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  • 1
    Electronic Resource
    Electronic Resource
    Photoinhibition in the Antarctic moss Grimmia antarctici Card when exposed to cycles of freezing and thawing (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Freezing and thawing of the endemic moss species Grimmia antarctici Card, caused photoinhibition. When snow cover was removed from moss in the field, resulting in exposure to fluctuating temperatures and light conditions, photoinhibition, measured as a reduction in the ratio of variable to maximum chlorophyll a fluorescence (Fv/Fm), was observed. The extent of photoinhibition was highly variable and appeared to be reversible during periods of warmer temperatures. A series of controlled laboratory studies found that the light conditions that prevail between freezing and thawing events influenced the recovery from photoinhibition observed during freezing and thawing, with low light conditions facilitating the greatest rates of recovery. After four cycles of freezing and thawing, recovery from photoinhibition in hydrated moss was achieved within 12 h of transfer to 5°C and 15 μmol quanta m−2 s−1. These results favour the hypothesis that photoinhibition observed during freezing represents a protective process involving the down-regulation of photo-system II when photosynthetic carbon assimilation is limited by low temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00200.x
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  • 2
    Electronic Resource
    Electronic Resource
    Field photosynthetic activity of lichens in the Windmill Islands oasis, Wilkes Land, continental Antarctica (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 90 (1994), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to ascertain whether the major species of continental antarctic macrolichens are photosynthetically active during summer conditions, the chlorophyll fluorescence of three lichen species [Umbilicarin decussata (Vill. Zahlbr., Pseudephebe minuscula (Ny-l. ex Arnold) Brodo and Hawksw. and Usnea sphacetala R. Br.] was monitored in the vicinity of Casey Station. Wilkes Land, continental Antarctica using a PAM-2000 modulated fluorescence system. Lichens were studied when in equilibrium with the atmosphere as well as when moistened by snow showers. Photochemical quantum yield was estimated as ΔF/F′m and related to thallus water content as well as microclimatic conditions. 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 efficiency occurred when thalli were at intermediate water contents. 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 which is related to its observed distribution patterns. Umbilicaria decussata studied in the laboratory did not become photosynthetically active even when exposed to 95% relative humidity (RH) for 51 h and. when dehydrating after artificial wetting, showed an optimum thallus water content for photosynthesis of ca 90% dry weight and a thallus water compensation point of about 35% dry weighl. In the field U. decussata did not become pholosynthetically active except when moistened by snow. Usnea sphacelata exposed to the atmosphere had low thallus water contents (ca 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 i.s important when modelling carbon gain and growth rates of continental antarctic lichens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1994.tb08816.x
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  • 3
    Electronic Resource
    Electronic Resource
    The accumulation of proline in Prasiola crispa during winter in Antarctica (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Samples of Prasiola crispa were collected in Antarctica throughout a 13-month period and analysed for free amino acids by HPLC. There was a marked increase in the levels of proline with the onset of winter, concurrent with a decrease in the other predominant amino acids. In January, proline constituted 1.2 ± 0.1 μ mol (g dry weight)−1. whereas by mid-April it was the major component at 28.4 ± 2.9 μ mol (g dry weight)−1. When winter samples were thawed in a growth cabinet, their proline content declined to 4.3 ± 0.5 μ mol (g dry weight)−1 after 7 days. Measurements of photosynthetic quantum yield indicated that winter samples of P. crispa also recovered photosynthetic activity upon thawing. Amino acids and other solutes are involved in the preservation of photosynthetic activities during freezing and it seems probable that proline is involved in cryoprotection in this species. In summer samples, there was no evidence that proline levels in P. crispa increased with the conductivity of the water in which they were found growing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00779.x
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  • 4
    Electronic Resource
    Electronic Resource
    Filamentous fungi of the Windmill Islands, continental Antarctica. Effect of water content in moss turves on fungal diversity (1999)
    Springer
    Polar biology 22 (1999), S. 389-394 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study presents the effect of water content in moss turves from the Windmill Islands, Wilkes Land, continental Antarctica on the composition of associated filamentous fungi. The two most prevalent mosses were sampled: Grimmia antarctici and Bryum pseudotriquetrum. Results were expressed as dry weights. No relationship was found between water content of the mosses or the surrounding soil and fungal diversity. Ten species of fungi were recovered and all species belong to cosmopolitan taxa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050434
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  • 5
    Electronic Resource
    Electronic Resource
    Terrestrial vegetation at Canada Glacier, Southern Victoria Land, Antarctica (1992)
    Springer
    Polar biology 12 (1992), S. 397-404 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Bryophyte flushes in the vicinity of Canada Glacier in S.S.S.I. No. 12, Taylor Valley, Southern Victoria Land, were investigated in order to describe the vegetation present and to investigate factors affecting vegetation distribution. Biomass values from 950 to 1,250 g m−2 (dry weight) and vegetated areas up to 14,450 m2 indicate this is a significant area of bryophyte growth in Southern Victoria Land. The pattern of plant species in relation to water flow was investigated through detailed mapping. This is the first confirmed identification of Bryum argenteum, and Pottia heimii, and the first report of Bryum pseudotriquetrum from this area. Tissue nitrogen values for plants at this site are lower than other reported data, but it seems unlikely this would be a limiting factor for growth. It is concluded that, in this area, summer water flow in conjunction with microtopography has the greatest influence in determining where mosses, cyanobacteria and algae grow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243110
