Colorado Agriscience Curriculum
Section:
Plant & Soil Science
Unit:
Plant Physiology and Growth
Lesson Number:
5
Lesson Title:
Plant Hormones and Their Effects
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 overall functions of hormones
2. Identify the major types of plant hormones
3. Analyze the different types of plant responses
Time: Instruction time for this lesson: 50 minutes
Resources:



Biology; The Dynamics of Life, Glencoe
http://www.biologycorner.com/worksheets/planthormones.html
http://www.chadevans.co.uk/asite/gcse/b02/t12.html
Tools, Equipment, and Supplies
One Needed of the following per pair of students (available from Wards Science Cat.):
2 Petri Dishes
Damp Paper Towels
8 Little Marvel Pea Seeds
8 Alaska Pea Seeds
4 Small Pots for transplanting seedlings
Cotton Swabs
Gibberellic Acid
Masking Tape
Permanent Marker
Unit 3, Lesson 5, Plant Hormones and Their Effect
1
Ruler
One Copy, per student, U3, L5, Lab (pages 6-8)
One copy, per student, U3, L5, Notes Worksheet (page 5)
White board with markers
Small candy bars for reward
One copy, per student, U3, L5, Evaluation (page 9)
Key Terms
Hormone
Auxin
Gibberellin
Cytokinin
Ethylene
Cytokinesis
Interest Approach
Write the following terms on the board: Paylean, Thyroxin, Somatotrophin, Ralgro, Oxytocin,
and Androgens.
I am going to give you a list of substances, or drugs that may be found in an animal or humans
body. Anyone that can tell me the function of one of these substances will win a mini candy bar
as a reward. Each term may be defined only once.
Allow students to take guess at what each of these substances do to the body. Hand out rewards
if the students get it right.
Paylean: Substance given to market hogs to minimize fat and maximize muscle
Thyroxin: Controls the body’s metabolic rate
Somatrotrophin: Accelerates muscle building in humans
Ralgro: Implant given to market steers or heifer to increase growth
Oxytocin: Releases milk in the pregnant or new mother
Androgens: Sexual development hormone in humans that stimulates production of testosterone
All of these substances have something in common. Can you tell me what it is? The answer is
that each of these are a type or brand of hormone. Some may be man-made, while others are
found naturally in the body. Our topic for today is going to be plant hormones, and the effect that
these have on the production of crop plants.
Summary of Content and Teaching Strategies
Objective 1 Understand the overall functions of hormones
Now that we understand and can name some common animal or human hormones, we need to
understand what a hormone is and how it works in organisms. As I project the next slide, capture
the definition on the notes worksheet I am handing out.
Unit 3, Lesson 5, Plant Hormones and Their Effect
2
Hand out notes worksheet for this unit. Project slide number 2 on the function of plant
hormones. Have students copy the definition onto their notes worksheet.
Functions of Plant Hormones:
Plant hormones are chemicals that are produced in one part of the plant
and transported to another part, where it causes a physiological change.
Ok, let’s review one more time! When I say plant hormones, you respond with “cause a
physiological change in plants” Do this as many times as needed until students remember the
definition of a hormone.
Objective 2 Identify the major types of plant hormones
Great job scientists! Just as we can take steroids to improve our growth, plants can take
advantage of both natural and man-made hormones to help improve their growth and
development. We are going to spend a couple more minutes discovering the different types of
hormones that plants can utilize. Although this may seem a little “out there”, and not relevant to
agriculture, be thinking about the different plant hormones that producers can apply to increase
their yield or better their product for a certain market. As I project these notes, be sure to write
them accurately on your notes worksheet.
Project slides 3-7. Each slide has a different type of plant hormones. Students should copy the
notes onto their worksheet.
I.
Types of plant hormones
There are four common types of plant hormones:
a. Auxins
b. Gibberellins
c. Cytokinins
d. Ethylene
II.
Description of Auxins
a. Auxins promote cell elongation.
b. It weakens the connections between the cellulose fibers in the cell wall,
which allow them to stretch and grow longer.
c. Auxins promote stem growth
III.
Description of gibberellins
a. Gibberellins also promote cell elongation.
b. Dwarf plants are often so because they cannot produce gibberellins
or can’t process it.
c. Farmers use it to enhance fruit formation.
IV.
Description of cytokinins
a. Cytokinins stimulate cell division (cytokinesis).
b. They produce more proteins by promoting mitosis.
c. Cytokinins are produced in the roots.
V.
Description of ethylene gas
a. Ethylene is a simple, gaseous compound composed of carbon and
hydrogen that speeds the ripening of fruit.
Unit 3, Lesson 5, Plant Hormones and Their Effect
3
b. Ethylene causes the cell walls to become soft and causes the fruit to
become sweet.
Objective 3 Analyze the different types of plant responses
Complete the lab at the end of the document (pages ). Resources must be located in advance, as
they aren’t all readily available.
