Dou Haijie, Li Xin, Li Zhixin, Song Jinxiu, Yang Yanjie, Yan Zhengnan
College of Intelligent Science and Engineering, Beijing University of Agriculture, Beijing 102206, China.
College of Horticulture, Qingdao Agricultural University, Qingdao 266109, China.
Plants (Basel). 2024 Aug 5;13(15):2169. doi: 10.3390/plants13152169.
Adding far-red (FR, 700-800 nm) light to photosynthetic active radiation (400-700 nm) proved to be a possible approach to increasing plant biomass accumulation for lettuce production in indoor vertical farms with artificial lighting as a sole-source lighting. However, how FR light addition influences plant growth, development, and metabolic processes and the optimal value of FR photon flux density for greenhouse-grown lettuce under sunlight are still unclear. This work aims to quantify the value of supplementary FR light with different intensities on lettuce morphological and physiological characteristics in a greenhouse. Lettuce 'Dasusheng' ( L.) was grown in a greenhouse under seven light treatments, including white plus red LEDs with FR photon flux density at 0, 10, 30, 50, 70, and 90 µmol m s (WR, WR + FR10, WR + FR30, WR + FR50, WR + FR70, and WR + FR90, respectively), and lettuce grown with sunlight only was marked as natural light (NL). FR light addition improved the electron transport flux per cross section and performance index (PI, PI) and decreased the changes in relative variable fluorescence of lettuce leaves compared to plants under NL. Specifically, the PI of lettuce leaves were 41%, 41%, 38%, 33%, 26%, and 25% lower under control than in plants under treatments WR + FR90, WR + FR70, WR + FR50, WR + FR30, WR + FR10, and WR, respectively. Leaf number, leaf area, and biomass accumulation of lettuce followed a quadratic function with increasing FR light intensity and were the highest under treatment WR + FR50. The shoot fresh weight and dry weight of lettuce were increased by 111% and 275%, respectively, under treatment WR + FR50 compared to NL. The contents of vitamin C, reducing sugar, total soluble sugar, and starch in lettuce showed a similar trend with biomass accumulation. In conclusion, with commonly used photosynthetic photon flux density (PPFD, 400-700 nm) around 200 μmol m s, supplementary FR light intensity of 30~50 μmol m s was suggested to enhance the photochemistry efficiency, biomass accumulation, and carbohydrates' contents in greenhouse-grown lettuce.
在以人工照明作为唯一光源的室内垂直农场中，在光合有效辐射（400 - 700纳米）中添加远红光（FR，700 - 800纳米）被证明是一种增加生菜产量中植物生物量积累的可行方法。然而，添加FR光如何影响植物生长、发育和代谢过程，以及在阳光下温室种植生菜时FR光子通量密度的最佳值仍不清楚。这项工作旨在量化不同强度的补充FR光对温室中生菜形态和生理特征的影响。生菜品种“达速生”在温室中进行七种光照处理，包括FR光子通量密度分别为0、10、30、50、70和90微摩尔·米⁻²·秒⁻¹的白色加红色发光二极管（分别为WR、WR + FR10、WR + FR30、WR + FR50、WR + FR70和WR + FR90），仅在自然光下生长的生菜标记为自然光（NL）。与NL处理下的植物相比，添加FR光提高了生菜叶片每横截面积的电子传递通量和性能指数（PIabs），并降低了生菜叶片相对可变荧光的变化。具体而言，对照处理下生菜叶片的PIabs分别比WR + FR90、WR + FR70、WR + FR50、WR + FR30、WR + FR10和WR处理下的植物低41%、41%、38%、33%、26%和25%。生菜的叶片数、叶面积和生物量积累随FR光强度增加呈二次函数变化，在WR + FR50处理下最高。与NL相比，WR + FR50处理下生菜的地上部鲜重和干重分别增加了111%和275%。生菜中维生素C、还原糖、总可溶性糖和淀粉的含量与生物量积累呈现相似趋势。总之，在常用光合光子通量密度（PPFD，400 - 700纳米）约为200微摩尔·米⁻²·秒⁻¹的情况下，建议补充30~50微摩尔·米⁻²·秒⁻¹的FR光强度，以提高温室种植生菜的光化学效率、生物量积累和碳水化合物含量。
