Azolla root structure

by Laura Kent

Azolla root cross-section, showing the tetrahedral apical meristem in the centre

Azolla is a genus of aquatic ferns that are highly productive and can grow at great speeds in the summer months. Azolla species are useful for studying the mechanics of cell division and differentiation in the roots due to their simple structure and determinate growth.

In 1978, Adrienne Hardham, Brian Gunning and Joanne Hughes published several papers about the mechanics of root meristem function and cell division in Azolla plants. The root apical meristem is where all new root cells are formed through cell division and differentiation. The single root apical meristem in Azolla is tetrahedral in shape and there is a genetically determined limit of cell division as the meristem only divides 50-55 times. The study by Drs Hardham, Gunning and Hughes described all the cell lineages formed from the division of the root apical meristem. They showed that the proliferation of the cells is highly specific, division occurs in regular sequences and determined the orientation and location of all cells after cell division. The study also showed that you can predict the location of new cell walls after division due to the location of certain microtubules that form the skeleton of the cell. The work at ANU was instrumental in understanding the process of cell division and differentiation in Azolla which was needed to understand the growth and development of plants.

The main image above shows the actual cross section of an Azolla root with the hexagonal vascular tissue derived from three sides of the tetrahedral apical cell in the centre. The other image, in the gallery below,  is a depiction of the root made from tiles which decorates the foyer entrance of the Research School of Biology Linnaeus Building (Linnaeus Way entrance foyer). 

In 2017, we celebrate 50 years of Biology at ANU. This article is one of a set featuring the achievements and memorable occasions of ANU biologists those first 50 years.
Read more at Biology at ANU – the first 50 years.

Image gallery

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