Wonders of an Old-Growth Forest, Part 28: Ode to the Goddess Flora | Warren Woods State Park, Michigan, USA

Taken just after a drenching shower, in upland old-growth forest near the northern bluff of the Galien River. Looking generally southward.

 

To see the amazing, physical-metaphysical process of photosynthesis at its most rampant, stand in a woodland like this just after a summer rain. Everything glows green. The air crackles with oxygen.

 

The most important chemical formula in the world is

 

6CO2 + 6H2O → C6H12O6 + 6O2

 

(Forgive the lack of subscripts. Apparently Flickr does not permit the appropriate HTML coding for them.)

 

There are some ecosystems (at midocean vents, for instance) that don't rely on this formula, but we and most of the rest of life certainly do. To put its chemical symbols and numerals into plain English: plants and other organisms using this type of photosynthesis take basic chemical compounds—carbon dioxide and water—and somehow transform them, as we animals certainly can't, into both free oxygen and food in the form of sugar.

 

Note my emphasizing the word "somehow." It's easy to slap that equation up on a blackboard or projection screen and just say, "That, my friends, is how photosynthesis works!" But to actually disambiguate the chain of arcane and convoluted chemical reactions that must take place in sequence, like the workings of a Rube Goldberg machine, is no easy job for either teacher or student.

 

When presenting horticulturally oriented botany at the adult-education level, I was told to cite the equation, and stop there. But in the upper-level, botany-for biology-majors course I taught in college, we went all the way down the rabbit hole.

 

But the more I did the latter, the more convinced I became that something important was missing in the textbook explication of chlorophyll, chloroplasts, light reactions, the Calvin Cycle, carbon fixation, RuBisCo, electron donors, ATP, Crassulacean Acid and C4 metabolisms, and all the other processes and paraphernalia of photosynthesis.

 

I think I've had this unsettled feeling because the historical-geologist side of me knows that direct and indirect fossil evidence suggests something rather arresting. This hyper-complicated process originated not long after—and maybe just after—the Late Heavy Bombardment. This cataclysmic infall of asteroids and meteorites occurred between 4.1 and 3.8 Ga ago, in the late Hadean eon and Eoarchean era.

 

Despite that truly hellish assault on the Earth's surface, the fossil evidence alluded to above points to something almost unbelievable: an early form of photosynthesis existed by 3.5, and maybe even as far back as 3.8 Ga. How did something as mind-bendingly elaborate as that start so early in the evolution of life, when our planet was populated only with the simplest unicellular microorganisms?

 

And the kind of oxygen-liberating photosynthesis cited in the formula above, the kind we depend on, was also operating no later than 3.0 Ga ago.

 

In contrast, plants developed much, much, later. If you have a broad definition of what it is to be a plant, they're a little less than 1.0 Ga old; but if you just restrict them to those that have evolved on land, they're about half of that. And trees—the forerunners of those shown in this image—didn't evolve till the Upper Devonian, about 0.38 Ga (380 Ma) ago.

 

So, while advanced multicellular life was a slow starter, it seems that Planet Earth was blessed with a remarkably potent and complex chemical pathway, no less magical for being explicable, at a very early date in its development.

 

Of course, this all begs the question of why. I've thought about this endlessly, and am now quite sure I've figured it out. Just as the Titan Prometheus brought fire to humankind, it was the Roman goddess Flora, descending from some Eoarchean proto-Olympus, who bestowed this priceless gift of life on our little world. I hope that the next edition of botany textbooks will point that out.

 

To see the other photos and descriptions of this series, go to my Wonders of an Old-Growth Forest album.

 

Done