Biology M4 Growth Substances in living things

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IN ANIMALS AND PLANTS

Module 4 Unit 11 Lesson 3

GROWTH SUBSTANCES

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http://www.arkive.org/media/FD/FDC2CCA6-5475-4A9F-A243-F9D2BB2FCF78/Presentation.Large/photo.jpg

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GROWTH SUBSTANCES IN

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In this slide presentation, you will examine Module 4 Unit 11 lesson 3Growth 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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INTRODUCTIONAmong 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 plantshoots always growupwards 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 GROWTHSUBSTANCES, 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 development2. 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 hormonesare 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 GROWTHThe auxin is produced in the shoot tip but is redistributed and transported downwards during unilateral stimulation by light.

http://resources.edb.gov.hk/biology/english/environment/plant/plant_hormone_effect.html

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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.


Source: http://vle.havant.ac.uk/Biology_web/5__plant_hormones.htm

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


http://www.youtube.com/watch?v=zctM_TWg5Ik&NR=1

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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 suppressescell elongation. Theupper side of the rootcontinues to grow, causing the roots to bend downward,showing positivegeotropic growth.

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OTHER FUNCTIONS OF AUXINSGrowth 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

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OTHER PLANT GROWTH SUBSTANCES

Adapted from >>www.worldofteaching.com

http://www.worldofteaching.com/

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OTHER PLANT GROWTH SUBSTANCESGIBBERELLINS – influence stem elonga-tion, flowering, fruit development andseed 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

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 TELL1. 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?

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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 Tell2. 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

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Think and Tell3. 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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SUMMARYPlant 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

Tomato (Top), Orange, Guava (Right),

http://www.tradewindsfruit.com/guava.htm

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exocarp or skin

4. The middle layerof 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 problemis common to bothstories?

http://www.gigantism.com/david-goliath.html

http://www.gigantism.com/giant.html

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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 gonadsinfluence 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

http://upload.wikimedia.org/wikipedia/commons/c/c6/Illu_endocrine_system.jpg

http://upload.wikimedia.org/wikipedia/commons/c/c6/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 GLANDThe 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 GlandDisorders: 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

http://www.gigantism.com/david-goliath.html

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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

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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 hormonescontrol 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

http://en.wikipedia.org/wiki/File:Thyroid_system.png

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FEEDBACKDid 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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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

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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.comhttp://www.tradewindsfruit.com/guava.htmhttp://www.vivo.colostate.edu/hbooks/pathphys/endocrine/hypopit/gh.htmlhttp://vle.havant.ac.uk/Biology_web/5__plant_hormones.htm

http://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

Education

Biology M4 Growth Substances in living things