The Gas We Pass*

Take out your pencils. It’s time for a quiz! (I always hated pop quizzes, so you can rest assured this one will end up being self-corrected and won’t count towards your final grade.)

Below, I have a picture of a seed. Next to that is a picture of a tree. The question (just one for today): How does the seed gain all that mass to become a towering tree? In other words, where does the mass come from?**

Sequoia tree and seeds

Got your answer? Write it down, please. Be committed!

This is a common question in introductory biology classes around the nation: How does a plant gain mass? Students begin learning this concept in elementary school, planting seeds and watching them grow, drawing pictures, and watching videos of time-lapsed photography. By the time a student reaches freshmen biology, this question should be a classic no-brainer.

Now, raise a hand if you remember reciting a little chemical equation, H2O + CO2 (and sunlight) => C6H12O6 + O2. (Whoops, that’s two questions for today’s quiz!)

If you do remember that little chemical equation, you’re in good company. Most freshmen can easily recite that equation; many will even provide a balanced version. But somewhere within all their schooling, the big idea – where the CO2 actually comes from – is lost, muddled, or never really communicated. Our students simply don’t know where the mass comes from.

In our easily memorized equation, let’s reflect on the carbon joined with two oxygen to form CO2. Carbon dioxide. Molar mass 44.01 g mol-1, a frequent additive to create fizzy beverages and Pop Rocks, comprising 0.039% of our atmosphere and indeed, contributing the vast majority of the mass to a tree.

Every day, terrestrial plants open tiny pores (called stomata) in their leaves, taking up CO2 from the atmosphere to create sugar, with the help of a little sunlight (aquatic plants do this too, but they lack stomata). It is this process that sustains life on earth, not only by supplying the necessary energy for life but also by maintaining atmospheric levels of oxygen that we humans so cherish. Without plants cycling carbon from the atmosphere, life as we know it would end.

This month in Religious Education, our UU kids are learning about plants and the carbon cycle. Some may ask how such a curriculum reflects spirituality or UU principles. As one of my graduate school professors was fond of saying, believe in God or something bigger than you, like the endless movement of carbon from atmosphere to plant, to animal, to decomposer, to atmosphere. What could be more profound but to realize that the carbon exhaled by Emilie du Chatelet, Susan B. Anthony, or Elizabeth Blackwell might be part of me today and part of my great-great-great granddaughter some decade in the future?

*With apologies to Shinta Sho and The Story of Farts.

**Don’t worry if you weren’t sure of your answer to this pop quiz – you certainly weren’t the only one!

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