From Seed to Seed:
Plant Science for K-8 Educators

 

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Photosynthetic process

The importance of photosynthesis cannot be overstated.

ALL LIFE ON EARTH DEPENDS ON IT.

Every living organism depends either directly or indirectly on the products of photosynthesis, a process that takes place only in green plants (and a few types of microorganisms).

Photosynthesis is the chemical reaction by which plants manufacture carbohydrates. Plants, like animals, need "food," or carbohydrates, to provide energy for metabolism. Animals get their food by consuming it; plants manufacture their own carbohydrates using energy from light.

The chemical reaction for photosynthesis is:

CO2 + H2O ---> (CH2O) + O2

The reactants (left side of the equation) are carbon dioxide and water. Carbon dioxide enters the leaf from the air through the stomata on the underside of the leaves. Water is absorbed through the roots and transported to the leaves through the vascular tissue (xylem). The products (right side of the equation) are carbohydrates and oxygen. CH2O is not the formula for a specific carbohydrate, but represents the basic ratios. All carbohydrates have a 1:2:1 ratio of carbon:hydrogen:oxygen molecules. For example, glucose is C6H12O6.

So far, this chemical reaction seems pretty straightforward. But think for a moment about what happens if you simply mix carbon dioxide with water-imagine exhaling under water, for example. You certainly don't end up with sugar and oxygen!

The process of photosynthesis is actually quite complex and
involves several intermediate steps.







 

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