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A Limiting Factor Is the One in Shortest Supply, and It Caps the Rate of Photosynthesis
- Photosynthesis needs light intensity, carbon dioxide concentration, and a suitable temperature.
- The limiting factor is whichever of these is in shortest supply at that moment.
- It sets a ceiling on the rate, so raising the other factors does nothing until the limiting one is increased.
Note
- At any moment only one factor is limiting, and it is usually the scarcest.
- Fix that factor and the rate rises until a different factor becomes limiting.
Light Intensity: Rate Rises Then Plateaus When Another Factor Takes Over
- As light intensity increases, the rate rises because more energy is available for the light-dependent reactions.
- Beyond a saturation point the line levels off because carbon dioxide or temperature now limits the rate.
- On a graph of rate against light intensity, the plateau marks where light has stopped being the limiting factor.
