Investigating the factors that will affect the rate of photosynthesis.

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Investigating the factors that will affect the rate of photosynthesis

Aim: I will be investigating how light intensity affects the rate of photosynthesis, whether it decreases or increases the rate of photosynthesis.

Background Knowledge: Photosynthesis is the process by which plants make their own food. For photosynthesis to occur, plants need:

  • Light energy from the sun
  • Chlorophyll to absorb light energy
  • Carbon dioxide from the atmosphere and from respiration in plant cells
  • Water which is absorbed by the roots and transported to the leaves by the xylem tubes.

Photosynthesis can be summarised by the equation:

                                       

       6CO2 + 6H2O                                   C6H12O6 + 6O2           

The reactants are Carbon dioxide and Water; the products are Glucose and Oxygen.

The factors that affect the rate of photosynthesis are:

  • Light intensity- if the light is brighter, then the rate of photosynthesis increases and visa versa.
  • Water supply- if a plant cannot absorb enough water, then the rate of photosynthesis decreases.
  • Carbon dioxide concentration- if the percentage of carbon dioxide in the atmosphere increases, so does the rate of photosynthesis.
  • Temperature- if the temperature increases, then the rate of photosynthesis also increases, (however, temperatures above 40OC can damage a plant and photosynthesis stops because the chlorophyll gets too hot).

The factor I will be investigating is light intensity; how it affects the rate of photosynthesis.

The factors I will be keeping constant are:

  • Water supply- by using same millimetre of water each time.
  • Temperature- by using a thermometer to make sure the water is at the temperature each time.
  • Carbon dioxide- by not adding any thing in the water which increase the carbon dioxide level, such as Hydrogen carbonate.
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By keeping these factors constant I will only be investigating how light intensity affects the rate of photosynthesis and the other factors will not affect my results.

Prediction: I predict that the closer the lamp is to the plant the more oxygen bubbles will be produced, hence the higher the rate of photosynthesis, for example when the lamp is 10cm away from the Elodea plant, the number of oxygen bubbles produced will be the greatest, and the further away the plant is to the lamp, the lower the number of oxygen bubbles are produced, for example when the lamp is ...

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