Sexual Plant Reproduction

, Volume 23, Issue 4, pp 291–300 | Cite as

Reduction in the critical dark length for flower induction during aging in the short-day plant Pharbitis nil var. Kidachi

  • Hiroshi Hasegawa
  • Mizuki Yamada
  • Yuiko Iwase
  • Kaede C. Wada
  • Kiyotoshi Takeno
Original Article


The stress-sensitive short-day plant Pharbitis nil var. Kidachi flowers under a 16-h light and 8-h dark regime and non-stress conditions when grown for long periods of time. Such flowering was found to occur from the third week, and the floral buds were formed from the eighth node of the main stem. When young plants were grafted onto aged plants, the scions were induced to flower early. This flower induction by grafting was more effective when older plants were used as rootstocks. Grafting experiments using a single leaf as a donor revealed that younger leaves are more responsive to flower induction, suggesting that this age-mediated flowering response is not induced by aging or senescence of individual leaves. Rather, the plant may obtain the ability to flower as the whole plant ages. Flowering does not occur under continuous light conditions. A night break given in the 8-h dark period inhibits flowering. These results suggest that 8-h dark conditions, which are normally considered to be long-day conditions, actually correspond to short-day conditions for this plant. The 8-h dark conditions caused early flowering more efficiently in older plants. The critical dark length determined by a single treatment was 12 h in 0-week-old plants and was reduced to 6 h in 2- and 4-week-old plants. These results suggest that the critical dark length becomes shorter when plants get older. The expression of PnFT1 and PnFT2, orthologs of the flowering gene FLOWERING LOCUS T, was analyzed by reverse transcription-polymerase chain reaction revealing that the expression of PnFT at the end of dark period is correlated with flowering.


Aging Flowering FLOWERING LOCUS T Grafting Pharbitis nil 



Continuous light






Reverse transcription-polymerase chain reaction




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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Hiroshi Hasegawa
    • 1
  • Mizuki Yamada
    • 1
  • Yuiko Iwase
    • 1
  • Kaede C. Wada
    • 1
  • Kiyotoshi Takeno
    • 1
    • 2
    • 3
  1. 1.Graduate School of Science and TechnologyNiigata UniversityIkarashiJapan
  2. 2.Department of Biology, Faculty of ScienceNiigata UniversityIkarashiJapan
  3. 3.Center for Transdisciplinary ResearchNiigata UniversityIkarashiJapan

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