In the case of
the pond weed if they enzymes within the plant became denatured then
it would become unable to photosynthesise, as well as not being able
to complete other functions.
(1) QB, which is more solvent exposed than QA, accepts the excited electron to form QB-. QA is now back in its oxidized state. Fully reduced QA can hold two electrons, which QA- is the "semiquinone" form. Even though two electrons will pass from the special pair through the entire cycle for one complete photosynthetic cycle, the QA never is in its fully reduced form.
This would indicate that less photosynthesis
would take place, as carbon dioxide is one of the 2 products required
by a green-plant for photosynthesis to take place.
This meant that our investigation was difficult to
start, as the pond weed was finding the conditions we were working
under inadequate for photosynthesis, whereas other groups were finding
the investigation much easier to conduct.
My reasons for believing my results are reliable & accurate are
firstly, they agree with the theory behind the rate of photosynthesis
when light intensity is increased, secondly the result which I gained
compared accurately to my prediction, which was well thought out
before it was made, and finally the results I gained for my final
experiment differed so much to the results of my preliminary procedure
which was very inaccurate.
To summarise: For the rate of photosynthesis to increase beyond a
certain point, it cannot be relied on for just 1 of the 4 limiting
factors to increase, after a certain point ALL must increase for the
rate to increase.
The reason for this being that the other 3 "limiting
factors" (CO2, water & chlorophyll) are required in a higher quantity
too, for photosynthesis to continue increasing in rate.
At a point (which was not
displayed on my graph, so logically this point is higher than the
highest light intensity I provided the pond weed with) the rate of
photosynthesis will stay steady , it will increase no further (see
(see page 1 Light in Photosynthesis)
However, this theory would not continue forever as long as the light
intensity was increased further & further.
This procedure (measuring volume of
oxygen) also enables us to prove that the gas given off was indeed
oxygen & therefore prove photosynthesis occurred.
The most probable explanation for the results I gained; as mentioned
previously in my introduction, as light is one of the factors required
in order for photosynthesis to take place, as the intensity of the
light is increased, photosynthesis is able to take place at a higher
See diagrams c
& d belowâ€¦
Diagram c Diagram d
Results obtained from experiment : "Investigating if light intensity
effects the rate of photosynthesis in an aquatic plant."
As mentioned previously, the results I have obtained from the
experiment will be of measured in 5 intervals, ranging from 0cm
-100cm, 1 repeat reading taken as well as an original reading & an
average of the 2 results calculated.
Here are the equations for photosynthesis. If you have understood the aerobic respiration equations, these are easy. If you have not understood, just learn them.
On considering my experiment, in hindsight, perhaps I would have
gained an even higher rate of photosynthesis if I had made the
temperature of the water slightly lower.
Although this is slightly high for
the temperature in which a plant generally photosynthesises best, (20
degrees centigrade) it was the first temperature at which the
experiment worked successfully, and so we decided that it should be
kept constantly at this in order to conduct a fair test.