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The 2009 ASHS Annual Conference

1821:
Long Day Promotes Growth and Flowering of Dwarf Purple Loosestrife

Tuesday, July 28, 2009: 1:15 PM
Lewis (Millennium Hotel St. Louis)
Hyun Jin Kim, Department of Plant Science, Seoul National University, Seoul 151-921, South Korea
Jong Hwa Shin, Plant Science, Seoul National University, Seoul, South Korea
Hyun Hwan Jung, Plant Science, Seoul National University, Seoul, South Korea
Ki Sun Kim, Department of Plant Science, Seoul National University, Seoul 151-921, South Korea
Dwarf purple loosestrife (Lythrum salicaria L.) is a Korea native plant, which has a long flowering period for two months in hot summer. This dwarf type plant has a potential to use for potted flowering plant as well as ground cover plant. For a potted flowering plants, the proper photoperiod condition in greenhouse is required to control growth and flowering. To determine the optimum photoperiod for flowering, seedlings (3-5 cm plant height) of dwarf purple loosestrife with 8 leaves were grown under 10, 12, 13, 14, 16, and 24 h daylength, and night interruption (NI, provided by 5 μmol·m-2·s-1 three-wave lamps from 22:00 to 02:00 HR) in a greenhouse. Secondly, to evaluate the effect of short day treatment (SD, 10 h) followed by long day treatment from NI (LD), plants were grown under SD for 1, 2, 3, 4, 5, 6, 7, and 9 weeks after sowing, and then were moved to LD. The number of lateral shoots and plant height were increased as daylengh increased. Though the highest number of inflorescences was obtained in 24 h daylength, there was no significant difference in the number of inflorescences among 16, 24 h, and NI. Plants when grown in NI flowered 90%, while plants grown under 14, 16, and 24 h daylength flowered 24, 76, and 71%, respectively. Plants grown under 10, 12, and 13 h daylength did not flower until the end of the study. While the number of nodes was not influenced by photoperiod, plant height and the number of lateral shoots decreased as SD exposure after sowing increased from 1 to 9 weeks. Continuous SD exposure inhibited the growth of dwarf purple loosestrife and remained vegetative rosettes throughout the experiment. These results suggest that seedlings should be grown under LD with NI after germination to promote vegetative growth and flowering for potted flowering plants.
T 82-2-880-4571, green17@snu.ac.kr
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