Plant Hormones

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Plant Hormones
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Plant sensitivity
Can you explain what is happening. Click to
reveal the answer.

• The animation shows the growth of a young shoot
  towards the light.

3
Plant sensitivity
Can you explain what is happening. Click to
reveal the answer.
The animation shows the growth of a young shoot
towards the light.
The auxins diffuse down the shoot and cause
cells behind the tip to elongate. There is
greater growth on the shady side of the young
shoot. The shoot grows towards the light - this
is known as PHOTOTROPISM.
Auxins are produced in the shady side of the tip.
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Experiments

• Predict what will happen in each of these
  experiments.
• Click on each shoot to show its growth response.

Normal young shoot
Tip removed from shoot
Tip covered with a foil cap
Tip removed and replaced with an agar block
containing auxin
Tip removed and replaced on one side with a small
agar block containing auxin
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
Fresh fruits are shipped around the world. Plant
hormones are used to slow the ripening of the
fruit, so they are just ripe as they reach the
supermarket.
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
When a gardener takes cuttings from a plant, the
base of each cutting is first dipped into a
rooting compound to stimulate the growth of
roots. Many rooting compounds contain auxin.
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
10
Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
Auxins can be sprayed onto flowers so that the
fruits develop without pollination or
fertilisation. These fruits are seedless.
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Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
12
Applications of plant hormones
Can you explain the use of hormones in each
diagram. Click to reveal the answer.
Weeds have broader leaves than the grass on a
lawn. The weeds will take up more auxin than the
grass when the lawn is sprayed.
Auxins can be used as herbicides.
The weeds will grow too quickly and die.
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True or false?
Which of the following statements is true? Click
to reveal the answer.
Gardeners prune to create bushier plants. This
is because pruning causes plants to create... 1.
more auxin and this enables side shoots to
grow 2. less auxin and this enables side shoots
to grow 3. more auxin and this inhibits side
shoots from growing 4. less auxin and this
inhibits side shoots from growing
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True or false?
Which of the following statements is true? Click
to reveal the answer.
Gardeners prune to create bushier plants. This
is because pruning causes plants to create... 1.
more auxin and this enables side shoots to
grow 2. less auxin and this enables side shoots
to grow ? 3. more auxin and this inhibits side
shoots from growing 4. less auxin and this
inhibits side shoots from growing
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True or false?
Which of the following statements is true? Click
to reveal the answer.
Young roots always grow downwards. This is
because roots are... 1. positively phototropic 2.
negatively hydrotropic 3. positively geotropic
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True or false?
Which of the following statements is true? Click
to reveal the answer.
Young roots always grow downwards. This is
because roots are... 1. positively phototropic 2.
negatively hydrotropic 3. positively geotropic ?
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Plant Hormones

• The End

R Heppell 2000 Beauchamp College Biology
Department