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Growth Control in Plants

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Positive Phototropism Negative Geotropism Negative Phototropism Positive Geotropism Lets review the homework from last lesson Using Plant Hormones In groups of ... – PowerPoint PPT presentation

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Title: Growth Control in Plants


1
Growth Control in Plants
2
Learning Objectives
  • Explain how plant growth is controlled by
    hormones.
  • Describe how these hormones can be used to change
    plant growth.

3
  • Numbered Heads Together Revision
  • Number based on shoe size
  • Smallest Shoe Person 1
  • Biggest Show Person 4
  • Write down your ideas to answer the question
  • Stand up when you are ready to share with your
    group
  • As a group decide on 1 answer for the whole
    group
  • Sit down when ready
  • Random number to be called on to answer.
  • SO EVERYONE MUST BE READY TO ANSWER!

4
Chemical Messengers
Coordinate systems
Oestrogen
What is a Hormone? What do hormones do?
Insulin
Glucagon
Testosterone
Can you think of any examples?
ADH
HGH
Causes a change in how the body works
Travel in the blood, secreted by glands
Control Growth, blood sugar, sex development,
mood, metabolism.
5
Hormones in Plants What do hormones control in
plants?
Anything Relating to Growth! Roots and Shoots
Seed Germination Leaf Fall Disease
Resistance Fruit Formation and Ripening
Flowering Time Bud formation
6
Sensitivity Responding to the environment
  • Plants respond to stimuli to
  • Avoid stress
  • Avoid being eaten
  • Enhance survival
  • Improve chances of having offspring
  • The way a plant grows is controlled by the
    hormones
  • These are sensitive to the environment can make
  • adjustments to help plant survive

7
Tropisms
  • Directional growth response
  • Plants grow in a certain direction in response to
    a stimulus

Lets Explore Tropisms!
8
Use your observations from the following to
complete the table
Tropism Stimulus Response
Phototropism
Geotropism
Chemotropism
Thigmotropism
Hydrotropism
9
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10
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11
Important minerals in soil
12
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13
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14
Review your learning partners work to be sure
they have completed the table
Tropism Stimulus Response
Phototropism
Geotropism
Chemotropism
Thigmotropism
Hydrotropism
15
Task Draw a Diagram for Each Tropism
  • Example Hydrotropism

16
Copy and Complete
Tropism is how plants respond to their
environment. When sunlight is the stimulus this
is known as ______tropism. Positive phototropism
is where the plant grows _______the light. This
happens at the _____tip. ________ phototropism is
where the plant grows away from the______, this
happens at the_____. When gravity is the stimulus
this is known as ______tropism. ________Geotropism
is where the plant grows in the direction
of_______. This happens at the roots. Negative
___tropism is where the plant grows apposing
gravity, this happens at the _____tips. .
17
What Causes Tropisms?
  • Hormone ? Auxin
  • Auxin promotes growth

18
What Causes Tropisms?
  • Shoots of plants contain Auxin
  • A) When light shines directly above tip, growth
    is equal towards light source

19
What Causes Tropisms?
  • B)When light shines from an angle
  • Sunlight breaks down Auxin
  • So the side of the tip that has the most direct
    sunlight will have the least amount of Auxin
  • Area of the plant that is more shaded will have
    more Auxin
  • More growth on shaded side
  • Lop sided growth plant bends towards light

20
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21
Tropisms Montage!
22
Match the correct scenario to the tropism.
Roots Growing Downwards into Dark Soil
Positive Phototropism
Negative Geotropism
Roots Growing Upwards towards light.
Shoots Growing Upwards
Negative Phototropism
Roots Growing Downwards.
Positive Geotropism
23
Lets review the homework from last lesson
24
Using Plant Hormones

In groups of four, use your homework to make a
list of how plant hormones are used in agriculture
25
Weed killers
  • Selective weed killers kill some plants but not
    others.
  • This can be useful for getting rid of dandelions
    in a lawn without killing the grass, or getting
    rid of thistles in a field without killing the
    wheat plants.
  • The selective weed killer contains growth hormone
    that causes the weeds to grow too quickly.
  • The weed killer is absorbed in larger quantities
    by the weeds than the beneficial plants

26
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27
Agent Orange
28
Rooting Powders
  • Powder contains auxins
  • Cuttings are dipped in powder
  • Promotes root growth

29
Fruit Ripening
  • Ethene promotes fruit ripening
  • Naturally given off by ripe fruit
  • Converts starch into sugar

30
Plenary Using Plant Hormones
  • Match the sentences

Auxiins cause
upwards
from cell to cell in solution
Hormone rooting powder
Cuttings can produce
clones of the parent plant
Hormone weed killers
cell growth
Shoots grow
downwards
Flowering can be induced
a source of light
to ripen fruit
Plant hormones can be used
causes roots to grow
Roots grow
by the use of plant hormones
Auxins can diffuse
are not usually harmful to animals
Plants grow towards
31
Using Plant Hormones
Hormone rooting powder
causes roots to grow
Auxiins cause
cell growth
Cuttings can produce
clones of the parent plant
Hormone weed killers
are not usually harmful to animals
Shoots grow
upwards
Flowering can be induced
by the use of plant hormones
Plant hormones can be used
to ripen fruit
Roots grow
downwards
Auxins can diffuse
from cell to cell in solution
Plants grow towards
a source of light
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