The rate of photosynthesis depends on several environmental factors. The main ones are light intensity, carbon dioxide concentration and temperature. Water and mineral ions also matter, but in most conditions they are not the ones controlling the rate.A limiting factor is the factor that is in shortest supply relative to what is needed, so it is the one holding the rate back. If you increase the limiting factor, the rate of photosynthesis increases. If you increase any other factor, the rate stays the same.This happens because photosynthesis is a series of linked reactions. The light-dependent reaction needs light to produce ATP and reduced NADP. The light-independent reaction (the Calvin cycle) needs carbon dioxide and is controlled by enzymes such as rubisco, so it depends on temperature. The whole process can only go as fast as its slowest step.On a graph of rate against one factor, the line rises while that factor is limiting. When the line levels off (plateaus), a different factor has become limiting. Only one factor limits the rate at any given moment, but which one it is can change during the day.
Example: At dawn, light intensity is usually limiting. On a bright, warm afternoon, carbon dioxide concentration often is. On a sunny but frosty morning, temperature may be.Understanding limiting factors lets growers decide which condition to change to get a faster rate, and which changes would be a waste of money.
Example: At dawn, light intensity is usually limiting. On a bright, warm afternoon, carbon dioxide concentration often is. On a sunny but frosty morning, temperature may be.Understanding limiting factors lets growers decide which condition to change to get a faster rate, and which changes would be a waste of money.