Determining the Effect of Light Intensity on Photosynthesis

Determining the Effect of Light Intensity on Photosynthesis

Aim

In this experiment, I intend to alter the light intensity and measure

its effect on photosynthesis through the production of oxygen

Introduction

Photosynthesis is the process by which green plants provide a source

of energy for respiration. The formula is as follows-

Carbon dioxide + water

Carbon dioxide and water are chemically combined to produce glucose

(the energy source) and oxygen (a waste product).

Since it is impossible to measure the uptake of carbon dioxide in

school laboratory conditions and water uptake is not an accurate

measure of photosynthesis due to the loss of water through the stomata

in transpiration, I will need to measure the products in order to have

an idea of the rate of photosynthesis. Glucose is stored within the

plant and is therefore not a feasible way of measuring photosynthetic

rate. However oxygen is released as a waste gas through the stomata

(pores located mostly on the underside of the leaves) and can be

collected and measured. I will use this information to formulate my

plan.

Other factors to consider

As the equation for photosynthesis shows, both carbon dioxide and

water can be limiting factors, i.e. if they are not present in

sufficient quantities, they will slow the rate of photosynthesis.

However, the chemical equation does not show four other important

factors, which will need to be taken into account. These are as

follows-

1. The reaction is endothermic. This means it takes energy from the

surroundings in order to provide the activation energy for the

reaction. The energy that is taken in duri...

... middle of paper ...

...ave already mentioned. Firstly, I have found out that

chlorophyll absorbs light at different wavelengths. I could

investigate the effect of different wavelengths on photosynthesis.

This might give me an indication as to whether or not the wavelength

of the light was the cause of my graph not levelling off. I would

expect, if I used a red light source, the graph would level off fairly

quickly because all of the light would be being absorbed and used

effectively.

In conclusion, I believe that the results I have gained in this

investigation are extremely reliable due to the use of a computer

simulation. As discussed, in the lab, my method has many sources of

error, but if I were to repeat this investigation I would make the

changes suggested above to try to eliminate the possible sources of

error as far as possible.