Download Hormones in Plants - Noadswood Science

Plant Hormones
L.O: To understand how plants use
hormones to respond to light, gravity
and moisture
What is the stimulus and response
in a venus fly trap and mimosa
plant?
Why do Sunflowers track the Sun?
Can you write a hypothesis to
explain this observation?
Why do roots always grow DOWN?
Can you write a hypothesis to
explain this observation?
Why do plants deprived of light do this?
Can you write a hypothesis to explain this
observation?
Plant given
plenty of
light
Plant placed
in a dark
environment
Our hypotheses…
•
•
•
•
Shoots grow towards the light.
Shoots grow against the force of gravity
Roots towards moisture.
Roots grow in the direction of the force of
gravity.
Tropisms
 “Directional growth response”
 Plants grow in a certain direction in
response to a stimulus
Let’s Explore Tropisms!
A growth movement towards a stimulus is called a
positive tropism.
A growth movement away from a
stimulus is called a negative tropism.
Use your observations from the
following to complete the table
Tropism
1. Phototropism
2. Geotropism
(gravitropism)
3. Chemotropism
4. Thigmotropism
5. Hydrotropism
Stimulus
Response
Important minerals in soil
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
Phototropism experiment
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Do plants have hormones too?
Like humans, plants use hormones,
(chemical messengers)
to control their development.
Hormones produced by plants
control growth, flowering and
fruit ripening.
The growth of shoots and roots is
controlled by a group of hormones
called auxins. These chemicals are
produced in the tips of the shoots
and roots.
What environmental stimuli might
cause a plant to produce auxins?
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Hormones and phototropism
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Discovery of auxins
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Which way up?
How do plants always grow the right way up?
Plants respond to gravity to grow in the right direction.
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Hormones and geotropism
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Plant hormones
In the shoot the growth hormones
collect on the ____ side, causing it to
_____ more there and bend _____ away
from the force of ______.
Hormones STIMULATE growth in
SHOOTS.
In the root hormone also collects on the
lower side, but this time it _____ _____
growth, causing the root to grow
_______ towards gravity.
Hormones RETARD growth in ROOTS.
Words: upwards, downwards, slows down, lower, grow, gravity
Weed killers
• Selective weed killers kill weeds but not
other plants. Eg kill dandelions but not grass
• 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
Agent Orange
Rooting Powders
• Powder contains auxins
• Plant cuttings are dipped in powder
• Promotes root growth
Fruit Ripening
• Ethene – promotes fruit ripening
• Naturally given off by ripe fruit
• Converts starch into sugar
Plenary
Using Plant Hormones
Auxiins promote Match the sentences
upwards
Hormone rooting powder
from cell to cell in solution
Cuttings can produce
clones of the parent plant
Hormone weed killers
cell growth
Shoots grow
downwards
Flowering can be induced
a source of light
Plant hormones can be used
Roots grow
Auxins can diffuse
Plants grow towards
to ripen fruit
causes roots to grow
by the use of plant hormones
are not usually harmful to animals
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