Light-emitting diodes allow for the application of specific wavelengths of light to induce various morphological and physiological responses. In lettuce (Lactuca sativa), far-red light (700–800 nm) is integral to initiating shade responses which can increase plant growth. In the first of two studies, plants were grown with a similar photosynthetic photon flux density (PPFD) but different intensities of far-red light. The second study used perpendicular gradients of far-red light and PPFD, allowing for examination of interactive effects. The far-red gradient study revealed that increasing supplemental far-red light increased leaf length and width, which was associated with increased projected canopy size (PCS). The higher PCS was associated with increased cumulative incident light received by plants, which increased dry matter accumulation. In the perpendicular gradient study, far-red light was 57% and 183% more effective at increasing the amount of light received by the plant, as well as 92.5% and 162% more effective at increasing plant biomass at the early and late harvests, respectively, as compared to PPFD. Light use efficiency (LUE, biomass/mol incident light) was generally negatively correlated with specific leaf area (SLA). Far-red light provided by LEDs increases the canopy size to capture more light to drive photosynthesis and shows promise for inclusion in the growth light spectrum for lettuce under sole-source lighting.

中文翻译：

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补充远红光刺激生菜生长：消除形态和生理效应

发光二极管允许应用特定波长的光来诱导各种形态和生理反应。在生菜 ( Lactuca sativa ) 中，远红光 (700–800 nm) 对于启动遮荫反应至关重要，从而促进植物生长。在两项研究中的第一项中，植物在具有相似的光合光子通量密度（PPFD）但远红光强度不同的情况下生长。第二项研究使用了远红光和 PPFD 的垂直梯度，可以检查交互效应。远红梯度研究表明，增加补充远红光会增加叶子的长度和宽度，这与预计冠层尺寸（PCS）的增加有关。较高的 PCS 与植物接收的累积入射光增加有关，从而增加了干物质积累。在垂直梯度研究中，远红光在增加植物接收的光量方面分别有效 57% 和 183%，在早收和晚收时增加植物生物量方面分别有效 92.5% 和 162%。分别与 PPFD 相比。光利用效率（LUE，生物量/摩尔入射光）通常与比叶面积（SLA）呈负相关。LED 提供的远红光增加了树冠的尺寸，以捕获更多的光来驱动光合作用，并有望纳入单一光源照明下生菜的生长光谱中。