The rate falls gradually, and at a certain CO2 concentration it stays constant (from point B to C). One reason might be that some of the enzymes of photosynthesis are working at their maximum rate. Carbon dioxide is used to make sugar in the photosynthesis reaction. The concentration of carbon dioxide in the Earth’s atmosphere varies between 0.03% and 0.04%. Without enough light, a plant cannot photosynthesise very quickly - even if there is plenty of water and carbon dioxide and a suitable temperature. Green plants and algae use light energy to make glucose and oxygen from carbon dioxide and water. highlight how temperature affects the rate of photosynthesis at low temperatures (less than/equal to 30 degrees) - a general rule the trend: as long as water and carbon dioxide are sufficient, (+ temperature is the ONLY limiting factor), the rate of photosynthesis will increase as temperature increases It is difficult to do this out in the open air but is possible in a greenhouse. Photosynthesis Green plants and algae use light energy to make glucose and oxygen from carbon dioxide and water. The rates of these reactions can be increased somewhat by increasing the carbon dioxide concentration. An increase in the concentration of carbon dioxide gives an increase in the rate of photosynthesis. Temperature, carbon dioxide concentration and light intensity can affect the rate of photosynthesis. Here a rise in CO2 levels has no effect as the other factors such as light intensity become limiting. At high concentrations, the rate of photosynthesis begins to level out due to factors not related to carbon dioxide concentration. The rate of photosynthesis increases linearly with increasing CO2 concentration (from point A to B). As carbon dioxide concentration increases, the rate of photosynthesis increases. Carbon dioxide Included among the rate-limiting steps of the dark stage of photosynthesis are the chemical reactions by which organic compounds are formed by using carbon dioxide as a carbon source.