Find out what factors affect the rate of photosynthesis. Rate being the amount of photosynthesis produced per minute.

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Aim: To find out what factors affect the rate of photosynthesis. Rate being the amount of photosynthesis produced per minute.

Variables:  

Equation for Photosynthesis:

                                 Representing sunlight                    

 Co2 + H2O                                                                  Glucose, ATP and O2

  • Temperature. Because Photosynthesis is an enzyme based reaction and enzymes dependant on the temperature. As we know, enzymes work better when the temperature increases, and they can be frozen if the temperatures are too low. However, when the temperature is too high, the enzymes could denature and therefore the plant would die and no photosynthesis would occur at all.

  • Light intensity, Because sunlight is needed for photosynthesis to occur. Sunlight is needed for the plant to turn into food. This process is Photosynthesis, so without Sunlight, there is no photosynthesis. So then this basically means if u give the plant more sunlight (higher light intensity), there is more photosynthesis to make more food.

  • Concentration of Co2 in water. Because Co2 is needed for Photosynthesis to occur. So then if there were a higher supply of Co2, there would be more photosynthesis. Therefore the concentration of Co2 in the water is able to affect the rate of photosynthesis.

  • Amount of water. Because water is needed for photosynthesis to occur. Without water, a plant cannot photosynthesize; meaning that Photosynthesis is also dependent on the amount of water. So then if we change the amount of water, so will the rate of photosynthesis.

  • Colour of light. Different frequencies of light can affect the rate of photosynthesis. Since the colour of chlorophyll is green, it means that the plant will reflect green colour light and absorb the other colours of light accordingly.

 

  • Different type of plant. Because the leaf structure, and amount of chlorophyll is different in each plant. For example, if a plant has more leaves (chlorophyll), it is likely to photosynthesize more than a plant that has less leaves (less chlorophyll)

  • Surface area of the pondweed. If there is more surface area, it is likely to have more chlorophyll and is therefore capable of trapping more sunlight and therefore photosynthesizing more.

Chosen variable: Light intensity. I chose this variable because the amount of light is very important to the rate of photosynthesis. It is the key to the equation and can be easily measured. Light intensity is dependent on distance. The further the distance, the less light intensity, so we could measure distance instead of light intensity. And distance is very easy to measure. It is a more reliable variable that would most likely produce results that are not biased due to the fact that it can be easily manipulated.

Prediction and hypothesis:

The rate of photosynthesis will increase as the light intensity increases at a proportional rate. However, as I am measuring distance, then it is correct to say that as the distance increases, the light intensity decreases. But this is not simply inversely proportional. It is inversely proportional squared (taken from . This means that as the distance increases at a rate of x1, the light intensity is decreasing at a rate of y3. Therefore if my results are according to distance vs. rate of photosynthesis, I predict the graph will be a negative curve. 

Without sunlight a plant does not grow and will die. This is because the sunlight is the source of energy that the plant needs. We can simply see this from the equation of photosynthesis, which is:

                                 

                                 Representing sunlight                    

 Co2 + H2O                                                                  Glucose, ATP and O2

Through this, we can see that a plant cannot produce ATP when there is no sunlight and therefore has no energy to carryout active transport and would therefore die. Even though there are many more reasons why sunlight is essential to a plants life, but this reason on its own is already enough to prove that plants must need sunlight. If we can say that sunlight helps to make the energy in a plant, then it is also logical to say that when there is more sunlight, more energy is produced. When energy is being produced it means Photosynthesis occurring, so we can immediately make the assumption that if there is more energy when there is more sun light, and when there is more photosynthesis when there is more energy, so when there is more sunlight, there must be more photosynthesis. However, I think that a limiting factor will prevent this from happening when there is too much sunlight. Sunlight contains I.R rays, and I.R to a certain extent are bad for cells (taken from ). They penetrate cells easily and because Microvibrations. These basically heat up the cells including important Enzymes. As we know, Photosynthesis is an enzyme-based reaction. Also, enzymes denature once they reach certain temperature, meaning they do not function. So if the light intensity is too great (meaning that the I.R is strong) then the enzymes would be heated up and therefore be denatured and no more photosynthesis will take place. Since the plant is a living organism, there is limit to the speed of which photosynthesis can be carried out in the chloroplasts no matter how much supply of water, sunlight and Co2 is supplied to the plant. Also, other factors that are able to affect photosynthesis will limit the photosynthesis from going higher and higher. For example, even if the plant has maximum light intensity, the fact that the Co2 and H20 is kept constant will prevent the plant from further photosynthesizing.

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Preliminary results

Apparatus:

  • Gas collection tube to measure length of bubbles produced in certain period of time.
  • Funnel, to direct the bubbles into the gas measuring tube.
  • Beaker to hold the solution.
  • Sodium hydrogen bicarbonate solution.
  • Pond weed (16cmlong).
  • Lamp
  • Ruler
  • Clamp

Method

  1. Fill beaker with 250ml of sodium hydrogen bicarbonate
  2. Take a piece of 16cm pondweed and put it into the beaker.
  3. Connect the Funnel the gas measurer and t the clamp.
  4. Cut the end of the pondweed at an angle (to allow the bubbles of ...

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