CHAPTER I

Introduction
All living organisms begin in the same form: as a single cell. That cell
will divide and the resulting cells will continue dividing and differentiate
into cells with various roles to carry out within the organism. This is life
and plants are no different. Plant growth can be determinate or
indeterminate, meaning some plants will have a cycle of growth then a
cessation of growth, breakdown of tissues and then death (think of a
radish plant or a tomato plant) while others (think of a giant cedar tree)
will grow and remain active for hundreds of years. A tomato plant is fairly
predictable and is said to have determinate growth, while the cedar tree
has indeterminate growing potential. Development refers to the growth
and differentiation of cells into tissues, organs and organ systems. This
again all begins with a single cell.
Genetic information directs the synthesis and development of
enzymes which are critical in all metabolic process within the plant. Most
enzymes are proteins in some form or another, are produced in very
minute quantities and are produced on sitemeaning they are not
transported from one part of the organism to another. Genetic information
also regulates the production of hormones, which will be addressed shortly.
The major difference is that hormones are transported from one part of the
plant to another as needed. Vitamins vital in the activation of enzymes
and are produced in the cytoplasm and membranes of plant cells. Animals
and humans utilize plants in order to provide some vitamin resources. In
general, hormone and vitamin effects are similar and are difficult to
distinguish in plants, and both are referred to in general as plant growth
regulators.Occasionally we hear or read of experiments often associated
with school science fairs-that suggest plants respond in some positive way
to good music or soothing talk ; conversely, some plants are said to grow
poorly when exposed to loud rock music or to being harshly yelled at.
There is currently much debate about global warming and the
potential effects on life as we know it. Are those who proclaim that global

warming will eventually have disastrous effects on modern civilization and

living organisms simply exaggerating.
Plant life constitutes more than 98% of the total biomass (collective
dry weight of living organisms) of the earth. Plants and other green
organisms have the exclusive capacity to produce oxygen while converting
the suns energy into forms vital to the existence of both plant and animal
life. At the same time, plants remove the large amounts of carbon dioxide
given off by all living organisms are totally dependent on green organisms
for their existence. If some disease were to kill off all or the green
organisms on land and in the oceans and lakes, all the animals on land, in
the sea, and in the air would soon starve. Even if some alternative source
of energy were available, animal life would suffocate within 11 years-the
time estimated for all the earths oxygen to be completely used up if it
were not replaced.

CHAPTER II
DISCUSSION
What are Plant Hormones ?
Plant hormones affect how plants grow. Unlike animal hormones, plant hormones are
organic molecules. They aid in plant growth and survival. Cellular events like division and
cell morphology are driven by hormone levels. In plants, meristematic tissue is composed of
cells that are actively growing. This is where one is expected to find a relatively large
concentration of plant hormones. Also, one will find higher hormone levels in root tips.
The major known types of plant hormones are auxins, gibberelins, cytokinins, abscis
acid, and ethylen.
Regulating Growth: Plant Hormones
Plant cells are in constant chemical communication with one another and with their
environment. They recognize and respond to stimuli of many kinds, using a system of
chemical messengers that receive and transmit the stimuli via ordinary body cells (unlike the
highly specialized cells of animal nervous systems). Control of the plant system apparently
resides in the genes of each cell, which are turned on and off by the chemical messages they
receive. The response may be stimulatory (initiating cellular division and enlargement, for
example) or inhibitory (such as stopping a metabolic process)
The chemical messengers are hormones, organic substances manufactured in small
amounts in one tissue and usually transported to another where they initiate a response. (A

few act in the tissues where they are produced.) The hormone molecule itself carries little
information and produces a reaction only when it binds to appropriate receptor molecules at
the response site.
Plants, in comparison to animals, have both fewer hormones and fewer kinds of
responses. Plant hormones, however, usually act in combination, thus producing more varied
responses than if acting individually. The same hormone also can produce different effects
when acting in different tissues or in different concentrations in the same tissue. The
developmental stage of the plant additionally determines what effects the hormone activates.
Growth and development depend upon a successful coordination of the activities of
hormones, not just the presence or absence of individual ones

How Do Plant Hormones Act ?

