Abstract
Rates of net photosynthesis and respiration were determined for Pithophora oedogonia (Mont.) Wittr. acclimatized to 56 combinations of light (7–1200 μE m −2 s −1) and temperature (5–35°C). Conditions for maximum net photosynthesis were estimated to be 26°C and 970 μE m −2 s −1. The rate of net photosyntheses varied considerably with temperature, with the maximum measured value (9.67 mg O 2 h −1 g dry wt. −1) occurring at 25°C. Respiration rate increased with temperature and the light received just prior to measurement. The maximum respiration rate (7.05 mg O 2 g −1 h −1) occurred at 30°C and 1200 μE m −2 s −1. Exposure of Pithophora to light levels of 600 or 1200 μE m −2 s −1 prior to determination of the respiration rate resulted in significantly elevated levels of oxygen consumption at temperatures ≥ 15°C. The relationship between light, temperature and photosynthesis and respiration were summarized as three-dimensional response surfaces.
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