Leaves are a mystery to most of us—they make a plant green and somehow are responsible for photosynthesis--whatever that is. Simply put, photosynthesis is a method of capturing light energy and using that energy to manufacture food from simple compounds, and the leaf is the factory where this is done.
Any efficient manufacturing unit has certain characteristics: an optimal arrangement of the factory floor, incoming raw materials, machinery, and outgoing products and wastes.
The raw materials are water, drawn through "pipes" from the soil, and carbon dioxide, a gas that enters through stomata—"doors" in the walls of the leaf. Inside, these materials enter the machinery—the cells—where the chemical reactions of photosynthesis occur. As carbon from carbon dioxide and hydrogen from water are combined to form sugars, the left-over oxygen is released as a waste product, passing from the leaf through the stomata to the air outside.
A system of vessels distributes the sugars throughout the plant,
supplying it with food for energy and basic materials for manufacturing other building
blocks of life.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Left: The Factory. Leaf of a Mulberry tree. Right: Distributon System. Magnified vascular system of a leaf. Scanned specimen of a preparation by Ed Freeman, University of Texas at El Paso.