Cornell scientists engineer tomatoes that change colour when nitrogen is low
The RedAlert plants turn red-purple to provide a visible warning of nutrient shortages to farmers, according to the Times of India.
Scientists at Cornell University have created genetically engineered tomato plants that shift to a red-purple hue when nitrogen levels are insufficient. According to a report by the Times of India, these plants, named RedAlert, are currently undergoing real-world testing at the Musgrave Research Farm in Aurora, New York.
The project is part of the Centre for Research on Programmable Plant Systems at Cornell. Plant scientist Margaret Frank conceived the idea, while researchers Brandon Williams and Yinan Wu, along with doctoral students Jacob Belding and Ava Forystek, worked on the nitrogen-sensing system.
The engineered plants use a biological signalling pathway to detect nitrogen levels near their roots and transmit that information to their shoots. This process triggers the production of betanin, a red-purple pigment, to make nitrogen stress visible.
Researchers aim to use these plants as living sensors to help growers identify nutrient shortages and apply fertiliser more precisely. The plants are not intended for the food supply but could be grown alongside conventional crops to monitor soil nitrogen.
During the 2026 field season, researchers established a plot with RedAlert plants alongside non-engineered tomatoes. Doctoral student Sam Mosher, who is leading the field trials, said that if nitrogen is proven to drive the colour changes, the line would be a promising sensor candidate.
The team is currently analysing field data, soil, and leaf samples to determine how reliably colour intensity matches nitrogen concentrations. They are also using drones and handheld spectrophotometers to measure plant colour systematically.