Question

A potted plant with variegated leaves was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours and then placed in bright sunlight for a few hours. Observe the diagram and answer the questions.

1. What aspect of photosynthesis is being tested in the above diagram?
2. Represent the process of photosynthesis in the form of a balanced equation.
3. Why was the plant kept in the dark before beginning the experiment?
4. What will be the result of the starch test performed on leaf 'A' shown in the diagram? Give an example of a plant with variegated leaves.
5. Draw a neat labeled diagram of a chloroplast.

Answer 1

Experimental Setup:

1. In the given experiment, the necessity of chlorophyll for photosynthesis was tested.
2. For that, a variegated leaf plant was taken. Variegated leaves are those which have both green and non-green portions (in the given condition periphery of the leaf is pale yellow).
3. The plant was kept in dark for 2-3 days for destarching (removal of starch from the plant's body).
4. Then kept in the sunlight for a few hours.
5. One of the leaves from that plant was plucked and tested for starch.
6. It was found that the starch-containing area (green portion) turned blue-black inferring a positive result for starch presence.
7. However, it was observed that the pale-yellow or non-green area showed a negative result for the presence of starch.
8. So, it was concluded that chlorophyll is an important aspect of the process of photosynthesis.

1. The aspect tested by the given experiment:

1. Chlorophyll, a green pigment present in the photosynthetic plant, was tested through the given experiment.
2. It is an important aspect of starch production in the process of photosynthesis.

2. Balanced equation of photosynthesis:

1. Photosynthesis is a chemical equation in which six molecules each of water and carbon dioxide, in the presence of chlorophyll and sunlight, convert into one glucose and six oxygen molecules.
2. The balanced equation of photosynthesis is represented by the following equation:

$$\begin{gathered} 6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}\to {\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2 \\ \mathrm{Carbon}\mathrm{Water}\mathrm{Glucose}\mathrm{Oxygen} \\ \mathrm{dioxide} \end{gathered}$$

3. Reason for keeping plant in dark before conducting the experiment:

1. The plant was kept in dark, before doing the experiment, for destarching.
2. Destarching is the process of starch removal from the plant's body.

4. Results of the experiment and examples of variegated plants:

1. Results of the experiment: Leaf-A is a variegated leaf and when it was tested for starch, it was found that the green portion of the leaf (photosynthesis occurred there) turned blue-black inferring a positive result for starch presence. However, the non-green area (photosynthesis absent there) showed a negative result for the presence of starch.
2. Examples of variegated plants: Variegated plants are plants having leaves that are partially green and partly white or non-green. For example, Croton and Coleus plants.

5. A labeled diagram of chloroplast:

1. Chloroplasts are the cell organelles present in photosynthetic organisms and are bound by a double membrane that encloses chlorophyll pigment on the thylakoid membranes.