1. Green plants are producers.


2. Only green plants possess the amazing ability of trapping solar energy to produce food.


3. Photosynthesis is the process in which green plants absorb
solar energy to make food from carbon dioxide and water.


4. Oxygen is released as a by-product.


5. Chlorophyll is the green pigment present in leaves that can absorb sunlight.


6. The glucose produced during photosynthesis is then converted into starch. Starch is stored in the stems, fruits or roots of plants.


7. Photosynthesis can be represented by the following equation:



Requirements Of Photosynthesis

1. The necessary factors for photosynthesis:

    (a) Sunlight

    (b) Chlorophyll

    (c) Water

    (d) Carbon dioxide


2. Photosynthesis will not take place if any one of these factors is absent.


3. We should test for the presence of starch in leaves to determine whether photosynthesis has taken place in a plant.


Testing For The Presence Of Starch In Leaves

1. Below are the steps to test for the presence of starch in a leaf:

   (a) Immerse a leaf in boiling water for a minute to soften and break the cells.


   (b) Transfer the boiled leaf into a boiling tube containing alcohol. Place the boiling tube
         in a water bath for a few minutes to decolourise the leaf.


   (c) Remove the leaf and put it back into the hot water for a few seconds to soften the leaf.


   (d) Spread the leaf onto a white tile. Add a few drops of iodine solution to test
        for the presence of starch.


2. The presence of starch can be tested using iodine solution after the chlorophyll of the leaf is removed.


3. The areas containing starch will be stained blue-black when iodine solution is added.


The importance Of Photosynthesis

1. Photosynthesis is an important process. This process manufactures food for all organisms on Earth.


2. All organisms need food but only green plants are capable of trapping solar energy to manufacture food from simple substances.


3. All other organisms, animals or non-green plants, are directly or indirectly dependent on green plants for food.


4. Green plants start the food chain and they are the producers in any ecosystem.


5. Therefore, photosynthesis is an important process that provides food for all organisms.


6. Photosynthesis replaces the oxygen that is used up in the following processes.

    (a) Respiration of living things.

    (b) Combustion of fuel.

    (c) Decomposition of dead plant and animal materials.


7. On the other hand, photosynthesis absorbs carbon dioxide in the atmosphere that is given out during respiration, combustion and decomposition.


8. The concentration of oxygen and carbon dioxide in the atmosphere are maintained by the oxygen and carbon cycles.


9. Therefore, photosynthesis and respiration are important in maintaining a balanced level of oxygen and carbon dioxide in the atmosphere and hence maintain a balanced ecosystem.