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# An Experiment Study to Test the effects of changes in light intensity on the rate of photosynthesis of small leaf disks cut from Hibiscus plants. And how a change in the rate can be seen.

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Introduction

SKILL P : Planning and Experimental Procedures MARK: NAME: Andy Robertson Centre Number INVESTIGATION: An Experiment Study to Test the effects of changes in light intensity on the rate of photosynthesis of small leaf disks cut from Hibiscus plants. And how a change in the rate can be seen. Research question and how this will determine the investigation. My research question for this experiment is "The rate of photosynthesis will decrease with a decrease of light intensity". This gives me one thing to vary (a cause) and one thing to measure (an effect). In this case the light intensity is the cause and the rate of photosynthesis is the effect. What variables may have an effect on the quantity being measured? Give reasons. Type Of Variable Name Of Variable How The Variable is Made To Act Like It Should Manipulated Variable Light Intensity I varied the light intensity by using a lamp with a 75W bulb in it and when the light intensity needed to be decreased the lamp was moved further away. If the light intensity was needed to be increased the lamp was moved closer to the sample. Responding Variable Fixed (Controlled) Variables Rate of Photosynthesis (Amount of time for leaf disks to generate enough gas to float) Temperature Amount Of Sodium Bicarbonate solution Method Of Measuring The Rate Of Photosynthesis Wattage Of Bulb My responding variable was measured by the amount of time it took the leaf disks to produce enough gas contained inside the disk before it had a sufficient amount of gas to make the disk float. ...read more.

Middle

* White Tile When conducting my experiment I had to plan and follow a certain method. The method I used is shown below: 1) The apparatus is collected and set up as shown in diagram. 2) 6 leaf disks are put into syringe containing 8ml of NaHCO3. 3) Release air gas out of the leaf disks by the following 'sub-steps': * Place thumb or finger over nose of the syringe. * Pull the plunger back to the furthest point possible. * Shake the syringe as violently as possible in order to release all the bubbles, contained within the solution, into the air bubble at the top of the syringe. * Depressurise the syringe by taking your finger/thumb off the nose of the syringe in order to take gasses out of the leaf disks. 4) If the disks sink immediately and do not float on the surface of the solution this part of the procedure is complete. However if any of the disks are floating repeat step 3 entirely until all the disks sink. 5) Then make sure there is still 8ml of NaHCO3 in the syringe, if not add more NaHCO3 until 8ml is reached. Then take the plunger out of the syringe and the solution and disks are poured into the small beaker. 6) The distance at which the lamp is away from the middle of the beaker is set, starting at 5cm away and moving the distance further later. ...read more.

Conclusion

Therefore the disk goes through a very small part of the Z-Scheme that only uses the ETC and uses ADP and Inorganic Phosphorus to produce ATP and excited electrons to loop the process over and over again. However the important thing is that it does not use or produce any gas and would therefore have no effect on the rate at which the disk takes to float. Also the results I personally obtained agree with my prediction because there is less resistance for the light and therefore the light intensity would be greater, I predicted that there would be rise proportionally between the distances changed but I cannot confirm this part of my prediction as I do not have any where near enough results to measure that statement to any degree of accuracy. Concluding, I think my prediction was fairly accurate; I predicted that the distance would have a direct effect on the light intensity and therefore the rate of photosynthesis, measured by the amount of time that it took for the leaf disks to rise to the top of the NaHCO3 solution in the beaker. Also my prediction was confirmed that it would take a longer time if there were less resistance, as the measured aspect was not actually measuring the rate of photosynthesis but actually the amount of gas exchanged inside the leaf disk. DA i) DA ii) ADR last printed 02/05/2007 16.06 ...read more.

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