Light-Modifying Films and Coatings for Agricultural Applications

This review evaluates light-modifying films and coatings engineered to manipulate the solar spectrum and optimize crop development in protected and open-field agriculture. Traditional agricultural covers act as passive shading, whereas advanced functional polymers actively alter light quality to enhance photosynthesis and regulate morphogenesis. We analyze polymer matrices—such as low-density polyethylene (LDPE), polymethyl methacrylate (PMMA), and biodegradable polylactide (PLA)—integrated with luminescent agents, including rare-earth complexes, organic dyes, quantum dots, and carbon dots. These materials convert underutilized or harmful ultraviolet (UV) and green wavelengths into photosynthetically active radiation (PAR), specifically targeting blue–violet (400–480 nm) and red–orange (600–700 nm) spectral shifts. Additionally, structural modifications like micro-layer texturing for light diffusion, infrared-reflecting additives for thermal insulation, and selective UV-blocking thresholds are evaluated across high-value crop categories. Spectral optimization successfully triggers predictable photomorphogenic responses: blue–violet enrichment promotes compact vegetative architecture and prevents stem elongation in leafy greens, while red–orange matrices accelerate biomass accumulation and increase fresh fruit mass in vining crops by up to 25%. Fine-tuning the red-to-far-red (R:FR) ratio regulates ornamental morphogenesis. Furthermore, micro-layer diffusion eliminates canopy sunburn, thermal additives mitigate nocturnal flower abortion, and selective UV-B thresholds stimulate secondary metabolites in berries while disrupting pest navigation and fungal sporulation. Consequently, crop-specific light-modifying coatings offer a scalable, energy-free approach to maximize yields and enhance crop protection in sustainable agriculture.