Volatile organic compounds (VOC)
play important roles in atmospheric
chemistry, plant ecology, and physiology, and biogenic VOC (BVOC)
emitted by plants is the largest VOC source. Our knowledge about how
environmental drivers (e.g., carbon, light, and temperature) may regulate
BVOC emissions is limited because they are often not controlled. We
combined a greenhouse facility to manipulate atmospheric CO2 ([CO2]) with proton-transfer-reaction mass spectrometry
(PTR-MS) and cavity ring-down spectroscopy to investigate the regulation
of BVOC in Norway spruce. Our results indicate a direct relationship
between [CO2] and methanol and acetone emissions, and their
temperature and light dependencies, possibly related to substrate
availability. The composition of monoterpenes stored in needles remained
constant, but emissions of mono-(linalool) and sesquiterpenes (β-farnesene)
increased at lower [CO2], with the effects being most pronounced
at the highest air temperature. Pulse-labeling suggested an immediate
incorporation of recently assimilated carbon into acetone, mono- and
sesquiterpene emissions even under 50 ppm [CO2]. Our results
provide new perspectives on CO2, temperature and light
effects on BVOC emissions, in particular how they depend on stored
pools and recent photosynthetic products. Future studies using smaller
but more seedlings may allow sufficient replication to examine the
physiological mechanisms behind the BVOC responses.