Question

The figure given alongside represents an experiment to demonstrate a particular aspect of photosynthesis. The alphabet A represents a certain condition inside the flask. Observe the diagram and then answer the following questions.

1. What is the aim of the experiment?
2. What happens to the leaf when tested with iodine?
3. Which chemical can be used as an alternative to KOH?
4. What happened to leaf A and leaf C at the end of the starch test?

Answer 1

Photosynthesis:

1. It is a process that occurs in the green plants to manufacture food in presence of sunlight using carbon dioxide and water.

1. Aim of the experiment:

1. The aim of the experiment is to show the presence of carbon dioxide is necessary for photosynthesis.

2. Leaf when tested with iodine:

1. KOH solution present in the bottle absorbs all CO₂ present in a bottle.
2. Thus, starch is not formed in the leaf and it does not give a blue-black color when tested with iodine.

3. Alternative of KOH:

1. NaOH (sodium hydroxide) can be used as an alternative to KOH solution as both functions is to absorb CO₂.

4. At the end of the starch test:

1. Leaf A is present in the bottle containing KOH which absorbs CO₂ and thus photosynthesis does not take place.
2. So, it will not show any color difference when tested with iodine.
3. On the other hand, leaf C is present outside the bottle where CO₂ is present in abundance and so photosynthesis does take place.
4. Thus, leaf C turns to a blue-black color when tested with iodine to confirm the presence of starch.