Assignment: Effect of Synthetic Hormone (as a part of MS Course)

1. An Assignment
on
Effect (Beneficial & Detrimental) of
Synthetic Hormone
Ripon Kumar Sikder
MS Student
Department of Horticulture
Sher-e-Bangla Agricultural University
Dhaka, 1207

2. CONTENTS
Sl. No. Topic Page no.
1. Introduction 1
2. Brief description about plant hormone 2-8
3.
Beneficial and detrimental effect of
synthetic hormone
9-32
4. Conclusion 33
5. References 34-37

3. 1
Introduction
A hormone is any chemical produced in one part of the body that has a target
elsewhere in the body. Plants have five classes of hormones. Animals, especially
chordates, have a much larger number. Hormones and enzymes serve as control
chemicals in multi cellular organisms. One important aspect of this is the obtaining of
food and/or nutrients. The regulation of animal cells is largely based upon
macromolecular effectors like peptide hormones, etc. The production of synthetic
compounds has not yet proceeded further, though the strengthening of genetic
engineering shows possibilities to yield peptide hormones in larger amounts. The
situation is different with phytohormones. Their chemical structures shown before are
rather easy, and the synthesis of analogous substances is no larger problem for
chemists. The biosynthesis of phytohormones is in many regards interesting. On one
hand is the effect of a hormone, its reaction kinetics (dose-effect-curve), its catabolic
and anabolic pathways in the plant cell, as well as species-specific and
developmentally specific differences of interest. In order to solve the existing
problems are either synthetic components simulating the effects of phytohormones
used, or inhibitors of the biosynthesis of phytohormones are taken to generate a lack
of hormones in the cells. In agriculture and forestry are herbicides used to stop the
growth of unwanted plants – like the presence of yield-reducing weeds.

4. 2
Brief description about plant hormone
Plant hormones (also known as phytohormones) are chemicals that regulate plant
growth, which, in the UK, are termed 'plant growth substances'. Plant hormones are
signal molecules produced within the plant, and occur in extremely low
concentrations. Hormones regulate cellular processes in targeted cells locally and
when moved to other locations, in other locations of the plant. Hormones also
determine the formation of flowers, stems, leaves, the shedding of leaves, and the
development and ripening of fruit. Plants, unlike animals, lack glands that produce
and secrete hormones; instead each cell is capable of producing hormones. Plant
hormones shape the plant, affecting seed growth, time of flowering, the sex of
flowers, senescence of leaves and fruits. They affect which tissues grow upward and
which grow downward, leaf formation and stem growth, fruit development and
ripening, plant longevity, and even plant death. Hormones are vital to plant growth
and lacking them, plants would be mostly a mass of undifferentiated cells.
Characteristics
The word hormone is derived from Greek, meaning 'set in motion.' Plant hormones
affect gene expression and transcription levels, cellular division, and growth. They are
naturally produced within plants, though very similar chemicals are produced by fungi
and bacteria that can also affect plant growth. A large number of related chemical
compounds are synthesized by humans, they are used to regulate the growth of
cultivated plants, weeds, and in vitro-grown plants and plant cells; these manmade
compounds are called Plant Growth Regulators or PGRs for short.
Plant hormones are not nutrients, but chemicals that in small amounts promote and
influence the growth,[2]
development, and differentiation of cells and tissues. The
biosynthesis of plant hormones within plant tissues is often diffuse and not always
localized. Plants lack glands to produce and store hormones, because, unlike animals,
which have two circulatory systems (lymphatic and cardiovascular) powered by a
heart that moves fluids around the body, plants use more passive means to move
chemicals around the plant. Plants utilize simple chemicals as hormones, which move
more easily through the plant's tissues. They are often produced and used on a local
basis within the plant body; plant cells even produce hormones that affect different
regions of the cell producing the hormone.

