Researchers at North Carolina State University have developed a patch that plants can “wear” to continuously monitor for plant diseases or other stressors such as crop damage or extreme heat.

“We developed a wearable sensor that non-invasively monitors plant stress and disease by measuring volatile organic compounds (VOCs) emitted by plants,” said Qingshan Wei, co-author of an article on the work. Wei is an assistant professor of chemistry and biomolecular engineering at NC State.

Current methods of testing for plant stress or disease include taking plant tissue samples and performing a test in a laboratory. However, this only gives the breeders one measurement and there is a time lag between when a sample is taken and when the test results are received.

Plants emit different combinations of VOCs in different circumstances. By targeting VOCs that are relevant to specific diseases or plant stress, the sensors can alert users to specific issues.

“Our technology continuously monitors the plant’s VOC emissions without damaging the plant,” says Wei. “The prototype we demonstrated stores this monitoring data, but future versions will transmit the data wirelessly. What we have developed enables farmers to spot problems in the field – they don’t have to wait to get test results from a laboratory. “

The rectangular patches are 30 millimeters long and are made of a flexible material with graphene-based sensors and flexible silver nanowires. The sensors are coated with various chemical ligands that respond to the presence of specific VOCs, allowing the system to detect and measure VOCs in gases given off by the plant’s leaves.

The researchers tested a prototype of the device on tomato plants. The prototype was set up to monitor two types of stress: physical damage to the plant and infection by P. infestans, the pathogen that causes late blight in tomatoes. The system detected VOC changes related to the physical damage within one to three hours, depending on how close the damage was to the location of the patch.

The detection of P. infestans took longer. The technology only recorded changes in VOC emissions three to four days after the researchers inoculated the tomato plants.

“This is not noticeably faster than the onset of visual symptoms of late blight,” says Wei. “However, the monitoring system means that breeders don’t have to rely on seeing tiny visual symptoms. Continuous monitoring would enable growers to identify plant diseases as quickly as possible and limit the spread of the disease. “

“Our prototypes can already detect 13 different plant VOCs with high accuracy, so users can design a bespoke sensor array that focuses on the stresses and diseases a grower deems most relevant,” says Yong Zhu, co-author of the paper Andrew A. Adams Distinguished Professor of Mechanical and Aerospace Engineering at NC State.

“It’s also important to note that the materials are relatively inexpensive,” says Zhu. “If manufacturing were upscaled, we think this technology would be affordable. We’re trying to come up with a practical solution to a real problem, and we know cost is an important consideration. “

Researchers are currently working on developing a next-generation patch that can monitor temperature, humidity and other environmental variables as well as VOCs. And while the prototypes were battery-powered and stored the data on site, the researchers plan that future versions will be solar-powered and enable wireless data transmission.

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The article “Real-Time Monitoring of Plant Stresses via Chemiresistive Profiling of Leaf Volatiles by a Wearable Sensor” is in the journal. published matter. Co-first authors of the paper are Zheng Li, a former postdoctoral fellow at NC State who is now an assistant professor at Shenzhen University, and Yuxuan Li, a Ph.D. Student at NC State. The paper was co-authored by Jean Ristaino, William Neal Reynolds Distinguished Professor of Plant Pathology at NC State; Oindrila Hossain, Rajesh Paul and Shuang Wu, the Ph.D. Students at NC State; and Shanshan Yao, a former postdoctoral fellow at NC State who is now an assistant professor at Stony Brook University.

The work was carried out with the support of the NC State Chancellor’s Faculty Excellence Program; the Kenan Institute for Engineering Technology & Science; NC State’s groundbreaking research incentive program for the Plant Science Initiative (GRIP4PSI); the U.S. Department of Agriculture’s NC State Center for Human Health and the Environment Pilot Project Award, number 2019-67030-29311; USDA APHIS Farm Bill Grant number 3.0096; and the National Science Foundation, under grant 1728370.

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