Dynamics of belowground volatile diffusion and degradation

Abstract

Above ground herbivory can induce release of plant volatiles that attract natural enemies of the herbivores. Similarly, roots can release herbivore induced volatiles that attract beneficial organisms such as entomopathogenic nematodes belowground. Unlike their aboveground counterparts, belowground volatile signals interact with solids, liquids, and gases as they move through soil pore spaces. These interactions influence belowground signaling, can create non-linear diffusion profiles, and result in surface adsorbtion and degradation of volatiles in space and time. By examining diffusion and degradation in sand-filled microcosms, we found that the diffusion profiles of E-β-caryophyllene, d-limonene, pregeijerene, α-pinene, germacrene-d, and linalool were affected by moisture and pH. Furthermore, the common plant volatile linalool was non-diffusive below ground. In addition, we discovered a novel pathway for the degradation of linalool into rapidly diffusing belowground signals. These findings suggest areas for future exploration and highlight the importance of abiotic factors when studying belowground semiochemically-based interactions such as attraction of beneficial entomopathogenic nematodes to plant roots infested by host insects.