The aim of my experiment is to determine whether or not the intensity of light would affect the rate of photosynthesis in a plant.

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Rajiv Patel Leytonstone School 8152

Aim

The aim of my experiment is to determine whether or not the intensity of light would affect the rate of photosynthesis in a plant.

Introduction

Photosynthesis is a biochemical reaction in plants to create glucose using light energy, water and carbon dioxide. Chlorophyll absorbs the light energy.

                                   Light energy

Water+                                                                      carbon dioxide + glucose oxygen  

 

6H20 + 6CO2                       C6H12O6 + 6O2

Light energy is needed by plants in order to break down the bonds in water and carbondioxide, and also to create new bonds between atoms in order to form glucose and oxygen. Energy is required for this procedure and this energy is retrieved from light energy.

Light energy is absorbed by chlorophyll found in chloroplasts in mesophyll cells (found in green leaves). Chlorophyll is placed in the top cells of a leaf so that it can absorb as much light as possible. The manifestation of chlorophyll is green as it reflects green light and absorbs red and blue light. Magnesium and iron are main factors for the manufacture of chlorophyll.

When the light energy is absorbed by chloroplasts it is trapped and is then made available for chemical reactions in the plant, so more photosynthesis takes place in specific a given time.

Prediction

I predict that the stronger the light intensity there is i.e. more light energy the more bonds between water and carbon dioxide are broken while more bonds will be created between glucose and oxygen. This, therefore increasing the rate of photosynthesis.

Furthermore, I hypothesised that if the light intensity proliferates, the rate of photosynthesis will increase at a proportional rate until a certain level is reached, and the rate of increase will then go down. Eventually, a level will be reached where an increase in light intensity will have no further effect on the rate of photosynthesis, as there will be another limiting factor. In this case either the amount of CO2 or the temperature.

Also the rate of photosynthesis could be affected by limiting factors. As the law of limiting factors states that any procedure requiring two or more factors will have its rate determined by the lowest or slowest factor. In photosynthesis there are five possible factors, see below:

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  • CO2
  • H20
  • Light energy
  • Chlorophyll
  • Temperature

Preliminary work

Initially, to ascertain a suitable range of distances at which to record results for my experiment, I did a preliminary investigation in which I recorded the number of bubbles of oxygen given off in a given time at various light intensities. To alter the light intensity, I placed a lamp at various distances from the plant. I got the following results:

Results of preliminary experiment

10                                16

Although this is a very quick, simple and efficient way of obtaining an idea of ...

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