Colorado Agriscience Curriculum
Section:
Plant & Soil Science
Unit:
Plant Physiology and Growth
Lesson Number:
8
Lesson Title:
Leaf Structures and Functions
Colorado Agricultural Education Standards:
Agriculture Science 11/12.4: The student will demonstrate and understanding of
physiological processes in agriculturally important plants.
Enabler AGS 11/12.4.8: Identify plant structures and their functions
Colorado Science Standards:
SCI 3.3.1, SCI 3.3.5
Student Learning Objectives (Enablers)
As a result of this lesson, the student will …
1. Understand the functions of a leaf
2. Understand the internal structure of a leaf
3. Understand the external structure of a leaf
4. Identify the different types of leaves by structure
Time: Instruction time for this lesson: 90 minutes plus presentations at a later date.
Resources:
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AgriScience Lesson Plan Library, Unit C, Problem Area 4, lesson 2
AgriScience Fundamentals and Applications, Third Edition, Cooper and Burton
Principles of Field Crop Production, Fourth Edition, Martin, Waldren, and Stamp
Biology; The Dynamics of Life, Glencoe
Tools, Equipment, and Supplies
One copy, per student, of all slides from PowerPoint. (Use these as notes packet)
Projector or overhead
White Board
Key Terms
Photosynthesis
Phototropism
Stomata
Unit 3, Lesson 8, Leaf Structures and Functions
Guard Cells
Cuticle
Upper Epidermis
1
Lower Epidermis
Midrib
Lamina
Petiole
Stipule
Lamina
Ligule
Auricle
Sheath
Leaf Margin
Leaf arrangement
Palisade Mesophyll
Vascular bundle
Xylem
Phloem
Spongy mesophyll
Palmately Compound
Pinnately Compound
Bipinnately Compound
Alternate
Whorled
Opposite
Interest Approach
Project slide number 10 on white board or screen (last slide). Students are asked to identify the
plant simply by its leaves. This will encourage students to think about the different methods used
to classify crops as well as getting them to think about leaf formation and structure.
Do we have any agronomy majors in the classroom? If so, I will ask you to identify the crops or
trees that I am projecting on the board at this time. Is there anyone in the classroom who can tell
me the names of sample 1,2,3 and 4?
Allow students to take guesses. #1 is Maple, #2 is corn, #3 is wheat, and #4 is sunflowers
Great job! Some of you may have known a few of them, but not all. In this exercise, I wanted
you to see that in many cases, plants can be identified simply by their leaves. We are going to
use the leaf for the rest of the class today, as we understand why leaves are needed and how their
structure allows them to get the job done.
Summary of Content and Teaching Strategies
Objective 1. Understand the functions of a leaf
Hand out notes packets, which should include copies of slides 1-10. Project slide number 2 as
students follow along in their notes packet.
What is the function of a leaf?
Allow answers from class, should include the ideas of photosynthesis and transpiration.
You are correct, and you are all on the right track! The function of a leaf is actually very simple,
and it’s to assist with photosynthesis. Remember, photosynthesis is the creation of food by the
plant. Photosynthesis requires sunlight, which means that leaves are actually responsible for
absorbing that sunlight. Leaves have a built-in mechanism that allows them to twist and turn as
the angle of the sun changes throughout the day. Has anyone ever driven past a field of
sunflowers early in the morning and seen them facing one direction, and then driven past the
same field early in the afternoon and noticed them facing another direction? The ability of a leaf
Unit 3, Lesson 8, Leaf Structures and Functions
2
to do that is called phototropism.
Students will complete the following definitions in their notes packet, slide 2, as you read the
definitions.
• The most important function of the leaf is to manufacture food for the plant by using light
energy
– Photosynthesis:
– Phototropism:
Photosynthesis is the process by which plants trap energy from sunlight with
chlorophyll and use this energy to turn carbon dioxide and water into simple
sugars (food).
Phototropism is the ability of leaves to change their angle to better absorb the sunlight.
Objective 2. Understand the internal structure of a leaf
Project slides 3 and 4 for this objective.
Now that we understand to function of a leaf, our next task is to understand how each component
works inside that leaf to help photosynthesis happen. If we were to take a knife and cut a square
out of a leaf, and then magnify each horizontal layer, we would see something similar to the
picture you see on the board. The leaf actually has a number of horizontal layers that get
squished together like a sandwich to form an entire leaf structure. We are going to take some
time to discuss the function of each of these structures. As I give you the definitions, capture
them in your notes.
