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How Are Leaves Adapted to Photosynthesis?

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How Are Leaves Adapted to Photosynthesis?

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Overview

Leaves conduct photosynthesis by using energy from the sun to turn carbon dioxide from the air and hydrogen from water into glucose and oxygen. The leaf has evolved several parts to conduct photosynthesis including pores, cells guarding the pores, veins that carry water to the leaves, and cells containing chlorophyll that conduct the chemical conversion.

Stomata

A stoma is a pore. The plural is stomata. A waxy substance called the cuticle protects the exterior of a leaf, called the epidermis. Leaves use stomata in the cuticle to breathe, or get the air it needs for photosynthesis.

Guard Cells

Leaves take carbon dioxide from the air and release oxygen. In exhaling oxygen, the leaves also lose water, a process called transpiration. To let in air and eliminate oxygen, leaf pores need to open and close. This is done by guard cells that flank stomata.

Mesophyll Tissue

Plants need chlorophyll to conduct photosynthesis. Tissue called mesophyll in the center of the leaf contains chloroplast cells. This is what we know as chlorophyll, the protein that conducts photosynthesis. The palisade layer is composed of one to five rows of long chloroplast cells just beneath the top of a leaf. These cells are separated so they can absorb carbon dioxide through the stomata, but they are not so far apart as to prevent the capillary action need to distribute water inside the leaf. The palisade layer contains the most chloroplasts in a leaf, and they conduct most of the photosynthesis. Just above the bottom of the leaf and below the palisade layer is the spongy layer of a leaf. It also contains chloroplast cells, but they are more rounded than those in the palisade layer and there is more space between them.

Veins

Plants need water for photosynthesis. A bundle of vascular tubes called xylem transport water throughout the plant. Xylem are found in the roots of a plant, in the stalk or trunk, and in the leaves. After photosynthesis, leaves transport nutrient sugars to the rest of the plant through tubes called phloem.

Absorbing Light

Particles of light come in waves. Each color of the spectrum has a different wave length, the distance between the peaks and troughs of the wave. Shorter wave lengths are bluer; longer wave lengths are redder. A pigment is a substance that absorbs light. Chlorophyll absorbs all visible light except green. That is why leaves are green. When a pigment absorbs light, it can dissipate the energy as heat, it can emit a longer wavelength (fluorescence is an example), or it can react chemically. When light hits a leaf, chloroplasts in the mesophyll add hydrogen from water to carbon dioxide from the air to form carbohydrates that turn into glucose. In the process, it releases oxygen through the stomata.

Keywords: photosynthesis leaves, leaves plant food, plant photosynthesis

About this Author

Richard Hoyt, an internationally published author of 26 mysteries, thrillers and other novels, is a former reporter for Honolulu dailies and writer for "Newsweek" magazine. He taught nonfiction writing and journalism at the university level for 10 years. He holds a Ph.D. in American studies.