Fig. 3: Individual and combined effects of in situ air pollution exposure on the VOC emissions of Scots pine seedlings exposed to damaged and control emitters.

Filled bars denote herbivory phase: unfilled = phase 1 (pre-herbivory), filled = phase 2 (post-herbivory). a Emission rates (mg m^-2 needle area h⁻¹) of MTs, other VOC groups and the total VOC emission. MT, non-oxygenated monoterpenes; oMT, oxygenated monoterpenes; SQT, sesquiterpenes; GLV, green-leaf volatiles; BZ, benzenoids; ONI, other non-isoprenoids. b Emission rates (mg m^–2 needle area h⁻¹) of other VOC groups, oMTs, SQTs, GLVs, BZs and ONIs. c Bark damage area (DA)-based increase in emissions for MTs together with other VOC groups and total VOCs (mg m^-2 h⁻¹ cm^-2 DA), based on emission factors = emission rates standardized to a temperature of 30 °C and a photosynthetic photon flux density (PPFD) of 1000 μmol m^–2 s⁻¹. d Bark damage area-based increase (mg m^–2 h⁻¹ cm^-2 DA) for other VOC groups. n = 8 for ozone (O3) and diesel exhaust (D) treatments, n = 12 for Ambient and O3 + D treatments. Error bars show standard error of the mean of total emissions.