Minerals in Plants

Some minerals are very important to plants, especially those minerals which contain the elements nitrogen, phosphorus and potassium. You will find these three elements in all the fertilizers given to plants.

Here are the results of an experiment where wheat plants were grown with different fertilizers:

You can see that the plants grow better if they are given fertilizer which contains minerals but it is important to understand that all the minerals must be present to give the best growth.

Organic Matter 

Green plants are special because they need sunlight if they are to grow strong and healthy. A plant growing in the dark grows tall but very thin and weak, with small, yellow leaves. If you measure its mass you will find that it is a lot less than the mass of a similar plant growing in the light.

The green colour of these plants is caused by a pigment called chlorophyll (which comes from the Greek and means "the colour of leaves"). Light is necessary for the plant to make chlorophyll. Light is also needed for the chlorophyll to function properly in the process called photosynthesis. (This word also comes from the Greek and it means "making things using light".)

Johnny's Fact File No.24 The largest leaves are found on the raffia palm which grows naturally on islands in the Indian ocean. These leaves can reach up to 19,8 m in length.

The plant uses light from the sun and chlorophyll to make organic matter from carbon dioxide gas and water. Oxygen gas is produced by this process. Therefore, in daylight, green plants absorb a lot of carbon dioxide and release oxygen.

When they photosynthesize, green plants grow bigger and stronger as they make more organic matter.

Johnny's Fact File No.25 In a single year 1 hectare of forest absorbs 22 tonnes of carbon dioxide and gives out 16 tonnes of oxygen. When a wheat seed germinates and grows into a fully mature wheat plant, it increases its mass 325 times. A farmer who sows 100 kg of seeds per hectare in the spring will harvest 7,5 tonnes of seeds per hectare in September.

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© Paul Billiet and Shirley Burchill 2008