Three criteria must be true to stimulate plant hormonal action (Salisbury
and Ross,1992):

The hormone must be present in the correct quantity in

the correct location.

There must be good recognition and strong binding between the hormone
and the responding molecules.

The receptor molecule must then trigger some other metabolic

change which will trigger the amplification of the hormonal signal.

There are two generally accepted mechanisms by which hormones will act.
1. The first type deals with a steroid hormone. In this type the hormone

can pass through the plasma membrane into the cytoplasm. Here it
binds with its receptor molecule to form a hormone-receptor
complex. From this point, the complex may dissociate (If there is not
tight binding) or it may enter the nucleus and affect mRNA
synthesis. The effect of the hormone on mRNA synthesis ultimately
results in the physiological response(Arteca,1996 Moran et.al., 1994;
Wolfe, 1993)

2. In the second type, a peptide hormone binds to a receptor protein

on the target cell. The receptor protein will then undergo a
conformational change leading to a cellular cascade ultimately
resulting in modification of enzyme activity, altered metabolic
processes, and differentphenotypes (Arteca, 1996)

How Do Hormones Regulate the Plant Life Cycle?

Types of Hormones In Plant And Their Function
1) Auxin
Hormone growth hormone auxin is on all types of plants. Another name of this
hormone is the IAA or indole acetic acid. the location of the hormone auxin is located
on the tip of the stem and root ends, the function of the hormone auxin is to assist in
the process of accelerating growth, the growth of both root and stem growth,
accelerate germination, helps in the process of fruit ripening sel.mempercepat division,
reducing the number of seeds in the fruit and aging, and abortion. these hormones
work synergistically with hormones auxin and cytokinin hormone giberelin.tumbuhan
that on one side illuminated by the sun, then the growth rate will be slower because
kerjka auxin is inhibited by the sun but the plants were not illuminated by the sun
growing very fast because the work is not auxin dihambat.sehingga this will cause the
end of the crop tends to follow the direction of the sun or the so-called phototropism.
To distinguish plants that have a lot of hormones or the little we have to know the
anatomy and physiology of the plant so that it easier to find out. while for the plants
put into place that light and dark them for the plants put into place that dark very fast
growing plant besides the texture of the stem is very weak and pale colors tend
kekuningan.hal is due to the hormone auxin is not inhibited by the sun. while for the
plants you put into place the light slightly slower growth rate than the plants you put
into place was dark, but the texture is very strong stems and fresh green color, it is due
to the hormone auxin is inhibited by sunlight.
2) Giberelin
Gibberellins often abbreviated as GA is a diterpenoid which puts it in the same
chemical family and karotein chlorophyll. All the organs of the plant contain a variety
of GA, the richest source of biosynthesis as well as a place that is in the fruit and seeds