5. 3
Hormones are transported within the plant by utilizing four types of movements. For
localized movement, cytoplasmic streaming within cells and slow diffusion of ions
and molecules between cells are utilized. Vascular tissues are used to move hormones
from one part of the plant to another; these include sieve tubes that move sugars from
the leaves to the roots and flowers, and xylem that moves water and mineral solutes
from the roots to the foliage. Not all plant cells respond to hormones, but those cells
that do are programmed to respond at specific points in their growth cycle. The
greatest effects occur at specific stages during the cell's life, with diminished effects
occurring before or after this period. Plants need hormones at very specific times
during plant growth and at specific locations. They also need to disengage the effects
that hormones have when they are no longer needed. The production of hormones
occurs very often at sites of active growth within the meristems, before cells have
fully differentiated. After production they are sometimes moved to other parts of the
plant where they cause an immediate effect or they can be stored in cells to be
released later. Plants use different pathways to regulate internal hormone quantities
and moderate their effects; they can regulate the amount of chemicals used to
biosynthesize hormones. They can store them in cells, inactivate them, or cannibalise
already-formed hormones by conjugating them with carbohydrates, amino acids or
peptides. Plants can also break down hormones chemically, effectively destroying
them. Plant hormones frequently regulate the concentrations of other plant hormones.
Plants also move hormones around the plant diluting their concentrations. The
concentration of hormones required for plant responses are very low (10-6
to 10-5
mol/L).
Classes of plant hormones
In general, it is accepted that there are five major classes of plant hormones, some of
which are made up of many different chemicals that can vary in structure from one
plant to the next. The chemicals are each grouped together into one of these classes
based on their structural similarities and on their effects on plant physiology. Other
plant hormones and growth regulators are not easily grouped into these classes; they
exist naturally or are synthesized by humans or other organisms, including chemicals
that inhibit plant growth or interrupt the physiological processes within plants. Each
class has positive as well as inhibitory functions, and most often work in tandem with
each other, with varying ratios of one or more interplaying to affect growth regulation.
The five major classes are:

6. 4
1. Abscisic acid
Abscisic acid also called ABA, was discovered and researched under two different
names before its chemical properties were fully known, it was called dormin and
abscicin II. Once it was determined that the two latter compounds were the same; it
was named abscisic acid. The name "abscisic acid" was given because it was found in
high concentrations in newly abscissed or freshly fallen leaves. This class of PGR is
composed of one chemical compound normally produced in the leaves of plants,
originating from chloroplasts, especially when plants are under stress. In general, it
acts as an inhibitory chemical compound that affects bud growth, seed and bud
dormancy. It mediates changes within the apical meristem causing bud dormancy and
the alteration of the last set of leaves into protective bud covers. Since it was found in
freshly abscissed leaves, it was thought to play a role in the processes of natural leaf
drop but further research has disproven this. In plant species from temperate parts of
the world it plays a role in leaf and seed dormancy by inhibiting growth, but, as it is
dissipated from seeds or buds, growth begins. In other plants, as ABA levels decrease,
growth then commences as gibberellin levels increase. Without ABA, buds and seeds
would start to grow during warm periods in winter and be killed when it froze again.
Since ABA dissipates slowly from the tissues and its effects take time to be offset by
other plant hormones, there is a delay in physiological pathways that provide some
protection from premature growth. It accumulates within seeds during fruit
maturation, preventing seed germination within the fruit, or seed germination before
winter. Abscisic acid's effects are degraded within plant tissues during cold
temperatures or by its removal by water washing in out of the tissues, releasing the
seeds and buds from dormancy.
2. Auxins
The auxin indoleacetic acid

7. 5
Auxins are compounds that positively influence cell enlargement, bud formation and
root initiation. They also promote the production of other hormones and in
conjunction with cytokinins, they control the growth of stems, roots, and fruits, and
convert stems into flowers. Auxins were the first class of growth regulators
discovered. They affect cell elongation by altering cell wall plasticity. Auxins
decrease in light and increase where it is dark. They stimulate cambium cells to divide
and in stems cause secondary xylem to differentiate. Auxins act to inhibit the growth
of buds lower down the stems (apical dominance), and also to promote lateral and
adventitious root development and growth. Leaf abscission is initiated by the growing
point of a plant ceasing to produce auxins. Auxins in seeds regulate specific protein
synthesis, as they develop within the flower after pollination, causing the flower to
develop a fruit to contain the developing seeds. Auxins are toxic to plants in large
concentrations; they are most toxic to dicots and less so to monocots. Because of this
property, synthetic auxin herbicides including 2,4-D and 2,4,5-T have been developed
and used for weed control. Auxins, especially 1-Naphthaleneacetic acid (NAA) and
Indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when
taking cuttings of plants. The most common auxin found in plants is indoleacetic acid
or IAA. The correlation of auxins and cytokinins in the plants is a constant (A/C =
const.).
3. Cytokinins
The cytokinin zeatin , Zea, in which it was first discovered in immature kernels.
Cytokinins or CKs are a group of chemicals that influence cell division and shoot
formation. They were called kinins in the past when the first cytokinins were isolated
from yeast cells. They also help delay senescence or the aging of tissues, are
responsible for mediating auxin transport throughout the plant, and affect internodal
length and leaf growth. They have a highly synergistic effect in concert with auxins
and the ratios of these two groups of plant hormones affect most major growth periods

