Kranz Anatomy and the Role of Bundle Sheath Cells in C4 Plants
Biology · Photosynthesis in Higher Plants · NEET
Kranz anatomy is the special leaf structure found only in C4 plants, where large bundle sheath cells form a ring around each vascular bundle. These bundle sheath cells are packed with many chloroplasts, have thick walls with no gaps between them, and are the only place where RuBisCO and the Calvin cycle work. Memory hook: "Kranz" means "wreath" in German, so picture a green wreath (ring of cells) hugging the vein.
In a C4 leaf, large bundle sheath cells form a wreath (Kranz) around the vein. They are packed with chloroplasts, have thick walls with no gaps, and are the only cells holding RuBisCO and running the Calvin cycle. Mesophyll cells outside use PEP carboxylase.
Your doubts, answered
Do C3 plants have Kranz anatomy, or only C4 plants?
Only C4 plants have Kranz anatomy. This is a very common NEET trap. In C4 plants the bundle sheath cells become large and form a ring (wreath) around the vascular bundle. C3 plants do not show this ring of special cells. NCERT says C4 plants have a 'special type of leaf anatomy' called Kranz anatomy, so never link Kranz to C3.
Why do bundle sheath cells have so many chloroplasts?
Because the whole Calvin cycle (C3 cycle) runs inside the bundle sheath cells in C4 plants. In C4 plants, CO2 is first fixed in mesophyll cells as a 4-carbon acid, then this acid moves to the bundle sheath and releases CO2 there. The many chloroplasts give the space and enzymes needed to trap this CO2 and make sugar. NEET 2022 asked this exact point: the role of large bundle sheath cells is to increase the number of chloroplasts for the operation of the Calvin cycle.
Where is RuBisCO found in C4 plants?
RuBisCO is present only in the bundle sheath cells, not in the mesophyll cells. This is why mesophyll cells use PEP carboxylase (PEPcase) instead. Keeping RuBisCO inside the bundle sheath, where CO2 is concentrated, is the reason C4 plants avoid photorespiration. Remember: mesophyll = PEPcase, bundle sheath = RuBisCO.
Why do bundle sheath cells have thick walls and no gaps between them?
The thick walls (with no intercellular spaces) stop CO2 and oxygen from leaking out. This keeps the CO2 level high around RuBisCO. A high CO2 to O2 ratio makes RuBisCO act as a carboxylase, not an oxygenase, so photorespiration is prevented. So the wall design is not random; it is what makes the C4 CO2-concentrating pump work.
What is the difference between mesophyll cells and bundle sheath cells in a C4 leaf?
Mesophyll cells sit outside and fix CO2 first using PEP carboxylase to make oxaloacetic acid (OAA, a 4-carbon acid); they lack RuBisCO. Bundle sheath cells form the inner ring, have many chloroplasts and thick walls, contain RuBisCO, and run the Calvin cycle. Two cell types working together is the whole point of the C4 pathway.
⚠️ The NEET trap ✗ C3 plants exhibit Kranz anatomy. ✓ C4 plants (not C3 plants) exhibit Kranz anatomy; the bundle sheath cells hold RuBisCO and run the Calvin cycle. 🧠 NEET repeatedly writes 'C3 plants show Kranz anatomy' as a wrong option (NEET 2026). Kranz belongs to C4 only. Also do not say photorespiration happens in bundle sheath cells; C4 plants show no photorespiration at all.
Real NEET questions
NEET 2022
What is the role of large bundle sheath cells found around the vascular bundles in C4 plants?
A · To provide the site of photorespiratory pathway
B · To increase the number of chloroplast for the operation of Calvin cycle ✓
C · To enable the plant to tolerate high temperature
D · To protect the vascular tissue from high light intensity
Solution: In C4 plants the large bundle sheath cells (Kranz anatomy) are packed with many chloroplasts. The CO2 released here from the 4-carbon acid enters the Calvin cycle, which in C4 plants runs only in the bundle sheath cells. So their role is to give a chloroplast-rich site for the Calvin cycle. Option A is wrong because C4 plants show no photorespiration.
NEET 2026
Find the incorrect statement(s) about photosynthesis: A. The water splitting complex is associated with PS I. B. C4 plants use the C3 pathway of CO2 fixation as the main biosynthetic pathway. C. In C4 plants, photorespiration does not occur. D. C3 plants exhibit 'Kranz' anatomy. E. ATP synthesis in chloroplast occurs through chemiosmosis.
A · B and C only
B · B only
C · B and E only
D · A and D only ✓
Solution: Statement A is wrong: the water-splitting complex is with PS II, not PS I. Statement D is wrong: C4 plants, not C3 plants, show Kranz anatomy. B, C and E are all correct. So the incorrect statements are A and D only.
NEET 2022
Statement I: The primary CO2 acceptor in C4 plants is phosphoenolpyruvate and is found in the mesophyll cells. Statement II: Mesophyll cells of C4 plants lack RuBisCo enzyme.
A · Both Statement I and Statement II are correct ✓
B · Both Statement I and Statement II are incorrect
C · Statement I is correct but Statement II is incorrect
D · Statement I is incorrect but Statement II is correct
Solution: Statement I is correct: PEP (a 3-carbon molecule) is the primary CO2 acceptor in the mesophyll cells, fixed by PEP carboxylase. Statement II is also correct: NCERT clearly states mesophyll cells lack RuBisCO, which is confined to the bundle sheath cells. Hence both statements are correct.
Solved Photosynthesis in Higher Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Kranz is a German word meaning 'wreath' or 'ring'. The bundle sheath cells form a wreath-like ring around the vascular bundle, which is why the structure is called Kranz anatomy.
Which plants show Kranz anatomy?
Only C4 plants such as maize, sugarcane, sorghum and many tropical grasses show Kranz anatomy. C3 plants do not.
Do bundle sheath cells run the Calvin cycle?
Yes. In C4 plants the Calvin cycle (C3 cycle) runs only in the bundle sheath cells because RuBisCO is present only there.
Why does Kranz anatomy prevent photorespiration?
The thick-walled bundle sheath keeps CO2 concentration high around RuBisCO. A high CO2 to O2 ratio makes RuBisCO work as a carboxylase, so oxygenation (photorespiration) does not occur.
Is RuBisCO present in mesophyll cells of C4 plants?
No. Mesophyll cells of C4 plants lack RuBisCO; they use PEP carboxylase. RuBisCO is only in the bundle sheath cells.
