Required practical 6

• To investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism like pondweed, follow these steps:
• 1. Varying Light Intensity:

  • Change the distance of the white light source from the pondweed (e.g., 10, 20, 30, 40 cm)
  • Allow the pondweed to acclimatize to the new light intensity for 5 minutes
• 2. Controlling Other Variables:

  • Use the same length of pondweed or the same pondweed
  • Control temperature by placing the tube in a thermostatically controlled water bath or by placing a beaker of water between the lamp and tube to absorb heat produced by light
  • Maintain a set concentration of sodium hydrogen carbonate solution to control CO2 concentration
• 3. Measuring Photosynthesis Rate:

  • Count the number of bubbles of oxygen released or collect gas in a syringe
  • Measure within a set period of time (e.g., one minute) and calculate the rate by dividing the volume by time
  • Repeat the measurements three times at each light intensity to identify anomalies and calculate a mean