Light Limited Photosynthesis under Energy-Saving Film Decreases Eggplant Yield

Glasshouse films with adjustable light transmittance have the potential to reduce the high energy cost for greenhouse horticulture operations. Whether these films compromise the quantity and quality of light transmission for photosynthesis and crop yield, remains unclear. A “Smart Glass” film ULR-80 (SG) was applied to a high-tech greenhouse horticulture facility and two experimental trials were conducted by growing eggplant () using commercial vertical cultivation and management practices. SG blocked 85% of ultraviolet (UV), 58% of far-red, and 26% of red light, leading to an overall reduction of 19% in photosynthetically active radiation (PAR, 380 - 699 nm) and a 25% reduction in total season fruit yield. There was a 53% (season mean) reduction in short-wave radiation (385 nm to 2105 nm upward; 295 to 2685 nm downward) that generated a net reduction in heat load and water and nutrient consumption that improved energy and resource use efficiency. Eggplant adjusted to the altered SG light envi...