An Investigation Into The Factors Affecting The Rate Of Photosynthesis.

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An Investigation Into The Factors Affecting The Rate Of Photosynthesis

Aim

        The aim of this investigation is to find out which factors determine the rate of photosynthesis in pondweed.

Equipment List & Diagram:

  • Sodium Hydrogen Carbonate
  • Lamp
  • Scales
  • Beaker
  • Photosynthometer
  • Water
  • Spatula
  • Stop Clock
  • Pondweed (Elodea)
  • Retort Stand with Clamp

Possible Variables:

The key variables that may determine the rate of photosynthesis are:

  • Light Intensity – The lamp’s distance from the beaker containing water shall be varied.
  • Concentration of CO² - Sodium Hydrogen Carbonate (NaHCO²) shall be added to the H²O in the beaker. Amounts of NaHCO² shall be varied.
  • Temperature – This is not an option in this investigation because altering the temperature may denature the plant’s enzymes, thus killing the pondweed.

Measurements:

The following measurements will be taken during the experiment:

  • Amount of NaHCO² (g)
  • Light Intensity (calculated via the formula 1/d²)
  • Time Taken (secs/mins)
  • Amount of O² Given Off By Plant

The results of the experiment will be recorded in a simple table.

Prediction:

I predict that as the amount of NaHCO² increases there will also be an increase in the amount of Oxygen (O²) given off. This is because when the NaHCO² is added, the amount of Carbon Dioxide (CO²) increases. Therefore the pondweed will respire more quickly than before the NaHCO² was added, taking in more CO² and giving off more O².

Scientific Theory:

Photosynthesis is the “[combination] of organic compounds from carbon dioxide and water (with the release of oxygen) using light absorbed by chlorophyll.” [COLLINS ENGLISH DICTIONARY]

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Here is the formula for photosynthesis:

Carbon Dioxide + Water           Sunlight        Energy + Oxygen  

        6CO²         H²O                             C6H12O6        6O²                 

From the above formula we can see that as the plant takes in more carbon dioxide and water it produces more oxygen and energy. This is similar to human respiration, except we take in oxygen and give out carbon dioxide to produce energy.

In this experiment the NaHCO² increases the amount of carbon dioxide in the solution. Therefore more carbon dioxide molecules diffuse into the plant than before the NaHCO² was added. ...

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