I think every one of us would agree that Eucalypts definitely are an Australian icon, but here are some things about our gum trees that you may not know!
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History
The term eucalypt — meaning well (eu) covered (calyptos) — was first coined by French botanist Charles Louis L'Héritiert de Brutelle in 1788.
The roots of the eucalypt go back to when Australia was part of the supercontinent Gondwana.
The oldest known examples of eucalypt fossils are 52 million-year-old flowers, fruits and leaves found in Patagonia.
Botanists have identified around 900 species of eucalypts divided into three different groups: Eucalyptus, which make up the bulk of the species; Corymbia, the bloodwood eucalypts mainly found in the north; and Angophora.
The mighty mountain ash Eucalyptus regnans, is the world's tallest flowering tree.
Gum leaves
Eucalypt leaves are packed with oil glands that produce the aromatic compounds that give us their distinctive scent.
These compounds help protect the tree from attack by pests.
Oil glands make the leaves unpalatable to insects.
However there are some insects that have adapted to eating those sorts of leaves.
In 2013, biologists discovered that a Yellow Box tree Eucalyptus mellidora in a sheep paddock in New South Wales could change the smell of its leaves from one side to the other to protect itself against attack.
Scientists, using sophisticated imaging techniques, have also discovered the leaves of trees in the Kimberley contain microscopic traces of gold.
Eucalypt leaves also change over the lifetime of a tree.
The leaves of a young sapling are held horizontally to maximise the surface area for gathering light.
As the tree ages, the stalk of the leaf twists so that the leaf becomes vertical and is not exposed to as much radiation.
But it's not just the shape that changes, the whole structure of the leaf changes. The anatomy inside the leaf changes.
Instead of having an upper and lower surface both sides will have photosynthetic tissue.
This enables the leaves to maximise photosynthesis and minimise exposure to heat.
Leaves also have a lot of thick-walled cells, a lot of fibres – so they are really, really tough.
If you want to find out more about eucalypts, check out my source website on the ABC at goo.gl/YvcgyQ.
Until next time – take care all and keep cool!
