Journal Article

Release of developmental constraints on tetrad shape is confirmed in inaperturate pollen of <i>Potamogeton</i>

Elaine Lopes Pereira Nunes, Cleusa Bona, Maria Cecília de Chiara Moço and Alessandra Ike Coan

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 104, issue 5, pages 1011-1015
Published in print October 2009 | ISSN: 0305-7364
Published online June 2009 | e-ISSN: 1095-8290 | DOI:
Release of developmental constraints on tetrad shape is confirmed in inaperturate pollen of Potamogeton

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry


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Background and Aims

Microsporogenesis in monocots is often characterized by successive cytokinesis with centrifugal cell plate formation. Pollen grains in monocots are predominantly monosulcate, but variation occurs, including the lack of apertures. The aperture pattern can be determined by microsporogenesis features such as the tetrad shape and the last sites of callose deposition among the microspores. Potamogeton belongs to the early divergent Potamogetonaceae and possesses inaperturate pollen, a type of pollen for which it has been suggested that there is a release of the constraint on tetrad shape. This study aimed to investigate the microsporogenesis and the ultrastructure of pollen wall in species of Potamogeton in order to better understand the relationship between microsporogenesis features and the inaperturate condition.


The microsporogenesis was investigated using both light and epifluorescence microscopy. The ultrastructure of the pollen grain was studied using transmission electron microscopy.

Key Results

The cytokinesis is successive and formation of the intersporal callose wall is achieved by centrifugal cell plates, as a one-step process. The microspore tetrads were tetragonal, decussate, T-shaped and linear, except in P. pusillus, which showed less variation. This species also showed a callose ring in the microsporocyte, and some rhomboidal tetrads. In the mature pollen, the thickening observed in a broad area of the intine was here interpreted as an artefact.


The data support the view that there is a correlation between the inaperturate pollen production and the release of constraint on tetrad shape. However, in P. pusillus the tetrad shape may be constrained by a callose ring. It is also suggested that the lack of apertures in the pollen of Potamogeton may be due to the lack of specific sites on which callose deposition is completed. Moreover, inaperturate pollen of Potamogeton would be better classified as omniaperturate.

Keywords: Alismatales; callose; microsporogenesis; pollen aperture; Potamogeton illinoensis; P. polygonus; P. pusillus; tetrad shape

Journal Article.  3093 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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