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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
 Describe Crasslacean acid metabolism.


It can be described in following ways :

1. Crasslacean acid metabolism (CAM) refers to a mechanism of photosynthesis that is different than already discussed C3 and C4 pathways.

2. This occurs only in succulents and other plants that normally grow in dry conditions.

3. In CAM plants C02 taken up by leaves or green stems through stomata, which remain open at night.

4. However during the day the stomata remain closed in these plants to conserve moisture.

5. The CO2 taken up in the night is fixed in the same way as in C4 plants to form malic acid, which is stored in the vacuole.

6. The malic acid thus formed during the night is used during the day as a source of CO2 for photosynthesis to proceed via the C3 pathway.

Significance : Thus CAM is a kind of adaptation that allows certain plants (for example, pineapple) to carry out photosynthesis without much loss of water.


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.

Name the first stable compound formed in C3 cycle.

3-phosphoglyceric acid (PGA)