Pre-Activity 0.2PT: Plants Growth Investigation Setup (45-60 min)

Tell students that in 2 - 4 weeks from now, they will begin to study plant growth. To prepare for that, they will set up the investigation by planting seeds today, recording data, and making sure the plants grow over the next few weeks.

Read the handout together as a class or have students read it in groups to prepare for setting up the investigation. This will establish the problem for students.

Optional: View the Measuring Plant Growth Video to prime a conversation about how plants grow and the importance of measuring dry mass.

• This video focuses on the gel protocol. Since you are using the paper towel protocol, you can show from 0-2:50min and from 5:53-7:25min.
• Discuss as a class the purpose for measuring the dry mass of the plants.
• Tell students that they are going to walk through some of these steps together as a class today.

Each student group will plant 20 radish seeds in a container.

• Four to six containers of plants will allow the class to do at least 1 replication of the experimental treatments in Activity 3.3 Plants in the Light and Dark and have multiple measures to compare for Activity 3.2 and 3.4 Observing Plants’ Mass Changes, Part 1 and 2.

Follow the steps in Part A: Pre-Lesson 0.2PT Plant Growth Investigation Setup Worksheet.

• Show students slide 3 and 4 of the Pre-Lesson 0.2PT Plant Growth Investigation Setup PPT.
• Have students label their containers.
• Have students poke a small hole or two in the bottom of their container and thread through the yarn (half inside, half outside) as a wick. This is so that water can be drawn up into the growing containers and keep all of the paper towel you will add moist.
• Have students count out 20 seeds for their container, mass, and record in the worksheet table.
• Have student groups crush up a few small strips of paper towel first and place them in the bottom of the container. Next, lay a strip or a small sheet of paper towel over these crushed up pieces (like a pie crust over cherries). This will allow you to sprinkle radish seeds on top of this flat piece of paper towel so that they don’t get too saturated with water and so that the germination process is completely visible for students.
• Have students record the mass of the dry paper towel in their containers – either by taking it out and adding it back in or taring the container prior to adding the paper towel.

Tell students the dry mass measures will be important evidence for them to use later as they investigate where the mass of a growing plants comes from.

• Have students place their 20 seeds carefully on top of the flat piece of paper towel in their containers. Spread them out a bit for good germination.
• Have students carefully set their containers in the big class trays.
• Gently add water to the big class tray until the paper towel in the containers has wicked it up and is wet.

Remind students that the plants will need 1-3 weeks to grow before they are large enough to begin the rest of the Plants Unit.

Place the trays about 12-16 inches under the grow lights (highly recommended) or in a sunny windowsill.

Use the table in Part B in the Pre-Lesson 0.2PT Plant Growth Investigation Setup Worksheet for students to track their observations and ongoing watering of their radish plants.

• Show students slide 5 of the Pre-Lesson 0.2PT Plant Growth Investigation Setup PPT.
• Prepare about 4 L (~1 gallon) of a weak nutrient mixture (~1/2 of that recommended on the box/jar) to add to the containers once the cotyledons have turned green and the water is starting to dry up from the trays. Only add an inch or two of the mixture to the trays at a time. Adding to much risks drowning the plants or creating an optimal environment for algal growth.
• Note: It’s important to have a discussion with your students about the dry mass of the nutrients that are added via the nutrient solution (which is negligible).

Class discussion:

Ask your students: 1) Do you think the radishes will grow in paper towel without soil?