Supplemental lighting in controlled environment agriculture: Enhancing photosynthesis, growth, and sink activity
Authors: Paponov Ivan A. , Paponov Martina 
Published: February 2025

Abstract
Rising demand for reliable crop production has accelerated the adoption of controlled environment agriculture (CEA), such as greenhouses and vertical farms, where growth conditions are carefully controlled and tailored to improve efficiency and productivity. Light is a critical factor in these systems, driving photosynthesis through complex mechanisms involving pigments and biochemical processes while also regulating plant morphology and resource allocation via photoreceptors, influencing the source–sink balance. Advances in LED technology enable precise control over light parameters, creating opportunities to enhance these physiological processes while addressing energy efficiency challenges, given that lighting constitutes the highest operational cost. Optimizing lighting, including intensity and photoperiod, enhances photosynthetic efficiency, sink capacity, and energy use, thereby maximizing yield and quality. Extending photoperiods with supplemental lighting increases the Daily Light Integral (DLI) by allowing plants to utilize light within the linear phase of the photosynthetic response curve, where the increase in light intensity has the highest impact on growth. This approach enhances biomass accumulation and yield while increasing energy efficiency. However, extending photoperiods to continuous lighting can disrupt essential metabolic processes in some species, leading to photoinhibition, leaf chlorosis, or reduced growth. Dynamic lighting strategies, such as adjusting supplemental lighting to solar irradiance or utilizing nighttime supplemental lighting, offer innovative approaches to improve energy efficiency and productivity. These methods also mitigate risks associated with excessively long photoperiods, paving the way for more sustainable and efficient crop production systems. Specific light spectra not only optimize photosynthesis and sink capacity but also regulate crop quality traits, such as flavor, nutritional value, and antioxidant activity. Far-red light enhances sink strength by regulating sugar transport; blue light improves stomatal conductance and carbohydrate export; green light penetrates deeper into the canopy, enhancing photosynthesis in lower leaves; and orange light contributes to resource distribution and overall canopy photosynthesis; and UV light influences secondary metabolite production and stress resistance. Consequently, supplemental lighting has expanded from traditional red and blue wavelengths to include far-red, orange, green, and UV light, improving canopy penetration, resource allocation, and enhancing crop quality. Additionally, genetic variability influences plant responses to artificial light, offering opportunities to breed crops specifically adapted to CEA environments, focusing on traits like enhanced sink capacity and light-use efficiency. By integrating advanced LED technologies and leveraging genetic insights, CEA systems can achieve higher productivity while minimizing energy consumption, paving the way for sustainable and efficient crop production.