Rate of acclimation of the capacity for isoprene emission in response to light and temperature

Isoprene emission from plants accounts for nearly half of all non-methane h ydrocarbons entering the atmosphere. Light and temperature regulate the ins tantaneous rate of isoprene emission but there is increasing evidence that they also affect the capacity for isoprene emission (i.e. the rate measured under standard conditions). We tested the rate of acclimation of the capac ity for isoprene emission following step changes in growth conditions. Accl imation to new growth temperatures was very rapid, with most of the change occurring within a few hours and complete adjustment occurring within a day . Acclimation to new light levels was more complicated. Following a switch from low-light growth conditions to standard assay conditions (30 degreesC and 1000 mu mol photons m(-2) s(-1)), there was a rapid (5-10 min) and a sl ightly slower (10-50 min) acclimation of the capacity for isoprene emission . After accounting for these shortterm changes, there was also a small, lon g-term (4-6 d) acclimation of the isoprene emission capacity to the light l evel of growth conditions. We found no effect of growth conditions on the c oefficients used to describe the instantaneous light and temperature respon se of isoprene emission. Therefore, current models of isoprene emission wil l only need to be altered to account for changes in the capacity for isopre ne emission.