The Influence of Light and Temperature on Isoprene Emission Rates from Live Oak

Abstract

Abstract There is a growing awareness of the role of vegetation as a source of reactive hydrocarbons that may serve as photochemical oxidant precursors. A study was designed to assess independently the influence of variable light and temperature on isoprene emissions from live oak ( Quercus virginiana Mill.). Plants were conditioned in a growth chamber and then transferred to an environmentally controlled gas‐exchange chamber. Samples of the chamber atmosphere were collected; isoprene was concentrated cryogenically and measured by gas chromatography. A logistic function was used to model isoprene emission rates. Under regimes of low temperature (20°C) or darkness, isoprene emissions were lowest. With increasing temperature or light intensity, the rate of isoprene emission increased, reaching maxima at 800 μE m ‐2 s ‐1 and 40–44°C, respectively. Higher temperatures caused a large decrease in emissions. Since the emissions of isoprene were light‐saturated at moderate intensities, temperature appeared to be the main factor controlling emissions during most of the day. Carbon lost through isoprene emissions accounted for 0.1 to 2% of the carbon fixed during photosynthesis depending on light intensity and temperature.