%:50% LED:HPS and two for the 100% HPS section (135 μmol·m −2 ·s −1 ). The control section did not have any supplemental lighting. The red bottom treatment lights were placed at the bottom of the section (at the level of the first leaves) and shone upward
growth. The type, spectra, intensity, and timing of supplemental lighting can each have a large influence on the effects of light on plants ( Choong et al., 2018 ; Craig and Runkle, 2016 ; Demotes-Mainard et al., 2016 ; Gomez and Mitchell, 2015
depend on the intended transplant use, because morphological preferences for scions, rootstocks, or non-grafted production seedlings are different ( Chia and Kubota, 2010 ). Supplemental lighting promotes growth of greenhouse-grown vegetable seedlings by
February ( Korczynski et al., 2002 ). Supplemental lighting is often needed to produce high-quality crops in controlled-environment agriculture but can substantially increase production costs. For example, van Iersel and Gianino (2017) estimated that the
yield and quality of vegetables can be achieved only by using supplemental lighting ( Dorais et al., 1991 ; McAvoy and Janes, 1984 ; Rodriguez and Lambeth, 1975 ; Tibbitts et al., 1987 ). However, the use of supplemental lighting represents an expense
providing supplemental lighting. These lights are expensive to use. Combining the ballast and bulb, a single 400-W HPS light consumes ≈465 W of electrical energy ( Nelson, 2003 ). To provide supplemental light at a PPF of ≈85 μmol·m −2 ·s −1 requires
Supplemental lighting can improve the profitability of greenhouse crop production, and a better quantitative understanding of plant responses to PPFD can facilitate the development of more efficient crop-specific control strategies for greenhouse
winter and early spring (from January through March in the northern hemisphere) when the photosynthetic daily light integral (DLI) can be a limiting production factor. For example, without supplemental lighting (SL), young plants are typically grown under
-quality young plants ( Currey et al., 2012 ; Lopez and Runkle, 2008 ; Oh et al., 2010 ). Previously, the only way for young-plant producers to appreciably increase ambient greenhouse DLI was to provide supplemental lighting (SL) from high-intensity discharge
environment and supplemental lighting treatments. On 4 Nov. (Rep. 1) and 18 Nov. 2013 (Rep. 2), 35-d-old plants were moved to a glass-glazed greenhouse where the day and night air temperature set points were a constant 18 °C. Five plants of each variety were