Summary
A pathway that concentrates CO2 in bundle sheath cells to reduce photorespiration in hot climates, as in maize.
In depth
Mesophyll cells fix CO2 with PEP carboxylase to form 4-carbon acids; these move to bundle sheath cells where CO2 is released near rubisco, reducing photorespiration. It uses extra ATP but is more efficient in heat and light.
The spatial separation of initial fixation and Calvin cycle reduces photorespiration. It has evolved independently over 60 times. It costs two extra ATP per CO2 but wins above about 30 °C.
Common mistake: C4 plants still use rubisco and the Calvin cycle.
Frequently asked questions
What is C4 Photosynthesis?
A pathway that concentrates CO2 in bundle sheath cells to reduce photorespiration in hot climates, as in maize.
Which area of biology covers C4 Photosynthesis, and how advanced is it?
C4 Photosynthesis is one of the 56 topics in Plant Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include CAM Photosynthesis, Cyclic Photophosphorylation, Calvin Cycle.
Can you give an example of C4 Photosynthesis?
Maize, sugarcane and sorghum.
What should I learn before C4 Photosynthesis?
Work through the Beginner topics in Plant Biology first, such as Plant Kingdom, Photosynthesis, Chlorophyll, then return to C4 Photosynthesis. Advanced topics assume the Intermediate vocabulary.
What topics are related to C4 Photosynthesis?
The closest topics to C4 Photosynthesis are CAM Photosynthesis, Cyclic Photophosphorylation, Calvin Cycle, Photosynthesis. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand C4 Photosynthesis?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for C4 Photosynthesis. To practise the whole of Plant Biology, use the Plant Biology quiz.
How is C4 Photosynthesis different from CAM Photosynthesis?
C4 Photosynthesis: A pathway that concentrates CO2 in bundle sheath cells to reduce photorespiration in hot climates, as in maize. CAM Photosynthesis: Desert plants open stomata at night to fix CO2 into organic acids for daytime use. Read both side by side and note what each one explains.
What is a common mistake about C4 Photosynthesis?
C4 plants still use rubisco and the Calvin cycle.
How should I study C4 Photosynthesis step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with CAM Photosynthesis and explain the difference aloud. Finally, take the Plant Biology quiz and come back to this page for any question you miss.