Planta

, Volume 215, Issue 1, pp 67–78

The shoot apical meristem of Sinapis alba L. expands its central symplasmic field during the floral transition

  • Sandra Ormenese
  • Andrée Havelange
  • Georges Bernier
  • Chris van der Schoot
Original Article

DOI: 10.1007/s00425-002-0746-0

Cite this article as:
Ormenese, S., Havelange, A., Bernier, G. et al. Planta (2002) 215: 67. doi:10.1007/s00425-002-0746-0

Abstract.

The shoot apical meristem (SAM) is functionally subdivided into zones with distinct tasks. During vegetative growth the peripheral zone of the meristem gives rise to leaf primordia that develop into dorsiventral leaves under the influence of signals from the central zone. During the floral transition the function of the SAM is altered and its peripheral zone starts to form floral structures in a specific pattern. This requires alterations in the signal networks that coordinate the activities of the peripheral and central zone of the SAM. These signal networks are partly housed in the symplasmic space of the SAM. Dye-coupling experiments demonstrate that in the superficial layer of the Sinapis alba meristem this space is radially subdivided. The cells of the central zone are coupled into a symplasmic field, which is shielded from the peripheral zone by the positional closing of plasmodesmata. In the vegetative meristems, most of these central symplasmic fields have a triangular geometry and are relatively small in size. Plants that are induced to flower by exposure to a single long day alter the geometry as well as the size of their central symplasmic field. After two subsequent days under short photoperiod the central symplasmic fields exhibit a circular form. Simultaneously, their size strongly increases both in an absolute sense and relative to the enlarging meristem. The geometric change in the fields is hypothesized to be due to recruitment of extra initial cells, required to support the increase in phyllotactic complexity. The proportional increase in field size is interpreted as an adjustment in the balance between the central and peripheral zone of the SAM, accompanying the shift from leaf production to flower formation.

Central zone (shoot apex) Floral transition Plasmodesmata Shoot apical meristem Sinapis (flowering) Central symplasmic field 

Copyright information

© Springer-Verlag 2002

Authors and Affiliations

  • Sandra Ormenese
    • 1
  • Andrée Havelange
    • 1
  • Georges Bernier
    • 1
  • Chris van der Schoot
    • 2
  1. 1.Laboratoire de Physiologie, Département de Biologie végétale, Université de Liège, Sart-Tilman, 4000 Liège, Belgium
  2. 2.ATO, Bornsesteeg 59, P.O. Box 17, 6700 AA Wageningen, The Netherlands
  3. 3.Present address: Plant Developmental Physiology, Department of Biology & Nature Conservation, Agricultural University of Norway, P.O. Box 5014, 1432 Aas, Norway, (e-mail: chris.vanderschoot@ibn.nlh.no, Fax: +47-6494-8502)

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