Diverse Plant Responses to Blue Light Manipulation: Application of Photo-Selective Materials in Protected Crop Production

Blue light (BL) plays important roles in regulation of plant physiological processes, such as growth, morphogenesis, flowering, and pigment biosynthesis. While narrow-band LED studies have provided insights into underlying mechanisms, results often differ under natural broad-spectrum light conditions. Increasing attention has, therefore, turned to electricity-free, photo-selective materials that passively manipulate the spectral composition of sunlight to optimize crop performance in protected cultivation. Among these, BL-manipulating materials, including shade nets, spectral films, and plastic mulches, have been explored for their ability to modify canopy light environments, microclimate, and ultimately plant traits. Evidence shows that such materials can influence flowering time, stem elongation, crop yield, and secondary metabolite accumulation; however, responses vary greatly among crop species and production systems, with some reports showing growth promotion and others indicating inhibitory or negligible effects. Challenges remain in achieving consistent outcomes, largely due to species-specific differences, environmental variability, and the complex interactions between spectral quality and other microclimatic factors. This review synthesizes current knowledge on BL manipulation through photo-selective technologies, evaluates their effects on some key traits, including plant flowering, yield, product quality, growth, morphology, and secondary metabolites across different horticultural crops, and highlights opportunities and limitations for future adoption in protected production systems.