Pollen grains of Ephedra tweediana C.A.Mey., recent species of the Ephedraceae in Brazil

Abstract

Ephedra tweediana is one of few gymnosperms native to Brazil and the sole species of the Ephedraceae family. The present work examines the pollen grains of E. tweediana using light and scanning electron microscopy in order to obtain additional morphological data and to help to identify it in its fossil forms. Ephedra tweediana pollen grains are monad, medium sized, ellipsoidal, inaperturate, characterised by a series of psilate longitudinal ridges (or plicae), typically ten, with small polar apices that protrude. The wide gently domed ridges are straight and psilate, separated by a psilate region (furrows) with a distinct, unbranched, slightly undulating hyaline line formed by the thinning of the sexine located in the middle of the furrow area. The granular sexine at the crest of a plica is composed of a homogeneous tectum, below which an infratectum is apparent. The infratectum disappears into the furrows. The nexine is uniform in thickness in all regions. Pollen of E. tweediana is characterised by the merging of the Steeves and Barghoorn’s Type C and D. However, occasional pollen grains of the Type B occur with undulant ridges. The pollen grains of E. tweediana resemble those of E. trifurca and E. chilensis (syn. E. andina in Steeves and Barghoorn’s work). Few pollen grains resemble the E. chilensis presented by these authors in Type B. This similarity hinders the identification of these American species in sediments containing microfossils.

Keywords:

• pollen morphology
• palynotaxonomy
• Ephedra tweediana

Acknowledgements

The authors thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for a fellowship of ‘Productivity in Research’ (process 301134/2013-8). Thanks to Erik Bernhard Lidgren for the English translation and to Catarina Rydin and Carina Hoorn for helpful suggestions to improve the manuscript.

ORCID

Cynthia Fernandes Pinto da Luz http://orcid.org/0000-0001-7908-155X