are not ripe, shoots, leaves and roots (Rismunandar, 1988). GA biosynthesis involves 3
chemical metabolites, ie mevalonic acid that acts as a precursor for the formation of
isoprene, which is the base of the carbon-19 and carbon-20 framework giban, kaurena
formed from isoprene, GA formed from kaurena (Leopold and Kriedemann, 1975 in
Gardner, et al ., 1991).
Gibberellins work synergistically with auxin, cytokinins and perhaps some
other substances (synergism) to influence the peak dormancy, growth cambium,
geotropisme, abscission and partenokarpi (due to the activity of auxin and gibberellin),
effectively increasing fruit set, thus stimulating the growth of inter-books are not
stunted plants , the release of a-amylase for starch hydrolysis and germination
(Gardner, et al., 1991). Giberilin reacts in the cells surrounding the endosperm which
led to the formation of a number of specific hydrolytic enzymes (such as amylase and
protease) that digests starch and protein endosperm dengam thus making supplies
sugars and amino acids for cell growth (Kimball, 1983). He also explained that the
amino acids provided by the action of the protease enzyme is precurson formation of
another type of growth hormone, as triptopan which is an early form of auxin.
According Kusumo (1989), that gibberellins play a role in cell division and
supports the formation of RNA resulting in protein synthesis. Cell division is
stimulated by active amylase hydrolyzes starch into sugar is reduced so that the
increased sugar concentration also increased as a result of the osmotic pressure.
Increased osmotic pressure inside the cell causing water to easily enter the cells, so it
can be triggers all physiological processes in plant cells.
Gibberellins function is to stimulate cell division and stimulate the activity of
amylase and proteinase enzymes that play a role in germination. Gibberellins also
stimulates the formation of buds, remove seed dormancy, and stimulate fruit growth
by parthenogenesis.
3) Cytokines
Cytokines in accordance with its name derived from the cytokines are growth
hormones that affect cell division. According to Kimball (1983), cytokines when
reacted with Auxin, strongly stimulate mitosis in tissue merestematik, a real explosion
of RNA synthesis occurs when plant cells or isolated nuclei treated with cytokines.
Furthermore, according to Wereing and Philips (1981), in the metabolic processes of
cytokines thought to have an important role in protein synthesis, the process of
translation.
Cytokines can be found on the network are split as follows: At the root,
embryo and fruit, to move from the roots to other organs. Cytokinins were discovered
first is kinetin. Contained cytokinin is zeatin in Zea mays. The function of cytokines is

Stimulate cell division, stimulate the formation of buds on the stem and on the
callus, inhibits the effects of apical dominance, and accelerate the growth of elongated
4) Abscisic acid
Not all hormones serve to stimulate growth, because there are also inhibits
growth, abscisic acid. Abscisic acid (ABA), as growth inhibitors (Inhibitor / retardant)
when plants experience stress, is used to mengompakkan fitohormon stem growth so
that plants look very good. Abscisic acid function is to inhibit cell division and
elongation, delayed growth or dormancy, stimulate closure leaves the mouth dry
season, and helped the decay of leaves in the dry season
Place it generates: Leaf; stems, roots, fruits green.
5) Ethylene
Ethene or ethylene is the simplest alkene compounds consisting of four
hydrogen atoms and two carbon atoms connected by a double bond. Because of this
bond, ethene also called unsaturated hydrocarbons or olefins.
At room temperature, the molecules can not rotate the ethene double bond so
that all constituent atoms are on the same plane. The angle formed by two carbonhydrogen bonds in the molecule is 117 , very close to 120 are estimated based on
ideal sp2 hybridization. Ethylene function is to encourage ripening; give the opposite
effect with some influence auxin; encourage or inhibit the growth and development of
roots, leaves, stems and flowers.
Place generates: Ripe fruit, a book on the stem, leaf aging.
6) Brassinolide (brassinosteroid group)
Brassinolide is similar fitohormon steroids in animals and have a response
similar to gibberellin. Several functions brassinolide are as follows: increase the rate
of plant cell elongation, inhibit leaf aging (senescence), resulting in a bend on the
leaves of grasses, inhibiting the leaf drop, inhibiting the growth of plant roots, shoots
of plants increases resistance to environmental stress, stimulates cell renewal in shoots
of plants, stimulate the growth of plant shoots, stimulating plant xylem differentiation,
inhibit the growth of shoots at deficient (deficient) and endogenous carbohydrate air.
Brassinolide synthesized from acetyl CoA via the acid mevalonik.
7) Polyamines
Polyamines have a major role in the most fundamental genetic processes such
as DNA synthesis and genetic expression. Spermine and spermidine bind to phosphate
chains of nucleic acids. This interaction kebanyakkan based on electrostatic interaction
between the positively charged ions of ammonium groups of the polyamine and the
negative charge of the phosphate.
Polyamine is the key to cell migration, proliferation and differentiation in
plants and animals. Level metabolic precursor of polyamine and amino acids is very

important to be maintained, therefore the biosynthesis and degradation must be tightly

