Question 1

What is Kranz anatomy?

Accepted Answer

Kranz anatomy is the leaf anatomy of C4 plants in which large bundle sheath cells form a wreath ('Kranz') around the vascular bundles. Bundle sheath cells have many chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.

Question 2

What is the primary CO2 acceptor in C4 plants?

Accepted Answer

The primary CO2 acceptor in C4 plants is phosphoenol pyruvate (PEP), a 3-carbon molecule present in the mesophyll cells. The enzyme PEP carboxylase (PEPcase) fixes CO2 to form the 4-carbon oxaloacetic acid (OAA).

Question 3

Why is there no photorespiration in C4 plants?

Accepted Answer

In C4 plants the C4 acid is broken down in the bundle sheath cells to release CO2, raising the intracellular CO2 concentration. This ensures RuBisCO functions as a carboxylase and minimises its oxygenase activity, so photorespiration does not occur.

Question 4

Do C4 plants use the Calvin cycle?

Accepted Answer

Yes. C4 plants form the C4 acid OAA as the first CO2 fixation product, but they use the C3 pathway or Calvin cycle as the main biosynthetic pathway. In C4 plants the Calvin cycle takes place only in the bundle sheath cells.

Kranz Anatomy Lab — C3 vs C4 Leaf and the Hatch–Slack Pathway in 3D

About this lab

Practice