8. 6
during a plant's lifetime. Cytokinins counter the apical dominance induced by auxins;
they in conjunction with ethylene promote abscission of leaves, flower parts and
fruits. The correlation of auxins and cytokinins in the plants is a constant (A/C =
const.).
4. Ethylene:
Ethylene
Ethylene is a gas that forms through the Yang Cycle from the breakdown of
methionine, which is in all cells. Ethylene has very limited solubility in water and
does not accumulate within the cell but diffuses out of the cell and escapes out of the
plant. Its effectiveness as a plant hormone is dependent on its rate of production
versus its rate of escaping into the atmosphere. Ethylene is produced at a faster rate in
rapidly growing and dividing cells, especially in darkness. New growth and newly
germinated seedlings produce more ethylene than can escape the plant, which leads to
elevated amounts of ethylene, inhibiting leaf expansion. As the new shoot is exposed
to light, reactions by phytochrome in the plant's cells produce a signal for ethylene
production to decrease, allowing leaf expansion. Ethylene affects cell growth and cell
shape; when a growing shoot hits an obstacle while underground, ethylene production
greatly increases, preventing cell elongation and causing the stem to swell. The
resulting thicker stem can exert more pressure against the object impeding its path to
the surface. If the shoot does not reach the surface and the ethylene stimulus becomes
prolonged, it affects the stems natural geotropic response, which is to grow upright,
allowing it to grow around an object. Studies seem to indicate that ethylene affects
stem diameter and height: When stems of trees are subjected to wind, causing lateral
stress, greater ethylene production occurs, resulting in thicker, more sturdy tree trunks
and branches. Ethylene affects fruit-ripening: Normally, when the seeds are mature,
ethylene production increases and builds-up within the fruit, resulting in a climacteric
event just before seed dispersal. The nuclear protein Ethylene Insensitive2 (EIN2) is
regulated by ethylene production, and, in turn, regulates other hormones including
ABA and stress hormones.

9. 7
5. Gibberellins:
Gibberellin A1
Gibberellins, or GAs, include a large range of chemicals that are produced naturally
within plants and by fungi. They were first discovered when Japanese researchers,
including Eiichi Kurosawa, noticed a chemical produced by a fungus called
Gibberella fujikuroi that produced abnormal growth in rice plants. Gibberellins are
important in seed germination, affecting enzyme production that mobilizes food
production used for growth of new cells. This is done by modulating chromosomal
transcription. In grain (rice, wheat, corn, etc.) seeds, a layer of cells called the
aleurone layer wraps around the endosperm tissue. Absoption of water by the seed
causes production of GA. The GA is transported to the aleurone layer, which responds
by producing enzymes that break down stored food reserves within the endosperm,
which are utilized by the growing seedling. GAs produce bolting of rosette-forming
plants, increasing internodal length. They promote flowering, cellular division, and in
seeds growth after germination. Gibberellins also reverse the inhibition of shoot
growth and dormancy induced by ABA.

10. 8
Other known hormones
Other identified plant growth regulators include:
 Brassinosteroids, are a class of polyhydroxysteroids, a group of plant growth
regulators. Brassinosteroids have been recognized as a sixth class of plant
hormones which stimulate cell elongation and division, gravitropism, resistance
to stress and xylem differentiation. They inhibit root growth and leaf
abscission. Brassinolide was the first identified brassinosteroid and was
isolated from organic extracts of rapeseed (Brassica napus) pollen in 1970.
 Salicylic acid - activates genes in some plants that produce chemicals that aid
in the defense against pathogenic invaders.
 Jasmonates - are produced from fatty acids and seem to promote the production
of defense proteins that are used to fend off invading organisms. They are
believed to also have a role in seed germination, and affect the storage of
protein in seeds, and seem to affect root growth.
 Plant peptide hormones - encompasses all small secreted peptides that are
involved in cell-to-cell signaling. These small peptide hormones play crucial
roles in plant growth and development, including defense mechanisms, the
control of cell division and expansion, and pollen self-incompatibility
 Polyamines - are strongly basic molecules with low molecular weight that have
been found in all organisms studied thus far. They are essential for plant
growth and development and affect the process of mitosis and meiosis.
 Nitric oxide (NO) - serves as signal in hormonal and defense responses.
 Strigolactones, implicated in the inhibition of shoot branching.
 Karrikins, a group of plant growth regulators found in the smoke of burning
plant material that has the ability to stimulate the germination of seeds.

