Name: Chloroplast
Uploaded: 2019-07-19
Duration: 3 min 5 s
Description: Chloroplast is the ‘chef’ that prepares food from raw materials through photosynthesis! Let's take a look at the cross-section of a leaf and check out these...

Question

How would you demonstrate that sunlight is necessary for photosynthesis?

Accepted Answer

Aim: To demonstrate that sunlight is necessary for photosynthesis.

Materials Required: A potted plant, black paper, clips, beaker, burner, test tube, dropper, water, alcohol and iodine solution

Procedure: Keep a green potted plant in dark for about 48 hours to de-starch its leaves. Pluck one leaf and test it for iodine to confirm that the plant is de-starched. Cover a part of a healthy leaf on both sides with a strip of black paper. Place this plant in sunlight for at least four hours or more. Pluck the leaf, remove the black paper strip. Boil the leaf first in water and then in alcohol. This destroys the chlorophyll and the leaf becomes colourless. Wash the leaf with warm water and put it in a petri dish. Pour few drops of iodine solution on the leaf to test for starch.

Observation: The uncovered part of the leaf that was exposed to sunlight turns blue-black, while the part of the leaf which was covered with the black strip does not turn blue-black.

Conclusion: This shows that starch is formed only in those parts which are exposed to sunlight. No starch is formed in the covered part which could not get sunlight. Hence, sunlight is necessary for photosynthesis.

How would you demonstrate that sunlight is necessary for photosynthesis?

Important Questions on Nutrition in Plants

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