Editorial: Light application in controlled environment horticulture

Introduction

Controlled environment horticulture (CEH) systems, such as greenhouses and vertical farms, are transforming under climate change, urbanization, and the demands for resource efficiency and product quality (Pattison et al., 2018). The use of artificial light-emitting diodes (LEDs) for plant cultivation, pioneered by NASA (Bula et al., 1991), has since evolved into large-scale vertical farming (plant factory with artificial lighting, PFAL) in Japan (Kozai, 2018; 2020) and into precision light recipes for greenhouse crops (Marcelis et al., 2019; Lazzarin et al., 2021). The research focus has shifted from biomass maximization to metabolic regulation. LEDs are recognized not merely as a source of photosynthetic photons but as tools for modulating phenotype, secondary metabolites, and nutritional value. However, significant gaps remain in the development and commercial implementation of cost-effective lighting regimes and canopy-level light management, limiting improvements in crop yield and quality.

This special issue was initiated by our esteemed colleague, Dr. Sasan Aliniaeifard (1981–2025). After training at Wageningen University, he founded a pioneering research centre for controlled environment agriculture at Tehran University in Iran. His work on stomatal conductance, photosynthesis, and photomorphogenesis under LEDs; spectral optimization for greenhouse crops (Ghorbanzadeh et al., 2021; Saeedi et al., 2023; Aliniaeifard et al., 2025; Azizi et al., 2025); and secondary metabolite manipulation (Eftekhari et al., 2023; Fallah et al., 2024) provided the basis for modern light recipes. We dedicate this issue to his memory.

Beyond single-plant studies, this issue offers a systems-based approach to modern light culture. The four studies presented here reveal how light recipes interact with alternative substrates, how light programs non-photosynthetic organisms (mushrooms), and their scaling within circular platforms like aquaponics. Collectively, they provide a framework for next-generation horticulture, linking fundamental regulatory mechanisms with sustainable, closed-loop ecosystems.

Light quality effects and light recipes

The study by Azad and Naznin contributes to our understanding of the effects of supplemental red (R) and far-red (FR) against a white (W) LED background on growth, phytochemicals, and antioxidant accumulation in indoor-grown lettuce and kale. The study revealed species-specific responses: in lettuce, R accelerated vegetative growth, increasing leaf area (+56.5%) and dry weight (+18.8%), while FR increased plant height and fresh weight and chlorophyll content by ~35%; in kale, the combined W+R+FR spectrum induced a dramatic (+572%) increase in anthocyanins, while W+R boosted phenolics by 10.7%. The authors conclude that the combined R+FR spectrum with W produced the most significant enhancement in biomass, pigments, and antioxidant activity for both species. This study highlights the power of spectrum optimization for producing antioxidant-rich functional foods. However, these benefits also present an important physiological challenge: R and FR supplementation also raised leaf nitrate levels by up to 69.1% in kale and by 53.6% in lettuce, underscoring the critical need for further research of light-regulated nitrogen metabolism.

Preharvest lighting for non-photosynthetic organisms

De Bonis et al. extended photobiology to mushrooms, showing that monochromatic LED lights applied during cultivation (not just post-harvest) alter morphology and programs quality of Pleurotus ostreatus (oyster mushroom). Blue (B) light increased cap size and glutamic acid (umami taste), while R light, especially when combined with a mixed specific substrate (wheat straw + cottonseed hulls), provides a pronounced biofortification effect, achieving the highest vitamin D₂ biosynthesis (up to 123 μg kg^-¹ dry weight). B and W light, as well as the R+B combination, maximized fruiting body yields (> 0.300 kg kg^-¹), and B light enhanced essential amino acids (histidine and valine) linked to the umami flavor profile. These findings suggest a potentially new biofortification protocol for producing nutritionally dense mushrooms in protected conditions, as well as underscoring the critical role of substrates in optimizing mushroom production systems.

Monitoring and scaling sustainable production ecosystems

To manage the light scenarios described above, non-invasive phenotyping is essential. Balasus et al. propose reliable visible-spectrum reflectance metrics for monitoring cucumber leaf development. By establishing precise optical markers associated with leaf ontogeny, with particularly strong correlations on the abaxial leaf surface, this work lays the foundation for smart horticulture, in which light spectra can be dynamically adjusted based on real-time plant spectral reflectance. This approach could reduce the need for destructive sampling, enabling automated phenotyping and adaptive lighting management in commercial greenhouses or indoor farming systems.

Finally, Heo et al. present a critical comparative analysis of resource efficiency between a convectional hydroponic system (HS) and an aquaponic system (AS) with Silurus asotus (catfish) for the cultivation of five leafy vegetables and herbs (white leaf beets (Beta vulgaris var. cicla), hooker chives (Allium hookeri), basil (Ocimum basilicum), lemon balm (Melissa officinalis), and spearmint (Mentha spicata)) in an indoor greenhouse facility. Under identical light inputs, AS demonstrates a significant advantage over HS, increasing plant yields due to the natural organic nitrogen source from aquaculture. Leaf yield increased in AS compared to HS, ranging between 60-70% in the case of basil and lemon balms, and a remarkable 200% in the case of chives. The system maintained an optimal NO₃–N concentration of 64 mg L^-¹ demonstrating AS as a highly efficient, organic, and climate-smart alternative.

Conclusions

Collectively, the studies published in this research topic demonstrate that CEH is evolving toward an integrated framework in which LED light spectra, substrate composition, and biological symbiosis (plants-fish-mushroom) are managed as interconnected variables rather than isolated factors. This systems-level perspective can enable more precise control over crop phenotype and nutritional quality while improving overall resource efficiency. Key advancements include non-invasive optical monitoring for real-time plant development assessment, zero-waste aquaponic plant cultivation platforms, and species-specific plant or mushroom light recipes for functional food production. Looking forward, priority research directions should address dynamic preharvest lighting strategies to minimize nitrate accumulation, AI-driven integration of phenotyping data with adaptive lighting control, and comprehensive economic assessments of hybrid system scalability. In a broader context, these technologies hold promise not only for urban agriculture but also for autonomous life-support systems in space exploration. We dedicate this issue to the memory of Dr. Sasan Aliniaeifard, whose vision continues to guide this evolving field.

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Footnotes

Edited and reviewed by: Francesco Di Gioia, The Pennsylvania State University (PSU), United States