Review/Summary
Use a Hieroglyphics e-moment to encourage students to draw what they remember from the
lesson. To assist with memory and the linking of the symbol to the term, make sure each icon is
different from the others. Students should draw what they think of when the terms hormones,
auxins, gibberellins, cytokinins, and ethylene gas are presented to them. Students should
complete the drawings on the back of the notes page and share their drawings with a partner.
Application
Extended Classroom:
 Complete the plant hormones lab with various crops common in your area, and discuss
potentials for improved crop growth.
 For those programs with a functioning greenhouse, further experiment with these
hormones and their effects on common houseplants.
FFA:
 Encourage students to become involved in the nursery/landscape CDE at the state level.
SAE:
 Encourage students with horticulture SAE’s to experiment with the various plant
hormones in order to discover whether or not their production could be increased.
Evaluation.
See page 9 of this document, could very well be completed orally to save paper since
there are few questions.
Answers to evaluation
1.
2.
3.
4.
Ethylene gas
Cytokinins
Gibberellins
Auxins
Unit 3, Lesson 5, Plant Hormones and Their Effect
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Unit 3, Lesson 5, Notes Worksheet
Name:
Date:
1. What is the function of plant hormones?
2. What are the four types of plant hormones?
3. Describe auxins.
4. Describe Gibberellins.
5. Describe cytokinins.
6. Describe ethylene gas.
Unit 3, Lesson 5, Plant Hormones and Their Effect
5
Unit 3, Lesson 5, Lab
Name:
Date:
Taken From: http://www.biologycorner.com/worksheets/planthormones.html
Materials Needed in Each Group:
2 Petri Dishes
Damp Paper Towels
8 Little Marvel Pea Seeds
8 Alaska Pea Seeds
4 Small Pots for transplanting seedlings
Cotton Swabs
Gibberellic Acid
Masking Tape
Permanent Marker
Ruler
Investigation of Plant Hormones
Introduction: Both plants and animals produce hormones that can regulate growth.
Gibberellins are a group of plant hormones that affect growth. The effects of these
hormones were first observed in the 1920s in rice plants that were attacked by a
fungus, these rice plants grew unusually tall. Scientists isolated the substance
responsible for the growth ( Gibberala fujikuroi ). Gibberellic acid is derived from this
chemical and is used to make plants grow taller.
Question: What is the effect of Gibberellic acid on the growth of normal and
dwarf pea plants?
Procedure
Little Marvel and Alaska Peas,
and Gibberellic acid can be
purchased from biological
supply companies (such as
Wards or Carolina)
First, take 8 pea seeds and set them in a petri dish with a
paper towel on both the base and the lid. Wet the paper
towels and leave undisturbed until germination occurs. You
may need to re-wet the paper towels if they become dry. (Make another petri dish as a
spare, in case something happens with your first batch). Label Petri dishes with your
group’s name. One will be empty, the other will have 8 seeds for germination.
After germination - record root and shoot length for each seedling. .After approximately
1 1/2 weeks after germination, transplant seeds to containers (put two seedlings in each
container and label with making tape, including group name and type of test in each
container.
Unit 3, Lesson 5, Plant Hormones and Their Effect
6
Apply Gibberellic acid to the four seedlings with the GA test by using a cotton swab apply to the leaves and the shoot tips of the seedlings after they have been
transplanted. You will need 4 pots each containing 2 -4 seedlings each (if one of them
dies, you can still use the data from the alternate.)
Record your data over a period of 8-10 days. You may also check with other groups to
get an average for each treatment. Complete the following chart (day 1 is first day of
germination):
Height
Day 1
Height
day 2
Height
day 3
Height
day 4
Height
day 5
Height
day 6
Height
day 7
Height
day 8
Alaska
Pea,
water, #1
Alaska
Pea,
water, #2
Alaska
Pea, GA,
#1
Alaska
Pea, GA,
#2
Little
Marvel,
water, #1
Little
marvel,
water, #2
Little
Marvel,
GA, #1
Little
Marvel,
GA, #2
Unit 3, Lesson 5, Plant Hormones and Their Effect
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Questions to be Answered:
1. Why was water applied to the 1st and 3rd pots?
2. Based on the graphs, which group had the fastest rate of growth?
3. Compare the growth of the Little Marvel Pea plants and the Alaska Pea plants with
and without the treatment of gibberellic acid.
4. Suggest real world applications for gibberellic acid.
Unit 3, Lesson 5, Plant Hormones and Their Effect
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Unit 3, Lesson 5 Evaluation
Name:
Date:
1.Which plant hormone is cited with ripening fruit?
2.Which plant hormone is cited with increasing plant size through cell division
(mitosis)?
3.Which plant hormone assists in growing dwarf plant varieties?
4.Which plant hormone assists with stretching the cells to allow the stem to grow?
Unit 3, Lesson 5, Plant Hormones and Their Effect
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