Each of us values the many bounties brought to us by our dedicated local farmers, but what about the underlying and fascinating biology that paves the way to harvest? This series of articles will take us on a journey from sun to seed and beyond.
Farmers harvest crops; plants harvest sunlight
But where does the sugar come from? Sugar is a form of matter but sunlight is pure energy, there’s no matter in it. The matter in sugar comes from two simple ingredients, water and carbon dioxide. Recall that water is H2O, that is, two hydrogen atoms attached to an oxygen atom, and those hydrogen atoms really like staying attached to the oxygen atom. It takes a lot of energy to strip them away. That’s where the Sun’s energy comes in. Plants use some of the energy that they receive from sunlight to pull the hydrogen of of oxygen, making the hydrogen available for combining with carbon dioxide. That’s what sugar is made of, hydrogen combined with carbon dioxide. Plants use another portion of the light energy to fashion the chemical bonds that hold the atoms in the sugar together. Those bonds contain energy that originally came from the Sun, so, in this sense, we are all solar powered!
And, you’re breathing the leftover from water right now; it’s the oxygen that was attached to the hydrogen atoms in H2O. We need oxygen, as do living crops, to extract the Sun’s energy that was packaged in sugar molecules. That unpackaging results in the very ingredients we started with, carbon dioxide and water. You’re exhaling them as you breathe. The cycle goes on as long as plants do what they do with sunlight.
Next: Nitrogen nitrogen everywhere but not a drop to drink.
© R. E. Morel 2009