Newly developed transparent soil could help shed light on the secret world of plant roots. The new material, developed by biologists, chemists and physicists, could improve crops and identify new ways of preventing outbreaks of food poisoning.
Plants absorb water and minerals with root systems that can encompass a volume larger than the above-ground parts of plants. Scientists would love to learn more about roots, but much about them remains hidden underground.
"There are so many things to discover in soil, and we don't know yet what they are," said theoretical biologist Lionel Dupuy at the James Hutton Institute in Dundee, Scotland.
Now, after two years of trial and error involving painstaking tinkering with the acidity, grain size and nutrient content of a variety of artificial soil-like materials, watered in a customized liquid solution, Dupuy and his colleagues managed to develop a transparent soil in which they could grow plants. The material allows 3-D imaging of the rhizosphere -- the realm of soil involving plant roots and the organisms associated with them.
The soil is made of 350-to-1,600-micron-wide pellets of a synthetic material known as Nafion. This compound often finds use in power-generating fuel cells because of how it can help control the flow of current-carrying ions. Past research revealed that the material had another talent: films of bacteria could grow on Nafion membranes. Also, the scientists could modify the Nafion grains to bind to ions dissolved in the surrounding liquid solution, mimicking natural soil chemistry.
This artificial soil is not especially transparent on its own. However, when saturated with a specially designed water-based solution, the way the soil and the solution each bend or "refract" light renders the combination transparent. A similar effect can be seen if you place one clear glass jar in another clear glass jar and fill the smaller jar and the space between jars with paint thinner — the smaller jar will seem to disappear.
Although this material does not perfectly mimic real soil, its physical and chemical qualities are close.