Abstract
Increasing temperature and atmospheric [CO2] can change plant VOC emissions, thereby providing a possible feedback to climate change by altering particle and greenhouse gas formation. While evidence gathered on isoprene emission generally indicated an inhibitory effect of elevated CO on emission at moderate temperature, it is unclear whether the emissions of other volatiles respond in a similar way. In a greenhouse study, we grew Artemisia annua plants under two [CO2] regimes (400/800 ppm) combined with two temperature regimes (25/15 and 30/20 °C) and determined emissions at two assay [CO2] (400/800 ppm) combined with two assay temperatures (30/37 °C). Foliar VOC concentrations were unaffected by growth conditions and resembled emissions consisting mainly of monoterpenes (>92%) and sesquiterpenes (>7%). Mean emission rates determined at 30 °C and 400 ppm [CO2 ] ranged between 1.2 and 2.5 μg g-1 h-1 (11-26 ng m-2 s-1) with lowest values observed for elevated-[CO2]-grown plants. However, this apparent negative effect of growth [CO2] was compensated by increased plant growth. Irrespective of growth conditions, doubling assay [CO2 ] significantly reduced emissions at 37°C by about 30% and had no effect at 30°C. Emissions always increased on the increase in assay temperature, with monoterpenes responding more strongly than sesquiterpenes (mean %-increase of 17.5 and 12.5 °C-1). Our results suggest that the future evolution of VOC release from A. annua depends mainly on the antagonistic emission responses to temperature and [CO2], while long-term acclimations play a minor role.