Monday, July 02, 2007

Home from the market

Friday is farmer's market day in Dingle, and for the weekend it's local breads and cheeses that sustain us (with wine, of course). Bread and winemaking yeasts are fungi, and cheese-making relies on fungi too. Throw in some mushrooms and half of what's for sale on the farmers' tables is fungus related. Doesn't sound particularly appetizing when you put it that way, does it?

But, really now, the fungi are not the point of a farmer's market. Mostly it's plants we're after -- wheat for bread, grapes for wine, and grass that feeds the cows that make the milk for cheese. Animals and fungi are parasites (of sorts) on plants. Only plants can tap the energy of the Sun. This Emerald Isle is one big solar panel.

Biologists are not sure how photosynthesis evolved, but that it happened early in the history of life is certain. In the Ancestor's Tale, Richard Dawkins puts the date at -- well, actually, he doesn't. By the time he gets to our common ancestor with the fungi he has given up any pretense that we know with much certainty when things happened.

Every high school student learns the basic equation of photosynthesis: Carbon dioxide plus water plus sunlight yields carbohydrates and oxygen (with all the C's, H's and O's appropriately balanced). The equation doesn't nearly convey an appreciation for the complex reactions that connect one side of the reaction arrow to the other. Crucial to the process is a boxy molecule (chlorophyll, of course) with a magnesium heart and a long tail. Atomic electrons in the molecule are bumped up in energy by sunlight. As they return their bounty, they energize reactions that create intermediate products called ATP and NADPH, which then move along the assembly line. When all is said and done, it is sugar that appears at the factory door -- where the animals and fungi wait to appropriate their share. I read somewhere that humans currently command between one-third and one-half of all the products of all terrestrial photosynthesis, as food for ourselves and our domesticated animals, or for fuel, building material, and clothing -- the lion's share, we might say, except that the lion gets slim pickings. That ratio sounds extreme to me, but then I look out my window at the grazed fields that stretch away to the horizon and it doesn't seem so far fetched.

I'm rambling. Never mind. Pass the bread and the Kerrygold butter. And I'll have another glass of wine.