As you discuss each structure, point to it on the picture so students can see the shape that it’s in.
The same graphic is found on slides 3 and 4.
Stomata: Openings in the cuticle of a leaf to allow exchange of gas and water in photosynthesis
and transpiration.
Guard Cells: Cells that control the opening and closing of the stomata.
Cuticle: Protective, waxy coating on the outer surface of the epidermis, important in reducing
water loss.
Upper Epidermis: Upper-most layer of cells in a plant that protects all other cells.
Lower Epidermis: Lower-most layer of cells in a plant that protects all other cells.
Palisade mesophyll: Photosynthetic tissue of leaf, made of column-shaped cells.
Vascular Bundle: Cells joined together to make “cord”, houses xylem and phloem.
Xylem: Vascular plant tissue that transports water and minerals from the roots up.
Phloem: vascular plant tissue that transports sugars (food) from the leaves to the rest of plant.
Spongy Mesophyll: Photosynthetic tissue of leaf, made of loosely-packed, irregular shaped
cells.
Objective 3. Understand the external structure of a leaf
Project slide #5. Students will copy the definitions as you go over them verbally.
Unit 3, Lesson 8, Leaf Structures and Functions
3
Great job so far! At this point, I will have you turn to slide 5 in your notes packet. Having
discussed the internal components of a leaf, we are now going to study the outside of a leaf. As I
project this slide, complete the definitions on the right side of the paper.
Project slide 5.
Define or list the functions of each of the following external leaf components:
• Midrib: Center vein of leaf blade.
• Lamina: Blade of leaf
• Petiole: Small stem connecting leaf blade to rest of plant.
• Stipule: Two small leaves at
the base of the
petiole.
• Lamina: Blade of grass leaf
• Ligule: Site of connection for lamina
• Auricle: Connection point for sheath
• Sheath: Portion of leaf wrapped around stem.
Objective 4. Identify the different types of leaves
Project slide 6. Students already have the definitions written on their papers.
First of all, there are two major types of leaves, and those include the grass plants and the broadleaf plants. As you can see from the definitions and the pictures, grasses have long, slender
leaves with all the veins running in the same direction. On the other hand, broad-leaf plants have
veins that from nets that run out from the center midrib.
• Parallel-Veined Leaves: Grasses, have veins that run parallel to each other and are joined
by inconspicuous tiny veins.
• Net-like veined leaves: a few prominent veins with a large number of minor veins. Built
like spider webs, out from midrib. Includes all crops other than grasses.
To take it one step farther, we can identify a leaf by its overall shape, margin, tip, and base. A
leaf margin is the edge of the leaf.
Project slide 7.
There are over 20 different leaf shapes, eight types of leaf margins, eight tips, and eight bases.
Because we only have one day to complete this lesson, we will only be able to focus on the leaf
arrangement, as seen on slide 7. Leaf arrangement is referred to as location of the leaves on a
stem.
On slide 8, you are going to define the leaf arrangements in your own words. Be sure to include
the number of leaves coming from a single point on a stem, whether leaves are on the same side
Unit 3, Lesson 8, Leaf Structures and Functions
4
of the stem, and so on. I went ahead and define the first three terms for you, so when I say
“define”, you will have 3 minutes to create the next three definitions. Define!
•
•
•
•
•
•
Palmately Compound: Blade divided into leaflets, , leaflets coming from one point and
only dividing once.
Pinnately Compound: Blade divided into leaflets, leaflets coming from more than one
point, dividing again.
Bipinnately Compound: Blade divided inot leaflets, leaflets coming from more than one
point, dividing two more times.
Alternate: (suggested) One leaf present at each point on the stem.
Whorled: (suggested) Three leaves present at each point on the stem.
Opposite: (suggested) Two leaves present at each point on the stem.
When time is up, go over all answers with students as you project slide 7 and go over the
answers to terms on page 8.
Review/Summary
Place students into pairs of your choice. They are going to work together to complete the
“Internal Leaf Structure Assignment”, located at the end of the slide show. They are going to
create their own semi-edible leaf using food or other things found in their house (Saran wrap,
Twizzlers, rice, etc.). Choose the date of the presentations ahead of time, and have them write
the date on the assignment. I would suggest giving them at least a week to meet with their
partners, create their presentation, and build their leaf. I would also suggest giving them one
day in class to work on the project. Give them the a portion of the class time today to get
organized.
