NEETBotanyPhotosynthesis in Higher Plants
In plants possessing Kranz anatomy, photorespiration is virtually absent. Which of the following mechanisms specifically ensures that RuBisCO functions primarily as a carboxylase in these plants?
Options
- AMesophyll cells actively pump gaseous CO ₂ directly into the bundle sheath cells to saturate the enzyme.
- BRuBisCO in these plants structurally lacks an oxygenase active site, preventing any binding with oxygen.
- CDecarboxylation of C ₄ acids in the bundle sheath cells creates a high intracellular concentration of CO ₂ .
- DPEPcase acts as a physical shield around RuBisCO in the mesophyll cells, blocking oxygen entry.
Correct answer
C. Decarboxylation of C ₄ acids in the bundle sheath cells creates a high intracellular concentration of CO ₂ .
Step-by-step solution
In C ₄ plants (which possess Kranz anatomy), photorespiration does not occur. This is because they have a mechanism that increases the concentration of CO ₂ at the enzyme site. This takes place when the C ₄ acid (like malic or aspartic acid) from the mesophyll is broken down (decarboxylated) in the bundle sheath cells to release CO ₂ . This results in increasing the intracellular concentration of CO ₂ , which ensures that RuBisCO functions as a carboxylase minimizing the oxygenase activity. The enzyme RuBisCO itsel