Simulating root exudation by reverse microdialysis

Kaltenburg-Lindau

2019

Sonderdruck

12672S

40000970

The release of labile compounds by plant roots commonly referred to as root exudates, dramatically increases C concentrations in the rhizosphere. While it is well known that root exudation significantly affects soil physical and chemical properties as well as microbial activities at the soil microscale, studying such effects remains a challenge due to the sheer complexity of soils and plant root systems. Current methods for simulating root exudation are often unsatisfactory, since the injection of exudate solution into soil is punctual and severely changes the natural soil water balance. Here, we present a novel approach based on microdialysis enabling the controlled and gradual release of exudates with minimum disturbance of the soil and, simultaneously, allowing monitoring its consequences at these spots. Microdialysis, a technique developed for neuroscience, has been successfully adapted to assess in situ soil nutrient fluxes in a non-invasive way. Briefly, microdialysis probes including a semi-permeable membrane are inserted into the soil and a perfusate (e.g. distilled water) is pumped through the probes. The concentration gradient between the soil solution and the perfusate induces the diffusion of compounds across the membrane, which can then be measured in the collected samples.