Question

Leaves from both plants were tested for stach after two hours. What

observation do you expect at the end of the experiment? Give reason for your

answe​

Answer 1

Answer:

The presence of starch in leaves can be tested by the Iodine test. When we remove chlorophyll from the leaf by boiling it in alcohol and then put two drops of iodine solution, it is colour change to blue indicates the presence of starch.

When chlorophyll breaks down, yellow pigments in leaves become visible. As days get shorter and colder in the autumn, chlorophyll molecules break down. Leaves quickly lose their green color. Some leaves begin to look yellow or orange because they still contain pigments called carotenoids.

Answer 2

Answer:

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Explanation:

The leaf of the potted plant was covered with a piece of black cloth to destarch it. Potassium hydroxide solution is to absorb the carbon dioxide gas from the air present in the glass bottle so that no carbon dioxide is left in the air inside the glass bottle. He will find that the leaf which was inside the glass bottle having no carbon dioxide around it, does not turn blue on adding iodine solution showing that no starch is present in this leaf. From this observation, we conclude that the photosynthesis to make starch in the leaf does not take place without carbon dioxide. And by covering the flask containing leaf B with black cloth, the leaf wont get exposure of sun light and photosynthesis won't happen. From this observation, we conclude that photosynthesis (to make starch) takes place in the presence of sunlight. Hence both the leaves do not have starch.