Follow along on the last page of your handout with me. This is your assignment. You will work
in partners, and the groups are as follows…… Your job is going to be creating a leaf in 3-D
using any materials you can think of.
In order to help you understand the internal structure of a leaf, you are going to create your own
leaf. The following are some guidelines. Presentations will take place on _______.
1. “Leaf” must be in actual leaf shape.
2. Inner “leaf” structure must be made of at least five edible components (Twizzlers, rice,
etc.)
3. “Leaf” must include the following: Cuticle, upper epidermis, palisade mesophyll,
vascular bundle, xylem, phloem, lower epidermis, spongy mesophyll, guard cells, and
stomata.
4. Must work with a partner.
5. All presentations must be completed on assigned date.
6. Presentations will be graded on:
Creativity
Accuracy
Description of structure functions
Unit 3, Lesson 8, Leaf Structures and Functions
5
Inclusion of all structures
Application
Extended classroom activity:
 Have students label a grass plant, from roots to the parts of the leaves. Include this
diagram in their notebooks.
 If resources allow, bring in a number of plant leaves to categorize and identify.
 Teach a lesson in taxonomy classification and scientific keys to encourage students to
classify plants by type.
FFA activity:
 Encourage students to participate in the Range Judging CDE, whereby then will
identify plants by their leaf shape, size, and formation.
SAE activity:
 Encourage students with nursery SAE’s to learn as many potted plants and trees as
possible.
Evaluation.
See Attached Evaluation. Use it as an open book review, as there is a lot of information
in this lesson.
Answers to evaluation
1. Phototropism: Ability of a leaf to change directions with the sun
2. Stomata Openings in the cuticle of a leaf to allow exchange of gas and water
in photosynthesis and transpiration.
3. Guard Cells: Cells that control the opening and closing of the stomata.
4. Cuticle: Protective, waxy coating on the outer surface of the epidermis,
important in reducing water loss.
5. Upper Epidermis: Upper-most layer of cells in a plant that protects all other
cells.
6. Lower Epidermis: Lower-most layer of cells in a plant that protects all other
cells.
7. Palisade mesophyll: Photosynthetic tissue of leaf, made of column-shaped
cells.
8. Vascular Bundle: Cells joined together to make “cord”, houses xylem and
phloem.
9. Xylem: Vascular plant tissue that transports water and minerals from the
roots up.
10. Phloem: vascular plant tissue that transports sugars (food) from the leaves
to the rest of plant.
11. Spongy Mesophyll: Photosynthetic tissue of leaf, made of loosely-packed,
irregular shaped cells.
12. Midrib: Center vein of leaf blade.
13. Lamina: Blade of leaf
14. Petiole: Small stem connecting leaf blade to rest of plant.
15. Stipule: Two small leaves at
the base of the petiole.
Unit 3, Lesson 8, Leaf Structures and Functions
6
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
Lamina: Blade of grass leaf
Ligule: Site of connection for lamina
Auricle: Connection point for sheath
Sheath: Portion of leaf wrapped around stem.
Palmately Compound: Blade divided into leaflets, , leaflets coming from one
point and only dividing once.
Pinnately Compound: Blade divided into leaflets, leaflets coming from more
than one point, dividing again.
Bipinnately Compound: Blade divided inot leaflets, leaflets coming from
more than one point, dividing two more times.
Alternate: (suggested) One leaf present at each point on the stem.
Whorled: (suggested) Three leaves present at each point on the stem.
Opposite: (suggested) Two leaves present at each point on the stem.
Unit 3, Lesson 8, Leaf Structures and Functions
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Unit 3, Lesson 8, Evaluation
Name:
Date:
Define the following terms
1. Phototropism:
2. Stomata
3. Guard Cells
4. Cuticle
5. Upper Epidermis
6. Lower Epidermis
7. Palisade mesophyll
8. Vascular bundle
9. Xylem
10. Phloem
11. Spongy mesophyll
12. Midrib
13. Lamina
14. Petiole
15. Stipule
16. Lamina
17. Ligule
18. Auricle
19. Sheath
Unit 3, Lesson 8, Leaf Structures and Functions
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20. Leaf Margin
21. Leaf arrangement
22. Palmately Compound
23. Pinnately Compound
24. Bipinnately Compound
25. Alternate
26. Whorled
27. Opposite
Unit 3, Lesson 8, Leaf Structures and Functions
9