What are root VOCs?
We are all very familiar with Volatile Organic Compounds (VOCs). In fact, we all meet them on a day-to-day basis when we perceive a (not so) pleasant smell in our environment: when we mow the lawn of our garden, when we walk in a forest or sit in a grassland, and even when we cook.
To be a VOC, a molecule needs to have two characteristics: it has to be organic and have a high volatility at ambient temperature. This broad definition includes many compounds from a wide variety of chemical families including terpenes, fatty acid derivatives, and isothiocyanates for instance.
How can we analyse root VOCs?
To be able to play a role in belowground biotic interactions, VOCs must reach a concentration high enough to induce a physiological response in a recipient organism (e.g., a plant neighbour). Therefore, the environmental fate of VOCs in the soil environment after their release from plant roots is of great importance.
Depending on their physico-chemical properties, VOCs can interact with the solid, liquid, or gaseous components of the soil system in many different ways, and the strength of these interactions will affect the distance over which root-emitted VOCs can travel. For instance, VOCs can be adsorbed into soil particle surfaces, used as a carbon source by microorganisms, solubilized into the soil solution, or diluted in the soil gaseous phase.
If one wishes to investigate the implication of root volatiles in interplant signalling, being able to identify VOCs emitted by plant roots and quantify their actual emission rate in the soil environment requires the development of experimental devices and analytical methods allowing the sampling and analysis of VOCs emitted by unexcavated/undamaged root systems. This was one of the very first steps of my PhD!