Which of the following does not represent the internal factors which affect photosynthesis?

Atmospheric CO2 concentration, light, water and temperature are the external factors that affect photosynthesis. Internal factors which affect photosynthesis include the number, size, age and orientation of leaves, mesophyll cells and chloroplasts, internal CO2 concentration and the amount of chlorophyll. The plant or internal factors are dependent on the genetic predisposition and the growth of the plant.