アサガオ百科 ／ 生理学　

アサガオの花芽分化

Copyright 1998-2022　米田 芳秋

植物は発芽の後，茎を伸ばし，葉を展開しながら栄養成長をするが，ある時期になると茎先端にある栄養芽は花の基をつくる花芽に変わる。この栄養芽から花芽への転換はどのようにして起きるのだろうか。植物は一年のどの時期に花を咲かせるか夜昼の長さを測って決めていることを最初に指摘したのはGarner(1920)である。

アサガオでは 1950 年代から京都大学の今村駿一郎氏や滝本敦氏らによって「紫」という品種を用いて花芽分化の研究が始められた。子葉が展開中のアサガオに約８時間半（限界暗期）以上の暗期を繰り返し与えると花芽が分化し，また温度条件がよければ長い暗期を１回与えただけでも花芽ができること，この花芽形成刺激は子葉で生じ，子葉の柄や茎を通って茎の頂芽に伝えられることが分かってきた。この伝達性の花芽形成刺激はフロリゲン(花芽形成物質)と呼ばれているが，その実体はまだ分かっていない。

植物の種類によって時間の長さは異なるが，花芽分化にある暗い時間（限界暗期）より長い暗期を必要とする植物を短日植物という。これに対し，花芽分化にある一定時間より長い明期を必要とするものが長日植物である。アサガオは典型的な短日植物であり，しかも非常に鋭敏に反応するので，花芽分化の研究には国内外を問わず使われている。

以下は一般的な解説書とアサガオを研究材料とした文献の一部である。

一般的な解説書
  1. 瀧本敦 (1973)　ひかりと植物　大日本図書.
  2. 瀧本敦 (1979) 花ごよみ花時計 中央公論社.
  3. 瀧本敦 (1986) ひまわりはなぜ東を向くか 中央公論社.
  4. 瀧本敦 (1998) 花を咲かせるものは何か 花成ホルモンを求めて 中央公論社.
  5. 瀧本敦 (1988) アサガオのつぼみはどうしてできる さ・え・ら書房(やさしい科学).
  6. 十亀好雄（1996） ふしぎな花時計　身近な花で時間を知ろａC 青木書店.

他の植物文献
  1. Aukerman, M.J. and Amasino, R.M. (1998) Floral induction and florigen. Cell 93:491-494.
  2. Ma, H. (1998) Flowering time: From photoperiodism to florigen. Current Biol. 8: R690-R692.
  3. Colasanti, J., Yuan, Z. and Sundaresan, V. (1998) The indeterminate gene encodes a zinc finger protein and regulates a leaf-generated signal required for the transition to flowering in maize. Cell 93:593-603.

