Stomata in Equisetum

Photo credit: AOB

Drawings of Equisetum stomata. (A) E. palustre; fig. 10 from Duval-Jouve (1864). (B) E. fluviatile; fig. 12 from Riebner (1925).

The remarkable stomata of horsetails (Equisetum): patterning, ultrastructure and development

by Cullen E.,

Rudall P. J.paula-rudall-cropped


in Ann Bot (2016)doi: 10.1093/aob/mcw094 –

Equisetum myriochaetum (A, B, LM; C, DIC; E, F, SEM). (A) Thin paradermal section of a mature stoma showing radiating ribs on subsidiary cells. (B) Thick paradermal section of a mature stoma with radiating ribs. Both guard cells and superadjacent subsidiary cells are visible. (C) Oblique view of a mature stoma showing radiating ribs. (D) Transverse section of a mature sunken stoma, showing silica on the surface of subsidiary cells. (E) Macerated stoma showing radiating ribs. gc, guard cell; gcn, guard cell nucleus; rr, radiating ribs; sc, subsidiary cell; sc, silica. Scale bars: 10 μm in (A−D), 5 μm in (E). –


Background and Aims The stomata of Equisetum – the sole extant representative of an ancient group of land plants – are unique with respect to both structure and development, yet little is known about details of ultrastructure and patterning, and existing accounts of key developmental stages are conflicting.

Methods We used light and electron microscopy to examine mature stomata and stomatal development in Equisetum myriochaetum, and compared them with other land plants, including another putative fern relative, Psilotum. We reviewed published reports of stomatal development to provide a comprehensive discussion of stomata in more distantly related taxa.

Key Results Stomatal development in Equisetum is basipetal and sequential in strict linear cell files, in contrast with Psilotum, in which stomatal development occurs acropetally. In Equisetum, cell asymmetry occurs in the axial stomatal cell file, resulting in a meristemoidal mother cell that subsequently undergoes two successive asymmetric mitoses. Each stomatal cell complex is formed from a single precursor meristemoid, and consists of four cells: two guard cells and two mesogene subsidiary cells. Late periclinal divisions occur in the developing intervening cells.

Conclusions In addition to the unique mature structure, several highly unusual developmental features include a well-defined series of asymmetric and symmetric mitoses in Equisetum, which differs markedly from Psilotum and other land plants. The results contribute to our understanding of the diverse patterns of stomatal development in land plants, including contrasting pathways to paracytic stomata. They add to a considerable catalogue of highly unusual traits of horsetails – one of the most evolutionarily isolated land-plant taxa.


Published by

Willem Van Cotthem

Honorary Professor of Botany, University of Ghent (Belgium). Scientific Consultant for Desertification and Sustainable Development.

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s