Light/Dark Cycle Lighting Influences Growth and Energy Use Efficiency of Hydroponic Lettuces in an LED Plant Factory
The alterable light/dark cycle in a plant factory with artificial lighting eliminates the traditional concept of day and night in nature. Adjusting the light/dark cycle to closely align with the inherent circadian rhythm of plants can enhance biomass accumulation. In this study, we examined the effe...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
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| Series: | Biology |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2079-7737/14/5/571 |
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| Summary: | The alterable light/dark cycle in a plant factory with artificial lighting eliminates the traditional concept of day and night in nature. Adjusting the light/dark cycle to closely align with the inherent circadian rhythm of plants can enhance biomass accumulation. In this study, we examined the effects of different light/dark cycles on the photosynthetic performance, growth, and energy use efficiency of two hydroponic lettuce cultivars (<i>Lactuca sativa</i> L. cv. ‘Frillice’ and ‘Crunchy’). The lettuces were subjected to four light/dark cycle treatments—16 h light/8 h dark (L<sub>16</sub>D<sub>8</sub>, as control), 12 h light/6 h dark (L<sub>12</sub>D<sub>6</sub>), 8 h light/4 h dark (L<sub>8</sub>D<sub>4</sub>), and 4 h light/2 h dark (L<sub>4</sub>D<sub>2</sub>), all under LED lamps with white combined red chips at the same light intensity of 250 μmol m<sup>−2</sup> s<sup>−1</sup>. Photosynthetic performance and growth index were measured during the slow and rapid growth stages, corresponding to days 9 and 21 after transplanting, respectively. For Frillice, L<sub>12</sub>D<sub>6</sub> achieved the highest shoot dry weight and light and electricity energy use efficiencies on days 9 and 21 after transplanting, primarily due to the largest leaf area, leaf number, and net photosynthetic rate. For Crunchy, L<sub>12</sub>D<sub>6</sub> and L<sub>8</sub>D<sub>4</sub> increased shoot fresh and dry weights due to larger leaf area and leaf number on day 9 after transplanting compared with L<sub>16</sub>D<sub>8</sub>. Subsequently, the lettuces in L<sub>16</sub>D<sub>8</sub> exhibited a rapid increase in leaf area and leaf number, along with a high net photosynthetic rate during the rapid growth stage, resulting in fast shoot biomass accumulation. There were no significant differences in the shoot dry weight and energy use efficiency between L<sub>16</sub>D<sub>8</sub> and L<sub>12</sub>D<sub>6</sub> on day 21 after transplanting. Two lettuce cultivars in L<sub>16</sub>D<sub>8</sub> both exhibited the highest water use efficiency on day 21 after transplanting. In conclusion, the light/dark cycle lighting can alter lettuce biomass accumulation by modifying plant morphology and leaf net photosynthetic rate. Additionally, the physiological response to the light/dark cycle was cultivar-dependent. Our findings provide valuable insights for optimizing hydroponic lettuce production to achieve high yield in LED plant factories. |
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| ISSN: | 2079-7737 |