Scientists at the Department of Energy’s Oak Ridge National Laboratory have created a miniaturized environment to study the ecosystem around poplar tree roots for insights into plant health and soil carbon sequestration.

The rhizosphere-on-a-chip platform builds on the lab’s history of constructing lab-on-a-chip devices, in which tiny channels and chambers are etched on a microscope slide so that fluids can be introduced and studied for biochemical separations research and testing.

In this case scientists are mimicking soil on the chip, sprouting poplar trees in the fluid and studying the environment around their roots, known as the rhizosphere. Scientists observe how microbes are interacting with chemicals within the artificial soil to influence plant health and gain a better understanding of the processes governing carbon storage.

The rhizosphere is one of the most complex systems in the world, in which plant roots take up water and nutrients, create a unique physical and biogeochemical environment for microbes, and emit atmospheric carbon into the soil. There may be hundreds of different bacteria that are growing near plant roots or are influenced by the rhizosphere. ORNL researchers are particularly interested in how microbes like bacteria and fungi interact with plant roots to help plants grow faster and survive threats like drought, wildfire, disease and pests.

“It’s very difficult to see inside soil to observe those processes as the particles are very dark,” said Jack Cahill of ORNL’s Biosciences Division.

Rhizosphere-on-a-chip allows the researchers to create model systems and then use techniques like mass spectrometry to identify chemicals and their distribution around plant roots. That knowledge informs an analysis of chemical interactions in the ecosystem, such as chemical signals by plants in order to attract or repel microbes. Using the chip system also conserves samples by removing only a tiny amount of the liquid from the platform and allowing plants to continue growing.