Question

Write a single experiment to show that sunlight and carbon dioxide is necessary for photosynthesis.​

Answer 1

Answer:

Explanation:

              CARBONDIOXIDE IS NECESSARY FOR PHOTOSYTHESIS;

                                 $\huge\boxed{EXPERIMENT}$

1. We take a potted plant having long and narrow leaves and place it in a completely dark place for; about three days to destarch its leaves.

2. Take a glass bottle having a wide mouth and put some potassium hydroxide solution (KOH solution! in it. (This 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).

3. Take a rubber cork which fits tightly into the mouth of the glass bottle and cut it into two halves.

4. Put a destarched leaf of the potted plant (while it is still attached to the plant), in-between the two halves of the cut cork and then fit the cork in the mouth of the glass bottle. The; upper half of the leaf should remain outside the glass bottle and only the lower half of the leaf should: be inside the glass bottle.

5. The potted plant (with its one destarched leaf half inside the glass bottle containing potassium hydroxide solution) is kept in sunlight for 3 to 4 days. During this period, the upper half of the leaf (which is outside the glass bottle) gets carbon dioxide from the air but the lower half of the leaf (which is inside the glass bottle) does not get any carbon dioxide.

This is because all the carbon dioxide of the air present in the glass bottle has been absorbed by potassium hydroxide solution. And no fresh air can come into the closed glass bottle.

6. Pluck the leaf from the plant and take it out from the glass bottle. Remove the green coloured chlorophyll from the leaf by boiling it in alcohol. In this way, we get a decolourised leaf.

7. Wash the decolourised leaf with water to remove any chlorophyll which may be sticking to it.

8. Pour iodine solution over the colourless leaf and observe the change in colour of the leaf.

9. We will find that the lower half part of the leaf (which was inside the glass bottle having no carbon dioxide around it), does not turn blue-black on adding iodine solution showing that no starch is present in this lower half of the leaf.

From this observation we conclude that the photosynthesis to make starch in the leaf does not take place without carbon dioxide.

10. The upper half part of the leaf (which was outside the glass bottle, having carbon dioxide around it) turns blue-black on adding iodine solution showing that starch is present in this upper half of the leaf.

From this observation we conclude that photosynthesis (to make starch) takes place in the presence of carbon dioxide. In other words, carbon dioxide is necessary for the process of photosynthesis to take place.

                     SUNLIGHT IS NECESSARY FOR PHOTOSYNTHESIS;

                         

                                $\huge\boxed{EXPERIMENT}$

Requirements:-

A well watered potted green plant, two strips of black papers, small clips, spirit lamp or bun sen burner, test tube, beaker, Petr-dish, water, mentholated spirit or rectified spirit or ethanol, iodine solution.

Experiment for Sunlight is necessary for Photosynthesis

Procedure for the experiment

Before starting the experiment to prove Sunlight is necessary for photosynthesis an important step has to be carried out is known as De-starching.

De-starching is a process in which the starch present in the leaves will be eliminated by keeping the plant in dark room or closed cup-board for about 48 hours.

This step is done to ensure that previously manufactured food in the leaves get consumed when the plant was kept in dark place since photosynthesis doesn't occur at that time.

Next strips of black paper will be arranged one on either side of the selected leaf of the De-starched plant with the help of clips. Now the whole plant is kept in bright Sunlight for about 3-4 hours.

Then the strips of black papers are removed from the experimental leaf and then starch test or Iodine test is conducted for the experimental leaf.

Result of Iodine test

Iodine is a purple colored reagent used to test the presence or absence of starch in the leaf conducted for photosynthesis process.

When iodine test is conducted for the expermental leaf, the leaf where black paper was covered will turn into brown color and the part of the leaf which is not covered with black paper will turn into blue-black color.

This result clearly indicates starch is formed in the leaf where sunlight is available and starch is not formed where the leaf doesn't got the sunlight as it is covered by black paper.

Answer 2

Answer :-

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EXPERIMENT TO PROVE THE NECESSITY OF CARBON DIOXIDE IN PHOTOSYNTHESIS -

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To prove the necessity of carbon dioxide in photosynthesis following steps need to do

Insert a part of the leaf of a destarched plant into a conical flask containing potassium hydroxide.

Potassium hydroxide solution absorbs the carbon dioxide gas from the air present in the glass bottle.

Leave the plant sunlight.

After few hours, perform a starch test to this and another leaf of the same plant.

Observation-

Leaf exposed to the atmosphere are bluish black.

Leaf exposed to KOH does not change to blue-black colour

Result- Starch is present in the green part of the leaf.

Conclusion- Presence of starch proves that chlorophyll is necessary for photosynthesis as it traps sunlight

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EXPERIMENT TO SHOW THAT SUNLIGHT IS NECESSARY FOR PHOTOSYNTHESIS

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To prove the necessity of sunlight in photosynthesis following steps need to do

Take a plant with destarched leaf.

Leaf is partially covered with black paper on which a design is cut.

Expose this plant to sunlight for few hours and perform a starch test with iodine solution.

Observation-

Covered leaf part shows brown colouration.

Exposed leaf shows blue-black colour.

Result- Starch is present in the exposed leaf.

Conclusion- Leaf exposed to sunlight give iodine test, proving that sunlight is necessary for photosynthesis.

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