Monday, 31 March 2014

Plants and the destruction of man made structures.

Plants can often seem very passive, as they never do anything very fast. However, they can still be quite destructive and can demonstrate great physical strength by very slowly destroying man made structures. 

The image below shows a flag iris plant that has grown out past a garden fence and is now gradually ploughing its way through the tarmac (asphalt) of the pavement (sidewalk). The tarmac is very strong and it would be impossible for a person to tear it apart with their fingers. Finger strength is all produced by the action of muscles. But plant strength is produced by turgor pressure

The plant in this picture has pushed its way through the tarmac using turgor pressure. First it will have pushed tiny new plant cells into the minute cracks and holes in the tarmac. Then it will have used turgor pressure to inflate the new cells. The physical force of the inflating cell applies huge pressure to the tiny piece of tarmac surrounding the new cell. Under this force, the tarmac slowly gives way, creating a larger crack, into which the plant can push new tiny, uninflated cells. As this process takes place again and again, the tarmac is gradually pushed out of the way. The plant eventually pushes its way right through the pavement and makes its home in what initially seems a most inhospitable location. 





If plants are allowed to keep pushing through man made structures like this then the structures gradually are bulldozed out of the way and the environment returns to the wild state. A nice illustration of this is shown in the last page of the book "Asterix and the Mansion of the Gods" in which trees have grown right over some derelict buildings. (I have a photos of this, but I have written to the publishers to ask permission to post it.)


All views expressed are the opinion of the author only. They do not represent the views of any organisation or institute that she may be affiliated with.

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