Explain that sunlight is essential for photosynthesis.

Photosynthesis is a biochemical process by which green plants synthesize simple sugars. The most important factor for photosynthesis is light. The rate of photosynthesis depends on the quantity and quality of light.

Procedure to prove light is essential for photosynthesis:

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

2) Attach light proof black paper strips on both sides of the leaf with the help of paper clips.

3) Place the plant in sunlight for 3-4 hours.

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

5) Perform starch test by boiling leaf first in boiling water followed by boiling in alcohol over a water bath and then rinsing with cold water and again placing it in iodine solution.

Observation: The leaf turns blue-black except in the covered region. As the 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.