アサガオ文献
  1. Imamura, S. and Takimoto, A. (1955) Photoperiodic responses in Japanese morning glory, Pharbitis Nil Chois, a sensitive short-day plant . Bot. Mag. Tokyo 68: 235-241.
  2. Imamura, S. and Takimoto, A.(1956) Transmission rate of the photoperiodic stimulus across the graft union in Pharbitis Nil Chois. Bot. Mag. Tokyo 69: 23-29.
  3. Kimura, K. and Takimoto, A. (1963) Floral initiation in Pharbitis nil subjected to continuous illumination at relatively low temperatures. Effect of various temperatures. Bot. Mag. Tokyo 76: 67-73.
  4. Kimura, K. (1963) Floral initiation in Pharbitis nil subjected to continuous illumination at relatively low temperatures. II. Effect of some factors in culture medium on floral initiation. Bot. Mag. Tokyo 76: 351-358.
  5. Murashige, K. and Murashige, Y. (1963) Photoperiodic sensitivity of Pharbitis nil seedlings of different ages in special reference to growth patterns Bot. Mag. Tokyo 76: 92-99.
  6. Imamura, S., Muramatsu, M., Kitajo, S. and Takimoto, A. (1966) Varietal difference in photoperiodic behavior of Pharbitis nil. Bot. Mag. Tokyo 79: 714-721.
  7. Bennett, R.D., Ko, S.-T. and Heftmann (1966) Effect of photoperiodic floral induction on the metabolism of a gibberellin precursor, (-)-kaurene, in Pharbitis nil. Plant Physiol. 41: 1360-1363.
  8. Imamura, S. (ed.) (1967) Physiology of Flowering in Pharbitis nil (S. Imamura, ed.), pp.15-28. Japanese Society of Plant Physiologists, Tokyo.
  9. Takimoto, A. (1967) General methods of experimentation with Pharbitis nil. In: Physiology of Flowering in Pharbitis nil (S.Imamura.ed.), pp. I-5. Japanese Society of Plant Physiologists, Tokyo.
  10. Imamura, S. (1967) Photoperiodic induction and the floral stimulus. ln: Physiology of Flowering in Pharbitis nil (S. Imamura, ed.), pp.15-28. Japanese Society of Plant Physiologists, Tokyo.
  11. Harada, H. (1967) Flower induction in excised shoot apices of Pharbitis and Chrysanthemum cultured in vitro. Nature 214:1027-1028.
  12. Wada, K. (1967) Studies on the Flower Initiation in Pharbitis Seedlings. I. Ages of Shoot Apices and Initiation Rates of Leaf Primordia at the Shoot Apex. Bot. Mag. Tokyo 80: 161-171.
  13. Wada, K. (1969) Studies on the flower initiation in Pharbitis seedlings. IV. Influences of localized X- or gamma-irradiation Bot.Mag.Tokyo 82:1-5.
  14. Bhar, D.S. and Radforth (1969) Vegetative and reproductive development of shoot apices of Pharbitis nil as influenced by photoperioddism Canad. J. Bot. 47: 1403-1406.
  15. 島津斉徳・樫村勝司・小野沢芳郎・松永誠 (1969) アサガオ品種の日長反応 茨城大学農学部学術報告 17: 1-6.
  16. Chosi, A. (1970) Flowering Responses of Pharbitis nil Seedlings Cultured in Test Tubes to a Single Dark Period. Rep. Fac. Sci., Shizuoka Univ., 5: 55-61.
  17. Bose, T.K. and Harada, H. (1970) Effects of temperature and growth regulating substances on flowering of Pharbitis nil Bot. Mag. Tokyo 83: 281-284.
  18. Bhar, D.S. (1970) ln vitro studies of floral shoot apices of Pharbitis nil. Canad. J. Bot. 48: 1355-1358.
  19. 南谷忠志・中山至大 (1970) 無菌培養花芽に対する諸要因の影響 宮崎大学教育学部紀要自然科学 28: 6-20.
  20. hoshi, A. (1971) Floweringr responses of Pharbitis nil plumules excised after a single dark period. Rep. Faculty Sci., Shizuoka Unv. 6: 87-94.
  21. Zeevaat, J.A.D. (1976) Physiology of flower formation Ann. Rev. Plant Physiol. 27: 321-348.
  22. Groenewald, E.G. and Visser (1978) The effect of arachidonic acid, prostaglandins and inhibitors of prostaglandin synthetase, on the flowering of excised Pharbitis nil shoot apices under different photoperiods Z.Pflanzenphysiol. 88:423-429.
  23. Suge, H. (1980) Inhibition of flowering and growth in Pharbitis nil by the growth retardant Ancymidol. Plant & Cell Physiol. 21:1187-1192.
  24. Ogawa, Y. and King, R.W. (1980) Flowering in seedlings of Pharbitis nil induced by benzyladenine applied under a non-inductive daylength Plant & Cell Physiol. 21:1109-1116.
