Question

Which of the following characteristics out of I, II and III are exhibited by $C_4$ plants?
I. Kranz anatomy
II. The product of photosynthesis is oxalo acetic acid
III. Both PEP carboxylase and ribulose-bis phosphate carboxylase act as a carboxylating enzyme.
Choose the correct option.

• A. I and II, but not III
• B. II and III, but not I
• C. I and III, but not II
• D. All of these

Answer 1

The correct option is D All of these

$C_4$ plants have an alternative $C{O}_2$ fixation pathways called Hatch and Slack cycle where OxaloAceticAcid, a 4C compound is the first stable product. These plants have Kranz anatomy in leaf. Oxaloacetate is reduced to malate/aspartate that reaches into bundle sheath cells. In the bundle sheath cells, these C4 acids are broken down to release CO2 and a 3-carbon molecule i.e. pyruvic acid. The CO2 released in the bundle sheath cell enters the C3 cycle because these cells are rich in enzyme Ribulose bisphosphate carboxylase-oxygenase (RuBisCO).