Australian Antarctic Division   	     mark_hov at antdiv.gov.au
Channel Hwy Kingston TAS 7050
Australia









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