regulated.
Polyamine representing the plant growth hormone, but the recording also gives
effect to the skin, hair growth, fertility, depot fat, pankreatis integrity and growth of
regeneration in mammals. In addition, spermine is an important compound that is
widely used to precipitate DNA in molecular biology. Spermidine stimulate the
activity of the kinase and T4 polynucleotida T7 RNA polymerase and is then used as
the protocol in the use of enzymes
In addition to the hormones mentioned above, there are other hormones that
also produced plants are:
1) Kalin, which can be divided into four:
Kaulokalin, stimulate the formation of rod
Rizokalin, stimulates the formation of root
Filokalin, stimulate the formation of leaf
Antokalin, stimulate the formation of flowers
2) Acid traumalin
Role in repairing damaged parts of a plant.
What Is the Commercial Use of Plant Growth Regulators?
The ability to influence the growth and development of plants has become more
important as the agricultural industry has become increasingly mechanized and as the public
has demanded more high-quality produce. If one is going to mechanically remove all the fruit
from a plant at a given point in time, it is desirable that as many of the fruits be mature and of
desirable appearance as possible. If the harvesting process occurs over a period of days or
weeks, it also would be desirable to hold the crop in a good condition over that time. If larger
leaves add to the economic value of the crop, then it is desirable to treat the plants in such a
way as to reduce the production and growth of lateral branches with smaller leaves. In many
cases, naturally occurring plant hormones or synthetic substitutes have been found to have
effects beneficial to the agricultural industry in their efforts to deliver the types of high-quality
produce to the consumer. Of the five major plant hormones (review "What Are Plant
Hormones and How Do They Act?"), only abscisic acid or similar synthetic compounds have
not found practical uses, largely because of the high cost to synthesize these compounds and
because of their sensitivity to UV light.
Auxins (review "How Do Hormones Regulate the Plant Life Cycle?") and auxin-like
compounds are the oldest substances and probably the most abundantly used substances in
agriculture. While the naturally occurring auxin indole acetic acid (IAA) is too unstable to be
useful in an agricultural situation, a large number of synthetic compounds have been found to
behave in a similar fashion in the plant and have the properties necessary to be useful in the

fields. Indolebutyric acid (IBA) and naphthalene acetic acid (NAA) are commonly used to
promote root development in stem cuttings. Treating apple and pear trees with NAA just after
their full bloom will cause a thinning of up to 80% of the developing fruit, a situation that is
desirable because fewer large fruit have a greater market value than many small fruit. Later in
fruit

development,

NAA,

2,4-dichlorophenoxyacetic

acid

(2,4-D),

and

2,4,5-

trichlorophenoxypropionic acid (2,4,5-TP) may be used to delay fruit drop, extending the
harvest season. Many farmers, as well as many homeowners, will use 2,4-D as an herbicide to
kill broadleaf weeds in their fields or lawns.
Of the more than 90 forms of gibberellin that have been identified in higher plants and
in the fungus Gibberella, only the forms GA4 and GA7 have been found to have commercial
value. These gibberellins are used extensively to increase the size and quality of seedless
grapes. They are used to delay the ripening of lemons so that these can be harvested during
the months with the greatest demand. Application of gibberellins to artichokes promotes the
production of flower buds and allows for earlier harvesting dates. These gibberellins are also
used to increase the yields of malt from barley and sucrose from sugarcane.
The cytokinin-like compounds, benzyladenine and tetrapyranylbenzyladenine, are
used to promote lateral branching in white pine and carnations, respectively. A combination of
benzyladenine, GA4, and GA7, called Promalin, is used to promote the elongation of the
Delicious apple varieties so that they have the elongated shape expected by the public, rather
than a rounder shape. Promalin is also applied to young fruit trees to increase lateral
branching, producing a tree with the desired shape for mechanical harvesting.
Several treatments or compounds that increase ethylene concentrations in or around
the plants have found commercial uses. Among the oldest of these treatments is the burning of
fires or running of gas engines adjacent to fields of pineapple and mango, helping to
synchronize flowering in these plants. The incomplete combustion of fuels in both of the
cases adds ethylene to the environment to achieve the desired effect. A compound commonly
applied

to Hevea

brasiliensis (the

tree

that

produces

natural

rubber)

is

2-

chloroethylphosphonic acid or ethephon. Ethephon degrades to ethylene within the plant,

which in Hevea has been found to increase the flow of latex, raising rubber yields as much as
100%. Another use of ethephon is its application to cherry trees prior to harvest, decreasing
the force required and subsequent tree damage from mechanical harvesters. Ethephon
treatment of walnuts has also increased their market value. In grapes, ethephon is used to
promote color development and reduce acidity in the fruits.

