Factors affecting the rate of photosynthesis

Carbon dioxide concentration

Carbon dioxide is one of the reactants in photosynthesis. If the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase. At some point, another factor may become limiting and this is shown by the plateau (flattened section) of the graph.

Graph showing that if the concentration of carbon dioxide is increased, the rate of photosynthesis will therefore increase

Temperature

The chemical reactions involved in photosynthesis are controlled by enzymes. As with any other enzyme-controlled reaction, the rate of photosynthesis is affected by temperature.

At low temperatures, the rate of photosynthesis is limited by the number of collisions between enzymes and substrate. As temperature increases the number of collisions increases, therefore the rate of photosynthesis increases. However, at high temperatures, enzymes are denatured and this will decrease the rate of photosynthesis.

A graph with rate of photosynthesis on the y axis and carbon dioxide concentration on the x axis.  The plotted line rise steeply and then levels off to horizonal.  During the steep part carobn dioxide is the limiting factor.  During the horizontal part another factor has become limiting.