The document discusses growth substances in both plants and humans. In plants, growth substances like auxins, ethylene, gibberellins, cytokinins, and abscisic acid control processes like phototropism, fruit ripening, flowering, and seed germination. In humans, growth is regulated by hormones produced in endocrine glands like the pituitary, thyroid, and gonads. The pituitary is called the "master gland" as it controls other glands and produces growth hormone, which stimulates bone and tissue growth in children. Abnormal levels of growth hormones can cause diseases like dwarfism and gigantism.

1. X
IN
ANIMALS AND PLANTS
Module 4 Unit 11 Lesson 3
GROWTH SUBSTANCES
BEGIN

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IMPORTANT NOTE
In this slide presentation, you will examine
Module 4 Unit 11 lesson 3
Growth Substances in Living Things.
You can access these topics in the menu on
the right.
Read the objectives before exploring each
lesson.

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GROWTH SUBSTANCES IN LIVING THINGS
Introduction Plant Growth Substances Human Growth Substances
Module 4 Unit 11 Lesson 3

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INTRODUCTION
Among humans and other mammals
abnormality in growth, e.g. dwarfism and
gigantism, can occur. Why? What causes
those kinds of growth?
As fruits grow and mature they ripen
naturally. Can we cause ‘artificial’ ripening
of fruits? If so, how?
And, why do plant
shoots always grow
upwards to light?

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INTRODUCTION cont’d
What causes all of these growth changes?
As boys mature, they develop facial, pubic and
chest hairs and all female mammals normally
produce milk from breasts to feed their young.
Why do leaves grow old then fall off plants?

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OBJECTIVES
When you finish this section on GROWTH
SUBSTANCES, you should be able to:
1. name some plant growth substances.
2. describe the action of auxins in causing
growth changes in plants.
3. give examples of the use of plant growth
substances in agriculture.
4. discuss the role of selected growth
substances in controlling growth and
development in humans.

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PLANT GROWTH SUBSTANCES
What caused the growth in
these shoots towards the
light?
In the 1800s, Charles
Darwin suggested that a
growth substance acting as
a ‘chemical messenger’
was responsible for the
stem’s growth response to
a unilateral light source.
This has been found to be
correct.

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Plant cells can produce various growth
substances which control:
1. Plant growth and development
2. Plant responses to the environment
These substances are hormones --
chemical messengers that travel through
the plant causing other cells, called target
cells, to respond. e.g. Cells in one
blooming flower use hormones to signal
other flowers to open.
PLANT GROWTH SUBSTANCES

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HORMONE ACTION IN PLANTS
The most commonly known plant hormones
are the auxins.
1. Click and read ‘Phototropism’ from >>
http://www.scienceclarified.com/Oi-
Ph/Phototropism.html
2. Read through and discuss with your
teacher the experiment with auxin shown
on slide 53.

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AUXIN PROMOTES PLANT GROWTH

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http://resources.edb.gov.hk/biology/english/environment/plant/plant_hormone_effect.html
AUXIN PROMOTES PLANT GROWTH
The auxin is produced in the shoot tip but is
redistributed and transported downwards during
unilateral stimulation by light.

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The side away from
the light gets more
auxins so cells
elongate and grow
more than those on
the side facing the
light.
This elongation
results in bending
towards the light
source.
AUXIN PROMOTES PLANT GROWTH
Source: http://vle.havant.ac.uk/Biology_web/5__plant_hormones.htm

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In general, auxins cause either cell elongation
or suppression of cell elongation on one side
of a plant part, causing the plant to grow in a
particular direction.
The common tropic growth responses are:
photropism, thigmotropism and gravi/geo-
tropism.
http://www.youtube.com/watch?v=zctM_TWg5Ik&NR=1
AUXIN PROMOTES PLANT GROWTH

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Think and Tell
Use what you’ve understood about the action
of auxins to explain what happens to the root
and stem of the germinating corn grains,
shown in the photo.
FEEDBACK

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FEEDBACK
In stems turned sideways or upside down, as seen in
the corn grain, auxins are more concentrated on the
lower side of the stem, causing the cells there to
elongate. The stem responds to the stimulus of gravity
by growing upward. The shoot tip shows a negative
gravitropic (geotropic) growth response.

