Question

Compare and contrast the photosynthetic processes in C₃ and C₄ plants.

Answer 1

Contrast the photosynthetic processes in C₃ and C₄ plants:

C₃ Plants:

• CO₂ fixation takes place in mesophyll cells only.
• CO₂ acceptor is RUBP only.
• First product is 3C – PGA.
• Kranz anatomy is not present.
• Granum is present in mesophyll cells.
• Normal Chloroplast
• Optimum temperature 20° to 25° C.
• Fixation of CO₂ at 50 ppm.
• Less efficient due to higher photorespiration.
• RUBP carboxylase enzyme used for fixation.
• 18 ATPs used to synthesize one glucose.
• Efficient at low CO₂
• eg: Paddy, Wheat, Potato and so on.

C₄ Plants:

• CO₂ fixation takes place mesophyll and bundle sheath.
• PEP in mesophyll and RUBP in bundle sheath cells.
• First product is 4C – OAA.
• Kranz anatomy is present.
• Granum present in mesophyll cells and absent in bundle sheath.
• Dimorphic chloroplast.
• Optimum temperature 30° to 45° C.
• Fixation of CO₂ even less than 10 ppm.
• More efficient due to less photorespiration.
• PEP carboxylase and RUBP carboxylase used.
• 30 ATPs to produce one glucose.
• Efficient at higher CO₂.
• eg: Sugar cane, Maize, Sorghum, Amaranthus and so on.