What are the external factors affecting photosynthesis?

The main external factors affecting photosynthesis are light, carbon dioxide concentration, temperature, water, and pollutants. Photosynthesis is the process by which green plants make food using sunlight, carbon dioxide, and water. Although this process is natural, its rate depends on external factors in the environment. These factors can either increase or decrease photosynthesis.

Main External Factors

1. Light:
   • Intensity of light directly affects the rate of photosynthesis.
   • Low light reduces photosynthesis, while very strong light may damage chlorophyll.
2. Carbon Dioxide Concentration:
   • Carbon dioxide is the raw material for photosynthesis.
   • Higher concentration increases the rate up to a certain limit.
3. Temperature:
   • Enzymes involved in photosynthesis work best at an optimum temperature (25–35°C).
   • Too low or too high temperature reduces the rate.
4. Water:
   • Water is essential for photosynthesis as well as maintaining leaf structure.
   • Water shortage leads to stomata closure, reducing carbon dioxide intake.
5. Pollutants:
   • Dust, smoke, and harmful gases can block stomata or damage chlorophyll.
   • This reduces the photosynthetic efficiency of plants.