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How Does Photosynthesis Work in Plants?

The Roots

Photosynthesis requires water. Plant roots absorb water from the surrounding soil. Many roots have small, hair-like protrusions which help them increase their surface area and absorb more water. That water flows into tubes called xylem, which flow up the stem of the plant. The xylem distribute the water to the leaves, where most of the photosynthesis occurs.

The Leaves

Besides water, photosynthesis requires carbon dioxide and sunlight. Tiny pores called stomata in the leaves allow carbon dioxide to enter the leaves, and also allow waste oxygen to exit. These pores can open and close to control the flow of gasses through the leaves and to stop too much water from being lost. Besides stomata, leaves have a pigment called chlorophyll. Chlorophyll absorbs many wavelengths of light, including red, orange, blue and violet. Chlorophyll reflects green light, which is what gives most plants their characteristic green look.


The light absorbed by the chlorophyll is directed to reaction centers where the photosynthesis occurs. In the reaction centers, the plant transforms water and carbon dioxide into sugars and waste oxygen, which is vented through the stomata. The sugar produced is distributed through the plant by a system of tiny tubes called phloem. It feeds plant cells and provides the plant the energy it needs to grow, bud and produce fruit.

Importance of Photosynthesis

With the exception of anaerobic bacteria, pretty much all non-plant life depends on photosynthesis to survive. For plants, oxygen is a waste product generated in photosynthesis, but for animals it is necessary for survival. Plants are also the first level of the food chain. If they did not provide food for herbivores, which provide food for the carnivores that feed on them, there would be literally no animals on earth.

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