Pseudointegricorpus clarireticulatum (Samoilovitch) Takahashi: morphology and ultrastructure

Abstract

Dispersed tricolpate pollen of Pseudointegricorpus clarireticulatum (Samoil.) Takah. from the Upper Maastrichtian in Zeya-Bureya Basin, Amur (Heilongjiang) River area, Russian Far East/China has been studied with light and electron microscopy. Pollen size, pole outlines and the shape of equatorial projections show some variation within the species. The exine is striate-reticulate, semitectate and columellate. The species is characterised by highly complex structures that have harmomegathic function and include equatorial projections, endexinous thickenings, difference in the thickness of the infratectum, foot layer and endexine throughout the pollen grain, and equatorial furrows. Exine layers taper towards colpi regions while they break abruptly in furrow regions. The furrows could have helped to shed the exine quickly and enabled pollen germination. A non-extended region with a small cavity in the ectexine was observed in the equatorial region. We think that this region is characteristic of most Triprojectate species.

Keywords::

• Triprojectates
• ultrastructure
• harmomegathy
• pollen

Acknowledgements

We particularly thank Prof. A. Mihai Tomescu for correcting the English in our manuscript. The manuscript was improved through helpful comments from an anonymous reviewer. The work was carried out at A.A. Borissiak Paleontological Institute (LM, SEM) and at the Core Centrum ‘Cell and Molecular Technologies in Plant Science’ in the Komarov Botanical Institute, (CLSM).

Additional information

Funding

This study was supported by the Russian Foundation for Basic Research [grant number 12-04-01335] and by the grant of President RF [grant number MK-3156.2014.4]. The TEM work was performed at User facilities centre of M.V. Lomonosov Moscow State University under financial support of Ministry of Education and Science of RF.