Past Projects 

TIGER lights 

GLASE researchers developed TIGER LED light fixtures for tunable irradiance growth efficiency research, tailored for controlled environment plant growth studies. The LED lights provide flexibility in wavelength selection, high PPFD, uniform color mixing and canopy lighting, and a modular design for various cabinet types. The system, comprising six LED wavelengths (400 nm, 420 nm, 450 nm, 525 nm, 660 nm, and 735 nm), avoids phosphor-converted LEDs for precise wavelength control. Custom 6-in-1 LED packages ensure excellent color mixing without a diffuser. Each module, capable of pulsed and analog dimming, is equipped with six calibrated drivers for independent wavelength control, enabling high-speed operation for potential energy-efficient lighting protocols to enhance plant growth and biomass efficacy. 

IRGA LED attachment 

Plants rely on sunlight for energy, where photosynthesis converts carbon dioxide (CO2) and water (H2O) into oxygen (O2) and sugar. The infra-red gas analyzer (IRGA) is a tool used to measure photosynthetic rates by detecting gas absorption, specifically CO2 and H2O. At LESA we use the IRGA enhanced with a custom LED module, termed TIGER Cub. This module, adapted from the TIGER horticultural research LED fixture, includes six adjustable LED channels (three blue, one green, one red, and one far-red) for accurate simulation of growth chamber lighting conditions. The TIGER Cub is placed on the IRGA leaf chamber, facilitating precise photosynthetic studies under controlled light spectra including photosynthetic response analysis, spectral testing for crop growth, and high-frequency pulsed lighting studies. This setup enables real-time and direct comparisons of plant responses to various light conditions, aiding in the development of optimized growth lighting strategies. 

SASSy 

The Spectral Acquisition Sensor System (SASSy) was developed to monitor and record changes in the solar spectrum throughout the day and across seasons, which is essential for optimizing light conditions for plant growth. SASSy captures visible light spectra from 350 to 820 nm every 20 to 30 seconds and compensates for detector drift with an integrated shutter. This system outperforms traditional daily light integral (DLI) measurements by providing continuous spectral data, enabling precise adjustments to greenhouse lighting conditions. Initial data showed significant variability due to factors like cloud cover, which can impact plant growth. The collected spectral data helps to understand and predict light variations and informs adaptive lighting systems that stabilize light conditions. The integration of SASSy with Cornell University's Lighting and Shade System Implementation (LASSI) will allow for dynamic control using tunable LEDs and shades to maintain optimal lighting, ensuring consistent and high-quality crop growth. 

GHL1 Greenhouse Light 

The GHL1 light is spectrally tunable with six adjustable LED channels (405 nm, 423 nm, 450 nm, 525 nm, 660nm, and 735 nm) that enable direct comparison with the TIGER lights. Each light has three arrays, each with four lights, when mounted in a 1.2 x 1.2 m grid with adjustable chain height can illuminate a 4’ x 4’ area. GHL1 mixes colors effectively without a diffuser and at a close distance show individual colors, but white light appears at the plant canopy. The adjustable light spectrum and intensity is a valuable tool for both research and student projects. 

Lettuce response to blue light quality 

We tested lettuce growth following modifications in blue LED light quality. Monochromatic blue light responses showed that net photosynthesis (Pn) for 420 nm and 450 nm was quite similar, while 400 nm significantly lowered Pn. When blue light was combined with red and far-red light, the differences in Pn among the three blue wavelengths became minimal for the ‘Green Star’ cultivar. In the ‘Red Sails’ cultivar, 400 nm in the mixed spectrum led to significant reduction in Pn, particularly at lower light intensities. Growth under the various blue LED wavebands combined with red and far-red light showed minimal phenotypic differences. There was no significant blue light effect on biomass, though chlorophyll a fluorescence indicated reduced photosynthetic efficiency for spectra with 400 nm and 420 nm compared to 450 nm. The spectrum with 450 nm increased chlorophyll content index and chlorophyll a/b ratio, while spectrum with 400 nm only caused a slight decrease in violaxanthin pigment in terms of carotenoid content. Thus, lettuce can detect changes in the blue light spectrum affecting photosynthetic efficiency and chlorophyll composition, but overall growth and yield remain largely unchanged. 

Tomato response to blue light quality 

We compared the effects of different blue LED wavebands (400 nm, 420 nm, and 450 nm) on ‘Micro Tom’ tomato growth and yield under sole-source lighting. We conducted a comparative analysis of photosynthetic CO2 assimilation under mono- and poly-chromatic light following changes in the blue wavebands; second, we evaluated tomato growth and yield under poly-chromatic light with similar blue spectral differences. We found that only net photosynthetic rate, not photochemical efficiency, was affected by variations in blue light quality when measured at the single leaf level. Tomato growth and yield, however, was more sensitive to blue light quality than photosynthesis. Shorter wavelength blue light promoted larger leaf size, while longer blue wavelengths increased biomass and the fruit-to-leaf ratio (harvest index). Specifically, blue light at 450 nm was linked to a lower chlorophyll a/b ratio and higher ascorbic acid (vitamin C) content in the fruits. Overall, blue spectral quality had a subtle impact on leaf photochemistry but a more significant effect on tomato crop physiological outcomes. 

High-frequency pulsed lighting 

We tested the impact of multi-color pulsed LED irradiation on the growth, photosynthetic efficiency, and antioxidant properties of baby-leaf lettuce 'Defender'. The study compared the effects of continuous and pulsed lighting (0.5 kHz and 1 kHz with a 50% duty cycle) using blue (450 nm), green (520 nm), red (660 nm), and far-red (735 nm) light components, while keeping the total daily light integral (DLI; 14.4 mol m−2 day−1) constant over a 16-hour photoperiod. Our results indicated that lettuce grown under pulsed light exhibited superior growth, with notable increases in fresh weight, dry weight, and leaf area. Both pulsed treatments enhanced photosynthetic rate and chlorophyll and carotenoid content. However, the total phenol content and antioxidant activity depended on the specific pulsed light frequency, with the 1 kHz treatment being the most effective for boosting phenol levels and antioxidant activity. Our findings highlight the potential of high-frequency pulsed LED lighting to enhance photosynthetic performance and antioxidant properties in lettuce grown indoors. Future electrical lighting systems in CEA might be able to optimize energy use by integrate pulsed lighting techniques to produce high-quality crops. 

Student Alumni 

Graduate Students 

• Will Pepi, 2021-2024 

Undergraduate Research Projects 

• Hui Min Guo, URP 2022 
• Muyuan Tian, URP 2022 
• Cassandra Shore, URP 2022-2023 
• Jasmine King, URP 2023 
• Corinne Wingrove, URP 2023-2024 

RPI STEP  

• Julieta Gil-Marin, STEP Student 2022-2023 
• Edward Boakye, STEP Student 2023-2024 
• Hadeel Hamed, STEP Student 2023-2024