Floral Phytochemistry: Impact of Volatile Organic Compounds and Nectar Secondary Metabolites on Pollinator Behavior and Health

Plants produce a plethora of phytochemicals including sugars, amino acids (AAs), volatile organic compounds (VOCs) and secondary metabolites (SMs) with different ecological functions. To attract pollinators and defenders and ensure reproductive success, plants mainly rely on VOCs, while to reward insects, plants synthesize nectar rich in sugars and AAs. Furthermore, plant SMs can play various roles. Some components are able to interact with the nervous system of insects by binding to neuron receptor proteins and thus manipulate pollinator behavior. Others, like alkaloids and phenolics, protect from nectar robbers and enhance memory and foraging efficiency, or, as in the case of flavonoids, exhibit high antioxidant activities supporting pollinator well-being. This review discusses the impact of VOCs and nectar SMs on insect behavior and pollinator health.