Isoprene and monoterpene emission rate variability: model evaluations and sensitivity analyses

The temperature dependence of monoterpene emission varies among monoterpenes, plant species, and other factors, but a simple exponential relationship between emission rate (E) and leaf temperature (T), E = E_s [exp (β(T - T_s))], provides a good approximation. A review of reported measurements suggests a best estimate of β = 0.09 K^-1 for all plants and monoterpenes. Isoprene emissions increase with photosynthetically active radiation up to a saturation point at 700-900 μmol m^-2 s^-1. An exponential increase in isoprene emission is observed at leaf temperatures of less than 30°C. Emissions continue to increase with higher temperatures until a maximum emission rate is reached at about 40°C, after which emissions rapidly decline. This temperature dependence can be described by an enzyme activation equation that includes denaturation at high temperature. -from Authors