Light in Horticulture

Light is a fundamental environmental factor governing horticultural crop growth, development, and physiology. It serves as the primary energy source for photosynthesis, supplying the carbohydrates and energy necessary for biomass accumulation. In addition to its role in energy provision, light regulates morphogenesis, flowering, and stress responses, thereby influencing both crop productivity and quality.

In greenhouse systems, sunlight constitutes the predominant light source. However, its intensity and spectral composition vary with seasonal, meteorological, and diurnal conditions, which can significantly impact photosynthetic efficiency and developmental processes. To mitigate these fluctuations, growers employ strategies such as shading, supplemental lighting, and photoperiod control. Supplemental lighting with high-pressure sodium (HPS) lamps and, more recently, light-emitting diodes (LEDs), has been widely adopted to enhance photosynthetic activity during periods of low irradiance. These approaches not only stabilize growth but also increase crop yield and quality by extending the daily light integral (DLI) and improving canopy light distribution. Effective management of both natural and supplemental light therefore ensures uniform development, physiological resilience, and improved productivity.

In contrast, vertical farming systems predominantly utilize artificial lighting, particularly LEDs, allowing precise control over light intensity, spectrum, and photoperiod. Manipulation of light quality within the photosynthetically active radiation spectra (PAR, 400-700 nm) or extended PAR (ePAR, 400-750 nm) ranges optimizes photosynthetic performance and modulates plant structure. Beyond the PAR spectra, supplementation with ultraviolet radiation (UV-A and UV-B) has been shown to stimulate the biosynthesis of bioactive compounds, including phenolics, flavonoids, and antioxidants, thereby enhancing both nutritional quality and stress resilience. Artificial photoperiod regulation further enables the synchronization of flowering and acceleration of growth cycles independent of seasonal constraints, facilitating year-round production and consistent crop quality.

The optimization of light environments – whether via natural sunlight in greenhouses or artificial radiation in vertical farms – represents a critical component of modern horticultural practice. Advances in lighting technology and controlled-environment strategies enhance not only photosynthetic efficiency but also morphological development, nutrient composition, and commercial value. Consequently, light management is integral to achieving sustainable, high-quality, and resource-efficient crop production in enclosed growing systems.