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Improved Crop Production in Nutrient Film Technique Greenhouse Horticulture of Lactuca sativa L. ‘Coastal Star’ Romaine Lettuce using Quantum Dot Luminescent Films
Abstract
The spectral quality of sunlight in greenhouse production of leafy greens is a cultivation parameter that remains to be optimized. Quantum dots are novel, tunable, luminescent nanomaterials capable of efficiently absorbing and down-converting ultraviolet and blue light to more photosynthetically efficient colors, such as orange and red. Luminescent greenhouse films incorporating quantum dots with a photoluminescent emission centered near the peak of the action spectrum for photosynthetically active radiation can optimize the solar spectrum in greenhouses with minimal intensity loss, enabling improved biomass yields and plant growth rates without requiring electricity. This study represents the first set of trials of quantum dot greenhouse films installed over nutrient film technique-grown lettuce. Plastic greenhouse films hosting a layer of CuInS2/ZnS quantum dot (600 nm emission) resin were deployed above a 3.8 m x 6.2 m nutrient film technique system inside the Santa Fe Community College Research Greenhouse. An identical neighboring area in the greenhouse was chosen to serve as the control group, over which clear polyethylene film was installed to balance the light intensities and diffusivities between the two areas. Quantum light sensors monitored daily light integral on each side of the experiment. Seeding of groups of 27 plants were staggered to allow for weekly harvests, with harvest times ranging from 39 to 59 days after sowing. The first harvest was completed on August 20, 2021, and the final harvest was completed on November 23, 2021.Across 35 harvests and among 12 groups, the average wet weight was increased by +13.0% for plants grown under the luminescent greenhouse film compared to the control. Of these harvests, 83% showed heavier plants on the treatment side . For 26 of these harvests, dry weights were measured after a subset of harvested plants were dehydrated in a drying oven. The average dry weight was increased by +12.1 % for plants grown under the treatment, with 85% of these measurements showing heavier plants on the treatment side. Based on the results, greenhouse films incorporating quantum dots show promise in enabling passive, electricity-free spectral modification for improving food production in greenhouse cultivation. Further investigation exploring parameters such as emission color, quantum dot concentration, and secondary metabolite content is needed to fully validate the approach to sunlight modification studied in this set of experiments.