Rates of Photosynthesis and Respiration of the Moss Bryum Sandbergii as Influenced by Light Intensity and Temperature

Using differential respirometry and air enriched to 3% CO 2 (v/v), the rates of photosynthesis and dark respiration of the moss Bryum sandbergii were measured as influenced by temperature and light intensity. The optimal temperature for net (apparent) photosynthesis was between 24 to 30 C; however, the photosynthesis/respiration ratio was about 11 to 27 between 4 to 24 C and dropped to lower values at 34 C., which indicates a wide temperature tolerance for this moss in short‐term experiments. The maximum temperature for photosynthesis was about 41 C and the minimum was below –5 C. At 20 C light saturation was approached at 6.2 mw cm –2 (ca. 700 ft‐c) but not completely reached at 12 mw cm ‐2 ; the light compensation point was estimated to be 0.4 mw cm ‐2 (ca. 40 ft‐c). At 4 C light saturation and the compensation point were at lower levels and apparently solarization occurred at 12 mw cm ‐2 . Light intensity had little or no apparent effect on dark respiration. However, respiration increased with temperature over various ranges extending from –5 to 39 C with temperature quotients of about 2.5 to 1.2. The significance of these characteristics is discussed with respect to the ecological relationships of the species.