Investigating Green Plants
Complete instructions for conducting activities in this slide set, including materials needed, setup instructions, student sheets (in English and in Spanish), answer keys and extensions, can be found in The Science of Food Teacher’s Guide, which is available free-of-charge at http://www.bioedonline.org/lessons-and-more/teacher-guides/food/
Session 1: Observing dry seeds
Give each student a dry bean and a magnifier. Have students use their magnifiers to observe the bean seeds, then draw a seed on his or her “Seeds and Seedlings” sheet. Make sure that each student is able to observe the seed coat and the dark indentation on one side of the seed, corresponding to where the new plant will emerge.
Session 2: Observing and planting soaked seeds
1. Before proceeding with planting, give each student a soaked seed (on a paper towel) for observation. The students should compare the soaked seed to a dry seed. Ask, How is the soaked seed similar to the dry seed? How is it different? Have students remove the “skin” (seed coat) and spread apart the pieces of the tiny plant inside. They will be able to identify the cotyledons (seed leaves), other tiny leaves and the beginnings of what will become the plant root.
2. Have Materials Managers pick up 4 pots and 8 soaked seeds from a central location in the classroom. Direct the members of each group to pick a name for their group and to write it on the pots. They should number their pots: 1, 2, 3 and 4.
3. Have groups fill their pots about 3/4 full of soil.
4. Direct the students to make two indentations (about 1/2 cm deep) in the surface of the soil and to place one seed in each hole. Have them cover the seeds lightly with soil. Each group will have four pots, with two seeds in each pot.
5. Have students place the pots on trays near a bright, sunny window or under a fluorescent light. Over the next several days . . .
- Once the seeds sprout, have students “mark” one of the two plants within each pot by loosely tying a piece of string around its base. If a plant dies, students should continue to measure the remaining plant.
- Have students measure both plants in each pot every day or every other day and record the length of the stems in cm on their “Seeds and Seedlings” sheets.
- Let students water the plants every day or two with a squirt bottle. The soil should be moist but not wet.
Session 3: Light experiment
1. When most of the seedlings are approximately 10 cm tall, explain to the students that they will now investigate the effect of light on the growth of the bean plants. Ask, What do you think will happen if we give some of the plants less light?
2. Have each group move pots 3 and 4 to a new location that you have selected (in the back of the classroom or in a dark corner away from the windows or light source). Ask, Do you think that the plants in the new place will have as much light as the others? Why or why not? What do you think will happen to the plants receiving less light? Have students discuss possible outcomes and make predictions.
3. Students should continue to measure the plants for another 3–5 days and record their measurements on their “Just Growing Up” student sheets.
Session 4: Looking at data
1. After making their final observations, have students complete the remaining questions on the their student sheets.
2. Discuss results as a class. They should be able to conclude that the difference in available light led to any observed differences between the two groups of plants. Ask, Were the plants all about the same size before you moved pots 3 and 4 out of the bright light? Are all the plants still the same size? Why do you think that is so? Are there any differences other than size? Help students to conclude that the differences in growth (the plants with less light will have grown less or will have developed tall, narrow stems) and in color (the plants with less light will be lighter green) were caused by the differences in the availability of light. Ask, What is the only thing that was different about the two sets of pots? (Only the amount of light changed; all other aspects of the experiment—water, soil, seedlings, pots, planting method—were unchanged for both groups.)
3. Ask students, Where do you think the plants in pots 1 and 2 got the materials and energy to produce more stems and leaves? What were the plants in pots 3 and 4 missing? What do you think would happen if we put the plants in pots 3 and 4 back in the light?
- Moreno, N., and Tharp, B. (2011) The Science of Food Teacher’s Guide. Baylor College of Medicine: Houston. ISBN: 978-1-888997-76-7
- Illustration by M.S. Young © Baylor College of Medicine.
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Funded by the following grant(s)
My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932
Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education