Describe and explain the effect of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

Sourav PanNovember 2, 2024

Answered

The rate of photosynthesis is influenced by several environmental factors, including light intensity, carbon dioxide concentration, and temperature. Each of these factors plays a crucial role in the efficiency of photosynthesis, and their effects can be understood through various biological principles.

1. Effect of Light Intensity on Photosynthesis

Explanation

• Increased Light Intensity: As light intensity increases, the rate of photosynthesis typically rises. This is because light energy is essential for the light-dependent reactions of photosynthesis, where chlorophyll absorbs light to generate ATP and NADPH.
• Saturation Point: However, there is a saturation point beyond which increases in light intensity do not result in higher rates of photosynthesis. At this point, other factors (like carbon dioxide or temperature) may become limiting.
• Photoinhibition: At excessively high light intensities, photosynthesis can be inhibited due to damage to the photosynthetic apparatus (photoinhibition).

2. Effect of Carbon Dioxide Concentration on Photosynthesis

Explanation

• Increased CO₂ Concentration: Higher concentrations of carbon dioxide generally enhance the rate of photosynthesis, particularly in the Calvin cycle where CO₂ is fixed into organic molecules.
• Limiting Factor: Like light intensity, there is a saturation point for CO₂ concentration. Once all available RuBisCO enzymes are occupied with CO₂, further increases in concentration will not increase the rate of photosynthesis.
• Photorespiration: At very high CO₂ levels, some plants may also experience increased photorespiration, which can reduce overall efficiency.

3. Effect of Temperature on Photosynthesis

Explanation

• Temperature Increase: The rate of photosynthesis typically increases with temperature up to an optimal point (often around 25°C to 30°C for many plants). This is because higher temperatures provide more kinetic energy to molecules, facilitating enzyme activity involved in the photosynthetic processes.
• Enzyme Activity: Enzymes such as RuBisCO involved in the Calvin cycle are temperature-sensitive. As temperatures rise toward their optimum range, their activity increases, enhancing the rate of photosynthesis.
• Denaturation: Beyond the optimal temperature (usually above 40°C), enzyme activity declines sharply due to denaturation. This results in a decreased rate of photosynthesis as enzymes lose their functional shape.