Photosynthesis and transpiration (made easy)

Photosynthesis is the way a plant makes food for itself. Chlorophyll in the "green" part of the leaves captures energy from the sun and this powers the building of food from very simple ingredients - carbon dioxide and water. Oxygen is released as a by-product of photosynthesis.

Photosynthesis and transpiration (made easy)
Illustration by Ruth Grant
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Plants "breathe in" carbon dioxide and "breathe out" oxygen. They breathe through tiny holes in their leaves called stomata; they also lose water through the stomata.

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The tree draws up water through its roots and the water is then drawn up through the tree and comes out through the stomata in its leaves. The whole process of sucking up water and losing it again is called transpiration.

The basic principal is simple really - they just use long complicated words to describe it!

Photosynthesis (a bit harder)

Sunlight is absorbed into the leaf by a green pigment called chlorophyll, which absorbs red and blue light, but reflects green light, causing the leaves to appear green.  Chlorophyll is not a very stable compound and plants continuously have to make or synthesize more. 
 
This light energy is then converted into a chemical energy in the form of starch or sugar:

6H2O + 6CO2        >        C6H12O6 + 6O2

This equation translates as six molecules of water (6H2O) plus six molecules of carbon dioxide (6CO2) produce one molecule of sugar (C6H12O6) plus six molecules of oxygen (O2).

Transpiration (a bit harder)

Water (H2O) that contains valuable nutrients and minerals is sucked out of the soil by the plants roots and passed up through the leaves where they mix with carbon dioxide (CO2) from the air and are converted into sugars that are absorbed by the plant to make it grow.  During this process the plant releases oxygen (O2) into the air, and this is why we need to plant as many trees as we can to enable us to have enough oxygen to breathe. 

The fact that plants take in carbon dioxide is thought to be important in the fight against global warming since the overproduction of carbon dioxide from the burning of fossil fuels by human beings could be a major factor.

Other items that may be of interest:

• Why do leaves change colour in autumn?
• Wildlife for kids
• Recycling for the Cornwall Wildlife Trust
• Pond educational resource pack
• Discovering biodiversity

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