The rate of photosynthesis

• Why can the number of bubbles produced be used to calculate the rate of photosynthesis?


  Oxygen bubbles are formed as a product during photosynthesis. The number of bubbles produced in a given time is proportional to the rate of photosynthesis
• Describe how you would investigate the effect of light intensity on the rate of photosynthesis in an aquatic plant


  Place cut pondweed in a boiling tube (containing sodium hydrogen carbonate solution) at a fixed distance from a light source, count the number of bubbles produced in one minute using a stopwatch, repeat several times at a different distance/light intensity and calculate a mean for each distance, plot a graph of light intensity against a rate of photosynthesis
• Why is sodium hydrogen carbonate solution used during the photosynthesis RP?

  It releases C02 which is used by the pondweed during photosynthesis
• How can the measure of oxygen in the photosynthesis RP be more accurate?

  If the pondweed is placed under a filter funnel with an inverted measuring cylinder over the spout, the volume of oxygen produced can be determined
• Why is it best to use an LED light source rather than a lamp?

  A lamp will emit more heat energy than an LED - therefore it may change the temperature of the experiment and affect the rate of photosynthesis
• Why can the number of bubbles produced be used to calculate the rate of photosynthesis?

  Oxygen bubbles are formed as a product during photosynthesis. The number of bubbles produced in a given time is proportional to the rate of photosynthesis