Explain the effects of changes in light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

SouravOctober 31, 2024

Answer

Factors Affecting Photosynthesis: Light Intensity, CO2 Concentration, and Temperature

Overview:
Photosynthesis, the process by which plants, algae, and some bacteria convert light energy into chemical energy, is influenced by several environmental factors. Here, we’ll explore the effects of changes in Light Intensity, Carbon Dioxide (CO2) Concentration, and Temperature on the Rate of Photosynthesis.

1. Light Intensity:

• Effect on Photosynthesis:
  • Increasing Light Intensity: Initially, the rate of photosynthesis increases with rising light intensity, as more light energy is available for photon-dependent reactions.
  • Saturation Point: Beyond a certain light intensity, the rate of photosynthesis plateaus, as the light-dependent reactions become saturated, and other factors (e.g., CO2 availability, temperature) become limiting.
  • Decreasing Light Intensity: Below a certain threshold, the rate of photosynthesis decreases, as insufficient light energy limits photon-dependent reactions.
• Graphical Representation:
  • Light Intensity vs. Rate of Photosynthesis: A sigmoid (S-shaped) curve, illustrating the initial increase, saturation, and eventual decrease in photosynthetic rate with changing light intensity.

2. Carbon Dioxide (CO2) Concentration:

• Effect on Photosynthesis:
  • Increasing CO2 Concentration: The rate of photosynthesis increases with rising CO2 levels, as more substrate is available for the Calvin Cycle (CO2 fixation).
  • Optimal CO2 Concentration: Photosynthesis reaches its maximum rate at an optimal CO2 concentration, beyond which further increases have minimal effect.
  • Decreasing CO2 Concentration: Below a certain CO2 threshold, the rate of photosynthesis decreases, as limited substrate availability restricts the Calvin Cycle.
• Graphical Representation:
  • CO2 Concentration vs. Rate of Photosynthesis: A curve with an initial steep increase, followed by a gradual plateau, illustrating the effect of CO2 concentration on photosynthetic rate.

3. Temperature:

• Effect on Photosynthesis:
  • Optimal Temperature Range: Photosynthesis occurs within a temperature range (typically between 20°C and 30°C), where enzymatic reactions and metabolic processes are optimized.
  • Increasing Temperature (above optimal): The rate of photosynthesis decreases, as high temperatures:
    • Denature enzymes
    • Increase photorespiration (wasteful oxygenation of RuBP)
  • Decreasing Temperature (below optimal): The rate of photosynthesis decreases, as low temperatures:
    • Slow down enzymatic reactions
    • Reduce metabolic activity
• Graphical Representation:
  • Temperature vs. Rate of Photosynthesis: A bell-shaped curve, illustrating the optimal temperature range for photosynthesis, with decreasing rates at higher and lower temperatures.

Interactive Effects:
Keep in mind that these factors often interact with each other. For example:

• High Light Intensity + Low CO2 Concentration: Can lead to photoinhibition (damage to photosynthetic apparatus)
• Optimal Temperature + Sufficient CO2 Concentration: Can result in maximum photosynthetic rates, even at moderate light intensities