Investigation of limiting
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State three environmental factors that can limit the rate of photosynthesis.
The rate of photosynthesis can be limited by light intensity, carbon dioxide concentration, and temperature. These factors can restrict the photosynthetic rate if they are below their optimal levels.
Explain how increasing light intensity affects the rate of photosynthesis up to a certain point.
Initially, as light intensity increases, the rate of the light-dependent reactions increases proportionally, leading to a higher overall rate of photosynthesis. However, beyond a certain point, other factors become limiting, and increasing light intensity no longer increases the rate.
Describe how increasing carbon dioxide concentration affects the rate of photosynthesis, assuming other factors are not limiting.
As carbon dioxide concentration increases, the rate of the light-independent reactions (Calvin cycle) increases, leading to a higher overall rate of photosynthesis. This continues until another factor, such as light intensity or temperature, becomes limiting.
Explain the impact of increasing temperature on the rate of photosynthesis up to its optimum.
Increasing temperature increases the rate of enzyme-catalyzed reactions in photosynthesis, up to a certain optimal temperature. Above this optimum, enzymes denature, and the rate of photosynthesis decreases rapidly.
Outline the procedure for investigating the effect of light intensity on the rate of photosynthesis using DCPIP.
Prepare a chloroplast suspension. Add DCPIP, expose to different light intensities, and measure the time taken for DCPIP to decolourise. Faster decolourisation indicates a higher rate of photosynthesis (electron transport).
What does the rate of DCPIP decolourisation indicate in an experiment investigating photosynthesis?
The rate of DCPIP decolourisation indicates the rate of electron transport during the light-dependent reactions of photosynthesis. Faster decolourisation implies a higher rate of electron transport and therefore, a higher rate of photosynthesis.
Describe a method to investigate the effect of light intensity on the rate of photosynthesis in an aquatic plant.
Place an aquatic plant in water with a known concentration of CO₂. Vary the distance of a lamp from the plant (changing light intensity) and count the number of oxygen bubbles produced per unit time. This bubble count indicates the rate of photosynthesis.
How can you investigate the effect of carbon dioxide concentration on the rate of photosynthesis using an aquatic plant?
Use solutions of varying concentrations of dissolved carbon dioxide (
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