fresh air anyone?


Breathing sweet, clean, air is one of the simple pleasures of a walk in the woods. The air always seems fresher than that beyond the forest.

There is a reason for that. You are breathing brand new oxygen produced by the very trees surrounding you. How does this happen? It happens through a truly miraculous process known as photosynthesis.


What is photosynthesis?

Photosynthesis is the means by which trees and other plants turn sunlight into food. It’s a process that all green plants, as well as algae and some bacteria, use for their growth. Since I love trees I will concentrate here on the photosynthesis used by trees around the world.

watercolor by Cynthia Drinkwine

How does photosynthesis work?

In the most common form of photosynthesis, the chlorophyll in the tree’s foliage captures light energy in the form of photons. Through a series of of biochemical transformations, the tree uses that energy to turn carbon dioxide and water into simple sugars which fuel the tree’s growth.

The photons provide the energy needed for water and carbon dioxide (collected mainly in the tree’s leaves and roots) to be transformed into other molecules. Through a series of steps the carbon dioxide and water are changed into simple sugars, leaving oxygen as a waste product.

The general formula looks like this:
6 CO2 + 12 H20 + photons = C6H12O6 + 6 O2

In English that is:
6 carbon dioxide molecules plus 12 water molecules plus light energy leads to 1 glucose molecule and 6 oxygen molecules. (Doesn’t seem like much but multiply by trillions of molecules and it starts to add up.)

What is chlorophyll?

Chlorophyll is a molecule found in green plants. In fact, it is what gives the plants that green color. This essential molecule is what allows photosynthesis to happen, by combining with other molecules to transform light and carbon dioxide into oxygen and other byproducts.
The tree then transforms glucose (sugar) into the biochemical fuels needed to grow and reproduce. At the same time, the process releases excess oxygen into the air through pores in the tree’s leaves.

What is a photon?

Without getting into quantum
mechanics (!) you can think of a
photon as a sort of bundle (a quanta)
of light, an individual “thing” that
smacks into the tree as sunlight. Just
don’t tell your physics friends that I
described it that way, since photons
don’t actually have any mass.
A more sophisticated answer to the
question of what a photon is can be
found at

Why Should We Care?

To be selfish about it, one reason is because we can’t live without it.

More specifically, photosynthesis plays three important roles.
1) It feeds the tree. Without it we couldn’t walk in the woods because there would be no woods.
2) It “fixes” carbon, meaning it takes carbon dioxide, which is a greenhouse gas and puts the carbon into a solid form (such as in the glucose or other sugar produced), thereby reducing the amount of CO2 in the air.
3) It releases oxygen into the air as a waste product. In essence, trees and other plants “inhale” CO2 and “exhale” oxygen, while we humans and other animals do the opposite.

Misc. fact:
Green plants are essential in
helping stabilize the environment
by taking up CO2. Unfortunately,
we humans are presently
producing far more CO2 than
plants can take up. But without
trees doing their part we would be
in far worse shape than we are

So plant a tree today and then pat yourself on the back for taking a step towards making our planet a better place.

Next time you’re in the woods think about all the trees “breathing” around you and remember that without them we wouldn’t have the oxygen we need to live.

Miscellaneous Fact:
Poison Ivy loves CO2. You may notice it growing
next to the road. It uses the exhaust from the
traffic to help grow to truly prodigious sizes (see
bush to right).
That alone should make you think twice about the
amount of excess CO2 we produce, especially
here in the USA.


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