While the use of narrowband irradiance regimes containing different blue light fractions has proven useful to unravel blue light effects on plants at a fundamental level, it does not quantify the responses to blue light under natural daylight conditions. The objective of this study is to understand the blue light growth responses by combining photosynthetic measurements with measurements of whole plant light absorption in a simulated daylight spectrum enriched with different levels of blue light. To achieve this, tomato plants were grown under six different combinations of artificial solar light and blue LED light. Light treatments were defined by the blue light (400–500 nm) fraction of total photosynthetic photon flux density (400–700 nm) and included 27 % (no additional blue LED), 28 %, 31 %, 38 %, 43 % and 61 % blue light with a total photosynthetic photon flux density of 100 μmol m⁻² s^-1 in all treatments. Whole plant light absorption was estimated by using ray tracing simulation combined with measured 3-dimensional structure of the plant and optical properties of the leaves. The total dry weight of the plants decreased linearly with the increase of blue light fraction; the dry weight of the plants grown under 27 % blue being 1.6 times greater than that of the plants grown under 61 % blue. This large difference was related to lower light absorption by the plants when fraction blue light increased, due to more compact morphology, i.e. lower leaf area, leaf length/width ratio and shorter stem. Light-limited quantum yield and maximum photosynthetic capacity were not affected by blue light fraction. In the case of the latter, which in other studies has often been found to be positively related to blue light fraction, it may be that the blue light fraction already present in the daylight source had saturated this response. Overall, increasing the blue light fraction in a solar light background decreases growth mainly through its effect on plant morphology and light interception. It remains to be elucidated whether the responses observed using the low growth light intensity in the present study are maintained in high light growth environments more characteristic for tomato growth and production.

虽然已证明使用包含不同蓝光含量的窄带辐照制度有助于从根本上揭示蓝光对植物的影响，但它无法量化自然日光条件下对蓝光的响应。这项研究的目的是通过将光合作用测量与在富含不同水平蓝光的模拟日光光谱中对整个植物的光吸收进行测量相结合，来了解蓝光的生长响应。为了实现这一目标，番茄植物在六种不同的人造太阳光和蓝色LED灯组合下生长。光照处理由总光合光子通量密度（400-700 nm）中的蓝光（400–500 nm）部分定义，包括27％（无其他蓝色LED），28％，31％，38％，⁻² s ^-1在所有治疗中。通过使用射线追踪模拟，结合测得的植物三维结构和叶片的光学特性，估算了整个植物的光吸收。随着蓝光分数的增加，植物的总干重呈线性下降。在27％蓝色下生长的植物的干重是61％蓝色下生长的植物的干重的1.6倍。更大的差异与蓝光分数增加时植物吸收的光有关，这归因于更紧凑的形态，即较低的叶片面积，叶片长/宽比和较短的茎。受光限制的量子产率和最大光合能力不受蓝光分数的影响。对于后者，在其他研究中经常发现与蓝光分数呈正相关，可能是日光光源中已经存在的蓝光部分已经饱和了该响应。总体而言，增加太阳光背景下的蓝光比例会降低生长，主要是因为其对植物形态和光的截留作用。有待阐明在本研究中使用低生长光强度观察到的响应是否在更具有番茄生长和生产特征的高光生长环境中得以维持。