Enhancing Light Quality Using Tunable Quantum Dots in Luminescent Films To Improve Lettuce and Tomato Yields

Abstract

The spectral distribution of light contributes to plant photosynthetic efficiency, morphology, and phytochemical content. The solar spectrum in a greenhouse can be passively modified by installing luminescent films containing quantum dots, which absorb and convert ultraviolet and blue photons into specifically designed emission peaks from green through far-red. Red romaine lettuce (Lactuca sativa L. cv. Outredgeous) was grown under six quantum dot films and a polyethylene control film. The quantum dot films were manufactured with different optical properties, including peak emissions centered at 590 nm, 600 nm, 620 nm, 660 nm, 705 nm, and a 5:1 combination of 600 nm and 705 nm. All environmental plant growth parameters, except for spectral quality, were uniform across treatments and throughout each 28-day experiment. Compared to the control, the high-concentration 660 nm quantum dot film had the highest light use efficiency (plant efficiency) (+25%), and the 620 nm, high-concentration 660 nm, and 705 nm quantum dot films had the highest radiation use efficiency (combined film and plant efficiency) (+26%, +21%, and +26%, respectively). All quantum dot films were more efficient than the polyethylene control film at manipulating the available light to promote biomass accumulation. After reviewing the data from the lettuce experiments, two films were selected for use in an experiment on fruiting plants. Dwarf cherry tomato plants (Solanum lycopersicum cv. Red Robin) were grown in a climate-controlled test stand under the two quantum dot film treatments, with peak emissions centered at 620 nm and 660 nm and compared to plants grown under a polyethylene control film. Plants grown under the 620 nm quantum dot film produced 29.7% more fruit and 14.8% more total fresh mass compared to the control, while plants under the 660 nm quantum dot film produced 10.3% percent fewer fruit and 8.6% less total fresh mass than the control. Plants grown under the 620 nm and 660 nm quantum dot films exhibited increased fresh mass light use efficiency (+26.4% and +15.5%, respectively) compared to the control film, and plants under both quantum dot films exhibited higher radiation use efficiency (+22.8% and +7.5%, respectively). Both films provided more efficient light environments that promoted fruit production in tomatoes compared to the polyethylene control film.