Question

Using the destarched plant describe step by step how would you proceed to prove that in the absence of light the leaf cannot manufacture starch?

Answer 1

1. In a dark room, a leaf on the destarched plant is covered on either side with strips of black paper which are kept in place by paper clips or cellophane tape.
2. Now the potted plant is kept in the light.
3. After a few hours, the leaf is detached from the plant and the black strips are removed.
4. Then the leaf is boiled in water for 2-3 minutes and then boiled in alcohol to remove the green chlorophyll.
5. The leaf is then washed in water and tested with iodine.
6. The region of the leaf that was under the black strip turns yellowish-brown showing that no starch was made, while the rest of the leaf turns bluish-black showing the starch was made in the presence of light.