Greenhouse Application of Luminescent Greenhouse Films Embedded with Quantum Dots to Improve Growth of Lettuce

Abstract

Many industries in arid environments, especially agriculture, are facing water and energy resource challenges, such as drought, increasing costs, and worsening pollution. Controlled environment agriculture (CEA) can increase water use efficiency and reduce environmental impact by producing crops within closed loop hydroponic systems. However, energy is required to power irrigation pumps, electrical lighting, and other environmental controls to achieve optimal plant growth and production in CEA. A new luminescent agriculture film technology presents a solution for improving crop production without requiring electricity. Quantum Dot (QD) technology embedded in the luminescent films and deployed in greenhouse covers can passively alter less photosynthetically efficient ultraviolet (UV) and blue wavelengths from the sun to red wavelengths inside a greenhouse, which are more efficient in promoting plant growth and increasing biomass. Two QD films with emission peaks in orange (625 nm) and red (650 nm) were selected for study in a greenhouse to determine the growth impacts of these films. Seven repeated experiments of red romaine lettuce (Lactuca sativa cv. ‘Outredgeous’) were grown in deep water culture (floating raft) tanks under the quantum dot films and simultaneously under a control film with the similar reflective and diffusive properties as the quantum dot films (four crops were grown under the 625 nm QD film and three under the 650 nm QD film). Each experiment was replicated under each film in two tanks of 56 plants each. The air (temperature, RH) and root zone (EC, pH) environments and the light received (PPFD) were monitored during growth, and upon harvest, the wet and dry biomass and morphological properties (leaf count and length) were measured. The light use efficiency (LUE), or the grams of biomass produced per mole of light received, and the daily light integral (DLI) were calculated. The lettuce plants grown under the quantum dot films increased in fresh mass (+10 to 27%), dry mass (+15 to 24%), and LUE (+7 to 35%) compared to the plants grown under the control film. The quantum dot films have demonstrated the potential to produce increased biomass in lettuce plants grown in greenhouses without increased energy cost, and have potential for numerous future applications.