Factors affecting rate of Photosynthesis.

Factors affecting photosynthesis

The rate of photosynthesis is affected by a number of factors; the level of which determines the yield of material by a plant. Before reviewing these factors, it is necessary to understand the principle of limiting factors.

The rate of photosynthesis increases as controlled by limited external and internal factors.

External factors

1. Light intensity
2. Carbon dioxide
3. Temperature
4. Water

i. Light intensity

The rate of photosynthesis increases as light intensity increases and vice versa. The rate of photosynthesis is proportional to the light intensity provided that other conditions are suitable.

ii. Temperature

This affects the activity of enzymes below the optimum temperature. The rate of photosynthesis increases as the temperature is raised; beyond the optimum temperature i.e. $60°C$. The enzymes are destroyed. The rate of photosynthesis therefore decreases.

iii. CO₂ concentration

Provided other conditions are suitable for this process the rate of photosynthesis increases as CO₂ concentration increases especially for C₃ plants.

iv. Water

Water is important in reaction i.e. photolysis.

The rate of photosynthesis depends on how much water is present in the plant body. The water present in plant body depends on the water present in the surroundings. When water is so scarce; the plant will wilt and the rate of photosynthesis decreases.

Internal factors

These are factors which are related to the plant structure.

1. Leaf surface area — A larger leaf surface increases the area available for light absorption and gas exchange, enhancing photosynthesis and transpiration.
2. Number of chloroplasts — More chloroplasts mean greater capacity for light absorption and glucose production during photosynthesis.
3. Number of stomata — More stomata increase gas exchange efficiency, allowing more carbon dioxide to enter for photosynthesis and more water vapor to exit during transpiration.
4. Orientation of plant body toward sunlight — The positioning of leaves and stems affects light interception; optimal orientation maximizes photosynthesis.