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Photosynthesis in Higher Plants

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
Give an experiment to prove that CO2 is necessary for photosynthesis.

To prove that CO2 is necessary for photosynthesis the following experiment can be formed:

1. A potted plant is kept in dark for three days so that the leaves become free from starch.

2. A healthy leaf is selected for experiment.

3. a wide mouth bottle is taken and a little KOH (it absorbs CO2) is added to it. 

4.Half part of the leaf is kept in the bottle with the help of split cork.

5. The apparatus in kept in bright sunlight for few hours.

6. The leaf is plucked and boil in 70% alcohol. It is stained with iodine solution.

Observation : It was observed that the portion of leaf which was out of the bottle turned blue showing the presence of starch. The portion on leaf which was enclosed within the bottle will not show the presence of starch .

Give an experiment to prove that CO2 is necessary for photosynthesis.


Conclusion : This shows that CO2 is essential for photosynthesis, because the portion inside the bottle did not get the CO2 as it was absorbed by KOH solution. Thus CO2 is necessary for photosynthesis.


Name the first stable compound formed in C3 cycle.

3-phosphoglyceric acid (PGA)

Where CO2 assimilation occurs in CPlants ?

In bundle sheath cells.

Why Rubisco is not affected by O2 in C4 plants ?

O2 is formed in mesophyll cells while Rubisco is present in bundle sheath cells. Therefore Rubisco does not come in contact with O2 and is thus not affected by it.

What are grana ?

Grana are the stacks of thylakoids embedded in the stroma of a chloroplast. They are the sites of light reaction of photosynthesis.

 What is stroma ?

Stroma is matrix or the cytoplasm of chloroplast where dark reaction of photosynthesis takes place.