I was recently sent the two photos below which appeared in a Landcare Research staff newsletter. They were taken in central Christchurch near the Arts Centre which was damaged in last years earthquake. The photos show Coprinopsis atramentaria (the inkcap) lifting and erupting through the asphalt. In this case, the inkcap is a wood decay fungus and will be growing on either dead roots of a tree or some other buried wood.
It is not just wood decay fungi that can break up paving but also mycorrhizal fungi, that is those associated with tree roots. Often the roots have been paved over so that when the fungal fruit bodies attempt to push to the surface they must break through the paving. I first encountered mycorrhizal fungi doing this when I lived in Dunedin and the following article appeared in the Otago Daily Times.
The pavement lifter was the scarlet flycap [Amanita muscaria] and I have not seen any other records of this species lifting pavement. The annoying thing for residents and the city council was that this pavement had only recently been laid.
In the book Why don’t penguins’ feet freeze? the question was asked:
Near where I live there are toadstools growing through the pavement, the surface of which they have displaced in fairly large chunks. What mechanism allows toadstools – essentially very soft and squashy items – to push through two inches of asphalt? John Franklin, London, UK
The rapid growth of mushrooms is well known, how they can come up overnight, but how they exert such force is not so obvious. The hollow stalk of the mushroom is made up of vertically arranged hyphae that grow at their tips, much like those balloon used to make balloon animals. The wall of a hypha is composed of fibres of chitin that are arranged helically and limits the ability of the hypha to expand in width. All the pressure of growth is through elongation and growth at the tip (Isaac 1999). It is this concerted pressure applied by each expanding hypha that can create the pressure to lift the pavement.
This ability was first investigated experimentally in the 1920s by the mycologist A.H.R. Buller (Estey 1986). Using simple equipment, illustrated by Buller (1931) below, he was able to show that Coprinus sterquilinus can lift a weight over 200g, many times its own weight (Webster 1980).
Recent studies, by Money and Ravishankar (2005), using much more sophisticated equipment compared the pressure exerted by individual hypha of Coprinopsis cinerea pushing through its food source and found it to be the same as those hyphae forming the elongating stipe of the fruitbody. This force was approximately 0.5 atmospheres and is close to the 2/3 of an atmosphere calculated by Buller.
Buller AHR 1931. Researchs on fungi. Volume 4. London, Longman, Green and Co.
Estey RH 1986. A.H.R. Buller: pioneer leader in plant pathology. Annual Review of Phytopathology 24: 17-25.
Isaac S 1999. Mycology answers. Mycologist 13: 137-138.
Money NP, Ravishanka JP 2005. Biomechanics of stipe elongation in the basidiomycete Coprinopsis cinerea. Mycological Research 109: 627-634.
O’Hare M 2006. Why don’t penguins’ feet freeze? New Scientist, Profile Books.
Webster J 1980. Introduction to fungi. 2nd ed. Cambridge University Press.