Low-cost chlorophyll fluorescence imaging for early detection of plant stress in greenhouses
A simple, low-cost chlorophyll fluorescence imaging method that detects abiotic and biotic plant stresses hours before visible symptoms appear. Designed for practical use in commercial greenhouse production settings where existing fluorescence systems are too expensive or complex to deploy.
Overview
This solution is a low-cost chlorophyll fluorescence imaging technique that enables greenhouse growers to detect a wide range of plant stresses well before any visible symptoms emerge. By illuminating plants with blue light and capturing images through a long-pass filter (>680 nm), the system produces clear fluorescence images that reveal stress-related changes in photosynthetic activity. In validation trials using atrazine, a photosystem II inhibitor, stress was detected within two hours, while visible damage took approximately 24 hours to appear. This early-warning capability gives growers more time to respond to irrigation, nutrition, temperature, or pest-related problems, reducing crop losses and improving production efficiency.
The technology is being developed by Candidus, an Athens, Georgia-based company specializing in smart lighting and crop monitoring solutions for the greenhouse industry. It complements Candidus's existing adaptive lighting control systems by adding a new layer of physiological insight into crop health, helping growers move from reactive to proactive crop management.
Technical specifications
- Imaging method: Plants are exposed to blue light and imaged with a camera fitted with a long-pass filter (>680 nm) to capture chlorophyll fluorescence emission.
- Stress detection sensitivity: Detected atrazine-induced damage within 2 hours, versus approximately 24 hours for visible symptom onset.
- Quantitative correlation: Pixel intensity in fluorescence images is strongly correlated with photosystem II quantum yield and with measured reflectance and fluorescence at 690 nm and 740 nm (P<0.001, R²>0.8).
- Cost advantage: Designed as a simple, effective alternative to expensive commercial chlorophyll fluorescence systems that are difficult to implement in commercial production environments.
- Spatial insight: Imaging clearly shows how a stress moves through the plant over time, supporting targeted diagnosis and intervention.
Technology readiness level
The technique has been validated in controlled trials using atrazine as a model stress, demonstrating reliable early detection and strong quantitative correlation with established photosynthetic measurements. Current and planned future validation will expand testing to cold and heat stress through controlled temperature ramps, nutritional stresses including soil pH and nutrient deficiencies, and subsequently insect and pathogen pressures. The technology is at an early-to-mid stage of development, with a working proof of concept and a clear roadmap toward broader stress detection and commercial deployment in greenhouse operations.
About Candidus
Candidus is an Athens, Georgia-based technology company that provides smart lighting solutions for the greenhouse industry. Founded in 2017 by Dr. Erico Mattos and Dr. Marc van Iersel, the company specializes in adaptive lighting control systems designed to optimize supplemental lighting in greenhouse environments. By integrating real-time monitoring of weather conditions, crop physiological parameters, and photoperiodic requirements, Candidus's technology enables growers to adjust light intensity and timing automatically. This approach ensures that crops receive the precise amount of light necessary for optimal growth while avoiding the inefficient use of electricity, which is often a significant variable production cost for greenhouse operators. The company partners with greenhouses and lighting firms to implement these data-driven strategies and deploy specialized LED controllers.
This technology is vital for growers aiming to improve profitability and operational efficiency, particularly when producing high-quality crops in regions with limited natural sunlight. By reducing electricity usage and enhancing the predictability of crop yields, the system helps growers achieve a better return on investment for their lighting infrastructure. The company's innovative control methods have been recognized with various industry honors, including the AE50 Outstanding Innovations Award from the American Society for Agricultural and Biological Engineers and recognition as a finalist for the Greenhouse Grower Technology of the Year award. Candidus has also collaborated on research projects, such as a USDA Natural Resources Conservation Service grant, to demonstrate the effectiveness of its lighting control technology across diverse commercial greenhouse operations.
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