Look at an oak tree and ask yourself, “where did the stuff of that tree come from?” Imagine an acorn in your hand and think about it growing by sending roots into the earth and shooting stems, branches and leaves toward the sky. Imagine this little tree growing bigger and taller until it is 72 feet tall, about the height of a three-story house, and weighing fifteen tons or 30,000 pounds.
That’s a lot of wood, leaves and roots, and the question is, where did it come from?
Take a moment to think about this question? Do you have a theory about where the substance originated?
Long ago, almost 400 years ago, in the year 1634, Jan Baptist van Helmont, a Flemish scientist, asked a similar question. He wanted to know where the stuff of oak trees, onions, bamboo, pumpkins, kale, tulips, blueberry bushes and all other plants came from.
It is easy enough to see where the substance of animals comes from. Many animals eat plants and they build their bodies from the matter in the plants they eat. But, with the exception of the carnivorous plants such as the venus flytrap, most plants have nothing that seems like a mouth and grow with no obvious source of food.
Most people in van Helmont’s time thought that plants grow by “eating” soil and some people still think that today. Van Helmont wondered about this so he came up with a plan that would show whether soil is “eaten” to become the stuff of plants. Van Helmont started with 200 pounds of dried soil. He put the soil in a big pot and planted a five-pound willow tree in it. Then, patiently, he cared for the potted tree, watering it with rainwater. He took great care to be sure that nothing extra entered the soil. He even put a covering over the soil so that dust would not settle there.
The little tree grew steadily and after five years Von Helmont decided to see how much of the soil had been transformed into roots, bark, wood and leaves. He carefully removed the tree, roots and all, from the pot and weighed it. The tree that had weighed five pounds when he planted it had grown to weigh 169 pounds and 3 ounces. He then dried the soil and carefully weighed it and discovered how much weight it had lost.
How much weight do you think it had lost?
Make your best guess!
The answer is only two ounces. The soil had lost only two ounces! So, while two ounces of the tree had come from the soil, the source of 169 pounds and 1 ounce was still a mystery.
Today, scientists know where the stuff of the tree came from. Von Helmont’s best guess after this willow tree experiment was that it came from water. He could think of no other explanation. We know today, that he was only partially correct. A living tree is between 50 percent and 80 percent water. But, if you harvest that tree and cut it into logs and let the logs dry, not much water remains in the logs. Where did most of that dry wood come from? We know from Von Helmont’s experiment that it didn’t come from the soil. Scientists also know the substance didn’t come from water. So, where did the substance of the dry wood come from?
Take some time to think about this!
Today we know that the dry substance of the tree and the substance of all plants actually comes from the air. Did you guess that? The part of the tree that is not water and did not come from the soil is made of an element called carbon. You can’t see the carbon when it is in the air as part of an invisible gas called carbon dioxide. It is totally invisible. But an apple tree or corn plant or an ivy vine and every other plant takes in a little bit of that carbon dioxide from the air through its leaves every day. Slowly, the plant has the ability to take the invisible and make it visible. This sounds like a magic trick, but plants have the ability to make the invisible carbon (which was part of carbon dioxide) not only visible but something tangible (that means you can touch it.) Plants create matter with color, texture and weight. This is the work that plants do everyday. The carbon in the air becomes the apples, lettuce, beans and pumpkins we eat, the wood that we use to build our houses and the cotton that becomes our clothing.
The leaves of the tree, using the process called photosynthesis, take in the carbon dioxide and separate the carbon from the oxygen. The plant keeps the carbon for its own use and sends the oxygen back to the atmosphere.The process of photosynthesis uses energy and this energy comes from sunlight.
Animals including humans need oxygen to breathe. So, we depend on plants to create oxygen from carbon dioxide.
You probably know about solar panels that can turn the sun’s energy into electricity, a form of energy used by people. Scientists have been inventing ways for making electricity from sunlight for about 115 years. But plants have been using the sun’s energy as a power source for at least 2,000 million years.
Let’s look out the window at the trees. Take a moment to consider the idea that the trees are made up of something they take from the air. This is scientific truth, not magic, but it feels magical, doesn’t it? It seems like plants, including very heavy trees, are something made from nothing. But of course air is not nothing. Air holds up birds and airplanes. You can feel the air against your skin when the wind blows. Air is full of substance, but since we can’t see it, it seems empty even though it is not.
I like to see plants as a condensed or thickened version of air. The branches, stems, leaves, roots and fruit are all made of the carbon in the air. When forming roots, plants actually bring carbon from the air into the soil. Grass, especially the deep-rooted grasses of prairies, bring enormous amount of carbon deep underground.
Today, begin to look at plants in a new way. When you look at a tree, think about how it uses energy from the sun to transform matter. When you look at the apple you are about to eat, think about a tree making that apple out of air. As you bite into that apple realize you are eating transformed air!
Today, our planet is enveloped by a blanket of carbon dioxide. We have to stop burning petroleum based fuels so we can lighten that blanket so the earth doesn’t overheat. What else can we do to lighten the blanket? After reading this, you can see plants remove crbon from the air. We help cool the planet when we protect forests and grasslands and plant trees.
Ask your child, your parent, your friend what trees “eat” to make them grow. If they don’t know, share this apparent magic and tell them how plants can help cool the earth.
And plant trees, a lot of trees!
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Kim Allsup was a grade school teacher for more than 20 years. She was also a gardening teacher at the Waldorf School of Cape Cod pioneering School Sunhouses. She is the author of A Gift of Wonder, A True Story Showing School as it Should Be.