AbstractSaxifraga cernua, a perennial herb distributed throughout the arctic and subarctic regions, shows high levels of dark respiration. The amount of respiration exhibited by leaves and whole plants at any temperature is influenced by the pretreatment temperature. Plants grown at 10°C typically show higher dark respiration rates than plants grown at 20°C. The levels of alternative-pathway respiration (or cyanide-insensitive respiration) in leaves of S. cernua grown at high and low temperatures were assessed by treating leaf discs with 0.25 mol m−3 salicylhydroxamic acid during measurements of oxygen consumption. Alternative pathway respiration accounted for up to 75% of the total respiration. Tissues from 20°C-grown plants yielded a Q10 of 3.37 for normal respiration, and of 0.97 for alternative-pathway respiration. Tissues from 10°C-grown plants yielded a Q10 of 2.55 for normal respiration, and of 0.79 for alternative-pathway respiration. The alternative pathway does not appear to be as temperature sensitive as the normal cytochrome pathway.
A simple energy model was used to predict the temperature gain expected from these high rates of alternative-pathway respiration. The model shows that less than 0.02°C can be gained by leaves experiencing these high respiration rates.