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Emma Bradford, James F. Hancock and Ryan M. Warner

and Waldo, 1934 ), and photoperiod-insensitive varieties are defined as day neutral (DN) ( Bringhurst and Voth, 1978 ). However, early on, Darrow (1936) described the influence of temperature on flower initiation in strawberry, indicating the

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Ryan M. Warner

, when light levels are low and ambient photoperiods are short, necessitating the use of supplemental lighting to promote flowering. Breeding efforts have been successful in reducing the strength of the photoperiodic response (i.e., reducing the delay in

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Erik S. Runkle, Royal D. Heins, Arthur C. Cameron and William H. Carlson

To determine the flowering requirements of Rudbeckia fulgida Ait. `Goldsturm', plants were grown under 9-hour photoperiods until maturity, then forced at 20 °C under one of seven photoperiods following 0 or 15 weeks of 5 °C. Photoperiods consisted of a 9-hour day that was extended with incandescent lamps to 10, 12, 13, 14, 16, or 24 hours; an additional treatment was a 9-hour day with a 4-hour night interruption (NI). Noncooled `Goldsturm' remained vegetative under photoperiods ≤13 hours, and essentially all plants flowered under photoperiods ≥14 hours or with a 4-hour NI. Flowering percentages for cooled plants were 6, 56, or ≥84 under 10-, 12-, or ≥13-hour daylengths and NI, respectively. Critical photoperiods were ≈14 or 13 hours for noncooled or cooled plants, respectively, and base photoperiods shifted from 13 to 14 hours before cold treatment to 10 to 12 hours following cold treatment. Within cold treatments, plants under photoperiods ≥14 hours or NI reached visible inflorescence and flowered at the same time and developed the same number of inflorescences. Fifteen weeks of cold hastened flowering by 25 to 30 days and reduced nodes developed before the first inflorescence by 28% to 37%. Cold treatment provided little or no improvement in other measured characteristics, such as flowering percentage and uniformity, flower number, plant height, and vigor.

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David C. Annis, Paul T. Gibson and Terri Woods Starman

The objective of this study was to investigate the influence of photoperiod and 0, 1, 5, or 10 applications at weekly intervals of GA3 foliar sprays at 500 mg·liter–1 on growth and flowering of Craspedia globosa `Drumstick' Benth. Long days (LD) hastened flowering and increased the number of flowers per plant. Short days (SD) increased foliage height and foliage fresh and dry weights. Foliage and total plant heights increased and days to bud and secondary inflorescence width decreased linearly as GA3 application frequency increased. Chemical name used: (1α,2β,4aα,4bβ,10β)-2,4a,7-trihydroxy-1-methyl-8-methylen egibb-3-ene-1,10-dicarboxylic acid 1,4a-lactone (gibberellic acid, GA3).

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J.E. Erwin, R. Warner, T. Smith and R. Wagner

102 POSTER SESSION 4F (Abstr. 224–233) Photoperiod/Temperature/Growth—Floriculture

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Shi-Ying Wang, William H. Carlson and Royal D. Heins

102 POSTER SESSION 4F (Abstr. 224–233) Photoperiod/Temperature/Growth—Floriculture

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A. Cutlan, J.E. Erwin, H. Huntington and J. Huntington

102 POSTER SESSION 4F (Abstr. 224–233) Photoperiod/Temperature/Growth—Floriculture

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John Erwin, Rene O’Connell and Ken Altman

colorful and/or uniquely shaped scions as potted plants ( Kim and Kim, 2006 ). Erwin (1996) subsequently researched temperature and photoperiod effects on grafted cacti growth to decrease scion losses. Little recent work has focused on desert cacti

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Anne Fennell and Emily Hoover

Abbreviations: KT, killing temperature; LD, long photoperiod; ND, natural photoperiod; SD, short photoperiod. 1 Present address: Plant Molecular Biology Center, Montgomery Hall, Northern Illinois Univ., Dekalb, IL 60115-2861. Science Journal Series

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Ariana P. Torres and Roberto G. Lopez

crop quality ( Erwin, 2009 ; Warner and Erwin, 2003 ). Tropical plants of equatorial origin are believed to be more sensitive to small differences in daylength (photoperiod) than those from temperate regions ( Sanford, 1974 ). Plant responses