A range of plant species, including crops, shrubs, herbs, and trees, was surveyed to determine the magnitude of isoprene emissions. In studies to determine if plants emitted isoprene, greenhouse-grown plants were encapsulated in impermeable plastic bags and kept in a growth chamber for 2 h at 30C and a photosynthetic photon flux density of ca. 350 micro E m-2s-1. To estimate emission rates, greenhouse-grown plants were conditioned in a growth chamber and transferred to a controlled-environment gas-exchange chamber. Gas samples from either the encapsulation bags or gas-exchange chamber were collected, concentrated cryogenically, and analyzed by gas-liquid chromatography.