The internal factors also play an important role in the rate of photosynthesis. Some of the internal factors which play a major role are: age of the leaf, anatomical characteristics, and internal carbon dioxide content.
Age of the leaf: When the leaf develops and then matures the rate of photosynthesis increases and reaches a maximum limit. Then it declines when the age of the leaf increases. The total rate of photosynthesis of the plants also depends on the number of leaves present and also the arrangement of the leaves in the plant.
Anatomical characteristics of leaf: The peculiar type of anatomy called as Kranz anatomy in certain plants makes them very efficient in photosynthesis. The degree of opening of the stomata and its arrangement also plays an important role in the rate of photosynthesis. Due to decreased amount of internal water the stomata get closed which results in less uptake of carbon dioxide inhibiting the photosynthesis.