Students evaluate the function of plant stems and identify edible stems belonging to certain plants.
agriculture: the science, art, or practice of cultivating the soil, producing crops, and raising livestock and in varying degrees the preparation and marketing of the resulting products
commodity: a primary agricultural product that can be bought and sold
edible: suitable or safe to eat
farm: an area of land used for growing crops or rearing animals
phloem: a portion of the vascular system in plants, consisting of living cells arranged into tubes that transport sugar and other organic nutrients throughout the plant
stem: the main supportive part of a plant; part of the transport system carrying water from the roots and food produced during photosynthesis to other parts of the plant
tuber: a thickened underground portion of a stem or rhizome which bears buds
xylem: the specialized cells of plants that transport water and nutrients from the roots to the leaves
Did You Know? (Ag Facts)
- A cactus can hold a lot of water in its stems. Even though this liquid is not pure water it was known to save people's lives when traveling through the desert.1
- We normally call the sharp spikes located on the stem of a rose bush "thorns." However, these sometimes painful spikes are technically called "prickles."2
- Plants with stems are called vascular plants because they contain tissue that move water and minerals from the roots to the leaves to help it grow.3
Background Agricultural Connections
This lesson is part of a series called, Edible Plant Parts. These lessons allow students and teachers to examine the six basic plant parts—roots, stems, leaves, flowers, fruits, and seeds—in a unique way. Through hands-on activities, students will learn about the different plant parts, as well as how to include fruits and vegetables into their daily meals as part of a healthy diet. Students will also learn about agriculture and the people who produce our food. The remaining lessons can be found at the following links:
- Why People Need Plants
- Dig 'Em Up
- Snappy Stems
- Luscious Leaves
- Fabulous Flowers
- Freshest Fruits
- Supreme Seeds
- Edible Plant Game
- Eat 'Em Up
In this lesson, students will be fascinated to learn that when broccoli or cauliflower is served at dinner, they are eating stems. Stems typically support the leaves, flowers, and fruit of a plant. They also connect the leaves to the roots for transporting water and minerals through the phloem and xylem. Liverworts, hornworts, and mosses are the only green plants that do not have stems. For this lesson student's experience for eating vegetables that live and grow above and underground would be required for helping them gain an understanding for the functions and varieties of stems.
Students will also learn about agriculture which is the business of growing crops and raising livestock by people commonly called farmers. This type of work is normally done on a piece of land called a farm. Commodities such as fruits, vegetables, nuts, grains, and various types of animal meat are the edible food products grown and raised by farmers. These food products are harvested, processed, packaged, and delivered to grocery stores, farmer's markets, and restaurants for us to enjoy.
Stems can be very short, as in lettuce plants, or very tall, as in the trunks of redwood trees. Stems can be hollow, as in daffodils, or somewhat solid, as in tree trunks. Food produced in leaves through photosynthesis travels down the stems through the phloem to the roots and fruits, while water and nutrients absorbed by the roots travel up the stems through the xylem to other parts of the plant. Edible stems include asparagus, bamboo shoots, and sugar cane. Celery and rhubarb are commonly classified as a stem we eat, however, this is a misconception. Scientifically speaking, celery and rhubarb are actually petioles or leaf stalks, and are classified as a leaf. Other edible plant stems include those in broccoli and cauliflower, even though they are not necessarily grown for their stems. All varieties of potatoes are special stems, called tubers, that grow underground. A tuber is a short, thickened, fleshy portion of a plant which grows an underground stem.
Many interesting products come from stems. Granulated sugar is processed from the above-ground stems of sugar cane or the below-ground tuber of sugar beets. Maple sugar is obtained from the trunks of maple trees. Cinnamon comes from the bark of trees in the Cinnamomum genus.
Interest Approach - Engagement
- Draw a sketch of a plant on the board. Include the roots, leaves, and a flower. Leave the area for the stem blank and ask the students what is missing (stem).
- Ask them if they think a plant could live without its stem. Why or why not?
