Abstract
Patterns of CO2 exchange in Spanish moss under various experimental conditions were measured using an infrared gas analysis system. Plants were collected from a study site in North Carolina and placed in a gas exchange chamber for several days of continuous measurements. No substantial seasonal effects on CO2 exchange were observed. High rates of nocturnal CO2 uptake were observed under day/night temperature regimes of 25/10, 25/15, 25/20, 30/20, and 35/20 C; however, daytime temperatures of 40 C eliminated nighttime CO2 uptake and a nighttime temperature of 5 C eliminated nocturnal CO2 uptake, regardless of day temperature. Constant chamber conditions also inhibited nocturnal CO2 uptake. Constant high relative humidity (RH) slightly stimulated CO2 uptake while low nighttime RH reduced nocturnal CO2 uptake.
Reductions in daytime irradiance to approximately 25% full sunlight had no effect on CO2 exchange. Continuous darkness resulted in continuous CO2 loss by the plants, but a CO2 exchange pattern similar to normal day/night conditions was observed under constant illumination. High tissue water content inhibited CO2 uptake. Wetting of the tissue at any time of day or night resulted in net CO2 loss. Abrupt increases in temperature or decreases in RH resulted in sharp decreases in net CO2 uptake.
The results indicate that Spanish moss is tolerant of a wide range of temperatures, irradiances, and water contents. They also indicate that high nighttime RH is a prerequisite for high rates of CO2 uptake.
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Selected References
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