A past issue of Tree Talk (Spring 2018) quoted an anecdote by Professor Jay O’Laughlin, retired director of the College of Natural Resource’s Policy Analysis Group at the University of Idaho, in which he described a tree as “Mother Nature’s Towers with Solar Panels.” Our first article focused on the components of the wooden tower which foresters call the trunk, bole or stem of a tree. Now let’s take a closer look at the tree’s solar panels – it’s leaves or needles. To understand their importance requires a basic explanation of photosynthesis and the photosynthetic process.
With Greek derivation, photosynthesis means “putting together with light.” Very simply stated, this process combines water, carbon dioxide, sunlight and chlorophyll to produce glucose, a sugar that provides energy for the tree to grow while giving off oxygen as a byproduct. An oversimplified chemical formula looks like this:
Carbon Dioxide + Water + Sunlight = Glucose + Oxygen
A tree absorbs water through its roots, which along with dissolved minerals, is transported through the xylem in the bole of the tree to the branches and leaves/needles. Also called sapwood, the xylem is the waterworks of the “tower.” Stomata, tiny pores in the surface of the leaf, allow carbon dioxide in and oxygen out in a process called transpiration. Chloroplast cells, containing a green pigment called chlorophyll, collect sunlight that energizes the photosynthetic process. The magic of Mother Nature has now transformed a simple-looking leaf into a complex solar panel that produces the sugar needed for growth throughout the tree.
Vern Bromgard, retired district conservationist with the USDA – Natural Resources Conservation Service, liked to use common sense, down-to-earth explanations when describing complex biological processes or conservation practices. He often told forest landowners, “The leaves are the factory of the tree. The more leaves, the better the tree will be growing.”
With this explanation of photosynthesis, you can now see why foresters place such a high importance on the live crown ratio – the percentage of a tree’s foliage to its total height.
After all, the more solar panels attached to the tower, the more productively the factory will produce glucose. As Professor O’Laughlin summed it up in his presentation, “we call them trees.”
— Bill Love, Certified Forester