Leaf-Level Models of Constitutive and Stress-Driven Volatile Organic Compound Emissions

This chapter provides a review of past and contemporary leaf-level emission algorithms that have been and currently are in use for modelling the emissions of biogenic volatile organic compounds (BVOCs) from plants. The chapter starts with a brief overview about historical efforts and elaborates on processes that describe the direct emission responses to environmental factors such as temperature and light. These phenomenological descriptions have been widely and successfully used in emission models at scales ranging from the leaf to the globe. However, while the models provide tractable mathematical functions that link environmental drivers and emission rates, and as such can be easily incorporated in higher scale predictive models, they do not provide the mechanistic context required to describe interactions among drivers and indirect influences on interactions such as those due to acclimation, accumulated stress and ontogeny. Following a discussion of these issues and the limitations they impose on the current state of model-based prognoses of BVOC emissions, we describe in some detail the knowledge gaps that need to be filled in order to move BVOC emission models into forms that are more directly coupled to physiological processes.