Factors affecting photosynthesis. Three factors can limit the speed of photosynthesis: light intensity, carbon dioxide concentration and temperature. Light intensity. Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide.ncreasing the light intensity will boost the speed of photosynthesis. Carbon dioxide concentration. Sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is plenty of light, a plant cannot photosynthesise if there is insufficient carbon dioxide.