Mc. Davey et P. Rothery, SEASONAL-VARIATION IN RESPIRATORY AND PHOTOSYNTHETIC PARAMETERS IN 3 MOSSES FROM THE MARITIME ANTARCTIC, Annals of botany, 78(6), 1996, pp. 719-728
Carbon fixation under controlled conditions was measured in three moss
es from the maritime Antarctic using an infra-red gas analysis system.
Gas exchange parameters were determined during each season in 1993 an
d 1994 using the Arrhenius equation and a hyperbolic tangent function
applied to respiration and photosynthesis, respectively. Environmental
data was collected in 1994 for comparison. All seasonal variations we
re greater in Brachythecium than in the species from less hydric habit
ats. Respiration rates were highest in summer and lowest in winter at
all temperatures in Brachythecium, but there was little change in Chor
isodontium or Andreaea. There was some seasonal variation in the initi
al slope (K-p) of the photosynthesis-irradiance curve in all species,
although,the environmental data suggested that this was of little ecol
ogical importance. In all species seasonal changes in the maximum rate
s of photosynthesis (GP(max), NPmax) were observed, generally with a p
attern of summer maxima, although there were some interannual differen
ces. These changes are considered to be the most important in affectin
g the overall annual productivity of the mosses. There were no seasona
l variations in the optimum temperatures for either gross or net photo
synthesis, or for the irradiance at the onset of light saturation (I-k
). The results have important implications for the use of models to es
timate the productivity of the Antarctic flora based upon present or p
redicted climate data. (C) 1996 Annals of Botany Company