Can Plants Communicate ?

If all plants were extremely small and lived in completely uniform, nonvararying
environments, most would probably be simple and would experience little selective pressure
for the evolution of complex shapes, tissues, organs, and metabolism. The most uniform,
constant conditions occur in oceans and large lakes, where water buffers rapid changes in
temperature, acidity, oxygen concentration, and other factors. Under such stable conditions,
small organisms exist in a heterogeneus environment: gravity comes from only one direction.
The sun is either to the side or overhead but never below. Temperatures are lower on the
shady side of a plant. Moisture of conditions changes over minutes, days, seasons, or longer
periods of time. It is selectively advantageous for plants to sense these differences and
changes and to respond to them (Mausth, 2011).
Most plants are so large that their bodies exist in several different microenvirontments.
Consider a small tree: its roots are in soil, which is usually moister, cooler, and darker than
air; the highest branches are in open air, exposed to full sunlight and the full force of wind,
storms, rain, and show. The trunk base and lower branches are in an intermediate
environtment less stable than soil and less variable and severe than open air. A vertical tree
trunk is isoriented to best resist gravitational attraction (its own weight), whereas horizontal
branches are highly stressed unilaterally by gravity (Mausth, 2011).
In springtime, the shoot can become warm enough for active metabolism even though
the soil remains cold or frozen. The plant parts must communicate with each other, or shoots
buds would become active and expand before roots were capable of transporting water to new
leaves. In autumn, increasing night length and declining air temperatures signal impending
winter and the need for dormancy: roots are informed about changing seasons by chemical
signals from the shoot (Mauseth, 2011).
The need for intercommunication and coordination also exists within a limited region of
the body. For example, leaf parts act in a coordinated fashion during development such that
the petiole has enough xylem and phloem to facilitate the transport needs of the blade. Too
little conductive tissue causes the blade to suffer water stress or an inability to export sugars;
too much conductive tissue is a of energy and material. Even on the intracellular level,
organelles must communicate with each other because their metabolims are interrelated
(Mauseth, 2011).

Communicate within plant

1. Perception and transduction
Many, possibly most, responses occur in tissues or organs different from those
that sense the stimuli. The site of perception is not the site of perception and response
are not specialized for those functions but seem to be rather ordinary cells. Day lenght
is probably perceived by all living leaf cells; no specialized region of cells specialized
region of cells has been discovered. Low temperatures for vernalization appear to be
detected by buds, which do not contain a particular group of cells specialized just for
temperature perception. In root caps, certain cells called statocytes do have large
starch granules, statolihs, that sink in response to gravity; statoliths are too dense to
float in crtoplasm and always settle to the bottom of the cell, thereby distinguashing
down from up. This is our best example of a set of speacialized perceptive cells.
The trigger hairs on Venus flytrap leaves are also a discrete perceptive mechanism,
but it is not known which cells within the hairs are responsible.
2. Taxis
Taxis is a response in which a cell swims toward (positive taxis) or away from
(negative taxis) a stimulus. Even in plants like mosses, ferns, cycads, and maidenhair
tree (Ginkgo), sperm cells swim to egg cells by following chemical gradient
(chemotaxis). In algae, chemotaxis is similarly important for reproduction, and in
many species, phototaxis allows them to swim toward light for photosynthesis or away
from light that is too intense.
After the stimulus has acted long enough to fulfill the presentation time, a
response aoccurs even if the stimulus is removed. For example, the vernalization of
many biennial plants has a presentation time of only one or a few days; after this, the
plants still flower at the proper time even if kept in warm, nonvernalizing conditions.
Tendrils of peaas do not bend thigmotropically in the dark, but if they are rubbed for
several seconds their presentation time in the dark, they bend when placed in light
even though they are no longer being touched.
3. Chemical Messengers
Almost all plant communication is by a slow mechanism: transport of
hormones through the plant. Hormones are organic chemicals produced in one part of
a plant and then transported to other parts, where they initiate a response. A critical
aspect is that hormones act at very low concentrations. Hormones are synthesized or
stored in regions of transductions. Hormones are synthesized or stored in regions of
transduction and are released for transport through either phloem or mesophyll and
cortex cells when the appropriate stimulus occurs. At the site of response, hormones

