Resolution of Net Dark Fixation of Carbon Dioxide into Its Respiration and Gross Fixation Components in Bryophyllum daigremontianum

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Abstract
Dark respiration rate increased with temperature between 10 and 24°C (Q10 =2.3–2.7). The rate of gross dark CO2 fixation (GDF) was affected by temperature, but irregularly. Cumulative GDF was not affected by temperature in this range. Cumulative respiration increased from 17 per cent of cumulative GDF at 10°C, to 72 per cent at 24°C and was thus responsible for the 65 per cent drop in net dark fixation between these two temperatures. and respiration rates were functions of the light intensity in the preceding light period. The function for cumulativeGDF was of the saturation form, maximum accumulation being obtained at 12 mW cm−2. It is concluded that both GDF and respiration rates depend on levels of substrates formed during the light period. However, the rate of GDF did not appear to be directly related to the rate of respiration.