Question

RuBisCO is an enzyme that acts both as a carboxylase and oxygenase . why do you think RuBisCO carries out more carboxylation C4 Plants?

Answer 1

C₄ plants have special type of anatomical arrangement called as Kranz anatomy in which two types of photosynthetic cells are present in leaves. These are bundle sheath cells and mesophyll cells unlike only mesophyll cells in C₃ plants. So in C₄ plants Rubisco is present only in bundle sheath cells not in mesophyll cells where oxygen is released during light reactions. So oxygen is not available in bundle sheath cells for oxygenase activity of Rubisco. That’s why only carboxylase activity of Rubisco is operated and there is no oxygenation occurs as we see in C₃ plants through photorespiration.