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  • 1
    Electronic Resource
    Electronic Resource
    Intraspecific variation in photosynthetic responses of trebouxioid lichens with reference to the activity of a carbon-concentrating mechanism (1998)
    Springer
    Oecologia 113 (1998), S. 360-369 
    Details
    ISSN: 1432-1939
    Keywords: Key words Lichen ; Phycobiont ; Photosynthesis ; Carbon-concentrating mechanism ; Carbon isotope discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic responses of a range of trebouxioid lichens were investigated to determine whether variations in net assimilation rates shown by populations of the same species collected from different habitats could be correlated with adjustments in carbon-concentrating mechanism (CCM) activity. The activity of a CCM was inferred from the high affinity for CO2 [i.e. low CO2 compensation point (Γ); low external CO2 concentration at which half-maximal assimilation rates are reached (K 0.5 CO2)], the release of a pool of accumulated dissolved inorganic carbon (Ci) during light/dark transient measurements of CO2 exchange and values for carbon isotope discrimination intermediate between those characteristic of C3 and C4 terrestrial plants. Higher net and gross assimilation rates were expressed by lichens collected from shaded woodland habitats. The higher rates were not accounted for by variations in chlorophyll content. Lichens with high assimilation rates also showed an increased affinity for CO2 as demonstrated by low CO2 compensation points and K 0.5 values and the magnitude of the Ci pool accumulated upon illumination and released after darkening of the thalli. However, there was no correlation between assimilation rates and organic matter or instantaneous carbon isotope discrimination measurements, with the latter remaining roughly consistent whatever the provenance or species of the lichen material. The data are discussed with reference to significant environmental factors which are likely to control photosynthesis in the habitats studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050387
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A pyrenoid-based carbon-concentrating mechanism is present in terrestrial bryophytes of the class Anthocerotae (1996)
    Springer
    Planta 200 (1996), S. 203-212 
    Details
    ISSN: 1432-2048
    Keywords: Anthoceros ; Carbon concentration ; Carbon isotope discrimination ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been widely accepted that carbon assimilation in bryophytes is exclusively based on the conventional C3 photosynthetic pathway. The occurrence of biochemical CO2-concentrating mechanisms (C4 or Crassulacean acid metabolism), which have developed in plants in the last 20–100 million years, has been discounted for bryophytes from studies of the carbon isotope composition (δ13C) of organic material. In contrast cyanobacteria and many algae show active accumulation of dissolved inorganic carbon via biophysical CO2-concentrating mechanisms which are also found in the photobiont partners in certain lichens. The presence of a pyrenoid, a granular particle within the chloroplast, has been linked with CO2-concentrating mechanism activity in green algae and lichens and we now show that such a mechanism is categorically associated with the occurrence of a pyrenoid in bryophytes belonging to the class of Anthocerotae. These observations have significant evolutionary implications for the development of terrestrial photosynthesis during the colonisation of the land, raising the intriguing question of why the pyrenoid-based CO2-concentrating mechanism did not persist in the terrestrial environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00208310
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    Paper (German National Licenses)
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