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<p>Lettuce (<i>Lactuca sativa</i> L.) is one of the main greenhouse vegetables consumed worldwide. Changes in radiation modes can considerably affect lettuce growth and quality under different nitrogen (N) levels; however, this important factor has not been thoroughly investigated in previous studies. Therefore, the primary aim of this study was to compare the effects of red (R) and blue (B) light supplied simultaneously or individually, using different alternating intervals while maintaining the same daily light integral (DLI). Different N levels—92 (control), 125, 156, and 208&#xa0;mg L⁻<sup>1</sup> (modified Yamazaki solution)—were evaluated to determine the maximum allowable N concentration in the nutrient solution without compromising lettuce quality. The results showed that supplemental lighting, particularly alternating R and B light, significantly increased lettuce shoot fresh and dry weight and improved quality attributes (soluble sugars, antioxidant capacity, vitamin C, total phenols, flavonoids, and photosynthetic pigments) compared with the control or sunlight treatments. Application of up to 156&#xa0;mg L⁻<sup>1</sup> N in the nutrient solution effectively regulated nitrate accumulation in lettuce when combined with intermittent lighting, maintaining nitrate levels below the permissible limit (4.5&#xa0;mg g⁻<sup>1</sup> FW). In contrast, plants exposed to sunlight exhibited a maximum quantum efficiency of photosystem II (Fv/Fm) below 0.79, indicating the presence of stress. Overall, lettuce growth can be enhanced by increasing N levels up to 156&#xa0;mg L⁻<sup>1</sup> without inducing excessive nitrate accumulation or compromising quality.</p>

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Harnessing the Power of Intermittent Red and Blue LED Irradiation for Nitrogen Management in Nutrient Solution: Enhancing Growth, Quality, and Photosynthetic Efficiency in ‘Little Gem’ Lettuce

  • 期刊论文

  • 发表日期：

    2026年4月21日

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  • Hossein Sheikhi,
  • Mojtaba Delshad,
  • Kamahldin Haghbeen,
  • Mesbah Babalar,
  • Sasan Aliniaeifard,
  • Silvana Nicola

摘要

Lettuce (Lactuca sativa L.) is one of the main greenhouse vegetables consumed worldwide. Changes in radiation modes can considerably affect lettuce growth and quality under different nitrogen (N) levels; however, this important factor has not been thoroughly investigated in previous studies. Therefore, the primary aim of this study was to compare the effects of red (R) and blue (B) light supplied simultaneously or individually, using different alternating intervals while maintaining the same daily light integral (DLI). Different N levels—92 (control), 125, 156, and 208 mg L⁻1 (modified Yamazaki solution)—were evaluated to determine the maximum allowable N concentration in the nutrient solution without compromising lettuce quality. The results showed that supplemental lighting, particularly alternating R and B light, significantly increased lettuce shoot fresh and dry weight and improved quality attributes (soluble sugars, antioxidant capacity, vitamin C, total phenols, flavonoids, and photosynthetic pigments) compared with the control or sunlight treatments. Application of up to 156 mg L⁻1 N in the nutrient solution effectively regulated nitrate accumulation in lettuce when combined with intermittent lighting, maintaining nitrate levels below the permissible limit (4.5 mg g⁻1 FW). In contrast, plants exposed to sunlight exhibited a maximum quantum efficiency of photosystem II (Fv/Fm) below 0.79, indicating the presence of stress. Overall, lettuce growth can be enhanced by increasing N levels up to 156 mg L⁻1 without inducing excessive nitrate accumulation or compromising quality.