Color-changing sensors can monitor health in both houseplants and crops, helping small farms respond to stress

Ever wish you had insight on whether the plants in your home garden are really thriving? A group of Northeastern University researchers recently developed sensors that change color to indicate the health status of plants. This can be used not only for your basic houseplant, but could be used to help small farms monitor their crops in the face of environmental stressors like weather shifts, pollution and disease.

“It’s filling a gap,” said Josie Cicero, a master’s student in marine biology at Northeastern and one of the co-authors on the research.

Current methods for checking plant health are very expensive, Cicero said.

“[They] take a long time to process, and aren’t accessible for a lot of people,” Cicero said, “whereas this device allows you to do an assessment on the stress level of plants in a couple of minutes in the field instead of having to collect samples, send them off and spend hundreds to thousands of dollars to get the results a week later.”

The idea for such a sensor, fittingly, came from the nesocodon, a flower found on the island nation of Mauritius believed to be pollinated by geckos. The nectar of the nesocodon will change in response to a concentration of a small molecule called proline, a universal biomarker for plant health, said Dan Wilson, principal research scientist at Northeastern’s Kostas Research Institute and a co-author on the research.

“We leveraged that reaction and color scheme to create sensors that undergo the same color change,” said Wilson, who is affiliated faculty at Northeastern’s Department of Chemical Engineering. “But (the sensors) do so in a dose-dependent manner, so that based on the intensity of the color change that we see, we can infer something about the health status of the plant and whether or not it’s in a state of stress.”

The research, co-authored by Cassandra Martin, Lillian Springer, Dorthea Geroulakos, Audrey Moos, Cicero and Wilson, was recently published in ACS Agricultural Science & Technology. Many of the co-authors joined the research while working as co-ops or interns in the lab.

What the researchers found was in response to stress—such as lack of water, harsh soil metals, too much sunlight and too much heat—plants will produce heightened levels of proline.

The color-changing nectar of the nesocodon is the result of proline mixing with the small molecule, sinapaldehyde, which Wilson said is also created inside the plant. This mixture results in the creation of a natural red pigment called nesocodin, which is how the nectar in the nesocodon goes from yellow to bright red.

Building off previous research from other institutions, Northeastern researchers were able to replicate this reaction with paper-based sensors embedded with sinapaldehyde. If a plant has high levels of proline, the sensor will produce nescodin, promoting the sensor to turn bright red. On healthy plants, the sensor remains pale yellow.

“If there is a lot of stress and proline is there in a high concentration, it’s bright red,” Cicero said. “It’s a qualitative response. You can look at it and see it’s yellow, it’s orange. … We can also scan it and get a quantitative number associated with it.”

To do this, Wilson said the researchers clip off a small piece of the leaf of the plant they want to test. They then grind up that leaf into smaller pieces, add ethanol to draw out the proline, and then dip the sensors into that liquid. This can be done within 15 minutes. The sensors are plastic, but the researchers are exploring making some that are biodegradable so they can be disposed of easily after use.

The team tested on several different types of crops, including cabbage, kale, brussel sprouts and broccoli, and hope to test it on different types of plants as well.

Most existing mechanisms for assessing plant health are designed for large-scale operations with hundreds of plants, Wilson said. Farms with thousands of acres use drones with specialized cameras, for example, to check their plants. There aren’t any assessments like this for smaller-scale farming operations.

“We went into this knowing that this would not be a solution that would be scalable,” he said. “But it might be helpful to family farmers and smaller farming operations who are in the developing world and may not have the resources to access drones or some of the more expensive specialized equipment. You could use it to check the status of your houseplant or you could use it on crops and agricultural goods.”

Wilson said farmers could use this to check how plants are doing in order to correct course if there are issues, enabling the growth of more crops.

Martin, now a staff scientist at KRI who got her Ph.D. in chemistry and chemical biology at Northeastern, said that moving forward, the team hopes to find ways for the sensor to provide more information to users.

“We’re really focused on trying to make all the technology as simple, self-contained and compact as possible so that it’s less expensive to make and more distributable,” Wilson added. “We try to incorporate design principles that will make the final product really easy to use so that, ideally, you don’t have to be a scientist to know how this works.”

More information: Cassandra L. Martin et al, Bio-Inspired Proline Sensors for the Diagnosis and Surveillance of Stress in Living Systems, ACS Agricultural Science & Technology (2025). DOI: 10.1021/acsagscitech.5c00207

This story is republished courtesy of Northeastern Global News news.northeastern.edu.