PLANT HORMONES MINI LAB- researching all about plant hormones

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WELCOME COME TO PLANT HORMONES MINI LAB!!!

In this mini lab blog, we posts our research to the public on the findings on plant hormones. Do read through the posts and you can pose questions if you have doubts. We have hyperlinked alot of websites to provide you with more information about plant hormones. There are also links to quizzes and experiments you can do. Be a PLANT HORMONE MINI LAB fan, read our reports,participate in our discussion, and try out the activites through the links.

Navigate by clicking on the words above. Hover over them for a while to see what they contain.

Enjoy! (:

INTRO
HI! WELCOME ONCE AGAIN! (:
SO now lets have an introduction on plant hormones to give you a brief idea what they are.

WHAT ARE PLANT HORMONES?
According to a standard definition, plant hormones are signal molecules produced at specific locations, occur in low concentrations, and cause altered processes in target cells at other locations.
Plant Hormones regulate or influence a range of cellular and physiological processes, including

Cell Division
Cell Enlargement
Cell Differentiation
Flowering
Fruit Ripening
Movement (tropisms)
Seed Dormancy
Seed Germination
Senescence (ageing)
Leaf Abscission
Stomatal Conductance

Broadly speaking, the mechanism by which hormones act at the cellular level is similar in plants and animals.
the hormone must first bind to a protein receptor , either on the cell surface or inside the cell.
This activates a signal transduction pathway which amplifies the signal and
leads to changes in enzyme activities, ion gradients, gene expression, and other physiological responses.

Phototopism --- response of plant due to auxin presence in plant

SPEAK!
HAVE ANY COMMENTS OR QUESTIONS? SHOOT THEM OUT TO OUR MINI LAB RESEARCHERS! ps. got some probs now will update it soon

Wednesday, February 28, 2007

HI TO ALL! THIS IS THE LAST ENTRY OF THIS MINI LAB RESEARCH. SO SUM IT ALL, our lab researchers has decided to include the commercial uses of the plant hormones!

Today, we will talk about the commercial uses of plant hormones, and illustrate them by giving you examples to aid you in the understanding of their uses! (: LET'S BEGIN NOW!

+ Plant hormones are used extensively in agriculture, horticulture, and
biotechnology to modify plant growth and development.

FOR EXAMPLE -- GEBERELLINS

+Used commercially to break dormancy, eg. germination in wheat seeds

THE PROCESS:

1. Seed takes up water

2. Embryo produces GA

3. GA diffuses to aleurone layer (surrounding endosperm)

4. Aleurone produces amylase

5. Amylase diffuses to endosperm and breaks down starch to glucose

6. Glucose feeds growing embyro

-- Can cause parthenocarpic (seedless) fruit development.

-- Can delay senescence in leaves and citrus fruits.

Plants hormones are used widely in agriculture in the following ways:

cutting dipped in rooting hormone powder some time later, roots are grown

>>> As selective weedkillers which are not harmful to the surrounding plants or to animals, eg. synthetic auxins

[VARIOUS USES]

+ To produce new plants from cuttings. With the use of hormone rooting powder, cut stems can develop roots and grow into clones of the parent plant.eg. auxin

+ To promote the ripening of fruit or induce flowering when required, eg. Ethylene

(accelerate fruit ripening and also promote pineapple flowering; flowering occurs more rapidly and mature fruits appear uniformly, hence a one-harvest mechanical operation is possible)

+ To speed up or slow down the growth of plants.

+ To produce fruit without seeds. Unpollinated flowers are treated so that they grow fruit without seeds

eg. usage of gibberellins to increase the size of seedless grapes, when applied at the appropriate time and with the proper concentration

+ To elongate fruits, eg. Gibberellins(fruits less tightly packed and less susceptible to fungal infections)

+ To increase the rate of malting in some breweries, eg. gibberellins (enhance starch digestion)

+ To prevent some rind disorders that appear during storage, eg. Gibberellins (spray on fruits and leaves of navel orange trees)

+ To increase sugarcane growth and sugar yields, eg. gibberellins

+ For usage in plant cell culture, particularly in cultivating genetically engineered plants, eg. cytokinins and auxins

+ To prevent overripening of picked fruits, eg. ethylene (carbon dioxide in high concentrations inhibits ethylene production)

+ To retard senescence in certain cut flowers and fresh vegetables, eg. Cytokinins

+ To prevent fruit abscission

This is the end of my research report on the commercial uses of plant hormones. I hope that it is useful to you and hope that you have learnt alot from all the seven reports we have done. Therefore this marks the end of our entries report!

4:45 AM

Tuesday, February 27, 2007

HI TO ALL !!! (: Today i will be introducing you all the final plant hormone on our research list.