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  • 6
    Electronic Resource
    Electronic Resource
    Invertebrates associated with moss communities at Canada Glacier, southern Victoria Land, Antarctica (1993)
    Springer
    Polar biology 13 (1993), S. 157-162 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The invertebrate faunal composition of moss-dominated flushes near the Canada Glacier was, as in similar habitats in continental Antarctic regions, numerically dominated by protozoa, rotifers, nematodes and tardigrades. Mites were of lesser abundance. Although collembola occur in the Taylor Valley, none were found at the study site. The finding of a catenulid flatworm is significant as microturbellarians have only rarely been recorded from Antarctica. Nematode, tardigrade and rotifer densities recorded were comparable to those in other Antarctic regions. These groups were found at a mean depth ranging from 5 to 10.83 mm in the moss. A greater percentage of all groups were in the upper 5 mm of moss cores in post-melt samples than in pre-melt samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238925
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  • 7
    Electronic Resource
    Electronic Resource
    Small-scale field mapping of lichen distribution in three dimensions with a computer-based position-tracking system (1999)
    Springer
    Oecologia 119 (1999), S. 552-556 
    Details
    ISSN: 1432-1939
    Keywords: Key words Electromagnetic Tracker ; Three-dimensional mapping ; Species composition ; Species distribution ; Topography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A trial was undertaken with an electromagnetic position-tracking (Tracker) system by mapping a small section of a lichen habitat near Cape Royds, Ross Island, Antarctica. This method facilitated the simultaneous collection of precise information about both the topography of the site and the distribution of lichen species. These data were used to produce accurate maps and three-dimensional reconstructions of the mapped area. The technique offers considerable savings in time over conventional methods used in plant and lichen surveys, and has potential to enhance the information collected from broader-scale transect surveys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050818
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  • 8
    Electronic Resource
    Electronic Resource
    Chlorophyll a fluorescence and CO2 exchange of Umbilicaria aprina under extreme light stress in the cold (1998)
    Springer
    Oecologia 113 (1998), S. 325-331 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsUmbilicaria aprina ; CO2 exchange ; Chlorophyll a fluorescence ; Low temperatures ; Photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A lichen growing in a continental Antarctic region with low temperatures and strong irradiance in summer was investigated for evidence of photoinhibition. Field experiments with Umbilicaria aprina from a sheltered site with heavy snowpack showed no effects of photoinhibition when the lichen was exposed to strong sun irradiance for nearly 11 h a day. This was evident from CO2 exchange and simultaneous chlorophyll a fluorescence measurements. CO2 exchange was also not affected if quartz glass allowing greater UV penetration, was used as a lid for the cuvette. The dependency of net photosynthesis on photosynthetic photon flux density suggests that the lichen is photophilous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050383
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  • 9
    Electronic Resource
    Electronic Resource
    Monitoring photosynthetic activity of crustose lichens using a PAM-2000 fluorescence system (1992)
    Springer
    Oecologia 92 (1992), S. 457-462 
    Details
    ISSN: 1432-1939
    Keywords: Antarctica ; Buellia frigida ; Fluorescence yield ; Net photosynthesis ; Water content
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary CO2 exchange and fluorescence yield of the crustose lichen Buellia frigida were measured in situ by means of a CO2 porometer and a PAM-2000, a newly developed portable fluorescence system. The pulse amplitude modulation system of the PAM-2000 allows measurements in the field under ambient light, temperature and moisture conditions without dark adaptation of the sample. CO2 exchange and fluorescence measurements were well correlated when measured under natural conditions in continental Antarctica during a drying cycle of melt-water-soaked lichen thalli. It was shown that the fluorescence parameter ΔF/Fm′ is a measure of the photosynthetic activity of the lichen. It proved possible, using the PAM-2000, to differentiate the physiological performance of the thallus centre and the marginal lobes. The distribution of water in the thallus during a drying cycle was shown to be inhomogeneous. The photosynthetic rates of B. frigida calculated on an area basis are comparatively high and indicate that this lichen is well adapted to its habitat conditions in this part of continental Antarctica.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317836
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  • 10
    Electronic Resource
    Electronic Resource
    The broad-scale distribution of microfungi in the Windmill Islands region, continental Antarctica (1998)
    Springer
    Polar biology 19 (1998), S. 92-100 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microfungi were isolated from soils, mosses, algae and lichens in the Windmill Islands region of Antarctica. From a total of 1,228 isolates, 22 genera were identified. The most frequently isolated fungi from mosses were Mycelia sterilia (47% of total isolates), Phoma spp. (18%), Penicillium spp. (11%), Chrysosporium spp. (7%) and Thelebolus microsporus (6%). Mycelia sterilia, Penicillium spp., Mortierella spp., Chrysosporium cf. pannorum and Thelebolus microsporus were also frequently isolated from algae. Fungal distribution and diversity were poor in samples of lichens, compared to samples from mosses and algae. The frequency of occurrence of microfungi was most often associated with strong biotic influence. There was a marked increase in fungal diversity in human-disturbed sites. Twelve taxa were restricted to soils from near the Australian Casey Station, suggesting significant introduction of fungi into this environment by human activities. Away from the station, fungal distribution appeared to be related to substrata and nutrient status rather than dispersal opportunities. Suggestions for future research and the need for constant monitoring to clarify the role of human disturbance on Antarctic fungi are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050219
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