Studying a plant's roots isn't an easy task. Some plants have evolved elaborate root systems -- ones you can't just dig up and look at.

Mesquite trees, for example, which inhabit the arid soils of southwestern United States and Mexico, grow roots capable of digging 165 feet beneath the surface in search of water.

Most of what botanists know about roots is the result of either digging up roots and observing or growing root systems in transparent mediums, like water, which typically don't reflect the species' natural habitat. Both methods are limiting.

"To visualize the intricate growth patterns and functions of roots we needed to develop a different approach," Jose Dinneny, a researcher at Carnegie Science, explained in a press release. "We were very mindful that the method had to allow us to vary conditions, in order to present roots with different combinations of environmental conditions that simulate important stresses such as drought or low-fertility soil."

Dinneny and his research partners developed a solution using the protein responsible for a firefly's glow. Scientists genetically engineered a variety of plant species to produce the protein luciferase. When grown in specially designed soil-filled vessels, researchers were able to image the bioluminescent root systems using light-sensitive cameras.

But employing multiple genetically encoded luciferases -- causing different genes to glow at different wavelengths -- researchers were able to track how certain genes affected the growth rate and architecture of the glow-in-the-dark root systems.

The new analysis process -- detailed in the journal eLife -- has been dubbed the GLO-Roots system.

"Roots grow through a pathfinding process, somewhat like neurons, and must make decisions regarding which direction to grow and when to branch," said Dinneny. "This is heavily influenced by soil quality and the location of water and nutrients. Our ability to track gene expression using GLO-Roots is a game changer that will enable an understanding of the molecular events enabling these root decisions."

The system has already been used to show how roots can be coaxed into growing deeper into the soil column via drought simulation.

Researchers hope their system can be used to better understand how root architecture is altered by environmental conditions, and ultimately inspire more sustainable, drought-resistant crop species.