  25. Nakayama, S., Hashizume, A., and Ono, H. (1981) Further studies on photoperiodism in Pharbitis nil Chois. strain Shifukurin Mem.Fac.Edu., Miyazaki Univ. 49: 29-33.
  26. Ogawa, Yukiyoshi (1981) Stimulation of the flowering of Pharbitis nil Chois. by gibberellin A3: Time dependent action at the apex. Plant & Cell Physiol. 22: 675-681.
  27. Shinozaki, M. and Takimoto, A. (1982) Correlation between long-day flowering and root elongation in Pharbitis nil, strain Kidachi. Plant & Cell Physiol. 23: 1055-1062.
  28. Wada, K. and Shinozaki, Y. (1985) Flowering response in relation to C and N contents of Pharbitis nil plants cultured in nitrogen-poor media Plant & Cell Physiol. 26:525-535.
  29. Dai, Y. and Wang, J. (1987) Relation of polyamine titer to photoperiodisc induction of flowering in Pharbitis nil. Plant Science 51: 135-139.
  30. Ishioka, N., Tanimoto, S.and Harada, H. (1990) Flower-inducting activity of phloem exudate in cultured apices from Pharbitis seedlings Plant & Cell Physiol. 30:705-709.
  31. Ishioka, N., Tanimoto, S. and Harada, H. (1991) Flower-inducting activity of phloem exudates from Pharbitis cotyledons exposed to various photoperioids Plant & Cell Physiol. 32: 921-924.
  32. Ono, M., Yamada, K., Sage, K., Okazaki, M.and Harada, H. (1991) Changes in vitro translated polypeptides of Pharbitis nil Chois., strain Violet cotyledons during the first flower-inductive and non-inductive photoperiods. Plant Science 78: 11-18.
  33. Takeno, K. (1991) Flowering response of Ipomoea batatas scions grafted onto Pharbitis nil stocks. Physiologia Plantarum 83: 682.
  34. Nakanishi, F. Fujii, T. (1992) Appearance of peroxidase isozymes in floral-initiated shoot apices of Pharbitis nil. Physiologia Plantarum 86: 197.
  35. Takeno, K. (1993) Evidence for the involvement of calcium ions in the photoperiodic inducition of flowering in Pharbitis nil Plant & Cell Physiol. 34: 221-225.
  36. King, R.W., Shinozaki, M., Takimoto, A. and Swe, K.L. (1994) Genes for dwarfing and photoperiod flowering response in Pharbitis nil Choisy. J.Plant Res. 107: 215-219.
  37. Wada, N., Shinozaki, M., Iwamura, H. (1994) Flower induction by polyamines and related compounds in seedlings of morning glory (Pharbitis nil cv.Kidachi). Plant & Cell Physiol. 35: 469.
  38. Hirai, N., Yamamuro, M. and Takimoto, A. (1994) Accumulation of phenylpropanoids in the cotyledons of morning glory(Pharbitis nil) seedlings during the induction of flowering by low temperature treatment, and the effect of precedent exposure to high-intensity light. Plant & Cell Physiology 35: 691-472.
  39. Nakanishi, F., Kusumi, T., Inoue, Y. and Fujii, T. (1995) Dihydrokaempferol glucoside from cotyledons promotes flowering in Pharbitis nil. Plant & Cell Physiology 36: 1303-1309.
  40. Takeno, K. (1996) Influences of plant hormones on photoperiodic flowering in Pharbitis nil: re-evaluation by the perfusion technique. Plant Growth Regulation 20: 189.
  41. Takeno, K. Maeda, T. (1996) Abscisic acid both promotes and inhibits photoperiodic flowering of Pharbitis nil. Physiologia Plantarum 98: 467-470.
  42. Wijayanti, L., Fujioka, S. and Sakurai, A. (1997) Involvement of abscisic acid and indole-3-acetic acid in the flowering of Pharbitis nil. J. Plant Growth Regulation 16: 115.
  43. Sage-Ono, K., Ono, M. and Kamada, H. (1998) Accumulation of a clock-regulated transcript during flower-inductive darkness in Pharbitis nil. Plant Physiology 116: 1479.
  44. Kondoh, M., Fukusada, Y. and Tanimoto, S. (1999) Flowering may be controlled by a quantitative balance between flower-inducing and -inhibiting substances in Pharbitis nil. Plant Growth Regulation 28: 101.


Edited by Yuuji Tsukii (Lab. Biology, Science Research Center, Hosei University)