bind to receptor molecules, usually located in the plasma membrane, and thereby
trigger a response. Hormones appear to be released into general circulation and are not
carried specifically to the target. Many regions that are not target regions are exposed
to the hormone but do not respond because they do not have the proper receptor
molecules. In some instances, a plant hormone acts directly on the cells that produce
it.
At one time, plant hormones were believed to carry in their structure much of
the information necessary for the response. We now know that plant hormones are
quite simple in structure. The receptor cell and its nucleus contain almost all of the
information necessary for proper response, and hormones serve only to activate the
response.
Can Plants Move Rapidly ?
movements result from varying growth rates in diferent parts of an organ. They are
mainly related to young parts of a plant and as a rule are quite slow, usually taking at least 2
hours to become apparent, although the plant may have begun microscopic changes within
minutes of reiving a stimulus.
Movements Resulting Primarily from Internal Stimuli
Nutations, Charles Darwin once attached a tiny sliver of glass to the tip of a plant growing in
a pot. The he suspended a piece of paper blackened with carbon over the tip, and as the plant
grew. He raised the paper just enough to allow the tip to touch the paper without hurting the
plant. He found that the growing point traced a spiral pattern in the blackened paper. We know
now that such nutations (also referred to as spiraling movements) are common to many plants.
Nodding Movements, members of the Legume Family (Fabaceae), such as garden beans,
whose ethylene production upon germinating causes the formation of a thickened crook in the
hypocotyl, exhibit a slow oscillating movement (i,e.. the bent hypocotyl nods from side to
side like an upside down pendulum) as the seedling pushes up through the soil. This nodding
movement apparently facilitates the progress of the growing plant tip through the soil.
Twining Movements, although twining movements are mostly stimulated internally, external
forces, such as gravity and contact, may also play a role. These movements occur when ncells
in the stems of climbing plants, such as morning glory, elongate to differing extents, causing
visible spiraling in growth (in contrast with the spiraling movements previosly mentioned,
which are not visible to the eye). Tendtril twining, which is initiated by contact, results from

an elongation of cells on one side, followes by differences in growth rates. Some tendtrils are
stimulated to coil by auxin, while others are stimulated by ethylene.
Contraction Movements, we noted that the bulbs of a number of dicots and monocots have
contractile roots, which pull them deeper into the ground. In lilies, for example, seeds
germinating at the surface ultimately produce bulbs that end up 10 to 15 centimeters (4 to 6
inches) below ground level because of the activities of contractileroots. There is some
evidence that temperature fluctuations at the surface determine how long the contracting will
continue. When the bulb gets deep enough that the differences between daytime and nightime
temperatures are slight, the contractions cease.
Nastic movements, when flattened plant organs, such as leaves or flower petals, first
expandfrom buds, they characteristically alternative in bending down and then upas the cells
in the upper and lower parts of the leaf alternate in enlarging faster than those in the opposite
parts. Such nondirectional movements (i.e.., movements that do not result in an organ being
oriented toward or away from the direction of a stimulus) are called nastic. Nastic movements
may involve differential growth or turgor changes in special cells. Epinasty is the permanent
downward bending of organ, often the petiole of a leaf, in response to either an unequal flow
of auxin through the petiole or to ethylene. Nastic movements that involve changes in
turgorpressure include sleep movements and contact movements, which are discussed later.
Movements Resulting from External Stimuli
Permanent movements resulting from external stimuli coming from one direction are
commonly referred to as tropisms. Tropic movements can be divided into three phases:
1. In the initial perception phase, the organ receives a greater stimulus on one side.
2. Then, transduction occurs, during which one or more hormones becomes unevenly
distributed across the organ.
3. Finally, asymmetric growth occurs as a result of the uneven distribution of the
hormone causing greater cell elongation on one side.
Phototropism. The main shoots of most plants growing in the open tend to develop vertically,
although the branches often grow horizontally. If a box is placed over a plant growing
vertically and a hole is cut to admit light from one side. The tip of the plant will begin to bend
toward the light within a few hours. If the box is later removed, a compensating bend
develops, causing the tip to grow vertically again. Such a growth movement toward light is
called a positive phototropism. A similiar bending away from light is called a negative

