Abstract When the natural photoperiod is short, electric lighting can be used to promote flowering of a wide range of ornamental long-day plants (LDP) grown inside greenhouses. A combination of red (R; 600–700 nm) and far-red (FR; 700–800 nm) radiation is effective when delivered at a low intensity (1–2 μmol m−2 s−1), but recent research shows blue (B; 400–500 nm) radiation can also be effective. We performed an experiment, replicated in time, that identified the B photon flux density that controlled flowering of four LDPs when delivered as a 4-h night interruption (NI) or 7-hour day extension (DE) during an otherwise 15-h night. Seedlings of four annual bedding plants were initially grown under a 9-h day, and then were transferred to one of seven lighting treatments, where subscripts indicate their photon flux densities: R+FR2–3 NI; B5, B15, or B30 NI; and B5, B15, or B30 DE. At a sufficiently high photon flux density, B radiation delivered as a 4-h NI or 7-h DE promoted flowering of all four LDPs. All species exhibited a dose-response relationship between B photon flux density and flowering time. The threshold B photon flux density above which flowering was promoted varied among the four LDPs, and was 5 μmol m−2 s−1 for coreopsis (Coreopsis grandiflora) and snapdragon (Antirrhinum majus) and 15 μmol m−2 s−1 for petunia (Petunia × hybrida) and rudbeckia (Rudbeckia hirta). A B photon flux density of 15 or 30 μmol m−2 s−1 delivered as an NI or DE was usually as effective as 2–3 μmol m−2 s−1 of R + FR radiation for all LDPs tested. We conclude that while flowering of LDPs is more sensitive to R + FR than B radiation, relatively low B photon flux densities are perceived as a long day when delivered as a DE or NI.

中文翻译：

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蓝色辐射信号并使几种长日照植物在作物特定光子通量密度下的光周期开花饱和

摘要 当自然光周期短时，电灯可用于促进温室内生长的多种观赏性长日照植物（LDP）开花。红色（R；600–700 nm）和远红（FR；700–800 nm）辐射的组合在以低强度（1–2 μmol m-2 s-1）传输时是有效的，但最近的研究表明蓝色（B；400–500 nm）辐射也可能有效。我们进行了一项及时复制的实验，确定了 B 光子通量密度，当在 15 小时夜间以 4 小时夜间中断 (NI) 或 7 小时白天延长 (DE) 交付时，控制四个 LDPs 的开花. 四种一年生垫料植物的幼苗最初在 9 小时内生长，然后转移到七种光照处理中的一种，其中下标表示它们的光子通量密度：R+FR2-3 NI；B5, B15, 或 B30 NI；和 B5、B15 或 B30 DE。在足够高的光子通量密度下，以 4 小时 NI 或 7 小时 DE 形式提供的 B 辐射促进了所有四种 LDP 的开花。所有物种都表现出 B 光子通量密度和开花时间之间的剂量反应关系。促进开花的阈值 B 光子通量密度在四种 LDPs 中各不相同，金鸡菊（金鸡菊）和金鱼草（Antirrhinum majus）为 5 μmol m-2 s-1，矮牵牛为 15 μmol m-2 s-1 (Petunia × hybrida) 和黄金菊 (Rudbeckia hirta)。对于所有测试的 LDP，作为 NI 或 DE 提供的 15 或 30 μmol m-2 s-1 的 AB 光子通量密度通常与 2-3 μmol m-2 s-1 的 R + FR 辐射一样有效。我们得出结论，虽然 LDPs 的开花对 R + FR 比 B 辐射更敏感，