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FEEDBACK cont’d: +ve Gravitropism in Root tips
In roots, however,
auxin concentration
on the lower side of
the root suppresses
cell elongation. The
upper side of the root
continues to grow,
causing the roots
to bend downward,
showing positive
geotropic growth.

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OTHER FUNCTIONS OF AUXINS
Growth of adventitious roots (roots that arise from
any plant part e.g. stem/leaf, other than the primary
root/radicle or its branches)

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Auxins released from
the shoot tip
stimulate cell
elongation in the
stem, but suppress
the lateral buds, so
no growth of
branches occurs.
Cytokinins produced in
roots can stimulate
lateral buds to grow
if the shoot tip and
auxin is removed.
Apical dominance
OTHER FUNCTIONS OF AUXINS

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ETHYLENE is a gas that fruit tissues give off. It stimulates
fruit ripening and also germination and cell elongation.
• As fruit become ripe, they
produce more and more
ethlyene, accelerating the
ripening process.
• Ethylene released by
apples, bananas and
tomatoes etc. causes
fruit to age quickly
.
OTHER PLANT GROWTH SUBSTANCES
Adapted from >>www.worldofteaching.com

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OTHER PLANT GROWTH SUBSTANCES
GIBBERELLINS – influence stem elonga-
tion, flowering, fruit development and
seed germination.
ABSCISIC ACID – produced in response to
environmental stressors such as drought.
Note. Abscisic acid induces seed dormancy, while
gibberellins and cytokinins break dormancy.
CYTOKININS - stimulate cell division, senescence, seed
germination, embryo and flower development.
NB. Auxins inhibit the growth of axillary/lateral buds,
while cytokinins promote their growth.
Watch the video at this website, starting at 2.45 mins.
http://www.5min.com/Video/Understanding-Plant-Hormones-151425731

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AGRICULTURAL USES OF PLANT GROWTH
SUBSTANCES
1. To produce new plants e. g. from stem cuttings
e.g. Coleus
2. To induce flowering (out of season).
3. To promote fruit ripening.
4. To produce seedless fruit e.g. bananas.
5. To produce entire plants from small
pieces of tissue e.g. micro-propagation.
Make a visit to or telephone your local Agricultural
Office and find out as much as you can about how
growth substances are used in various farming
practices.

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THINK and TELL
1. A horticulturist wants to produce Poinsettia plants in
time for Christmas. He buys the chemical shown below
to use to produce the plants.
Why? How will he use it to get the plants?
FEEDBACK

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FEEDBACK
1. The rooting hormone can be applied
to the cut ends of Poinsettia stem
cuttings, which are then planted in
potting soil, watered regularly and
exposed to mild sunlight. Within 1 –
2 weeks, growth of adventitious
roots on the stems should be
stimulated by the hormone, giving
young plants.

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Think and Tell
2. A farmer harvests air-freights his crop of mature
green paw-paws overseas. When they arrive at the
destination country, before distributing them,
he wants them to start to ripen.
Suggest what could be done to achieve that.
2. The paw-paws can be
sprayed with or
exposed to ethylene
to stimulate further
maturing and ripening.
http://www.fotosearch.com/FDC006/945811
FEEDBACK

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Think and Tell
3. How does
pinching back the
tips of branches
on a plant cause it
to become more
bushy?
3. When the apical bud is
pinched off, auxin is
no longer produced, so
the lateral buds can
now grow out as
lateral branches.
FEEDBACK

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Think and Tell
4. Explain why these yellow-flowered plants are all
growing in this direction. Click the next button for
feedback.

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FEEDBACK
4. From the light patches on the ground in the
right of the picture, it can be inferred that
sunlight comes from one direction only.
The yellow-flowered plants growing in the
shade are all blocked from light by the high
hedge (at left) behind them. They are all
getting a unilateral stimulus of light, so the
auxin in their shoots cause elongated growth
of stem cells on the shaded side of the shoots,
which results in the growth curvature towards
the light.

