ORIGINAL RESEARCH article
Front. Plant Sci.
Sec. Crop and Product Physiology
This article is part of the Research TopicAdvancements in Light Management Strategies for Crop ProductivityView all 15 articles
Continuous Lighting at Low PPFD Improves Energy Efficiency While Preserving Growth and Quality of Lettuce in Vertical Farming systems
Provisionally accepted
Onofrio Davide Palmitessa*
Leonardo Costanza
Alessio Elia
Ettore CantatoreBeniamino Leoni
Angelo Signore
Graziana Difonzo
Francesco Caponio
Pietro Santamaria- Universita degli Studi di Bari Aldo Moro Dipartimento di Scienze del Suolo della Pianta e degli Alimenti, Bari, Italy
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Vertical farming systems (VFs) offer high production efficiency in controlled environments (CEA), but their energy requirement and associated carbon footprint are strongly constrained by the high energy demand of artificial lighting. This study assessed whether different combinations of photoperiod and photosynthetic photon flux density (PPFD; 16 L:8 D at 250 µmol m⁻² s⁻¹, 12 L:12 D at 340 µmol m⁻² s⁻¹, and continuous 24 L:0 D at 170 µmol m⁻² s⁻¹) affect growth, physiology, and energy performance of two crisphead lettuce cultivars [Lactuca sativa L. var. crispa, 'Falstaff' (green) and 'Copacabana' (red)] when the daily light integral (DLI) is maintained constant (14.4 mol m⁻² day⁻¹). Yield, morphological traits, chlorophyll fluorescence, and gas exchange parameters did not differ among lighting treatments, indicating comparable photosynthetic functioning under all photoperiod–PPFD combinations. However, continuous lighting (24 L:0 D) improved energy use efficiency (EUE) and light use efficiency (LUE), while reducing lighting costs per unit of produced biomass and demonstrating a clear benefit in terms of resource utilization. Cultivar-related differences were more pronounced than treatment effects, with red lettuce showing higher levels of phenolic compounds, carotenoids, anthocyanins, and antioxidant capacity, while maintaining similar morphological responses. Overall, the results show that under a constant DLI, photoperiod manipulation obtained by adjusting PPFD has a limited impact on plant physiology but can substantially influence yield and energy efficiency. Continuous moderate-intensity lighting thus emerges as an effective strategy to enhance the economic and environmental sustainability of VFs without compromising crop performance.
Keywords: CEA, EUE, Growth chamber, leafy vegetables, LUE, photoperiod
Received: 08 Jan 2026; Accepted: 13 Feb 2026.
Copyright: © 2026 Palmitessa, Costanza, Elia, Cantatore, Leoni, Signore, Difonzo, Caponio and Santamaria. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Onofrio Davide Palmitessa
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