It is called Cytokinins .

this is the structure of cytokinins

HISTORY OF DISCOVERY

The first naturally occurring cytokinin, later called Zeatin (published in report by Letham as factor inducing cell division), was isolated from corn in 1961 by Miller (Miller, 1961). It is Miller and Letham that are credited with the simultaneous discovery of zeatin. Since that time, many more naturally occurring cytokinins have been isolated and the compound is found in all plant species in one form or another.

*WHAT ABOUT CYTOKININS?

I found out that cytokinins can be found both in plants and animals! It had compounds resembling adenine and it derived from the nucleotide adenine. So now, scroll down to see more details about cytokinin!

1.Concentrations highest in meristematic regions and areas of continuous growth potential such as roots, young leaves, developing fruits, and seeds

2.Believed to be synthesized in the roots and translocated via the xylem to shoots

3.Synthetic cytokinins include benzyladenine and kinetin (These growth stimulators are used extensively in plant tissue culture and are therefore important in biotechnology applications.)

3.1- If a medium's mix of growth-regulating compounds is high in cytokinins and low in auxin, the tissue culture explant (small plant part) will produce numerous shoots.

3.2-On the other hand, if the mix has a high ratio of auxin to cytokinin, the explant will produce more roots.

3.3-Though it is a natural compound, It is not made in plants, and is therefore usually considered a "synthetic" cytokinin

4.Determined by relative concentrations of auxin and cytokinin

*USES OF CYTOKININ

+ Promote cell division ("cytokinesis")

+ Promote the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.

+ Stimulate lateral bud growth

+ Stimulate cell division.

+ Stimulate morphogenesis (shoot initiation/bud formation) in tissue culture.

+ Stimulate leaf expansion resulting from cell enlargement.

+ May enhance stomatal opening in some species.

+ Used commercially in tissue culture media, and for growth control in fruit

+ - Delay senescence

I hope that my research report has been a great help to you in understanding more about this plant hormone--- cytokinin!

8:34 AM

HI!! Today i am going to introduce to you another new plant hormone!! It is called

Gibberellins (GAs).

structure of Gibberellins

HISTORY OF DISCOVERY

The origin of research into gibberellins can be traced to Japanese plant pathologists who were investigating the causes of the "bakanae" (foolish seedling) disease which seriously lowered the yield of rice crops in Japan, Taiwan and throughout the Asian continent.

Basic Information

>Largest group of hormones, currently 136 GAs identified from plants, fungi and bacteria

>Unlike the classification of auxins which are classified on the basis of function, gibberellins are classified on the basis of structure as well as function

>Gibberellic acid, GA3, the first gibberellin to be structurally characterised

>First isolated from a fungus (Gibberella fujikori)

- cause of "foolish seedling"

>Derived from the terpenoid pathway

>Produced in embryonic tissues (meristems)

WHAT CAN IT DO? :O

+ Promotes stem elongation
-Many "dwarf" plants are genetic mutants deficient in gibberellin synthesis

+ Promotes cell division

+ Enhances the effects of auxin

+ Stimulates germination in buds and seeds

+ Stimulates bolting/flowering in response to long days.

+ Stimulates enzyme production (a-amylase) in germinating cereal grains for mobilization of seed reserves.

+ Induces maleness in dioecious flowers (sex expression).

You have come to the end of the report on Gibberellins !! Check out the next hormone we are introducing to you!

7:56 AM

HELLO TO ALL! Another piece of fruitful information about a new hormone!

It is called Ethylene.

BRIEF HISTORY

In 1901, a Russian scientist, Dimitry Neljubow, discovered the presence of the active compound, ethylene. In the following years it was reported plants synthesize ethylene and that ethylene was the plant hormone responsible for ripening of fruits and inhibition of vegetative tissues.

this is the structure of ethylene

BASIC INFORMATION

> Gaseous Hormone

> Formed from the amino acid methione
-reaction involves cyclized intermediate 1-aminocyclopropane-1-carboxylic acid (ACC)

>Used commercially esp. in bananas

> Ethephon is a commercial fruit ripener that breaks down to liberate ethylene inside plant tissues

> Sex of flowers on monoecious plants is determined by ethylene and gibberellins.

USES OF ETHYLENE

+ Promotes epinasty (drooping in leaves)

+ Promotes abscission (dropping of leaves)

+ Promotes senescence

+ Promotes fruit ripening at the same time.

-Some fruits experience an increase in respiration called a climacteric.

-The climacteric begins just after a huge increase in ethylene production.

-Can control ripening of fruits.

+ Plants often increase ethylene production in response to stress,

> ethylene often is found in high concentrations within cells at the end of a plant's life.( part of reason leaves fall from trees)

-- Inhibits flowering in most plants. Mangos, pineapples and some ornamentals are stimulated by ethylene.

-- Can inhibit stem elongation.
(Thigmomorphogenesis is the mechanical disturbances of plants and the resulting effect it has on plants height.)

****Shaking the plant causes ethylene to be produced, causing a restructuring of the microtubules in the cell walls resulting in shorter, thicker stems.

