Science Notes: Cherry Blossom Buds

SCIENCE NOTES: Autumn Cherry Blossom Bud

How much of a tree is alive, do you think? Actually only about 1%, though all of it was alive at some time or other. Wood is made up of cells, and like all living things cells will grow and multiply, and they will die. All the wood in the middle of a tree is dead. There are only two places on a tree where you find living wood. One is a thin layer just underneath the bark, and the other place is the buds. I’m talking here not about the flower buds, but the buds which are forming the new twigs and leaves. Here’s one from the autumn-flowering Cherry Blossom, seen through Clodagh’s electron microscope.

Autumn Cherry Bud fig1

In this relatively low mag picture you can appreciate the shape of the whole bud. If we zoom in a little you notice that some parts of the delicate outer leaf structures have broken, revealing several layers of living cells.

Autumn Cherry Bud fig2

The cells in a tree multiply by dividing (which sounds like a mathematical contradiction!). A tree has different types of cells to do different jobs, such as bark, roots, leaves etc. All cells start off the same, and like the stem cells in your body they differentiate into specialist types. The cells in this picture are doing the job of protecting the growing bud: quite quickly they will break up and be replaced, in fact the strange wiggly things in the picture are the remnants of earlier protective layers.

Science Notes: Lichen on Trees

We found lichen on many of the trees around the campus. And that’s very good for us, because lichens only grow where the air is clean. In the 1970’s there was almost no lichen to be found on trees in urban environments because of air pollution and acid rain.

Lichens are fascinating organisms. In fact they are not one organism at all. They are made up of a fungus and one or more algae living together in a mutually-beneficial relationship – a kind of mini-ecosystem. The fungus makes up most of what you see: it surrounds and protects the algae. In return the algae feed the fungus (which is unable to feed itself) by photosynthesis.

The beauty of lichens is not easy to see: you need at least a magnifying glass to appreciate them, but an electron microscope is even better. Here are two photos which Clodagh took of lichen on the Oregon Maples:

 Lichen fig1

In the top photo you can see the filament structure of the fungus. The small circular shapes in the bottom photo may be cells of the algae.

Lichens are great survivors. You find them all over the planet in many different environments. And it turns out that they can even survive in space! The European Space Agency arranged to take some lichen up to the International Space Station where they brought them outside, exposing them to the ultra-cold vacuum of open space, where they would be bombarded by cosmic rays and everything. No space suits for them, but they still survived the trip: http://www.esa.int/Our_Activities/Human_Spaceflight/Lichen_survives_in_space