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Question
Given below is the figure of an experimental set-up, showing a physiological act of the plants. Study and answer the following questions:
- What is the objective of this experiment?
- Name and define the process shown here.
- Why do we destarch the leaves before performing the experiment?
- How do we destarch the leaves?
- What will be the observation when we pour iodine solution over the bleached experimental leaf?
- Write a well-balanced equation for the above process.
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Solution
- To demonstrate the need for sunlight for photosynthesis.
- Photosynthesis. Photosynthesis is the process by which plants produce glucose using water, carbon dioxide, sunshine, and chlorophyll pigment in their leaves. Photosynthesis produces glucose and oxygen as its end products. Plants use glucose to power their cells, while other species require oxygen for respiration.
- We remove starch from a plant to facilitate photosynthesis in the presence of sunlight. If starch is already present in the leaves, photosynthesis does not take place.
- By keeping the leaves in a dark room for 24 to 48 hours, we can destarch them. This is because darkness inhibits photosynthesis and enables the plant to use up any stored starch.
- If starch is present, the bleached experimental leaf will turn blue-black when iodine solution is applied. The leaf is said to be starch-free if there is no colour change and it stays brown.
- \[\ce{6CO2 + 6H2O ->[Sunlight][Chlorophyll] C6H12O6 + 6O2}\]
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RELATED QUESTIONS
The diagram is set up to demonstrate an experiment. Pond weed was placed in five water-filled tubes. The experiment was set up as shown in the diagram. The tubes were then left for 24 hours. Write the correct answer out of the five available choices:
(i) In which tube would you except to find the plant with the least amount of starch?
(a ) 1 (b) 2 (c) 3 (d) 4 (e ) 5
(ii) The tube in which most oxygen would be found is
(a ) 1 (b) 2 (c) 3 (d) 4 (e ) 5
(iii) The tube in which least carbon dioxide would be found is
(a ) 1 (b) 2 (c) 3 (d) 4 (e ) 5
(iv) The tube in which the plant would survive for the shortest length of time is
(a ) 1 (b) 2 (c) 3 (d) 4 (e) 5
Given below is a schematic diagram to illustrate some aspects of photosynthesis.
- Fill up the gaps, in blank spaces (1-4), by writing the names of the correct items.
- What phenomenon do the thick arrows A and B indicate?
The diagram below shows two test-tubes A and B. Test-tube A contains a green water plant. Test-tube B contains both a green water plant and a snail. Both test-tubes are kept in sunlight. Answer the questions that follow:
(a) Name the physiological process that releases the bubbles of oxygen.
(b) Explain the physiological process as mentioned above in (a).
(c) What is the purpose of keeping a snail in test-tube B?
(d) Why does test-tube B have more bubbles of oxygen?
(e) Give an example of a water plant that can be used in the above experiment.
(f) Write the overall chemical equation for the above process.
Where are the chlorophyll pigments present in a cell?
Name the following:
Light in which the maximum rate of photosynthesis takes place.
Give technical term:
Name the experiment to demonstrate the importance of light for photosynthesis.
Choose the Correct Answer:
The main difference between chlorophyll ‘a’ and ‘b’ is:
Write the overall chemical equation for photosynthesis.
Match the terms given in column A with column B:
| Column A | Column B | ||
| (a) | Chlorophyll | (i) | Removes/absorbs CO2 |
| (b) | Methylated spirit | (ii) | Tests presence of starch |
| (c) | Potassium hydroxide | (iii) | Traps solar energy |
| (d) | Iodine solution | (iv) | Produces oxygen |
| (e) | Water | (v) | Bleaches chlorophyll |
Give reasons/explain:
During the starch test, the leaf is boiled in water.
