Abstract
External pollen grain morphology has been widely used in the taxonomy and systematics of flowering plants, especially the Acanthaceae which are noted for pollen diversity. However internal pollen wall features have received far less attention due to the difficulty of examining the wall structure. Advancing technology in the field of microscopy has made it possible, with the use of a focused ion beam–scanning electron microscope (FIB–SEM), to view the structure of pollen grain walls in far greater detail and in three dimensions. In this study the wall structures of 13 species from the Acanthaceae were investigated for features of potential systematic relevance. FIB–SEM was applied to obtain precise cross sections of pollen grains at selected positions for examining the wall ultrastructure. Exploratory studies of the exine have thus far identified five basic structural types. The investigations also show that similar external pollen wall features may have a distinctly different internal structure. FIB–SEM studies have revealed diverse internal pollen wall features which may now be investigated for their systematic and functional significance.
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Acknowledgments
We are deeply grateful to Dr Thomas Malwela from the National Centre for Nanostructured Materials at the CSIR for his time and expertise conducting the FIB work and to Willem Froneman at the Lowveld Botanical Gardens for help with collection of sample species. This work was supported by the National Research Foundation [Grant Number 65704].
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House, A., Balkwill, K. Labyrinths, columns and cavities: new internal features of pollen grain walls in the Acanthaceae detected by FIB–SEM. J Plant Res 129, 225–240 (2016). https://doi.org/10.1007/s10265-015-0777-9
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DOI: https://doi.org/10.1007/s10265-015-0777-9