Day-extension Blue Light Inhibits Flowering of Chrysanthemum When the Short Main Photoperiod Includes Far-red Light

Author(s)Kohler, Annika E.
Author(s)Birtell, Eva M.
Author(s)Runkle, Erik S.
Author(s)Meng, Qingwu
Date Accessioned2023-05-10T15:43:13Z
Date Available2023-05-10T15:43:13Z
Publication Date2023-03-16
Description© American Society for Horticultural Science 2023. This article was originally published in Journal of the American Society for Horticultural Science. The version of record is available at: https://doi.org/10.21273/JASHS05294-23
AbstractChrysanthemum (Chrysanthemum ×morifolium) is a common ornamental crop with a qualitative short-day flowering response. Extending a short day with moderate blue [B (400–500 nm)] light inhibits flowering in greenhouse conditions with sunlight but does not indoors (without sunlight) under B + red [R (600–700 nm)] light or white light. We postulated that the contrasting responses to B light as a day extension depended on far-red [FR (700–800 nm)] light during the day, which is plentiful under sunlight but lacking indoors under B+R or white light-emitting diodes. To study this response in three chrysanthemum cultivars, we delivered indoor lighting treatments at two locations with an 11-hour main photoperiod of B, green [G (500–600 nm)], R, and FR light, where subscript values indicate the photon flux density (in µmol·m−2·s−1) of each waveband: B60R120, B60G60R60, and B60R60FR60. After each short main photoperiod, plants received 0 or 4 hours of day-extension lighting of 60 µmol·m−2·s−1 of B light (B60). Under all treatments except B60R60FR60 with day-extension B60, it took ‘Chelsey Pink’, ‘Gigi Gold’, and ‘Gigi Yellow’ 13 to 17 days to reach the first visible inflorescence and 42 to 51 days to the first open flower. In contrast, plants grown under B60R60FR60 with day-extension B60 took 41 to 67 days to reach the first visible inflorescence with few plants developing open flowers. Plants were tallest at the first open flower and after 9 weeks of treatments when grown under B60R60FR60 with day-extension B60. These results indicate that the inclusion of FR light, but not G light, in the main photoperiod is necessary for day-extension B light to inhibit flowering in chrysanthemum. On the basis of these results and those of other studies, we postulate that the spectral dependence of flowering in chrysanthemum depends on whether and how the phytochrome photoequilibrium changes during the day. In particular, a sufficiently high daytime phytochrome photoequilibrium (e.g., under B+R and B+G+R light) could establish a predominant mode of floral signaling that prevents perception of subsequent B light as a long day.
SponsorWe thank Syngenta Flowers, Lucas Greenhouses, and Raker-Roberta’s Young Plants for providing chrysanthemum cuttings, and JR Peters for fertilizers. This study was partially supported by the University of Delaware Graduate College through the Unidel Distinguished Graduate Scholars Award. We appreciate manuscript reviews by Jiyong Shin and Kishan Biradar.
CitationKohler, A. E., Birtell, E. M., Runkle, E. S., & Meng, Q. (2023). Day-extension Blue Light Inhibits Flowering of Chrysanthemum When the Short Main Photoperiod Includes Far-red Light, Journal of the American Society for Horticultural Science, 148(2), 89-98. Retrieved May 10, 2023, from https://doi.org/10.21273/JASHS05294-23
ISSN0003-1062
URLhttps://udspace.udel.edu/handle/19716/32730
Languageen_US
PublisherJournal of the American Society for Horticultural Science
dc.rights.uriThis is an open access article distributed under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywordscontrolled environment
Keywordsgreen light
KeywordsLEDs
Keywordsphytochrome
Keywordsshort-day plant
Keywordsaffordable and clean energy
TitleDay-extension Blue Light Inhibits Flowering of Chrysanthemum When the Short Main Photoperiod Includes Far-red Light
TypeArticle
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