You’ve Got Mail, And It’s From Spinach

Spinach plant. Photo by Jyotishmita Bhagawati, CC BY-SA 4.0, via Wikimedia Commons.

The idea of plant-to-human communication may seem far-fetched, but not for a certain team of chemical engineers. With the power of nanobionics, Dr. Michael Strano’s chemical engineering lab at MIT implemented a process in which the ordinary spinach plant can detect toxic nitroaromatic compounds found in explosives and relay such detections wirelessly — in the form of an email.

Plant nanobionics, according to Dr. Strano, aims to “introduce [structures] into the plant to give it non-native functions.” Strano’s lab previously created carbon nanotubes — cylindrical molecules made of rolled-up sheets of single-layer carbon atoms — able to sense a variety of compounds, ranging from hydrogen peroxide to TNT. He makes use of these nanotubes in a 2016 study in Nature Materials where he explores the potential for plants to monitor the environment. “Plants are very good analytical chemists,” he says. “They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves.”

Model of a carbon nanotube, which is inserted into spinach leaves to detect chemical compounds. Image by Jorge Stolfi, via Wikimedia Commons.

In order for the team to locate such organic compounds in the soil, they inserted carbon nanotubes that release a fluorescent signal — either once when a volatile compound is found or continuously as a reference — into spinach leaves. When the spinach plant’s roots draw in potentially explosive compounds from groundwater, they are detected by the leaves roughly ten minutes later, allowing the nanotubes to elicit a signal. An external infrared camera connected to a $35 Raspberry Pi computer then captures these signals, automatically alerting the scientists via email. An alternative could even be a smartphone camera (with its infrared filter removed), illustrating the study’s low equipment cost.

Today, Strano’s team is still hard at work to discover more applications of their spinach nanotube experiment. While their original 2016 study focused on the detection of explosive compounds useful for surveying landmine zones, the plants can be adjusted to detect compounds associated with pollution and climate change in the soil. Not to mention, the team engineered spinach plants that detect dopamine, which affects plant growth, and are also working on developing plant hormone sensors and increasing the distance from which signals are received, which is currently only about a meter away.

In this manner, Dr. Michael Strano and his team exemplify the surprising potential of using plants as nature’s sensors: they aid in the detection of rare compounds, reveal aspects of internal plant processes and plant health, and provide warnings of ecological change, all in real-time. This project demonstrates the future of the budding field of plant nanobionics and is a stepping stone toward scientific advancements in environmental analysis.

This article was edited by Hedy Goodman and Sarah McNamara.