Between-plant interactions in Scots pine are not impaired by air pollutants

Herbivore-induced plant volatiles (HIPVs), consisting of volatile organic compounds (VOC), can induce and prime defence-related responses in neighbouring plants. However, atmospheric pollutants such as tropospheric ozone (O3) and nitrogen oxides (NOX) can disrupt these interactions by accelerating VOC oxidation and inducing oxidative stress. Here, we investigated the effects of O 3 and diesel exhaust pollution on interactions between Scots pine (Pinus sylvestris) seedlings by examining the responses of undamaged receiver plants to cues from weevil-damaged neighbours. Using a novel Free-Air Diesel and Ozone Enrichment (FADOE) platform, we exposed seedlings to elevated O3, diesel exhaust (NOX), both in combination, and ambient air. Receiver seedlings exhibited a 49% reduction in bark damage, a 15% increase in net photosynthesis, and priming of green leaf volatile emissions compared to controls and altered blend of emitted VOCs. Despite air pollution affecting photosynthesis, stomatal conductance and VOC emissions, neighbour-induced defences against herbivory remained effective under polluted conditions.