Global first as researchers split pollen

South African researchers have become the first to cut sections through pollen grains and make it possible to view a three-dimensional image of the internal wall. This will allow the scientists to determine how the characteristics of the internal wall help to classify plants of particular interest.

Alison House, a PhD student at the University of the Witwatersrand, or Wits, is the international pioneer of this technique with her research on Acanthaceae, a large family of plants with a wide range of pollen features but whose classification remains contentious.

House says it is difficult to find features that define Acanthaceae as a family but one of the features that has been used is pollen. She says that until now, all of the research has been done by looking at the external features of the pollen – what it looks like on the outside.

Under the supervision of Professor Kevin Balkwill, House used a focused ion beam-scanning electron microscope to slice through the pollen grains of species belonging to Acanthaceae. She then used an ordinary scanning electron microscope to look at the inside walls exposed by the cut.

‘Kevin had the idea that this microscope could be used. People have used it to look at fossilised pollen but it’s the first time it’s been done on fresh pollen from living plants,’ says House.

The focused beam microscope is similar to the scanning electron version but where the latter uses a focused beam of electrons to image the surface of a sample in the chamber, the FIB uses a focused beam of ions to cut a section through a sample in a chosen position. Wits has one of only two or three of the focused beam microscopes in South Africa.

House’s experiments proved it was possible to use the technique to get a three dimensional image of the internal wall structure of the pollen grains. She says this means researchers can now see features in the internal wall that they could not see before using older technology which afforded only thin, two dimensional slices.

“Our plan now is to investigate whether the images are able to further prove similarities between different plants within the family, making the technique a good taxonomic tool,” House says.

“The hope is that these newly visible features of the internal walls of pollen grains will add to the body of information and enable more accurate classifications.”