Pollen wall and tapetum development in Plantago major L. (Plantaginaceae): assisting self-assembly

Abstract

We have attempted to elucidate the underlying mechanisms of sporoderm development and pattern determination in Plantago major through a detailed ontogenetic study, using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We aim to compare our observations and interpretation with those on other species. Our study of sporoderm development in Plantago from the early tetrad stage to mature pollen grains has shown that pure physical processes, including self-assembly, which are not under direct genetic control, play an important role and represent evidently one of the instruments of evolution. Our observations fit well with the sequence of self-assembling micellar mesophases and show reiteration of some of them, confirming our self-assembly hypothesis. Some attention was also paid to the possible role of rough and smooth endoplasmic reticulum in the cortical cytoplasm of the developing microspores. The tapetum and Ubisch bodies development are also traced. The importance of detailed ontogenetic studies for understanding the establishment of complex pollen walls in any species and for understanding mechanisms underlying sporoderm development was demonstrated. We also present a simulation, obtained in vitro experiments by self-assembly, mimicking pollen grain of Plantago major. It is clear that, in pollen wall development, biological processes and purely physical factors work in tandem.

Keywords:

• sporoderm ontogeny
• microarchitecture
• micelles
• interdisciplinary studies

Acknowledgements

The research was done using equipment of The Core Facility Centre ‘Cell and Molecular Technologies in Plant Science’ at the Komarov Botanical Institute, RAS (St Petersburg, Russia), with exception of Figure 16Aʹ–Cʹ, taken at Cardiff University, Cardiff, UK, and Figure 16B, taken at Moscow University, Moscow, Russia. The authors are sincerely grateful to the anonymous reviewers for all the comments and advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was provided in the framework of institutional research project of the Komarov Botanical Institute of the Russian Academy of Sciences and partly supported by the Russian Foundation for Basic Research [grant number 14-04-00737] to NG (chemicals, diamond knife and other facilities).