Previous studies have reported contrasting effects of light quality on plant growth and anthocyanin content in lettuce leaves. This study aimed to optimize the red-to-blue light ratio with a constant green light fraction to improve biomass and anthocyanin production in red lettuce (Lactuca sativa cv. ‘Lolla Rossa’) in a plant Factory. Six treatments with varying proportions of red (R, 660 nm) and blue (B, 450 nm), along with a constant fraction of green (G, 540 nm) light, recorded as R125:B25:G50, R120:B30:G50, R112:B37:G50, R100:B50:G50, R75:B75:G50, and R50:B100:G50 were set up in this study. The total photosynthetic photon flux density for all treatments was 200 μmol m−2s−1 with a green light intensity of 50 μmol m−2s−1. The results showed that, compared with treatment R50:B100:G50, the fresh and dry weights, leaf length, leaf area and stem width of lettuce plants under treatment R125:B25:G50 showed an increase of 73.4 %, 47.8 %, 35.5 %, 54.9 %, and 58.3 %, respectively. Additionally, red light was found to promote increased weight of lettuce plant roots. Further, the anthocyanin content, nitrate content, and stomata density under treatment R50:B100:G50 were 6.75, 1.5, and 1.42 times higher than those under treatment R125:B25:G50. Enzymatic activities such as hydrogen peroxide (H2O2), superoxide dismutase (SOD), ascorbic acid (AsA), and anthocyanin concentration per fresh weight of plant were higher under treatment R100:B50:G50, comparing with those under treatment R125:B25:G50. The above results indicate that a higher red-to-blue light ratio enhances plant biomass, photosynthesis, and certain nutrients, while increasing the blue ratio promotes anthocyanin accumulation and antioxidants, protecting cells from oxidative stress. Based on this analysis, treatment R100:B50:G50 can be considered as the suitable light spectrum for optimal growth, anthocyanin accumulation and antioxidant activity of lettuce plants. Further researches are needed to explain these effects and refine lighting methods for optimal lettuce production and nutritional quality.

中文翻译：

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在植物工厂中，通过优化红蓝光比和恒定的绿光分数，改善红生菜 （Lactuca sativa cv. Lolla Rossa） 的植物生长、花青素生产和氧化状态


以前的研究报道了光质对生菜叶片中植物生长和花青素含量的对比影响。本研究旨在优化绿光分数恒定的红蓝光比，以提高植物工厂中红生菜 （Lactuca sativa cv. 'Lolla Rossa'） 的生物量和花青素产量。本研究建立了 6 个处理，具有不同比例的红色 （R， 660 nm） 和蓝色 （B， 450 nm） 以及恒定比例的绿色 （G， 540 nm） 光，记录为 R125：B25：G50、R120：B30：G50、R112：B37：G50、R100：B50：G50、R75：B75：G50 和 R50：B100：G50。所有处理的总光合光子通量密度为 200 μmol m-2s-1，绿光强度为 50 μmol m-2s-1。结果表明，与R50：B100：G50处理相比，R125：B25：G50处理生菜植株的鲜重和干重、叶长、叶面积和茎宽分别增加了73.4 %、47.8 %、35.5 %、54.9 %和58.3 %。此外，发现红光会促进生菜植物根的重量增加。此外，R50：B100：G50 处理下的花青素含量、硝酸盐含量和气孔密度分别是 R125：B25：G50 处理下的花青素含量、硝酸盐含量和气孔密度的 6.75 倍、1.5 倍和 1.42 倍。与R125：B25：G50处理下相比，R100：B50：G50处理下过氧化氢（H2O2）、超氧化物歧化酶（SOD）、抗坏血酸（AsA）和花青素浓度等酶活性较高。上述结果表明，较高的红蓝光比可增强植物生物量、光合作用和某些营养物质，而增加蓝光比可促进花青素积累和抗氧化，保护细胞免受氧化应激。 基于此分析，处理 R100：B50：G50 可以被认为是生菜植物最佳生长、花青素积累和抗氧化活性的合适光谱。需要进一步的研究来解释这些影响并改进照明方法以实现最佳的生菜生产和营养质量。