Question

Class 07 describe an activity to show that light is necessary for photosynthesis.

Answer 1

Procedure:

1. Take the potted plant and keep it in a dark place for 2-3 days so that the leaves get destarched.

2. Cover a part of one of its leaves with the strip of black paper. Make sure that you cover both the sides of the leaf.

3. Now place this plant in sunlight for 3—4 hours.

4. Pluck the selected covered leaf and remove the black paper covering it.

5. Place this leaf in the beaker containing water and boil it for about 10 minutes.

6. Take out the leaf and now boil it in alcohol, using the water bath, for 10 minutes. This removes the chlorophyll.

7. Take out the leaf and wash it under running water.

8.Place this leaf in the Petri dish and put a few drops of iodine solution on it. Now observe the change in colour.

Observations:

The leaf turns blue-black except in the covered region. As this covered region did not receive light, photosynthesis did not occur. Hence no starch was formed there. The uncovered region received light and starch was formed there due to photosynthesis.

Result:

Light is essential for photosynthesis.

Precautions:

1. Before starting the experiment, the leaf must be distracted.

2. The leaf must be covered with black paper properly to prevent the entry of light.

3. Boiling the leaf in alcohol should be done in the water bath.

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Answer 2

Ans.The following activity should answer your query-

1.Take 2 plants and keep one in a dark room with no light source and the other outside in the garden.

2.Water both plantsfor one week.

3.After a week you will notice that the first plant will start dying or even die but second plant will stay alive.

Hope it will help