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Investigate the effects of light on the growth of newly germinated seedlings. Record the results of the seeds' length measurements and create a labelled scientific drawing to illustrate the effects of light.

Germination is the beginning of plant growth, and the plant will continue to grow if the correct conditions are available.

Mustard or cress seeds are a good choice for this investigation because they grow fast and their roots and stems are clearly visible.

Variables

The independent variable for this investigation is the direction of light the seeds are exposed to. Other suitable independent variables are: different colours of light, intensity of light, or the amount of light.

The dependent variable is the direction that the seedlings grow.

Control variables are the number of seeds on each dish, the distance between each seed, the volume of water the seedlings are given, and the temperature they are grown at.

Method

1. Put cotton wool into three Petri dishes, and add the same volume of water to each dish.
2. Add ten seeds to each dish and make sure they are evenly spaced.
3. Place the petri dishes in a warm place where they won't be disturbed.
4. Allow the seeds to germinate, and add more water if the cotton wool dries out.
5. Once the seeds have germinated, ensure the petri dishes each contain the same number of seeds, and remove any extra seeds if necessary.
6. One petri dish will have light to the left-hand side of the dish, one dish will have light to the right-hand side and one dish will have light directly from above. An easy way to do this is to place the dishes in a cardboard box with a hole in it for light to come through in one direction only.
7. Every day for one week, measure the angle that each seedling is growing and record the results in a table. You must record the angle of the individual seedlings on each day.
8. Calculate the mean angle of the seedlings each day, and compare the mean angles in the three different locations.