Download Lesson Plan - Colorado FFA

Colorado Agriscience Curriculum
Section:
Plant & Soil Science
Unit:
Environmental Factors
Lesson Number:
2
Lesson Title:
Light Affects of Plant Growth
Colorado Agricultural Education Standards:
Content Standard 11/12.1: The student will demonstrate/communicate an understanding of
current issues relating to agriscience.
Content Standard 11/12.2:
The student will gain practical experience in agriscience through
laboratory and field work.
Content Standard 11/12.4:
The student will demonstrate an understanding of physiological
processes in agriculturally important plants.
Content Standard 11/12.5:
The student will demonstrate team skills through problem-solving
activities in agriscience.
Colorado Science Standards:
1.03; 3.13; 3.15
Student Learning Objectives (Enablers)
As a result of this lesson, the student will …
Objective #1 Determine how light can affect plant growth.
Objective #2 Identify signs of light stress in plants.
Time: Instruction time for this lesson: 50 minutes.
Resources:
 Plants & Animals Biology and Production (Lee, Biodo, Hutter, Westrom, Patrick,
authors)
 Biology The Dynamics of Life (Briggs, Gregg, Hagins, Kapicka, Lundgren, Rillero,
National Geographic Society, authors)
Tools, Equipment, and Supplies
Radish Seeds
Potting soil
Small Styrofoam cups
Ruler
Graph paper
Small boxes
Red, Green, and Clear transparent plastic wrap
Three houseplants, such as Pathos
Heat lamp
Key Terms. The following terms are presented in this lesson and appear in bold italics:
Photoperiodism
Short-day Plants
Long-day Plants
Day-neutral Plants
Forcing
Etiolation
Light Intensity
Light Duration
Color
Interest Approach
Place three house plants, one in filtered direct light, one in a dark cupboard and one with
supplemental light, such as a heat lamp hung high enough to provide light but not increase
temperature dramatically. Have students hypothesize what will happen to the color of the plant.
Record daily observations on each of the houseplants under treatment for the remaining of the
unit, but for no less than 5 days.
Summary of Content and Teaching Strategies
Objective 1. Determine how light can affect plant growth
Utilize PowerPoint to have students take notes on important information.
I. How does light affect plant growth?
Plant life depends on light energy for food production through the processes of photosynthesis.
Light itself is the transfer of energy in the form of radiation. Plants convert this radiant energy to
a form of chemical energy. There are three key aspects of how light affects plant growth. They
are color, duration, and intensity.
A. Color
Visible light is a small segment of all the radiant energy given off by the Sun. X-rays,
gamma rays, ultraviolet rays, microwaves, and radio waves are other forms of radiant
energy. The different rays of radiant energy have been measured on the basis of their
wavelengths and placed on an electromagnetic spectrum.
Sunlight contains a blend of visible colors. We can see the colors when light passes
through a prism. The prism separates the colors. The phenomena of separating the colors
of visible light occur naturally through rainbows. Each color has a slightly different
wavelength. Light is absorbed or reflected by objects. Objects that appear black absorb
all colors of visible light. White objects, on the other hand, reflect all the colors of visible
light. If an object absorbs all of the colors but green, it will reflect green. This is the case
with green leaf plants. Because green wavelengths are reflected from the leaves, they
have little effect on plant growth. The colors that have the greatest influence on plant
growth are blue and red. In general, blue wavelengths affect photosynthesis, and red
wavelengths influence flowering and growth.
B. Light Duration
Plants are responsive to the length of exposure to light. A mechanism within plants
detects day lengths. The length of the days is known to play a role in different phases of
plant growth. Some of these phases are seed germination, enlargement of leaves,
development of buds, and flowering. A plant’s response to Light Duration is called
Photoperiodism.
Different plants respond differently to Light Duration. Chrysanthemums and poinsettias
are two plants that will begin to flower in the fall when the day lengths naturally get
shorter. They are said to be Short-day Plants. Radish and lettuce plants flower as days
lengthen in the summer. They are termed Long-day Plants. A third group of plants in
unaffected by day length and are classified as Day-neutral Plants.
Forcing is bringing a plant to a certain stage outside its normal season. This is
accomplished in growing structures with artificial light. Greenhouses are the common
structures for getting a plant to grown outside its natural cycle.
C. Light Intensity
The third effect light has on plants involves intensity or brightness. Intensity of light
depends largely on the angle of the Sun, clouds, and the dust in the atmosphere. Light
Intensity is greater in the summer months when the Sun is higher in the sky. Where
artificial light is provided, the source of light and the distance from the light source to the
plants are important. Different plant species have evolved to survive in conditions where
the intensity of light varies. The major agricultural crops produce the highest yields when
they receive full sunlight. Crops receiving bright sunlight will have an elevated rate of
photosynthesis and will produce more food. Other plants like impatiens are adapted to
shady environments and will suffer if placed in full sun.
Objective 2. Identify signs of light stress in plants
Show PowerPoint on signs of light stress in plants. Have students take important notes
on the content information provided below.
Plants will show symptoms of having inadequate light or too much light. A plant with adequate
light will have a compact shape and have excellent color. One that is experiencing low light
levels will stretch for light source; a condition known as etiolation. The leaves are also smaller
than normal and lighter in color. Plants that receive too high of light intensity may take on a
bleached look as chloroplasts are killed. Excessive light may cause of plant tissues.
Review/Summary.
Use “Graphic Artist Moment.” This can be used in two ways to review content. First, by
having students look up symptoms of plants with too severe light intensity and too low
light intensity, provide students with plain paper and colored pencils and draw pictures
of light damage on leaves. Second, have students create connections to the key words in
this lesson plan and then draw a graphic description of that word. Have students draw,
utilizing symbols, the words to help them remember the key phrases and their meaning.
Review “Graphic Artist Moment” in Strategies for Great Teaching by Reardon and
Derner for further details.
Students, don your drawing tools! You will need a plain piece of paper and colored
pencils for today’s summary activity. Having looked up the symptoms of light intensity
damage, and having completed this experiment ourselves, draw pictures of plants
showing too much light intensity and too low of light intensity. Then pick out key words
in this unit, draw them utilizing symbols as a way to reinforce their meaning. Use words
instead of letters to create a vocabulary list. Ready? When I say Picasso, draw! Picasso!
Application
Extended classroom activity:
Complete lab listed below (from Troy Schools online Labs) to determine the impact of
light on plants.
Environmental Factors: Light Effect on Plant Growth
Introduction:
Living things in an environment respond to other factors in that environment. This activity
enables the student to see how light might effect the growth response of a plant.
Materials:

