Making life from Light

Photosynthesis is nature’s way of making life from light. Chlorophyll allows a tree to capture photons, extracting a portion of their energy to make the sugars that make it a tree — the raw material for leaves and bark and roots and branches — then releasing the photons at lower wavelengths back into the atmosphere. A tree is a light-catcher that grows life from air.

Although the human mind has puzzled over why leaves fall and change color at least as far back as Aristotle, chlorophyll — which shares chemical kinship with the hemoglobin in our blood — was only discovered and named in 1817, by the French pharmacist-chemist duo Joseph Bienaimé Caventou and Pierre Joseph Pelletier. In a lovely touch of humility that distinguishes, always, the scientist from the explorer — the explorer, so eager to name the lands and landmarks he has “discovered” after himself — they wrote in their landmark paper:

We have no right to name a substance long-known, and to the story of which we have added only a few facts; however, we will propose, without granting it any importance, the name chlorophyll, from chloros, color, and φυλλον, leaf: a name that would indicate the role it plays in nature.

Red maple by Clarissa Munger Badger, who inspired Emily Dickinson. (Available as a print and as stationery cards, benefitting The Nature Conservancy.)

But chlorophyll, which is yet to be fully understood, is not the only pigment in trees. Throughout a leaf’s life, four primary pigments course through its cells: the green of chlorophyll, but also the yellow of xanthophyll, the orange of carotenoids, and the reds and purples of anthocyanins.

Life from Light and Air and Water and Earth and Space

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