Structure of the rhizome


Images by author.

The rhizome is often used as an analogy for systems that lack a rigid, linear structure. However, that does not mean that rhizomes are without any structure. The gross morphology of a typical rhizome (e.g. ginger or Bracken) appears to lack an easily definable structure. It grows in all directions and does not have a clear beginning or end. This is why it makes a nice analogy for educational systems where linearity is unhelpful.

However, once we start to look at the rhizome in section, it’s structure becomes evident. Figure A shows a low power image of a transverse section (top) and a longitudinal section (bottom) of a fern rhizome. The organisation of tissues is very obvious in transverse section. The longitudinal section is more difficult to interpret and the separation of tissues is not so clear. The red arrows indicate the position of xylem vessels.

Figure B is a high power image of the xylem vessels in transverse section. The separation of one vessel from another is very clear. Figure C shows the xylem vessels in longitudinal section, in which the spiral thickening of the vessel walls can be seen.

The point is that the shapeless rhizome does have a structure when viewed in section. Different sections show different details. These details need some interpretation, and that only comes with practice and is made easier when multiple images are available from different perspectives. It should also be noted that the structures of the vascular tissue only implies movement once we realise that the xylem vessels are transport tissues and their function is to move materials around the plant. The dynamism of these movements have to be interpreted from the static images presented. The more images we have, the easier it is to work out what is moving where.

As an analogy for learning, the rhizome offers a lot. However, we should not simply accept that it has no structure. It has a complex structure that is only visible using the right materials and methods.

It has been suggested that concept mapping can be used to observe cross sections through the educational rhizome. The same caveats for interpretation (as mentioned above) will apply.

Further reading:

Bell, A. (1980) The vascular pattern of a rhizomatous ginger (Alpinia speciosa L. Zingiberaceae). 1. The aerial axis and its development. Annals of  Botany, 46, 203–212. 

Bell, A. (1980) The vascular pattern of a rhizomatous ginger (Alpinia speciosa L. Zingiberaceae). 2. The rhizome. Annals of Botany, 46, 213–220. 



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