The link between pre-harvest lighting and leafy green quality

End-of-production (EOP) lighting, lighting applied for a short duration before harvest, is a strategy to potentially increase the quality of greenhouse-grown leafy greens; however, exact species-specific strategies to deploy lighting are needed.

Therefore, researchers evaluated the effects of EOP light intensity, quality, and duration of application on the growth, morphology, photosystem II efficiency, and postharvest longevity of 'Salanova ® Hydroponic Red Butter' lettuce ( Lactuca sativa L.), 'Astro' arugula ( Eruca sativa Mill.), 'Space' spinach ( Spinacia oleracea L.), and 'Amara' mustard greens ( Brassica carinata A. Braun). Leafy greens were grown in a common greenhouse environment with a 16-hour photoperiod and daily light integral of 8.6 ± 1.2 mol·m −2 ·d −1 for lettuce and arugula, and 9.4 ± 3.0 mol·m −2 ·d −1 for spinach and mustard greens. Seven days, 3 days, or 1 day before harvest, an additional 0 (control), ∼100, 200, 400, or 600 µmol·m −2 ·s −1 photosynthetic photon flux density (PPFD) of broad-spectrum white light [17:40:43 red (R):green (G):blue (B)], or ∼200 µmol·m −2 ·s −1 PPFD R-B (53:1:46 R:G:B) light was provided to plants. Across all species, fresh mass generally increased with increasing EOP light intensity and duration, with the greatest fresh mass observed under ∼600 µmol·m −2 ·s −1 applied for 7 days before harvest. Photosystem II efficiency response was species dependent but was generally lower when light intensity was increased 1 or 3 days before harvest and recovered when light intensity increased 3 or 7 days before harvest. The visual quality of lettuce, spinach, and mustard greens was largely unaffected by EOP light, whereas arugula visual quality improved by increasing the duration of broad-spectrum EOP light when evaluated 1 week postharvest.

These results provide insight on how to effectively leverage light intensity, quality, and duration at the EOP to improve the growth and postharvest longevity of hydroponic greenhouse-grown lettuce, arugula, spinach, and mustard greens.

Friedrich, Jacob & Armstrong, Sarah & Owen, W. & Walters, Kellie. (2026). End-of-Production Lighting Effects on the Growth, Morphology, and Postharvest Longevity of Greenhouse-Grown Leafy Greens. HortScience. 61. 2526-2538. 10.21273/hortsci19696-26.

Source: ResearchGate