Investigate and describe the effects of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis

SouravNovember 14, 2024

Answer

The rate of photosynthesis in plants is influenced by several environmental factors, primarily light intensity, carbon dioxide concentration, and temperature. Each of these factors can act as a limiting factor, affecting the efficiency and overall rate of photosynthesis. Here’s a detailed investigation of their effects:

Effects of Varying Light Intensity

• Low to Moderate Light Intensity: At low light intensities, the rate of photosynthesis increases proportionately with increasing light intensity. This is due to more photons being available to excite chlorophyll molecules, leading to enhanced production of ATP and NADPH during the light-dependent reactions.
• High Light Intensity: As light intensity continues to increase, the rate of photosynthesis reaches a plateau when other factors become limiting (e.g., carbon dioxide or temperature). Beyond a certain threshold, excessive light can damage chlorophyll and lead to a decrease in the rate of photosynthesis due to photoinhibition.
• Optimal Light Conditions: Different plant species have varying optimal light conditions for maximum photosynthetic efficiency, with specific wavelengths (like red and blue light) being more effective for photosynthesis than others.

Effects of Carbon Dioxide Concentration

• Low Concentration: At ambient levels (approximately 0.04% or 400 ppm), increasing carbon dioxide concentration significantly boosts the rate of photosynthesis. This is because higher CO₂ levels enhance the carboxylation reaction catalyzed by the enzyme Rubisco, which is crucial for incorporating carbon into organic molecules.
• Saturation Point: The rate of photosynthesis will continue to increase with rising CO₂ concentrations until it reaches a saturation point, beyond which additional CO₂ has little effect on the rate. This plateau occurs when other factors (like light or temperature) become limitin.
• Acclimation at High CO₂: Prolonged exposure to elevated CO₂ can lead to down-regulation of photosynthetic processes in some plants, resulting in decreased efficiency despite initially increased rates of photosynthesis. This phenomenon is known as photosynthetic acclimation.

Effects of Temperature

• Temperature and Enzyme Activity: The light-independent reactions (Calvin cycle) are particularly sensitive to temperature since they are enzyme-catalyzed processes. As temperature rises towards an optimal range (typically between 20°C and 30°C for many plants), the rate of photosynthesis increases due to enhanced enzyme activity.
• Optimal Temperature Range: Photosynthesis generally doubles for every 10°C increase in temperature up to an optimal point. Beyond this temperature, enzyme denaturation occurs, leading to a decline in the rate of photosynthesis as enzymes lose functionality.
• Impact on Plant Species: Different species have adapted to thrive at various temperature ranges, influencing their photosynthetic efficiency and growth under varying climatic conditions