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SUMMARY
Plant cells will use growth substances to send
chemical signals to other cells to tell them:
1. When to start new growth.
2. When trees are to drop their leaves.
3. When to cause fruit to ripen.
4. When to cause flowers to bloom.
5. When to cause seeds to germinate.
Leaf Drop Fruit
Ripening
Germinaing
Corn Seed
Poinciana
Blooming
Bud growing
ato (Top), Orange, Guava (Right),
http://www.tradewindsfruit.
com/guava.htm
/
exocarp or skin
4. The middle layer
of the fruit wall
is often fleshy
with stored
food. The outer
layer changes
colour when
ripe.

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HUMAN GROWTH SUBSTANCES
Introduction
There is a story that Christians
read in their Holy Book (Bible)
about David and a giant
named Goliath (seen in this
picture).
A fairy tale tells about Jack
who climbed a beanstalk to a
giant’s house.
What growth problem
is common to both
stories?
http://www.gigantism.com/david-goliath.html

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HUMAN GROWTH SUBSTANCES
From watching the video of the little girl too
short for her age, you know that growth
substances in humans are called hormones
and that they can influence your growth in
height and body size, especially in children.
Hormones are made in endocrine glands,
secreted directly into the blood and
transported to specific target organs or cells
where they induce specific responses.

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HUMAN ENDOCRINE GLANDS
The pituitary and
thyroid glands
and the male and
female gonads
influence growth
& development
in humans.
The pancreas also
exerts some influence
on growth and
development.
Find those glands on
this diagram.
http://www.worldofteaching.com/powerpoints/biology/Blood%20sugar.ppt#258,2,Slide 2
Illu_endocrine_system.jpg

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Pituitary - located in the brain just below
the hypothalamus, and is controlled by it.
http://www.becomehealthynow.com/article/bodyendocrine/734/#blood_flow_hypothal
PITUITARY GLAND & HYPOTHALAMUS

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LOBES OF THE PITUITARY GLAND
The pituitary has two lobes, which together
secrete nine different hormones.
Anterior lobe hormones affect the breasts,
adrenals, thyroid, ovaries and testes, as well
as several other hormones.
The posterior
lobe hormones
affect mainly the
kidneys.

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Pituitary hormones directly regulate many
body functions and control the functions of
other glands.
Because the hormones from the anterior
and posterior pituitary lobes influence
other glands, the pituitary is sometimes
called the “master gland”.
PITUITARY GLAND – ‘Master Gland’

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Growth hormone (GH - also called
somatotropin) stimulates growth, not only
of bone but of muscle and cartilage, and
essentially all the tissues of the body.
Growth hormone simultaneously stimulates
protein, fat and carbohydrate metabolism in
tissues as follows:
Protein metabolism: In general, growth
hormone stimulates protein anabolism in
many tissues, causing increased amino acid uptake,
increased protein synthesis and decreased oxida-
tion of proteins. Cont’d
ACTION OF THE PITUITARY GLAND IN GROWTH
Metabolism is how our cells break down,
build up and use substances.

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Fat metabolism: Growth hormone
enhances the utilization of fat by causing
its breakdown to provide the energy for
the stimulated growth.
Carbohydrate metabolism: Growth
hormone is one of various hormones that
serves to maintain blood glucose level
within a normal range. Growth hormone is
often said to have ‘anti-insulin activity’
because GH suppresses the abilities of
insulin to stimulate uptake of glucose in
peripheral tissues and enhance glucose
synthesis in the liver.
ACTION OF THE PITUITARY GLAND IN GROWTH

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Pituitary Gland
Disorders: Too
much growth
hormone in early
childhood can result
in a condition called
gigantism.
Certain types of gigantism
can be corrected in
children by the use of
growth hormone, but there
are risks in using the
hormone!
Robert
Wadlow
http://www.worldofteaching.com/powerpoints/biology/
Nerves.ppt#284,3,Pituitary Gland

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Too little GH (called growth hormone
defficiency) can result in extreme
shortness – dwarfism - in humans with
proportional body parts i.e. Pituitary
Dwarfism.
Note: Certain types of dwarfism are
inherited and can be the result of mutation
that affects the fibroblast growth factor.
Pituitary Gland Disorders

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PITUITARY GLAND cont’d
Remember the picture showing the dog nursing
its puppies? What controls its milk production?
The pituitary gland of course!
One of the hormones secreted by the anterior
lobe is prolactin (PRL). It stimulates the female’s
breasts to produce milk. Without milk as a
‘starter food’ many young mammals would not
grow and develop. In fact, they might not
survive!
Watch the video (mentioned in the SIM) now to
learn more about the pituitary gland.

