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Crops 2: What Plants Need to Grow

What You Need

Materials

  • A tomato
  • An apple or pear
  • A few green beans
  • A few pea pods
  • Other seeded fruits or vegetables (optional)
  • 6 clear plastic cups
  • Potting soil
  • Water
  • Sunlight
  • A knife
  • A hand shovel
  • Magnifying glasses
  • A ruler
  • Masking tape
  • Marker
  • Crayons
 
Crops 2: What Plants Need to Grow

Purpose

To familiarize students with the kinds of things that plants need to grow well.


Context

This is the second lesson of a two-part series on where food comes from. These lessons are intended to help students understand that most of the food they eat comes from farms.

In Crops 1: Where Does Food Come From?, students learn that most of the food they buy in stores originally comes from farms. Students are gathered together to sing a song about growing crops on a farm and learn from the lyrics the kinds of things that farmers do and need to grow plants well. They learn about the five steps in our food system and discuss its aspects in the context of a story about tomato farming and distribution.

In Crops 2: What Plants Need to Grow, students learn how to grow plants and about the kinds of things that promote growth (warmth, sunlight, water, soil). Their activities involve learning about how seeds and plants grow and participating in a simple, in-class gardening project.

While teaching, keep in mind that a lot of people never see food or fiber before those products get to retail stores and that primary-school children may have only vague ideas about where their food and fabrics come from. This series of lessons will seek to address this lack of awareness by introducing children to some of the basics of agriculture, such as: where most foods come from, how plants are grown, and what process farm products undergo before they arrive at stores. (Benchmarks for Science Literacy, pp. 183–184.)

Students will also benefit from knowing that many people are involved in the farming industry. These include workers who farm the land and produce farm equipment and those involved in the processing, storage, transportation, and distribution of food. It might also be helpful to point out that many forms of transportation, refrigeration, processing, and packaging enable food to be transported, stored, and consumed thousands of miles from where it is originally produced. (Science for All Americans, pp. 108–110.)

The basic experiences of students at this early level include seeing plants grow from seeds they have planted, eating the edible portions of the mature plants, and noticing what plants and other things animals eat. Comparisons can be made to see what happens if some plants don't get water or sunlight. (Benchmarks for Science Literacy, p. 184.) Since students at this early level are unfamiliar with how to conduct scientific investigations, the in-class gardening project should be conducted by the teacher with class observation.

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Motivation

Briefly review what students learned in the first lesson, paying particular attention to how plants are grown on the farm. See if they can remember the answers to questions like these:

  • What kinds of things did Miguel have to do to grow his tomato plants?
  • What kinds of things did the plants need to grow?
  • How do plants begin?
  • Do your parents have a garden or flowerbed at home? Have you ever helped them with it?

Accept all reasonable answers and encourage students to share their thoughts and examples. Then read Let's Think About…Plants, on the Jay Jay the Jet Plane site, which will give students a good, basic orientation to plants, where they come from, and what they need to grow. (If possible, allow students to watch the short Learn About…Plants video clip at the end of the page to further reinforce what they have learned from the reading.) When finished, check their comprehension by again asking questions like these:

  • Where do most plants come from?
  • What kinds of things do they need to grow?

Once it is clear that most plants come from seeds and that they need warmth, water, sunlight, and soil to grow, explain that many fruits and vegetables that are grown on farms and in gardens have seeds inside them. Show the class a tomato, a pear, a green bean, and a pea pod. Cut them open to show their seeds. Encourage up-close observation and a discussion about seeds and how they grow into plants under the right kinds of conditions.


Development

Set up the in-class plant experiment by following the steps below. If possible, allow students to help you. Explain that you are planting the seeds in warm soil and you'll all watch them grow.

  1. Place the six, clear plastic cups on a table.
  2. Fill the cups about two-thirds full with soil.
  3. Place one pea seed in three of the cups and one green bean seed in the other three cups.
  4. Separate the three pea cups from the three green bean cups and place labels on them to indicate what seeds are in them.
  5. Place more soil on top of the seeds in the six cups.

(The purpose of using two types of seeds is to offer students a bit of variety when they finally grow into plants. They will be able to observe the growth and structural differences of each of the plants. NOTE: For younger students, you may wish to grow only one type of seed in three cups.)

When these tasks have been completed, ask the class again about the kinds of things that plants need to grow (water, warmth, sunlight, soil). Explain that all the seeds have enough warmth in the soil and in the air in the classroom. Explain that, to see the importance of water and sunlight, you will divide the seed cups into three different groups:

  • Group 1 will be given water and sunlight
  • Group 2 will be given only water
  • Group 3 will be given only sunlight

Then water the Group 1 plants and place them in a sunny window; water the Group 2 plants and put them in a dark spot; and do not water the Group 3 plants and place them in a sunny window. Allow students to observe and participate in this stage of the experiment to the degree that they can. Place a piece of paper under each group and use a marker to label the groups and identify the conditions under which they are growing, like “with sunlight and water” or “with sunlight but no water.” (For lower-level students, you may choose to label the sheets with sun and water symbols instead.)

Next, encourage students to predict what will happen. Ask:

  • Which group of plants do you think will grow first—the ones getting both sunlight and water, only water, or only sunlight? Why?

Accept all answers and explanations. You may choose to record students' predictions and compare them with the results of the experiment.

After that, copy the Plant Growth Observation Chart teacher sheet on one side of the blackboard or on a large sheet of paper to use as an ongoing record of daily observations for the three plant groups. For the next 14 days, have students continue to lightly water the plants in groups 1 and 2 every few days and record student obserations on a daily basis about each group in the spaces provided. Allow students to use magnifying glasses to look for sprouting. At some point, you may also wish to use a ruler to document the height of the plants. After 14 days, there should be a definite difference in the growth of the plants in each group. Ask students how the results compare with their predictions. If none of the seeds sprout and grow, ask students why they think this happened. Explain that they may have gotten too much water, not enough sunlight, or that they may not have been healthy. In any case, make sure students understand that plants grow best when they have both sunlight and water.


Assessment

Once the plants in Group 1 begin to sprout, pass out the Plant Growth student sheet. Have students draw the plants and discuss what they observe. Then, every few days, have them observe and draw the growing plants again. (After Day 14, you may wish to have the class transplant the plants to a sunny area outside so they can continue to observe them.)

Ask questions like the following during the experimentation period to encourage students to make connections and extend what they have learned about plant growth:

  • What did you find interesting about this experiment?
  • Why do you think spring is the best season to grow plants?
  • Why are plants important to the world?
  • What do you think happens to a farmer's crops if they get too much rain and no sunlight? Or too much sunlight and no rain?
  • Do you think you will be a farmer or have a garden when you grow up? Why or why not?

Extensions

This lesson series may also be supplemented by the Science NetLinks lesson, What Parts Are There to a Plant?, which lets students observe and document similarities and differences between parts of plants.




For further reinforcement on the food-to-table process, students can visit the 4-H Virtual Farm, which includes an exhibit on Wheat: From the Farm to You. In addition to the other insightful features of this site, this exhibit takes students to a wheat farm to observe how crops grow, how they're processed, and the extensive, high-tech journey they take before becoming the products we buy in supermarkets. Encourage the class to explore the other virtual farms on the site, including horses, fish, dairy, beef, and poultry.


Students can further their understanding of our food system and how plants grow by visiting Kids Farm, a colorful, online resource that introduces children to many different types of farm animals, wild animals, farm equipment, and how certain fruits and vegetables grow. The site features music, activities, and much more.



The second Mystery Garden activity from the Jay Jay the Jet Plane site offers students more fun and practice with planting seeds and plant growth in general.


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