Bidirectional exchange of biogenic volatiles with vegetation: emission sources, reactions, breakdown and deposition

<jats:title>Abstract</jats:title><jats:p>Biogenic volatile organic compound (<jats:styled-content style="fixed-case">BVOC</jats:styled-content>) emissions are widely modelled as inputs to atmospheric chemistry simulations. However, <jats:styled-content style="fixed-case">BVOC</jats:styled-content> may interact with cellular structures and neighbouring leaves in a complex manner during volatile diffusion from the sites of release to leaf boundary layer and during turbulent transport to the atmospheric boundary layer. Furthermore, recent observations demonstrate that the <jats:styled-content style="fixed-case">BVOC</jats:styled-content> emissions are bidirectional, and uptake and deposition of <jats:styled-content style="fixed-case">BVOC</jats:styled-content> and their oxidation products are the rule rather than the exception. This review summarizes current knowledge of within‐leaf reactions of synthesized volatiles with reactive oxygen species (<jats:styled-content style="fixed-case">ROS</jats:styled-content>), uptake, deposition and storage of volatiles, and their oxidation products as driven by adsorption on leaf surface and solubilization and enzymatic detoxification inside leaves. The available evidence indicates that because of the reactions with <jats:styled-content style="fixed-case">ROS</jats:styled-content> and enzymatic metabolism, the <jats:styled-content style="fixed-case">BVOC</jats:styled-content> gross production rates are much larger than previously thought. The degree to which volatiles react within leaves and can be potentially taken up by vegetation depends upon compound reactivity, physicochemical characteristics, as well as upon their participation in leaf metabolism. We argue that future models should be based upon the concept of bidirectional <jats:styled-content style="fixed-case">BVOC</jats:styled-content> exchange and consider modification of <jats:styled-content style="fixed-case">BVOC</jats:styled-content> sink/source strengths by within‐leaf metabolism and storage.</jats:p>