Green Plants

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Green plants absorb light energy using chlorophyll in their leaves. They use it to react carbon dioxide with water to make a sugar called glucose. The glucose is used in respiration, or converted into starch and stored. Oxygen is produced as a by-product. This process is called photosynthesis. Temperature, carbon dioxide concentration and light intensity are factors that can limit the rate of photosynthesis. Plants also need mineral ions, including nitrate and magnesium, for healthy growth. They suffer from poor growth in conditions where mineral ions are deficient. Photosynthesis

Photosynthesis is the chemical change which happens in the leaves of green plants. It is the first step towards making food - not just for plants but ultimately every animal on the planet. During this reaction, carbon dioxide and water are converted into glucose andoxygen. The reaction requires light energy, which is absorbed by a green substance called chlorophyll. Photosynthesis takes place in leaf cells. These contain chloroplasts, which are tiny objects containing chlorophyll.

Cross-section through a leaf cell
Here is the equation for photosynthesis:
carbon dioxide + water (+ light energy)    →    glucose + oxygen 'Light energy' is shown in brackets because it is not a substance. You will also see the equation written like this:

Plants absorb water through their roots, and carbon dioxide through their leaves. Some glucose is used for respiration, while some is converted into insolublestarch for storage. The stored starch can later be turned back into glucose and used in respiration. Oxygen is released as a by-product of photosynthesis.

Plants and minerals
Plants need to take in a number of elements to stay alive. The most important are: * carbon
* hydrogen
* oxygen
Plants get hydrogen and oxygen from water in the soil, and carbon and oxygen from carbon dioxide and oxygen in the atmosphere. Water and carbon dioxide are used to synthesise food during...
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