Leaves & the Secret of Life

Enlarge Image Image Gallery Photo by David Cavagnaro

by Terry Krautwurst

Each autumn here in the mountains of western North Carolina, a crisis strikes that is so dire local emergency shelters are opened to house the refugees. The crisis is called coming to see the leaves and those refugees are the hapless travelers who find not only fall's spectacular scenery but also a panorama of no-vacancy signs at the area's motels, all packed solid as bushel baskets with countless other leaf-lookers.

This phenomenon is hardly limited to the woods that lead down the long, rumpled spines of the Blue Ridge and Great Smoky Mountains. Wherever there are frosty nights and deciduous forests there are pilgrims who come to see the trees emerge from their summer-green chrysalis, the leaves of scarlet, orange, yellow, purple and bronze fluttering like day-old butterflies drying their wings.

By the thousands, from coast to coast and border to border, we mortals seek the high ground to get a better view. We line ridgetops and overlooks, posted like sentinels, gazing outward at—what?

We're drawn by the colors, of course. But there's a deeper power at work, too, an attraction as compelling and primal as our pull to the sea. In summer, our species flocks to the beaches. In autumn, it's to the forests. In both places, we gain a sense of homecoming.

Maybe it's because we humans acknowledge instinctively the forces that make our world possible. The sea is the embryonic fluid from which all life has sprung. And the leaves? Within each leaf lies not only the secret of autumn's brilliant spectacle, but the secret of life itself.

GREEN MACHINE

In the minute space between a leaf's upper and lower surfaces, a space no thicker than the paper on which these words are printed, is the machine that drives our planet's food chain and helps to sustain its atmosphere. In this space, and especially near the upper surface (which receives the most sunlight) are cells that bear a concentration of protoplasmic hits called chloroplasts. Here, water drawn from roots far below and carbon dioxide inhaled by thousands of microscopic leaf pores, or stomata, meet. And here, in leaf chloroplasts, the secret of life-a process otherwise known as photosynthesis takes place.

Chloroplasts contain enzymes and several pigments, the most dominant of which is a substance called chlorophyll. All the pigments absorb light energy to be used by the leaf, but each absorbs only a particular range of wavelengths, or part of the spectrum.

Chlorophyll's taste for light runs to the high-energy violet-blue and low-energy redorange ranges, and completely rejects-in other words, reflects—green. That's why most leaves look green to us during the growing season.