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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    An assessment of the relationship between chlorophyll a fluorescence and CO2 gas exchange from field measurements on a moss and lichen (1998)
    Springer
    Planta 206 (1998), S. 611-618 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Bryum (photosynthesis) ; Chlorophyll a fluorescence ; Electron transport ; Lichen (photosynthesis) ; Photosynthesis ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The relationship between CO2 exchange and relative electron-transport rate through photosystem II (ETR, measured using chlorophyll a fluorescence) was determined for a moss and a green algal lichen, photobiont probably Trebouxia sp., in the field in Antarctica. Net photosynthesis (NP) and dark respiration (DR) were measured over temperatures from zero to 25 °C and gross photosynthesis (GP) calculated (GP = NP + DR). The strong response of DR to temperature in these organisms resulted in substantial changes in CO2 exchange rates. The moss Bryum argenteum Hedw. showed a strong, linear relationship between GP and ETR. This was an unexpected result since mosses are C3 plants and, in higher plants, this group normally has a curvilinear GP versus ETR relationship. It is suggested that suppression of DR in the light might be involved. The lichen, Umbilicaria aprina Nyl., had nonlinear relationships between ETR and GP that were different at each measurement temperature. In some cases the lowest ETR was at the higher CO2 exchange rates. It is suggested that these relationships are the result of strong quenching mechanisms that are inversely proportional to GP. The results support a growing impression that the relationships between ETR and CO2 exchange are complex in these organisms and different from those found for higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050439
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  • 3
    Electronic Resource
    Electronic Resource
    Antarctic terrestrial ecosystems: The Vestfold Hills in context (1988)
    Springer
    Hydrobiologia 165 (1988), S. 177-184 
    Details
    ISSN: 1573-5117
    Keywords: Antarctica ; terrestrial ecosystem ; mosses ; lichens ; algae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Antarctic terrestrial ecosystems are briefly described, with emphasis on Signy Island in the maritime antarctic region, and the McMurdo oasis, southern Victoria Land, and Vestfold Hills in the continental antarctic region. As the largest and best known coastal ice-free oasis, the Vestfold Hills contain excellent examples of terrestrial sublithic, epilithic, chasmoendolithic, epiphytic and terricolous algal communities, as well as epilithic, endolithic, and epiphytic lichen communities, and moss communities. Many of the numerous lakes support dense communities of aquatic algae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025586
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  • 4
    Electronic Resource
    Electronic Resource
    Plants and landscape in the Vestfold Hills, Antarctica (1988)
    Springer
    Hydrobiologia 165 (1988), S. 185-196 
    Details
    ISSN: 1573-5117
    Keywords: Antarctica ; algae ; mosses ; lichens ; ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maps are presented showing the recorded distribution and species density of terrestrial plants in the Vestfold Hills. The distribution, biomass and species diversity of terrestrial lithic algae, mosses and lichens is influenced positively by availability of meltwater from drift snow and by additional nutrient supply (probably N and P) near bird nest sites. The terrestrial plants are affected negatively by exposure (including sand blast) and salinity. These four factors are probably the most important environmental characteristics exercising local control over plant distribution and abundance within the limits set by temperature. Large changes in salinity, degree of exposure, water supply and nutrient supply occur across the Vestfold Hills, with the most favourable conditions generally occurring in the eastern half fairly close to the ice sheet. Plant distribution and abundance are also discussed in relation to the length of time that particular areas have been exposed as a result of ice retreat. With increasing time of exposure, plant diversity and abundance rise but subsequently fall sharply as conditions become more arid, saline, or both. This temporal sequence can be explained by considering changes in the important factors that control plant growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025587
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