Question

Can anyone explain abt the C4 pathway from photosynthesis in higher plants chapter
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Answer 1

C4 PATHWAY:

• This pathway mostly takes place in monocot plants and in some dicot plants.

• In this pathway, the first product of CO2 fixation is a 4 carbon compound, oxaloacetic acid, hence it is called C4 pathway.

• The anatomy of leaves of C4 plants is different from leaves of C3 plants (Calvin cycle).

• Palisade cells in the mesophyll tissues are absent.

• There is bundle sheath around the vascular bundles.

• In the bundle sheath cells, large chloroplasts without grana or less developed grana are present, whereas, in mesophyll cells, there are chloroplasts with well-developed grana. This type of anatomy is called Kranz anatomy.

• In C4 pathway, CO2 taken from the atmosphere is accepted by phosphoenol pyruvic acid present in the chloroplast of mesophyll cells, leading to the formation of a 4 carbon compound oxaloacetic acid.

• This is converted into malic acid (4 carbon compound) which enters into the chloroplast of bundle sheath cells.

• Here the malic acid dissociates into pyruvic acid and CO2.

• Pyruvic acid re-enters with RuBP gives rise to sugars and other carbohydrates in bundle sheath cells.

• There is no photorespiration in these plants.

• Examples: Maize, Sorghum.