The presidential campaign, Iranian nuclear ambitions and unemployment, it’s enough to make you pine for a long walk in the woods, not that I am actually near anything more foresty than a prickly pear cactus. I just want to see a little fall color, something not red or blue.
Leaves are green because of the pigment chlorophyll. Pigments have been all the rage lately, bioflavonoids in wine, and tannins in tea, all with supposed magical powers. This handy molecule looks green because it absorbs blue light (leaving green light behind), producing that nice forest ambiance.
But chlorophyll is good for a lot more than just making the place look pretty. It is the source for virtually all the oxygen on the planet. For the Zen enthusiasts among us, meditative breath counting would be challenging without oxygen; all that turning blue and gasping for air is just so “not serene.” But it would be quiet and peaceful, none of those pesky free radicals … trees falling and no one hearing, notwithstanding.
In the briefest of descriptions of photosynthesis: chlorophyll absorbs blue light from sunshine, uses that energy to combine carbon dioxide and water to make sugar. Oxygen is the waste product. What a system, this has to be the ultimate green technology! Try improving on that. There actually is a possible improvement: “black chlorophyll,” a molecule that absorbs full spectrum light, not just blue light. It is much more efficient, but it didn’t catch on evolutionarily. Black trees and grass. Must have been a primordial VHS/Beta type of thing.
The planet Earth is more water than land; chlorophyll lives in plankton on the ocean surface. These are little one-celled photosynthetic plants that occupy the first couple to 100 feet of seawater. Out there in the middle of the ocean there is no shortage of sunshine, water, CO2 or space. Ocean plankton account for 50% of the planetary oxygen production and conversion of uncounted tetra-tons of CO2 into biomass. This CO2 becomes more plankton, which eventually dies, settles to the marine floor, to become next millennium’s oil and natural gas.
The plankton side of the photosynthetic cycle is possibly easy to manipulate, if not to predict the long-term consequence. Iron in the seawater is the rate-limiting step in plankton reproduction. This may be relatively easily increased. Global warming of seawater may also dramatically increase plankton production and metabolism – a classic negative feedback arrangement to control CO2 (optimists see this as an environmental thermostat). Hope they’re right.
But it’s the land half of the chlorophyll operation that interests us this time of year. Deciduous trees have green leaves all summer because chlorophyll is the dominant pigment. Any day now, with the cooling temperatures and shorter days, the circulation to the leaf shuts down and the chlorophyll breaks down rapidly. Other pigments in the leaf are now visible, orange bête-carotene and yellow xanthophyll. These pigments have always been there, you just couldn’t see them before; like so many things in life. They have their moment of glory in the dying leafs. All the colors of the sunset, when I’m old I shall wear purple.
Enjoy the fall.
Image courtesy of [image creator name] / FreeDigitalPhotos.net