, Volume 165, Issue 1–3, pp 1–10 | Cite as

Location of cell cycle changes in relation to morphological changes in the shoot apex ofSilene coeli-rosa immediately before sepal initiation

  • Arlette Nougarède
  • D. Francis
  • P. Rondet


Changes in morphology, the mitotic index and the proportions of cells in G1 and G2 were measured in shoot meristems ofSilene coeli-rosa immediately before floral morphogenesis in order to determine whether the known changes to the cell cycle at this time are restricted to a particular region of the apex. Twenty-eight day-old plants were given either 7 long days (LD) plus 2 short days (SD) (day 8 of the LD treatment) or 9 SD [day 8 of the SD control (SDC) treatment]. Plants were sampled on day 8 every 2 h for 12 h and the various cell cycle measurements were performed on sections of the apical meristem. In the inductive LD treatment there was a peak in the mitotic index at 13.00 h and, possibly, the start of another at 19.00 h. At 21.00 h all meristems in this treatment initiated sepals. The mitotic activity at 13.00 and 19.00 h in the LD treatment was a result of significant increases in the mitotic index in the axial, lateral and central sub-axial areas of the apex compared with the corresponding zones in the SDC treatment. At 13.00 h of day 8, 80% of cells were in G2 phase in the axial region in the LD treatment whilst 85% of cells were in G1 in the axial zone in the SDC treatment. In the other zones significantly more cells were in G2 in the LD compared with the SDC treatment as was the case at 19.00 h although not to the same extent as the axial zone at 13.00 h. Thus these data emphasize, for the first time, the mitotic activation and predominance of the G2 population of cells particularly in the axial zone of shoot meristems in the LD treatment. These data are discussed in relation to the synchronisation of cell division which could occur in the prefloral shoot meristem at this time, affecting each shoot apical zone.


Cell cycle Flowering Nuclear DNA content Shoot apex Silene coeli-rosa 



long day


short day


short day control


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Copyright information

© Springer-Verlag 1991

Authors and Affiliations

  • Arlette Nougarède
    • 1
  • D. Francis
    • 2
  • P. Rondet
    • 1
  1. 1.Laboratoire de Cytologie Expérimentale et Morphogenèse VégétaleUniversité Pierre et Marie CurieParis Cedex 05France
  2. 2.School of Pure and Applied BiologyUniversity of WalesCardiff

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