Investigate the effect of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis using submerged aquatic plants and hydrogencarbonate indicator solution

Sourav PanNovember 2, 2024

Answered

To investigate the effects of varying light intensity, carbon dioxide concentration, and temperature on the rate of photosynthesis using submerged aquatic plants and a hydrogencarbonate indicator solution, we can design a series of controlled experiments. The use of submerged aquatic plants, such as Elodea, allows for easy observation of oxygen production as an indicator of photosynthetic activity.

Experimental Design

Materials Needed

• Submerged aquatic plant (e.g., Elodea)
• Hydrogencarbonate indicator solution (to monitor CO₂ levels)
• Light source (lamp)
• Water bath or temperature-controlled environment
• Measuring cylinder or gas syringe (to collect oxygen)
• Ruler (for measuring distance of light source)
• Stopwatch or timer
• Sodium bicarbonate (to provide a constant source of CO₂)

1. Effect of Light Intensity

Hypothesis: Increasing light intensity will increase the rate of photosynthesis, up to a certain point.Procedure:

1. Place a sprig of Elodea in a beaker filled with water and add a few drops of hydrogencarbonate indicator to ensure sufficient CO₂ levels.
2. Position a lamp at a fixed distance from the beaker.
3. Measure the initial color of the hydrogencarbonate indicator (which should be red at neutral pH).
4. Turn on the lamp and allow the plant to acclimate for 5 minutes.
5. Count the number of oxygen bubbles produced over a set time period (e.g., 5 minutes) or measure the change in color of the indicator.
6. Repeat the experiment at different distances from the light source to vary light intensity.

Control: Keep all other conditions constant (temperature, CO₂ concentration).

2. Effect of Carbon Dioxide Concentration

Hypothesis: Increasing carbon dioxide concentration will increase the rate of photosynthesis.Procedure:

1. Use another sprig of Elodea in a similar setup as above.
2. Prepare different concentrations of sodium bicarbonate solutions (e.g., 0%, 0.1%, 0.2%, 0.5%).
3. Place each sprig in separate beakers with varying concentrations while keeping light intensity constant.
4. Allow the plants to acclimate for 5 minutes under constant light.
5. Measure oxygen production by counting bubbles or observing color change in the hydrogencarbonate indicator over a set time period.

Control: Maintain consistent light intensity and temperature across all setups.

3. Effect of Temperature

Hypothesis: Increasing temperature will increase the rate of photosynthesis up to an optimum point, after which it will decline due to enzyme denaturation.Procedure:

1. Set up a beaker with Elodea in water containing sodium bicarbonate.
2. Use a water bath to control temperature, setting it at various levels (e.g., 10°C, 20°C, 30°C, 40°C).
3. Allow each temperature to stabilize before placing the plant in the water bath.
4. Maintain consistent light intensity throughout the experiment.
5. Measure oxygen production by counting bubbles or observing color change in hydrogencarbonate indicator over a set time period.

Control: Keep CO₂ concentration and light intensity constant during each trial.

Data Analysis

• For each experiment, record the number of oxygen bubbles produced or changes in color intensity of the hydrogencarbonate indicator solution over time.
• Plot graphs for each variable against the rate of photosynthesis to visualize trends and identify optimal conditions.

Expected Results

1. Light Intensity: Initially, an increase in light intensity should correlate with an increased rate of photosynthesis until saturation is reached.
2. Carbon Dioxide Concentration: Higher concentrations should lead to increased rates until another factor becomes limiting.
3. Temperature: The rate should increase with temperature up to an optimum point; beyond this point, rates should decline due to enzyme denaturation.