Seasonal temperature variations influence isoprene emission

Isoprene (2-methyl-1,3-butadiene) emission from plants is highly temperatur e dependent. The influence of long-term variations in growth temperature on isoprene emission rates from bur oak (Quercus macrocarpa) leaves was inves tigated under controlled environmental conditions. Trees were installed in a growth chamber and exposed to a series of daytime temperatures that were varied after a period of 3-6 weeks. Emission capacity (measured at leaf tem perature of 25 degreesC and photosynthetic photon flux density of 900 mu mo l m(-2) s(-1)) doubled when growth temperature was increased from 25 to 30 degreesC. Ten days after the growth temperature was decreased to 20 degrees C, isoprene emission capacity fell to 25 to 50% of its peak value. When gro wth temperature was returned to 30 degreesC, emission capacity doubled with in 5 hours and continued to increase over several days. The observed behavi or can be described by modifying existing algorithms.