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Improved Lettuce Production and Light Use Efficiency By Passive Quantum Dot Luminescent Layers Applied in Greenhouse Horticulture
Abstract
Greenhouse cultivation of leafy greens is becoming more pervasive as farmers consider sustainability, year-round production, proximity to markets, and crop freshness as major factors in modern farming. Despite recent advances in many aspects of greenhouse cultivation, manipulation of the spectrum of sunlight reaching plants in a greenhouse represents a vector for improvement. Quantum dots, electricity-free luminescent materials that efficiently convert colors of light, represent a promising material class for sunlight conversion in greenhouses. Color conversion via the passive use of these luminescent materials have shown the potential to improve plant growth and production without requiring electricity. In this study, passive greenhouse layers containing CuInS2/ZnS quantum dots were employed over nutrient film technique-grown ‘Coastal Star’ romaine lettuce in order to understand the effects of the quantum dot-layer spectrum on plant production. At the Santa Fe Community College Research Greenhouse in 2022 and 2023, this study monitored the growth and development of romaine lettuce crops grown under 650-nm emitting quantum dot-layers, compared with those grown under a color-neutral control film. Except for spectrum, both sides of the experiment were kept identical, with focus on daily light integral, temperature, humidity and nutrient regimen. This study demonstrated that 650-nm emitting quantum dot greenhouse layers increased leaf length and yields in both wet weight and dry weight in romaine lettuce, allowing growers to achieve faster crop turnover and higher productivity in the greenhouse. This greater productivity enables growers to realize another crop cycle per year or come to market with larger crops, depending on their preference.