- Display the four Plant Cards and have them point out the stem. Remember to point out the actual potato in its picture as the stem.
- Tell your students that today they will be learning about plant stems.
Activity 1: Function of Stems
- Demonstrate the function of the stem (vascular tubes that carry water and nutrients) by putting a stalk of celery with celery leaves in a jar of water with food coloring.
- Examine the celery in food coloring after a day or two to see how the stalk and leaves have changed color as a result of the xylem carrying the food coloring and water up the stem.
- Note: As explained in the Background Agricultural Connections section of this lesson, celery is not scientifically classified as a stem. However, it is used in this step of the lesson because it is the most visual way to illustrate the function of the xylem and phloem.
- Discuss the functions of the stem as a whole:
- Supports plants
- Transports water, food, and nutrients throughout the plant
- Connects the leaves to the roots
- Have students go outside and observe a variety of stems on campus. Clarify with students whether or not you want them to pick the stems that they will be observing or simply observe them without picking the plant.
- Discover and discuss that stems come in all shapes and sizes and that many are not edible.
- Give each student the Writing Worksheet and ask them to draw and write a paragraph about their favorite plant stem based on what they observed.
- Display their work in the classroom to use as a reference for the next activity.
Activity 2: Stems We Eat
- Ask your students to brainstorm types of edible stems that we eat. (Asparagus is a good example. Broccoli and cauliflower also have a stem below the floret.) Give clues or show pictures as needed.
- Teach your students that there are actually two kinds of stems. Some grow above ground and other types of stems grow below ground. They are called tubers.
- For more understanding, read the book Tops and Bottoms written by Janet Stevens. If the school library does not have a copy, view the Tops and Bottoms Read Aloud. Tell the students that this book is about a rabbit and a bear who decided to grow plants in a vegetable garden.
- During the reading, stop and ask the students to identify the stems of several plants and determine whether it is above or below the surface of the soil.
- At the conclusion of the book, ask the students:
- What are some plants that have good bottoms or stems to eat? (white potatoes and sweet potatoes)
- What are some plants that have good tops or stems to eat? (asparagus and broccoli)
- How is the hare similar to farmers who grow plants that we eat? (The hare knows about the different parts of a plant and which parts we can eat. He also knows how they should be grown and harvested.)
- What important lesson can we learn from the Bear about harvesting vegetables to eat? (The bear is not knowledgeable about plant parts and the book indicates his laziness. If farmers are lazy like the bear then they will harvest little food for us to eat.)
- Ask the students to read their sentences from the Writing Worksheet to a partner and call on each student to share one thing with the class that their partner wrote about their favorite plant stem.
Concept Elaboration and Evaluation
After conducting this activity, review and summarize the following key concepts:
- Stems of certain plants are edible.
- Stems come in all shapes and sizes.
- Farmers must be knowledgeable about the plants they grow and harvest.
- Eating stems such as asparagus, broccoli, and cauliflower are a healthy snack.
- This lesson incorporates hands-on activities. Kinesthetic learning events provide an excellent learning environment for the English learner.
- Demonstrate how to set up the experiment prior to allowing students to carry out their own experiments. ELL students will benefit from observing the procedures before they get started.
Do a class survey and calculate the percentage of students who prefer each type of broccoli topping.
Read the book Sugarbush Spring by Martha Wilson Chall. In this book students will learn that the maple which makes the syrup for their pancakes is collected from the trunk (stem) of a maple tree.
Stem potluck: In advance, ask students to bring tasty toppings to class. Examples include peanut butter, cheeses, hummus, dressing, and more. Provide stems such as asparagus, broccoli, or cauliflower for students to taste along with their toppings. Review with students by pointing out which portion of the broccoli or cauliflower is the stem. Discuss food allergies and wash hands before this activity. Next, make a bar-graph on the board that shows which toppings were most popular among the students.
This lesson update was funded by a grant from the Network for a Healthy California.
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