Elevated ozone and carbon dioxide affects the composition of volatile organic compounds emitted by Vicia faba (L.) and visitation by European orchard bee (Osmia cornuta)

Recent studies link increased ozone (O-3) and carbon dioxide (CO2) levels to alteration of plant performance and plant-herbivore interactions, but their interactive effects on plant-pollinator interactions are little understood. Extra floral nectaries (EFNs) are essential organs used by some plants for stimulating defense against herbivory and for the attraction of insect pollinators, e.g., bees. The factors driving the interactions between bees and plants regarding the visitation of bees to EFNs are poorly understood, especially in the face of global change driven by greenhouse gases. Here, we experimentally tested whether elevated levels of O-3 and CO2 individually and interactively alter the emission of Volatile Organic Compound (VOC) profiles in the field bean plant (Vicia faba, L., Fabaceae), EFN nectar production and EFN visitation by the European orchard bee (Osmia cornuta, Latreille, Megachilidae). Our results showed that O-3 alone had significant negative effects on the blends of VOCs emitted while the treatment with elevated CO2 alone did not differ from the control. Furthermore, as with O-3 alone, the mixture of O-3 and CO2 also had a significant difference in the VOCs' profile. O-3 exposure was also linked to reduced nectar volume and had a negative impact on EFN visitation by bees. Increased CO2 level, on the other hand, had a positive impact on bee visits. Our results add to the knowledge of the interactive effects of O-3 and CO2 on plant volatiles emitted by Vicia faba and bee responses. As greenhouse gas levels continue to rise globally, it is important to take these findings into consideration to better prepare for changes in plant-insect interactions.

Automated summary

Recent studies have found that increased ozone (O-3) and carbon dioxide (CO2) levels can affect plant-herbivore interactions. However, the effects of these gases on plant-pollinator interactions are less understood. In this study, we investigated the effects of elevated O-3 and CO2 levels on the emission of Volatile Organic Compounds (VOCs), nectar production, and visitation of a bee species to extra floral nectaries (EFNs) of the field bean plant. Our results showed that O-3 had negative effects on VOC blends, nectar volume, and bee visitation, while CO2 had a positive impact on bee visits. These findings contribute to our understanding of the interactive effects of O-3 and CO2 on plant-insect interactions and highlight the importance of considering these effects in the context of global climate change.