In 1905 F.F. Blackman measured the rate of photosynthesis under a variety of different conditions of light and carbon dioxide supply. His work lead him to formulate the principal of limiting factors which states “At any given moment,the rate of a physiological process is limited by one factor which is in shortest supply, and by that factor alone.” This means that the factor which is nearest its minimum value determines the rate of reaction. It is therefore known as the limiting factor. It is the only thing, which affects the reaction. An example of this is a plant with a good supply of carbon dioxide and at a high temperature but in the dark will not photosynthesise,as the light intensity is the limiting factor. If the light intensity is increased then the rate of photosynthesis will increase to a level until one of the other factors is the limiting factor. These changes are illustrated in the graph Blackman created.as the light intensity is the limiting factor. If the light intensity is increased then the rate of photosynthesis will increase to a level until one of the other factors is the limiting factor. These changes are illustrated in the graph Blackman created.