Plant volatiles: useful signals to monitor crop health status in greenhouses

This chapter focuses on the monitoring of crop health status via the measurement of volatile organic compounds (VOCs) emitted from the plants. It includes the most important factors that affect the emission of these VOCs from crops grown in greenhouses. Since both stressors as well as nonstressors have an effect on the emission, they are covered separately. The chapter provides an overview of processes that affect the gas balance of plant VOCs in the greenhouse including the loss processes. These processes are considered as important since they contribute to the time-dynamic concentration profiles of plant-emitted VOCs. In addition, we describe the most popular techniques currently in use to measure volatiles emitted from plants, with emphasis on greenhouse application. Dynamic sampling in combination with gas chromatography coupled to mass spectrometry is considered as the most appropriate method for application at greenhouse scale. It is recommended to evaluate the state of the art in the fields concerned with this method and explore the development of a new instrument based on the specific needs for application in greenhouse practice. However, to apply such an instrument at greenhouse-scale remains a challenge, mainly due to the high costs associated with it.