Science: It Takes Some to Grow One

This hands-on, in-class activity is a fun way to make a lasting impression on students. They’ll have a leaf-shaped print to help them remember how chlorophyll works in plants to turn sunlight into food.

Background from The Arbor Day Foundation

Explain to the class that the main difference between plants and animals is that plants have the ability to make their own food.

Green plants use light-energy from the sun to make a sugar-like food through a process called photosynthesis. Photosynthesis occurs only in plants that contain chlorophyll.

Chlorophyll is the enabler for the photosynthetic process. During photosynthesis chlorophyll, carbon dioxide, water and light-energy from the sun are used to make the sugar-like food that becomes the basic source of energy for the plant and other living things that might eat the plant.

While making this food, the green plant gives off water vapor and oxygen as byproducts of the process.

Looking through a microscope at a thin section of a leaf will reveal cells containing what looks like little green jellybeans. These jellybean-appearing structures within the cell are called chloroplasts. They are full of chlorophyll.

Explain to students that there is a green chemical stored in the cells of green plants that lets plants make their own food. This chemical is called chlorophyll. They are going to have an opportunity to beat the chlorophyll out of the chloroplasts in a leaf and make a leaf print.

What You Need
• Hammers
• Tacks
• 4-inch square wood blocks (check to see if a local lumber yard or building contractor will cut and donate pieces of scrap)
• Thumb tacks
• White cotton fabric cut into 4-inch by 4-inch squares (cut up an old sheet or pillow case); there should one piece of fabric for each child
• Optional:
- Spray bottle
- Vinegar
- Iron

What You Do
1. Tack a piece of the fabric to two corners of one side of the wood.
2. Collect a fresh, green leaf. Slide it under the fabric so it’s on top of the wood.
3. Tack down the remaining two corners of material.
4. Use a hammer and gently beat the fabric over the leaf to break the chloroplasts. Follow the contour of the leaf to get the best leaf print. As the cell structures are broken, the pigments in the leaf will stain the fabric.
5. Carefully continue beating the leaf–this can actually “trace” the leaf on the fabric with pigment. The green chlorophyll forced out of the chloroplasts will leave an imprint of the leaf shape.
5. After beating, remove the tacks, lift the fabric and gently pull off any “clinging” leaf pieces.
6. To make the leaf imprint permanent, mist the print with vinegar and press it with a hot iron.

Source: Adapted from The Arbor Day Foundation’s “Beat a Leaf”

Language Arts: What’s My Part?

A fun, in-class activity to get students thinking about the different parts of a tree and the roles they play.

What You Do

1) Write down each of the following parts of a tree on separate pieces of paper in large block letters.

Crown
Leaves
Roots
Trunk
Sapwood
Phloem
Bark

2) Draw a large picture of a tree (without any labels) on the blackboard. Off to one side, place the names of the tree parts along the blackboard rail or tack them to the wall.
3) Explain to students that like a good play or movie, a tree has different parts that work together to make it a success.
4) Read the first line listed below–or ask one of the students to read it. A little “dramatic acting” when reading the lines will be make the activity more fun.
5) Ask the class to raise their hands if they know the name of the part your describing.
6) Choose a student to answer. If the student is correct, ask him or her to pick up the correct label, go to the tree you’ve drawn on the board and put one hand on the right part of the tree. With the other hand, the student can display the card with the name of the tree part. (The trunk might become a little crowded once phloem and sapwood are added…so be sure to draw a tree with a long trunk!)
7) Read through all the lines until all the parts of the tree have been named.
8) Extension Idea: Ask students to invent their own lines and personalities for the different parts. They can do more research to add more dimension to their characters, and even create short plays.

Tree Part Lines

“I’m the top! No seriously. I’m the leaves and branches at the top of the tree. I filter dust and other particles through from the air and cool the air by creating shade.” (Crown)

“I’m the food factory of the tree. I am green because I have chlorophyll that I use in a process called photosynthesis. That’s how I use sun’s energy to make food.” (Leaves)

“I absorb water and nutrients from the ground. I have little hairs that help me soak up the water and minerals from the soil.” (Roots)

“I am the backbone of the tree. I hold up the top and give the tree its shape. Without me the tree would never get off the ground!” (Trunk)

“I am sometimes called inner bark. I act as a food supply line carrying sap–delicious sugar and nutrients dissolved in water–from the leaves to the rest of the tree.” (Phloem)

“I am the waterway of the tree. My network of thick-walled cells carries water and nutrients up from the roots to the leaves and other parts of the tree.” (Sapwood)

“I cover the trunk, branches and twigs of a tree. I’m like a suit of armor protecting the tree insects, disease, storms and extreme temperatures.” (Bark)

Source: Adapted from The Arbor Day Foundation’s “The Anatomy of a Tree”


Math: Give Me a Ring

A wonderful lesson that allows students to become tree detectives.

Ask students: What is a dendrochronologist? Explain that is a person who studies tree rings.
Each spring and summer a tree adds new layers of wood to its trunk. The wood formed in spring grows fast, and is lighter because it consists of large cells.
In summer, growth is slower; the wood has smaller cells and is darker. So when the tree is cut, the layers appear as alternating rings of light and dark wood.

For example, the tree rings above show that this tree lived to 62 years old.

How do we know? Count the dark rings, and you know the tree's age. Study the rings, and you can learn much more. Many things affect the way the tree grows, and thus alter the shape, thickness, color and uniformity of the rings.

Tell students that now is their chance to be like dendrochronologists.

Ask: A tree has 60 dark rings. How old is the tree? (60)

Ask: If a tree started growing in 1957 and is still alive today, how many dark and light rings would it have? (100) How many dark rings? (50) How old would the tree be? (50)

Ask: A tree has 20 dark and light rings. How old is the tree? (10)

Ask: If a tree was planted in 1888 and lived until 1988, how many light rings would it have? (50)

Ask: If you planted a tree today in 2007, in what year would the tree have a total of 20 light and dark rings? (2027)

Have students make up their own problems to challenge the class.

Source: Picture and tree ring facts adapted from
The Arbor Day Foundation’s “The Living Forest”