AQA GCSE FOUNDATION Biology: Limiting Factors in Photosynthesis

AQA GCSE Foundation Biology: Limiting Factors in Photosynthesis

Introduction

Photosynthesis is the process by which plants convert light energy into chemical energy in the form of glucose. This process is essential for life on Earth, as it provides the food and oxygen that we need to survive. Photosynthesis is influenced by several factors, known as limiting factors. A limiting factor is a factor that restricts the rate of a process, even if other factors are present in abundance.

Limiting Factors in Photosynthesis

The main limiting factors in photosynthesis are:

• Light Intensity: Light is essential for photosynthesis as it provides the energy needed to drive the reaction. As light intensity increases, the rate of photosynthesis increases proportionally. However, there is a point at which the rate of photosynthesis levels off, as other factors become limiting.

• Carbon Dioxide Concentration: Carbon dioxide is one of the raw materials for photosynthesis. As carbon dioxide concentration increases, the rate of photosynthesis increases. However, there is a point at which the rate of photosynthesis levels off, as other factors become limiting.

• Temperature: Temperature affects the rate of enzyme activity, which is essential for photosynthesis. As temperature increases, the rate of photosynthesis increases until an optimal temperature is reached. Beyond this point, the rate of photosynthesis decreases as enzymes become denatured.

Investigating Limiting Factors

To investigate the effects of limiting factors on the rate of photosynthesis, we can measure the rate of oxygen production.

• Light Intensity: You can investigate the effect of light intensity on the rate of photosynthesis by using a lamp and a light meter. Increase the distance between the lamp and the plant to decrease the light intensity.

• Carbon Dioxide Concentration: You can investigate the effect of carbon dioxide concentration on the rate of photosynthesis by using a solution of sodium hydrogencarbonate (NaHCO3), which releases carbon dioxide when it dissolves in water.

• Temperature: You can investigate the effect of temperature on the rate of photosynthesis by placing the plant in different temperature environments.

Graphing the Results

The results of the experiment can be presented on a graph. The independent variable (light intensity, carbon dioxide concentration, or temperature) is plotted on the x-axis and the dependent variable (rate of oxygen production) is plotted on the y-axis. The graph will show how the rate of photosynthesis is affected by the limiting factor.

Understanding the Graphs

• Light Intensity: The graph will show an initial steep increase in the rate of photosynthesis as light intensity increases. Eventually, the graph will level off, indicating that the rate of photosynthesis is no longer limited by light intensity and another factor is becoming limiting.

• Carbon Dioxide Concentration: The graph will show a similar pattern to the light intensity graph, with the rate of photosynthesis increasing as the carbon dioxide concentration increases. However, the rate of photosynthesis will eventually level off as other factors become limiting.

• Temperature: The graph will show an initial increase in the rate of photosynthesis as temperature increases. At the optimal temperature, the rate of photosynthesis will be at its highest. Beyond this point, the rate of photosynthesis will decrease as the enzymes become denatured.

Conclusion

Limiting factors play an important role in regulating the rate of photosynthesis. By understanding the effects of limiting factors, we can optimize conditions for plant growth and productivity.