In this accelerator, pupils are introduced to the factors that influence seed germination and plant growth by conducting an experiment using the exclusion method and by designing and constructing a garden plot to the schoolyard based on the results of the experiment. The exclusion experiment investigating the optimal growth conditions for plants is a popular experiment in the Finnish school context and it is aimed at 7 to 12-year-old pupils. The amount of structure and support can easily be varied to adapt the experiment according to pupils of different ages. Younger pupils may need the instructions on how to plant the seeds whereas older pupils may design their own experiment.

The descriptions of the activity do also include suggestions on how to collaborate with different stakeholders, however, the suggestions are meant to serve as guidelines rather than compulsory activities.The experiment is an application of the famous biology experiment in which a similar method studies the effects of a plant hormone on plant growth.

The factors that are investigated in the experiment include:

• light 
• moisture 
• air
• heat 
• potting soil

The preparations and the experiment include the following steps that are described in more detail in the following sections:

1) Introduction to the topic and the inquiry cycle

2) Pupils work in groups to design the experiment based on the introduction and their background knowledge

3) The planned procedure is presented to the rest of the class in order to receive feedback. The teacher needs to make sure that the groups are going to investigate different factors (light, moisture, air, potting soil).

4) Conducting the experiment (2 weeks of observation, 15 minutes a day):

• Preparing and labeling the cups (the amount of cups depends on the design of the experiment)

• Instructions can be provided for more structure and support 
• Planting seeds in the cups and eliminating 1 factor/cup

Cup 1: is left without light.

Fill the cup with a few centimeters of potting soil. Plant five sunflower seeds (or other types of seeds) in the potting soil and gently water the cup by spraying water so that the soil gets wet. Wrap the cup tightly in the aluminum foil so that the light does not get into the cup. Be careful to not break the aluminum foil.

Cup 2: is left without moisture.

The cup is filled with potting soil in the same way as the first cup. The seeds are also similarly planted but the potting soil will not be watered.

Cup 3: excludes air.

The seeds are placed on the bottom of the cup, followed by a layer of potting soil a few millimeters thick. Finally, carefully fill the cup with water. Make sure that the seeds do not reach the surface (they are lighter than the potting soil and the water).

Cup 4: excludes the potting soil.

Instead of potting soil, a paper towel is placed on the bottom of the cup on which the seeds are sown. Finally, the paper towel is carefully soaked with water.

Cup 5: is left without heat.

This is done by first filling the cup with half of the amount of potting soil compared to cup 1 and 2 and planting the seeds into the soil. The cup is then watered gently but be careful not to use too much water. Bring the mug to the coldest place in the schoolyard. 

The control cup is prepared by filling the cup with potting soil, planting five seeds and by watering the cup (not too wet).

Place the mugs in a bright place, for example on a windowsill (indoors), and make sure that the cups receive enough water during the experiment (for a couple of weeks). Cup no. 2 is an exception, as it should not be given water. Cup no. 5 should be kept in the yard during the entire experiment.

5) Taking care of the seeds by watering and providing enough sunlight (except for the cups that are placed in the dark)

• Making observations (each day for 2 weeks time)

6) Pupils can invite experts in agriculture to make investigations and to discuss the factors that affect plant growth. Pupils can present the results of their observations and receive feedback on the experiment. As a result of the collaboration, pupils and experts will share information on seed germination and design a garden plot based on the results of the experiment.

7) Pupils continue to design the garden plot by calculating the costs and the necessary equipment needed for the construction of the garden plot. Pupils may want to consult local stores that sell seeds and gardening equipment for a reliable estimation of the cost.

8) When the design of the garden plot is finished, pupils can attempt to book a meeting with a representative from the City Council in order to present the plan for the garden plot. The aim is to share information about the schoolyard garden project and to possibly receive support for the construction of the garden plot (some towns in Finland encourage the inhabitants to cultivate herbs in the urban environment by providing the wooden frame for the garden plot).

9) The construction of the garden plot and learning to take care of it.

10) Harvesting the herbs to be used in the school kitchen (collaboration with the cookers of the school kitchen)

11) Presenting the schoolyard garden for the local community to encourage inhabitants of the local community to start cultivating self-sustaining gardens with herbs and vegetables. The activity is also suitable for promoting awareness on healthy eating habits and the community benefits of locally produced food.

During this accelerator, pupils will learn how to design and conduct controlled experiments to find out how different factors affect seed germination. Pupils will also learn to draw conclusions about the condition(s) that offer the most optimal growth conditions for plants. The activity aims to promote awareness on why agriculture is challenging in different parts of the world (e.g. the Nordic regions).

This experiment is simple to conduct by using sunflower or oats seeds, but it can also be expanded to include other kinds of seeds (e.g. Cress seeds or mustard seeds) to understand how the optimal growth conditions for different plant species may vary.