Geology Reference
In-Depth Information
But, Like Robin Hood, mycorrhizal fungi take from the rich and give to the poor.
Our mycorrhiza gingerly steers the sugar molecule through its labyrinthine underground
pipelines towards the fine roots of a small oak seedling growing in the shade of its own
parent—the giant oak tree where our story began. The seedling's life is in danger, for it
can barely photosynthesise enough sugar of its own in the deeply shaded precincts of the
forest floor. A final stretch of fungal tube makes contact with one of the sapling's root
cells, into which our startled sugar molecule, along with many others, gently tumbles.
With its underground pipes linking distant trees, the fungus has given the young seedling
a much needed sugar fix together with a healthy dose of water, nutrients and minerals
garnered along the way. In payment for this umbilical service, the fungus has siphoned
off some sugar from the mother tree. For the moment, at least, the little tree's life is safe.
Fungal Lives
The smallest fungal pipeline, like the one that fed the oak seedling is called a hy-
pha—essentially a hollow tube made of pipe-shaped compartments joined end to end.
Hyphae are decidedly microscopic—their width commonly varies from around 1/500th
to 1/100th of a millimetre. Hyphae grow by extending their tips. Cellular fluids and
organelles such as mitochondria and nuclei can flow freely along the growing hypha,
unless they get blocked or redirected at the partitions called septa, which distinguish
between the compartments, like those along the length of a tube train. The walls of hy-
phal cells are toughened with chitin—the same material that one finds in the often out-
landish exoskeletons of insects. Chitin makes hyphae as rigid as fibreglass, but their
tips retain an exquisite flexibility that allows them to change direction. The toughened
walls can also be augmented with materials that confer the boon of extreme resistance
to desiccation and other stresses that most organisms could not endure, including expos-
ure to highly corrosive acids. Along with bacteria, fungi include some of the toughest
creatures on the planet. As they grow and explore their surroundings, individual hyphae
branch and often fuse with others of their own kind, creating a complex network of
fungal pipelines known as a 'mycelium'. These fusions between the individual hyphae
hugely amplify the distributive power of mycelial networks and are often so numerous
that mycelia become woven into thick sheets, cushions and cables as well as the fruit
bodies that emerge into our view.
Mycelia are everywhere. Speak to a mycologist and she will ask you to imagine what
the world would look like if everything on earth was dissolved away, leaving only in-
tact mycelia. The answer is, of course, that we would be able to see the ghostly outlines
of trees, bushes, topsoil, grasses, other organisms and many human artefacts in a del-
