Types of Photosynthesis: C3, C4 and CAM

Field C and Mooney HA (1986) The photosynthesis‐nitrogen relationship in wild plants. In: Givnish TJ (ed.) On the Economy of Plant Form and Function, pp. 25–55. Cambridge: Cambridge University Press.

Sage RF (2004) The evolution of C4 photosynthesis. New Phytologist 161: 341–370.

Photosynthesis is the process by which plants convert light energy into chemical energy for use in growth and cellular repair. The ability of plants to capture light energy, carry out photosynthesis and grow is affected by many environmental factors including temperature, water and nutrient supply. Plants living in natural environments are also subject to competition and shading from other plants and have a number of biochemical and morphological adaptations to increase the efficiency of light absorption, whilst avoiding light stress. Various adaptations of photosynthesis exist that allow plants to tolerate extreme environmental conditions. Ultimately, the overall net photosynthetic rate of ecosystems has a major impact on the global carbon budget. These impacts may be significantly altered by global warming and subsequent climate change.


Hibberd Lab | C4 Photosynthesis

Both C4 and CAM involve a separation of CO2 absorption and fixation: C4 spatially and CAM temporally.

Summary of the different photosynthetic pathways. C3 plants fix CO2 directly, using the enzyme ribulose bisphosphate carboxylase oxygenase (Rubisco), reaction CO2 with ribulose bisphosphate (RuBP) to form PGA in the chloroplasts of the mesophyll. C4 plants react PEP carboxylase to react CO2 with phosphoenolpyruvate (PEP) to form oxaloacetic acid, which is in turn converted to malate. This is transferred to the bundle sheath, where malate is broken down to release CO2, which is used by Rubisco. CAM plants use PEP carboxylase to fix CO2 at night and then break down the malate so produced during the day to provide CO2 for Rubisco.