Elevated O3 threatens biological communications mediated by plant volatiles: A review focusing on the urban environment

Plant volatiles, particularly biogenic volatile organic compounds (BVOCs), emitted in urban areas have attracted attention as olfactory signals between plants and other organisms, including insects. However, in urban areas, elevated ozone (O3) levels inhibit plant growth and degrade olfactory signals, including both insect pheromones and BVOCs, resulting in disrupted biological communication. In this article, we review recent findings on how O3 modifies olfactory interactions, focusing on both the emitters and receivers of these signals. The influence of O3 on herbivorous insects and their enemies alters the pressure caused by herbivorous damage in the field, which can affect the development of the defensive capacities of plants at the hereditary level. To address the challenges posed by O3 in biological interactions, BVOC characteristics (e.g., emission rate and species, blend composition, O3 reactivity, and oxidative products) and O3 effects on insects (e.g., preference and antennal detectivity) should be clarified. At the same time, BVOC emissions are expected to increase with rising temperatures, which will likely increase the impact of BVOCs on O3 formation in the future. Therefore, it is necessary to devise strategies, such as selecting non- or low BVOC emitters, to regulate BVOC emissions from urban greening plants and mitigate O3 risks to olfactory interactions and plant health.