Mc. Davey et P. Rothery, INTERSPECIFIC VARIATION IN RESPIRATORY AND PHOTOSYNTHETIC PARAMETERS IN ANTARCTIC BRYOPHYTES, New phytologist, 137(2), 1997, pp. 231-240
Rates of carbon flux in 14 species of Antarctic bryophytes were measur
ed under controlled conditions using an infra-red gas analysis system.
The results were used to produce estimates of model parameters for re
spiration and photosynthesis. The relationships between respiration; p
hotosynthesis, irradiance and temperature followed standard patterns.
Temperature optima for gross and net photosynthesis were 10-20 and 0-2
0 degrees C respectively, suggesting that the plants were not truly ps
ychrophilic. Photosynthesis was saturated at 30-270 mu mol m(-2) s(-1)
, consistent with the view that bryophytes are, physiologically, shade
plants, although there was no evidence of photoinhibition over the ra
nge of irradiances tested (up to 700 mu mol m(-2) s(-1)). Comparison o
f the results with environmental data suggests that photosynthesis is
usually temperature-limited during daylight in the growing season. The
refore, any change in the temperature of the habitat could affect the
productivity of the bryophytes. Rates of photosynthesis varied widely
between species, and these relationships were largely maintained over
the range of temperatures and irradiances tested. Photosynthetic ranki
ngs were correlated with the water availability in the plant habitats,
supporting the hypothesis that water is the important factor in deter
mining the distribution of populations in Antarctic habitats.