Cornell University scientists have developed genetically engineered tomato plants that turn red-purple when nitrogen becomes scarce, giving farmers a visible warning that crops may need fertiliser. Called RedAlert, the plants have moved beyond greenhouse experiments and are being tested under real-world conditions at Cornell’s Musgrave Research Farm in Aurora, New York. Visitors saw the experiment on July 30 during the 2026 Aurora Farm Field Day, which showcased agricultural research. According to a September report in the Cornell Chronicle, the plants produce betanin, the red-purple pigment found in beets, when deprived of nitrogen. Researchers hope these living sensors could help growers identify nutrient shortages sooner and apply fertiliser more precisely. The plants are not intended to enter the food supply. Instead, they could eventually be planted alongside conventional crops to monitor nitrogen availability in a field.
RedAlert tomatoes: how nitrogen deficiency triggers a red-purple colour change
The project is part of Cornell’s Centre for Research on Programmable Plant Systems (CROPPS), which investigates ways to engineer plants to communicate information about their surroundings.
Plant scientist Margaret Frank first conceived the idea behind…