5.4.4

Required Practical - Plant Hormones

Test yourself

Light Investigation

The effect of light on seedlings can be demonstrated with mustard or cress seeds. Complete the following steps:

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Step 1

  • Place the seeds in petri dishes with damp cotton wool, and leave them in a warm place to germinate (develop).
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Step 2

  • Randomly divide the petri dishes into three groups and assign each group to one of the following light conditions:
    • Full sunlight in a windowsill
    • Darkness
    • Partial light
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Step 3

  • Measure the height of each plant every day for a week.
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Step 4

  • Draw and label biological drawings to show the effects.
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Step 5

  • The independent variable is the lighting conditions.
  • The dependent variable is the growth of the plant.
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Step 6

  • Phototropism can also be demonstrated by placing a seedling in a container that is open only on one side.

Uses of Plant Hormones

People use plant hormones to control the growth of plants for agricultural (farming) and horticultural (gardening) purposes:

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Auxins

  • Auxins are used as weed killers as they can initiate (start) such rapid growth that the weeds use up all of their resources and die.
  • They are also used as rooting powders (growth supplement) and to promote growth in tissue culture.
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Ethene

  • Ethene is used in the food industry to control the ripening of fruit during storage and transport.
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Gibberellins

  • Gibberellins are used to promote flowering, increase fruit size, and initiate (start) seed germination.

Jump to other topics

1Cell Biology

1.1What's in Cells?

1.2Cell Division

1.3Transport in Cells

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

5.1Homeostasis

5.2The Human Nervous System

5.3Hormonal Coordination in Humans

5.4Plant Hormones

6Inheritance, Variation & Evolution

7Ecology

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