Radish Seeds

Potting soil

Small Styrofoam cups

Metric ruler

Graph paper

Small boxes

Red, Green, and Clear transparent plastic wrap
Procedure:

Divide the class into working groups and give each group an identifying number.

Each group will prepare 3 pots with potting soil.

Students will plant 15 seeds just below the surface of the soil in each pot. Water equally.

Allow 3 days for germination and initial development.

After the three day period, place the three pots next to each other. Select 5 plants from
each pot by weeding out the rest. Make sure all the remaining plants in the pots are
the same size.

At the end of this selection process you should have 3 pots with 5 plants in each.

Label each pot: 1A, 1B, and 1C.

Measure the height of each plant in centimeters and record the average height for each pot
in the chart below.

Place 1A in a box and cover it with red transparent wrap.

Place 1B in a box and cover it with green transparent wrap.

Place 1C in a box and cover it with clear transparent wrap.

Place the boxes in the sunlight and measure the growth of the plants for 5 days. Record
your data in the chart below.

Graph the data after the 5 day trial period.
Table 1
aaaaDayaaa Pot A Pot Baa Pot C
1
2
3
4
5
FFA activity:
Plants respond to their environment and to changes to their environment. Organizations
respond to their environment and to adequate leadership in their organizations. Have
students draw parallels between correct light and adequate environment to plant growth
and correct attitudes and environment to a healthy FFA Chapter.
SAE activity:
Great production in a student’s SAEP depends on adequate record keeping. Have
student monitor crop production growth and record daily cloud cover (and its relation to
temperature). Have students compare growth rates to light intensity in their programs.
Evaluation.
Have student write up a lab report on their observations of the interest approach and the
extended classroom activity. The lab report should include a hypothesis, all data
collected and a summary of results, including an explanation for the results noted.
Evaluate understanding of lesson concepts according to the completeness and accuracy
of information provided in the write-up.