Here we go, you have completed reading the research on the plant hormone ethylene. If you are starting to feel enthusiastic abou tplant hormones read on! Have any questions? Post them in our tagboard, we will try to answer your questions! (:

7:38 AM

HEYS! I had found another piece of research on another different plant hormone, it is called

Abscisic Acid (ABA).

this is a picture of the abscisic acid.

History of discovery

Abscisic acid was first identified and characterized by Frederick Addicott and his associates in 1963 while they were studying compounds responsible for the shedding of fruits (cotton). The study resulted in Abscisin I and Abscisin II being isolated and Abscisin II is now known as Abscisic Acid.

I have already typed the research found in point form for your easy understanding (:
Synthesized in plastids from carotenoids
- Derived from terpenoid pathway
Produced in leaves, stems, and green fruits
High concentrations of ABA in guard cells during periods of drought stress cause stomatal closure.(wilting of leaves)
+Promotes abscission of leaves, fruits, and flowers
+Promotes dormancy in seeds and buds BUT -inhibits cell growth
+Induces seeds to synthesize storage proteins
+Induces gene transcription, especially for proteinase inhibitors in response to wounding, which may explain an apparent role in pathogen defense
-- Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots.
-- Inhibits the effect of gibberellins on stimulating de novo synthesis of a-amylase.

This is already the 3rd hormone you have read about. If you have any questions, feel free to tag at the tagboard section and ask us. If you have any comments, pls go to the tagboard too, we will be happy to know how you feel (:

7:38 AM

HI TO ALL AGAIN! After yesterday's 1st part of the research on Auxins, i am here to post the 2nd part of my research!

For today's post, i will be basically reporting about the ways to control the amount of auxins in the tissues as well as its causes,

1.PHOTOTROPISM (The reaction of plants to light in which the plants bend toward the light)

2. GEOTROPHISM (plant response to gravity)

3 ways to control the amount of IAA present in tissues at a particular time

1. control the biosynthesis of the hormone

2. control the production of conjugates( inactive molecules which resemble the hormone)

a. formed from IAA via hydrolase enzymes

b. rapidly activated by environmental stimuli signaling a quick hormonal response

c. degradation of auxins

*PHOTOTROPISM

According to my research, i found out that auxins actually causes phototropism ( the reactions of plants to light in which the plants bend towards the light). I will show you a diagram to explain the whole concept and how everything works. The diagram below shows Phototropism in the coleoptile of a monocot.

Brief EXPLANATION : Auxin moves to the darker side of the plant, causing the cells there to grow larger than corresponding cells on the lighter side of the plant. This produces a curving of the plant stem tip toward the light, phototropism.

*GEOTROPHISM

On the other hand, auxins can also cause geotrophism ( the plant response to gravity). Roots of plants show positive geotropism, shoots show negative geotropism.

DIAGRAM : the diagram above shows geotrophism and how auxin plays a part in it.

You have now officially finished the report on Auxin. Our next report is on the hormone is Abscisic Acid. Read on to find out more about it!

7:15 AM

Monday, February 26, 2007

Hi to all!
I am sure that all of you have learnt some basic knowledge about plant hormones in the introduction page. So for today's entry i will talk about one of the plant hormones that exists. This hormone is called AUXIN.

BRIEF HISTORY ABOUT AUXIN

Auxins were the first plant hormones discovered. Charles Darwin was among the first scientists to dabble in plant hormone research The term comes from the Greek auxein meaning "to grow. IAA (the first auxin to be isolated from plants)

Here are some examples of the plant hormone

napthalene acetic acid (NAA) (controls fruit set and sucker growth on trees after pruning)

2,4-D (herbicide- causes uncoordinated growth in broad-leaved weeds when applied at high concentrations)

We found out that Indole-3-acetic acid (IAA) is the natural auxin .

AUXINS are

produced in the growing tips of plant shoots and roots, and diffuse into other parts of the plant

move through the plant by "polar transport"
- Unidirectional movement down the stem through parenchyma cells - Auxin apparently does not travel through the vascular tissue

IAA is derived from the amino acid tryptophan

They work by responding to light, gravity and moisture and making some cells in the plant elongate or grow faster than others.

Enzymes responsible for the biosynthesis of IAA are most active in young tissues such as growing leaves and fruits. The same tissues are the locations where the highest concentrations of IAA are found.

Congratulations to you for completing the reading of our very 1st research report. Hope that you have gain some useful information about plant hormones, read on to our part 2 report on the plant hormone AUXIN!

5:06 AM

LINKS

BLIBLIOGRAPHY
plant hormones related
commercial uses
uses of plant hormones
plant hormones

GAMES & QUIZZES

simple plant hormone quiz
fun game on plant hormones

EXPERIMENTS

testing effect of plant hormones
test for ethylene

ANIMATIONS

clear and easy understanding
colourful animation and easy quiz

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