The Effect of Light on the Organic Plant Elodea

The Effect of Light on the Organic Plant Elodea

Aim: To calculate the rate of photosynthesis from the number of oxygen

bubbles produced by the plant.

Photosynthesis: The process by which green plants use the sun's energy

to build up carbohydrate reserves.

Plants make their own organic food such as starch. Plants need Carbon

dioxide, water, light and chlorophyll in order to make food; and

starch and oxygen are produced. Carbon dioxide and water are the raw

materials of photosynthesis.

The equation of photosynthesis is:

6CO2 + 6H20 Þ C6H12O6 + 6O2

===========================

Carbon dioxide + water Þ glucose + oxygen

Green plants need sunlight. They use the light energy to make a sugar

called glucose.

Glucose can be turned into another type of sugar called sucrose and

carried to other parts of the plant in phloem vessels. Glucose can

also be turned into starch and stored. Both starch and sucrose can be

converted back into glucose and used in respiration.

Photosynthesis happens in the mesophyll cell of leaves. There are two

kinds of mesophyll cells - palisade mesophyll and spongy mesophyll.

The mesophyll cells contain tiny bodies called chloroplasts which

contain a green chemical called chlorophyll. This chemical is used to

catch the light energy needed in photosynthesis.

They take carbon dioxide from the air. Plants use sunlight to turn

water and carbon dioxide into glucose. Plants use glucose as food for

energy and as a building block for growing. The way plants turn water

and carbon dioxide into sugar is called photosynthesis. That means

"putting together with light"

During the winter, there is not enough light or water for

photosynthesis. The green chlorophyll disappears from the leaves. All

plants need light in order to photosynthesise. Photosynthesis can only

occur in the presence of light.

Hypothesis: The brighter the light intensity the more bubbles that

will be produced. As the light is increased so would the rate of

photosynthesis.

Apparatus: boiling tube, 250ml beaker, bench lamp, ruler, sodium