Biology Investigation How Light Affects Photosynthesis

Essay by sweeteliA+, May 2005

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Biology Investigation

How Light Affects Photosynthesis


I will carry out an investigation to find out how photosynthesis is affected by light intensity. I will use an aquatic plant (water plant) called Elodea. Elodea is a Canadian Pondweed.


To investigate how light affects photosynthesis in Elodea.

Prediction 1

I predict that the Elodea will produce more oxygen bubbles when the light is closer to it.

Prediction 2

I predict that the bubbles of gas produced from Elodea plant will be oxygen gas.


Below is the list of factors that affect the rate of photosynthesis in plants:



Amount of carbon dioxide (C02)

Size (surface area of plant)

Amount of water (H2O)

Temperature: At high temperature the plant cannot photosynthesise because the chlorophyll enzymes are damaged. Enzymes are denatured at high temperatures.

Light: In the dark, plants cannot photosynthesise at all. In dim light, they can photosynthesise slowly.

As light intensity increases, the rate of photosynthesis will increase until the plant is photosynthesising as fast as it can. At this point, even if the light becomes brighter, the plant cannot photosynthesise any faster.

Amount of Carbon Dioxide: The more carbon dioxide a plant is a given, the faster it can photosynthesise up to a plant, but then a maximum is reached. The carbon dioxide can get the leaf through the stomata. It does this by diffusion. Behind each stoma is an air space, which connects up with other air spaces between the spongy moesophyll cells, which are carbon dioxide. The carbon dioxide can therefore diffuse to all the cells in the leaf. It ca then diffuse through the cell wall and cell membrane of each, and into the chloroplasts.

Surface area of plant: the position of a leaf and its broad, flat surface helps it to...