How does the light intensity affect the rate of photosynthesis in Elodea measured by using a pH probe?

Heyy, i do IB Biology and i have to do my biology experiment design by next week. I am abroad so i don't have any textbooks and the internet doesn't seem to help!


My research question is "How does the light intensity affect the rate of photosynthesis in Elodea measured by using a pH probe?"





Can anyone help me? Give me some advice or websites that would help me?





THANKS!|||Sorry if this is obvious.





The photosynthesis increase until a certain intensity is reached. You use a pH meter because CO2 is incorporated during photosynthesis and that should raise the pH faster if the photosynthesis is faster.|||this is the experiment we use in ireland:





To Investigate the Influence of Light Intensity on the Rate of Photosynthesis





Textbook Diagram: set up of the investigation.





* Place a funnel over Elodea, pondweed, in a beaker of pond water at 25掳C.


* The funnel is raised off the bottom on pieces of blue-tack. This allows continuous free diffusion of CO2 to Elodea.


* Invert a test tube full of water over the stem of the funnel to collect any gas from the Elodea.


* Place the beaker on a hot plate at 25掳C.


* Maintain and monitor the temperature of the water with a thermometer.


* Excess sodium bicarbonate is placed in the water to give a constant saturated solution of CO2.


* Place the lamp (the only light source) at a predetermined distance from the plant.


* Use a light meter to measure the light intensity at this distance. Record the light intensity.


* Allow the plant five minutes to adjust to the new conditions.


* Count the number of oxygen bubbles given off by the plant in a five-minute period.


* Repeat the count twice more and calculate the average of the three readings. This is the rate of photosynthesis at that particular light intensity.


* The gas should be checked to prove that it is indeed oxygen 鈥?it relights a glowing splint.


* Repeat at different light intensities by moving the lamp to different distances.^


* Run a control: identical set up but at a constant light intensity.


* Result: no change in the rate of photosynthesis.


* Conclusion: change in light intensity causes a change in the rate of photosynthesis.


* Graph the results placing light intensity on the x-axis.





^intensity may also be changed by changing the wattage of the bulb.





a similar diagram is here: http://www.ichristianschool.com/biology/鈥?/a>





the result is, with an increase in light intensity there is an increased rate of photosynthesis.