Photosynthesis rate is limited by whichever required factor is least available, commonly light intensity, carbon dioxide concentration or temperature, connecting the mechanism to observable photosynthesis evidence.
Coverage 2010–2025 · Updated 15 Jul 2026
The rate of photosynthesis is controlled by the factor in shortest supply relative to the plant’s demand.
Light intensity, carbon dioxide concentration and temperature can each limit the rate. Increasing a non-limiting factor has little effect until another factor becomes limiting.
Design a limiting-factor investigation:
If increasing CO₂ raises oxygen production at low light but not high light, light becomes the limiting factor in the high-light treatment.
A plateau does not mean photosynthesis has stopped; it indicates that a different factor now limits the rate.
This objective is assessed through structured response, commonly using State / Identify / Determine.
State / Identify / Determine / Calculate / Describe / Compare / Explain / Suggest / Draw / Sketch / Predict / Outline / Discuss
Build the answer around this relationship: Photosynthesis rises with a limiting factor only while that factor restricts the rate.
Representative question
Explain methods by which the rate of photosynthesis can be measured, including conditions that affect the rate.
Photosynthesis converts light energy into chemical energy in carbon compounds. Carbon dioxide is reduced to carbohydrate using hydrogen from water, glucose is the main stored product, and released oxygen comes from photolysis of water. Pigment evidence is tested with chromatography and Rf, spectra questions separate absorption from action, and rate/evidence questions use limiting factors, controls, and CO2 enrichment context.
