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.
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.
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.