Question

Plz solve this question given in picture of biology .
I will mark uh as a brainliest ..

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Answer 1

This experiment is on photosynthesis.

6. Experiment to demonstrate that carbon dioxide enters the leaf through the stomata:

Requirements:

A de-starched plant having stomata only on lower surface of leaves, vaseline, beaker, water, iodine, soft rag.

Method:

1. Cut two leaves from such a de-starched plant in which the stomata are present only on the lower surface.

2. Apply vaseline on the lower surface of one leaf and on the upper surface of the other leaf.

3. Dip the petioles of both the leaves in water in a beaker.

4. Place the beaker, along with the leaves, in bright light for at least four hours, and then wipe off as much vaseline as possible with a soft rag. Care should be taken so that the leaf is not damaged during wiping of the vaseline.

5. Test for starch by the iodine method.

Observations and results:

The leaf, on which vaseline was applied on the upper surface, shows positive test for starch by becoming blue coloured. Therefore, the CO2 entered the leaf through the stomata present on its lower surface and the starch was formed.

On the other hand, the leaf, on which the vaseline was applied on the lower surface, shows negative test for starch, i.e., blue colour does not appear. It is because the stomata were present only on the lower surface. They were blocked due to vaseline application. Therefore, CO2 could not enter the leaf, and hence no starch formation takes place.

This shows that CO2 enters the leaf through stomata during photosynthesis.

1. Experiment to demonstrate Moll’s half-leaf experiment for showing that CO2, light, chlorophyll and water are necessary requirements for photosynthesis:

Requirements:

A potted plant, caustic potash, wide- mouthed bottle, iodine, split cork, water.

Method:

1. De-starch a potted plant by putting it in complete darkness for two days.

2. Fill partly a wide-mouthed bottle with strong solution of caustic potash and fit a split cork on its mouth.

3. Insert about half of the portion of a leaf of the de-starched plant into the bottle through the split cork (Fig. 36).

Demonstration of Moll's half-leaf experiment  

4. Place the whole apparatus in light after applying grease on the upper portion of split cork, and test the leaf for stach after about 10 hours.

Observations:

Portions of the leaf inside the bottle as well as in between the split cork show negative test for starch indicating the absence of photosynthesis while the portions outside the split cork show positive test for starch indicating the presence of process of photosynthesis in this region.

Results:

Negative starch test by the leaf portion present inside the bottle indicates that process of photosynthesis is absent in this region. This portion of leaf is getting all the essential requirements, i.e., light, chlorophyll and water except the CO2 because the latter is absorbed by the caustic potash. Thus, it can be concluded that CO2 is necessary for this process.

Negative test of starch, which is also shown by the portion of the leaf present in between the split of the split cork, can be explained that it is due to the lack of CO2 and light, thus indicating that both of them are essential requirements.

Positive test of starch shown by the portions of the leaf present outside the bottle indicates that photosynthesis process is continuously going on there because all the essential requirements, i.e., light, chlorophyll, water and CO2 are readily available to this portion.

That the chlorophyll is also an essential requirement for photosynthesis can be shown by testing starch in a variegated leaf. Only green portions of the leaf show positive starch test.

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Potassium hydroxide is used in this experiment played the role of absorbtion of carbon-dioxide from the plant surrounding. This is done so as to remove all carbon-dioxide from the jar or from the surrounding where pmnat is placed. KOH absorbs the carbon dioxide released by the germinating seeds and a partial vacuum is created because of the loss of carbon dioxide in the flask.

This vacuum causes the water level in the delivery tube to rise up.

Germinating seeds are used because they use up the oxygen in the flask to respire and release carbon dioxide as a result, which is absorbed by KOH, causing the weight of KOH to increase.