LAB 0007B
Chemical Effects on Plants
LAB OBJECTIVES
Describe the benefits of using growth regulators in plants
Understand that chemicals can regulate a plants growth
Discuss how using growth regulators to control the size of flowering plants
Differentiate between plant growth regulators and plant growth hormones
PURPOSE:
This lab is designed to help students understand that plant growth can be regulated by the use of
growth regulators or chemicals.
PRELAB:
The following items should be defined before starting this lab . Asisic acid, Auxin, Cytokinin,
Ethylene, Gibberellin, Hormone, Senescence Synthetic, and 2,4-D.
LAB BACKGROUND:
There are many things in the environment that can control plant growth. Some of them are how
much light or darkness are applied to the plant or the temperature surrounding the plant.
Chemicals are also an important way of controlling plant growth. Some of these are called plant
growth regulators. Today in lab we are going to focus on plant growth regulators and how they
effect plants.
Plant growth regulating compounds are divided into two groups, natural (hormones) and synthetic
(man-made). Both natural or synthetic growth substances regulate of influence cell division, cell
differentiation, root and shoot growth, flowering, senescence (plant aging). Both the natural
hormone compounds and the synthetic substances induce similar plant responses. These
substances are usually separated into groups as prooters or inhibitors of plant growth. Auxin,
gibberellin, cytokinin, absisic acid, and ethylener represent major classes of plant growth
regulators.
Plants manufacture organic compounds that regulate growth. These plants produce natural
compounds, called hormones, that can inhibit or produce plant growth. Hormones are chemical
messengers that are produced by plant tissue and then transported to other plant parts where they
control plant growth.
Synthetic plant growth regulators are applied to regulate or control plant growth. Some of these
chemicals stimulate, reduce, or stop the growth of shoots and branches. Other growth regulators
delay or prevent flower bud growth and development.
MATERIALS:
3 oats, 3 barley, 3 rye, and 3 rice seeds
6 bean seeds
6 flower pots
Soil
Water
2,4-D amine
Household detergent
1 paint brush
1 pair of plastic gloves
PROCEDURE:
CAUTION!!!!!!!!!! Do not get chemicals on or near the plants you want to keep. Wash
your hands after using chemicals.
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Select 12 cereal grass seeds, 3 oats, 3 barley, 3 rye, and 3 rice. Also select 6 bean seeds.
Obtain 6 flowerpots.
Fill the container with a ½ inch of soil from the top.
Plant 6 bean seeds 3/4 to an inch deep in two pots. 3 seeds to a pot.
Plant 12 grass seeds 1/4 to ½ inch deep in four pots. 3 seeds to a pot.
Wet the soil until the water runs out the hole in the bottom.
Grow the plants until they are 6 inches high. Water as needed to keep the soil moist.
PUT GLOVES ON BEFORE WORKING WITH CHEMICALS!!! Add three drops of
2,4-D amine to a cup of water. Add one cup of household detergent to this mixture and
stir.
Paint the solution on the bean and grass plants with a paint brush.
Observe each day for three weeks.
Record changes that take place to the plants appearance.
NOTE: growth regulators in this activity refer to chemicals only.
OBSERVATIONS:
Place your observations under the spots below. Remember to observe your plants for three weeks
and record any changes.
DATE
PLANT
OBSERVATION
CONCLUSIONS:
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What does natural and synthetic growth substances regulate or influence?
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On what day did you apply the chemical?
DATE:
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DATE:
When did the bean plants start to die?
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How long did it take to kill the bean plants?
# days:
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What effect did the 2,4-D amine have on the grass?
Oats?
Barley?
Rye?
Rice?
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How would you have explained the difference? What practical application would this
selective killing effect have on growing plants?