Question

Give a comparison between ${ C }{ 3 }$ and ${ C }{ 4 }$ pathway.

Answer 1

Some plants are found in temperate regions while some plants are found in warm regions. So, according to the environmental conditions, different plants have a different mechanism of production of energy and oxygen.

Complete answer:

S.no	${ C }{ 3 }$ Pathway	${ C }{ 4 }$ Pathway
1	The ${ C }{ O }_{ 2 }$ acceptor is RUBP (${ Ribulose } { 1,5 }-{ bisphosphate }\\\$)	The ${ C }{ O }_{ 2 }$ acceptor is PEP(Phosphoenolpyruvate)
2	Complete steps are performed in mesophyll cells of the leaves.	Initial steps are performed in mesophyll cells and the rest are performed in bundle sheath cells.
3	The first stable product is phosphoglycerate which is a 3 carbon compound.	The first stable product is oxaloacetic acid. which is a 4 carbon compound.
4	There is no secondary ${ C }{ O }_{ 2 }$ acceptor.	A secondary ${ C }{ O }_{ 2 }$ acceptor is present which is RUBP.
5	${ C }{ O }_{ 2 }$ fixation is slow.	${ C }{ O }_{ 2 }$ fixation is faster.
6	Examples of ${ C }{ 3 }$ plants are wheat, rice.	Examples of ${ C }{ 4 }$ plants are maize, sugarcane.

Additional Information: ${ C }{ 3 }$ Pathway: ${ C }{ 3 }$ plants use the Calvin cycle or ${ C }{ 3 }$ cycle for the dark reaction of photosynthesis. The majority of the plants on the earth are ${ C }{ 3 }$ plants and exhibit ${ C }{ 3 }$ pathway. The plants are called ${ C }{ 3 }$ because of the production of phosphoglycerate which is 3 carbon compounds. Photosynthesis occurs when the stomata are open. ${ C }{ 4 }$ Pathway: ${ C }{ 4 }$ plants use Hatch-slack pathway or ${ C }{ 4 }$ cycle for the dark reaction of photosynthesis. ${ C }{ 4 }$ plants are very less in number as compared to ${ C }{ 3 }$ plants. The plants are called ${ C }{ 4 }$ because of the production of oxaloacetate which is 4 carbon compounds. Photosynthesis occurs even when the stomata are closed.

Note: There is a specialized structure present in ${ C }{ 4 }$ plant which is known as Kranz anatomy. In these i.e ${ C }{ 4 }$ plants, mesophyll cells cluster around a bundle-sheath cell in the form of a ring. The entire structure plays an important role in ${ C }{ 4 }$ photosynthesis.