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The hypothalamus produces gonadotropin-
releasing hormone (GnRH). The anterior
pituitary lobe produces luteinizing
hormone (LH) and follicle-stimulating
hormone (FSH), and the gonads produce
estrogens (females) and testosterone
(males).
Together, these hormones influence the
growth and development of secondary
sexual characteristics at puberty.
THE GONADS AND GROWTH

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THE GONADS AND SEXUAL GROWTH
Some of the secondary sexual characteristics.
http://www.encyclopedia.com/topic/Sex_characteristics.aspx

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CONTROLING THE GONADS
1. What is the relationship
between the hypothala-
mus, pituitary & gonads?
2. Which organ does LH and
FSH act on in males?
3. What action does LH and
FSH produce in females?
4. Which of these hormones
influence growth and
development in females?

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CONTROLLING THE GONADS
What regulatory
mechanism does
the arrow from the
testes to the
pituitary and the
hypothalamus
represent?
A negative feedback
mechanism
FEEDBACK

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In males, Testosterone…..
• increases bone growth and muscle
development.
• causes growth of facial/chest/genital hair
• causes production of sperm and
deepening of the voice.
In females, Estrogens triggers….
• further development of breasts and the
start of the menstrual cycle
• growth of genital hair and fat deposits
THE GONADS AND GROWTH

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THYROID GLAND AND GROWTH
The hypothalamus and
pituitary gland affect
growth indirectly by
controlling the thyroid
gland whose hormones
control metabolism in
our body. This in turn
affects our growth and
development.

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ACTION OF THE THYROID GLAND IN GROWTH
Use this diagram to describe in your notebook how the
pituitary and thyroid glands control growth.
http://en.wikipedia.org/wiki/Thyroid
FEEDBACK

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FEEDBACK
Did your answer include the following?
The hypothalamus secretes Thyrotropin-
Releasing Hormone (TRH) into blood which
stimulates the anterior pituitary to produce
and secrete Thyroid -Stimulating Hormone
(TSH). Via the blood, TSH reaches the
thyroid and causes it to produce Thyroid
hormones – T3 and T4 (e.g. thyroxine)
Thyroxine mainly influences metabolism and
growth. It also can inhibit the hypothalamus
so that it decreases its secretion of TRH. So,
TSH production would also be inhibited.
This is a negative feedback mechanism.

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http://www.biology-online.org/4/3_blood_sugar.htm
HORMONES from the PANCREAS
The receptors of the pancreas are
responsible for monitoring glucose levels in
the blood. Since glucose is needed in every
cell for respiration, it affects growth.
Two types of cells release two different
hormones - insulin and glucagon - from the
pancreas . One or the other of these
hormones target the liver, depending on
the glucose concentration.
Discuss the diagram on the next slide with
your teacher.

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ACTION of HORMONES from the PANCREAS
FEEDBACK

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FEEDBACK: ACTION of HORMONES from the PANCREAS
In cases where glucose levels increase,
less glucagon and more insulin is
released by the pancreas and targets
the liver and muscles, changing glucose
to glycogen. So the set point for blood
glucose concentration is achieved.
Where glucose levels decrease, less
insulin and more glucagon is released
by the pancreas and targets the
liver/muscles to change glycogen into
glucose which then enters the
circulatory blood stream, restoring the
set point of blood glucose.

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SUMMARY
Growth in mammals such as humans and in
flowering plants is controlled by the
interaction of a range of growth substances
or hormones.
These hormones are normally produced
under various internal/external
environmental conditions, and their actions
help to maintain homeostasis within the
organism.

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Credits
www.worldofteaching.com
http://www.tradewindsfruit.com/guava.htm
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/gh.html
http://vle.havant.ac.uk/Biology_web/5__plant_hormones.htm