phototropism. The shoots tips of most plants are positively phototropic, while roots are either
insensitive to light or negatively phototropic.
Gravitropism. Growth responses to the stimulus of gravity are called gravitropisms. The
primary roots of plants are positively gravitropic, while shoots forming the main axis of plants
are negatively gravitropic. It was postulated that plant organs perceive gravity through the
movement of amyloplasts containing large starch grains located in special cells of the root
cap. The amyloplasts are also found in coleoptile tips and in the endodermis. When a potted
plant is placed on its side, the starch containing amyloplasts will, within a few minutes, begin
to float ao ruble down until they come to rest on the side of the cells closest to the gravity
stimulus. In roots, the cells on the side opposite the stimulus begin elongating within 10
seconds to an hour or two, bringing about a downward bend, while the opposite occurs in
stems.
Other Tropisms. A plant or plant part response to contact with a solid object is called a
thigmotropism. One of the most common thigmotropic responses is seen in the coiling of
tendrils and in the twining of climbing plant stems. Such responses can be relatively rapid,
with some tendrils wrapping around a support two or more times within an hour. The coiling
results from cells in contact becoming slightly shorter while those on the opposite side
elongate.

CHAPTER III
CONCLUSION
Plant hormones is a collection of organic compounds not nutrient (nutrients)both naturally
occuring and man-made, which in very small levels could encourage, inhibit, or alter the
growth, development, and movement (taksis) plants. Level of small is in the range of one
milimoles per liter one micromol per liter.
Types of Hormones In Plant And Their Function
1. Auxin is to assist in the process of accelerating growth, the growth of
both root and stem growth, accelerate germination, helps in the
process of fruit ripening sel.mempercepat division, reducing the
number of seeds in the fruit and aging, and abortion
2. Giberelin is to Stimulate cell division cambium,Stimulate early flowering
prematurely, Stimulate the formation of seedless fruit, Stimulate plaant grows very
quickly so as to have a giant size
3. Cytokinin to Stimulate the process of cell division, Delaying defoliaton, flower and
fruit, Affect the growth of shoots and roots, Enhace resistance to adverse effects such
as loe temperature, viral invections, weed killers and radiation, Inhibit (hold)
yellowing of the leaves by making the proteins and chlorophyll in the leaves of a
balanced
4. Ethylene gas to Help break dormancy in plants, Support the ripening fruit, Support the
abcission on the leaves, Supporting the flowering process, Inhibit root elongation in
some species of plants and can stimulate stem elongation, Stimulate germinate,
Support the formation of root hairs
5. Kalin , Rhizokalin to affecting root formation, Kaulokalin to affects the formation of
stem, Filokalin to affects leaf formation, Antokalin to affects the formation of flowers
6. Abscisic acid (ABA) to Inhibit seed germination, Affect the flowering plants, Extend
the dormancy of tubers, Affect bud dormancy plants to perform
7. Traumalin Acid / Acid traumalat Fix injury in plants (restitution process /
regeneration)
8. Brassinolide (brassinosteroid group) to Increase the rate of plant cell elongation,
Resulting in a bend on the leaves of grasses, Inhibiting the leaf drop, Inhibiting the
growth of plant roots

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