Class XI Practical: Physiology - Effect of Different CO₂ Concentrations on the Rate of Photosynthesis

Objective

To investigate how varying concentrations of carbon dioxide affect the rate of photosynthesis in aquatic plants (e.g., Hydrilla).

Guidelines

1. Setup: Place a sprig of an aquatic plant (e.g., Hydrilla) in a beaker of water. Invert a test tube over the plant to collect gas bubbles.
2. CO₂ Variation: Introduce different concentrations of CO₂ by adding varying amounts of sodium bicarbonate (NaHCO₃) to the water.
3. Measurement: Place the setup under a light source and count the number of oxygen bubbles evolved per unit time (e.g., per minute) for each CO₂ concentration.
4. Control Variables: Ensure light intensity and temperature are kept constant throughout the experiment.
5. Data Analysis: Plot a graph of the rate of photosynthesis (bubbles/minute) against CO₂ concentration.

Expected Outcome

Observation that the rate of photosynthesis increases with increasing CO₂ concentration up to a certain point, demonstrating CO₂ as a limiting factor.