The influence of elevated O-3 and CO2 concentrations on secondary metabolites of Scots pine (Pinus sylvestris L.) seedlings

Terpene, resin acid and total phenolic concentrations in five-year-old Scot s pine (Pinus sylvestris L.) seedlings were analysed after exposure to ambi ent and realistically elevated (2 x ambient) O-3 and CO2 concentrations and their combination in open-top chambers during two growing seasons. Under O -3 exposure, limonene concentration in needles and isopimaric concentration in stems decreased significantly. As a response to elevated CO2, alpha -pi nene and total phenolic concentrations in needles increased significantly, while bornyl acetate concentration in needles and palustric +levopimaric an d neoabietic acid concentrations in stems decreased significantly. Some ter penes and resin acids were found at lower concentrations in the combined O- 3 and CO2 treatment than in O-3 exposure or elevated CO2, A negative chambe r effect was found: seedlings growing inside the chambers with ambient air had significantly lower concentrations of some terpenes and resin acids tha n seedlings growing outside the chambers. There was a lot of between-tree v ariation in terpene and resin acid concentrations, which is typical of open -pollinated populations. The results of this study suggest that, at least i n shortterm experiments, Scots pine secondary metabolites are relatively in sensitive to climate change factors. Total phenolics in the needles were th e most responsive group showing about 25% increase in elevated CO2 and O-3 exposure did not mitigate this CO2 effect. Terpenes and resin acids were le ss responsive, although some individual compounds showed notable responses, e.g. alpha -pinene in needles, which increased about 50% in response to el evated CO2. As a consequence, although there were only slight effects on to tal pools of needle secondary metabolites, considerable O-3 and CO2 effects on certain individual compounds might have ecological significance via tro phic amplification, e.g. in decomposing processes of needle litter.