11. 9
Beneficial and detrimental effect of synthetic hormone
Effect of synthetic auxins:
In order to solve the existing problems are either synthetic components simulating the
effects of phytohormones used, or inhibitors of the biosynthesis of phytohormones are
taken to generate a lack of hormones in the cells. In agriculture and forestry are
herbicides used to stop the growth of unwanted plants – like the presence of yield-
reducing weeds. Auxin derivatives like 2,4-dichlorphenoxy acidic acid (2,4-D) or
2,4,5-trichlorphenoxy acidic acid (2,4,5-T) proved to be herbicides effecting
selectively dicots. Although the knowledge about the selectivity and the mode of
action of these substances is still very limited, do they belong to the most commonly
used herbicides effecting preferably dicots. 2, 4-D increases the rate of DNA, RNA
and protein synthesis and impedes thus an outbalanced, controlled growth. The plant
does actually grow to death. The phenotype of a thus treated plant is characterized by
the abnormal growth of the deformed shoots, a breakdown of chlorophyll (bleaching),
the dying of the roots and several more features. 2, 4, 5-T has shown to be especially
toxic for perennial wooden plants and is therefore most often used in forestry. It is less
easily degraded than 2,4-D. Auxin, in comparison, is very easily degraded and is
consequently of no use as a herbicide.
The most important member of the auxin family is indole-3-acetic acid (IAA). It
generates the majority of auxin effects in intact plants, and is the most potent native
auxin. And as native auxin its stability is controlled in many ways in plant, from
synthesis, through possible conjugation to degradation of its molecules, always
according to the requirements of the situation. However, molecules of IAA are
chemically labile in aqueous solution, so IAA is not used commercially as a plant
growth regulator.
 There are four naturally occurring - endogenous auxins. Apart from IAA, only
4-chloroindole-3-acetic acid (4-Cl-IAA), phenylacetic acid (PAA) and indole-
3-butyric acid (IBA) may qualify as such, because only those 4 were found to
be synthesized by plants.
 Synthetic auxin analogs include 1-naphthaleneacetic acid (NAA), 2,4-
dichlorophenoxyacetic acid (2,4-D), and many others.

12. 10
Gallery of native auxins:
Indole-3-acetic acid (IAA)
Indole-3-butyric acid (IBA)
4-chloroindole-3-acetic acid (4-CI-IAA)
2-phenylacetic acid (PAA)

13. 11
Gallery of synthetic auxins:
2,4-Dichlorophenoxyacetic acid (2,4-D)
α-Naphthalene acetic acid (α-NAA)
2-Methoxy-3,6-dichlorobenzoic acid (dicamba)
4-Amino-3,5,6-trichloropicolinic acid (tordon or picloram)
2,4,5-Trichlorophenoxyacetic acid (2,4,5-T)

14. 12
a) 2,4-Dichlorophenoxyacetic acid (2,4-D):
Properties:
Molecular formula C8H6Cl2O3
Molar mass 221.04 g mol−1
Appearance white to yellow powder
Melting point 140.5 °C (413.5 K)
Boiling point 160 °C (0.4 mm Hg)
Solubility in water 900 mg/L (25 °C)
2,4-Dichlorophenoxyacetic acid (2,4-D) is a common systemic pesticide / herbicide
used in the control of broadleaf weeds. It is the most widely used herbicide in the
world, and the third most commonly used in North America 2,4-D is a synthetic auxin
(plant hormone), and as such it is often used in laboratories for plant research and as a
supplement in plant cell culture media such as MS medium.
Mechanism of action:
2,4-D is a synthetic auxin, which is a class of plant hormones. It is absorbed through
the leaves and is translocated to the meristems of the plant. Uncontrolled,
unsustainable growth ensues, causing stem curl-over, leaf withering, and eventual
plant death. 2,4-D is typically applied as an amine salt, but more potent ester versions
exist as well.
Applications:
2,4-D is primarily used as a herbicide. It is sold in various formulations under a wide
variety of brand names. 2,4-D can be found in lawn herbicide mixtures such as "Weed
B Gon MAX", "PAR III", "Trillion", "Tri-Kil", "Killex" and "Weedaway Premium 3-

15. 13
Way XP Turf Herbicide". All of these mixtures typically contain three active
ingredients: 2,4-D, mecoprop and dicamba. Over 1,500 herbicide products contain
2,4-D as an active ingredient.
2,4-D is most commonly used for:
 Weed control in lawns and other turf
 No-till burndown
 Control of weeds and brush along fences and highway and railroad rights of
way
 Conifer release (control of broad-leaf trees in conifer plantings)
 Grass hayfields and pastures
 Cereal grains
 Corn and sorghum (occasionally)
 As a synthetic auxin analogue
2,4-D continues to be used, where legal, for its low cost. However, where municipal
lawn pesticide bylaws exist, such as in Canada, alternatives such as corn gluten meal
and vinegar-based products are increasingly being used to combat weeds.
Toxicity:
 Cancer risk: Different organizations have taken different stances on 2,4-D's
cancer risk. On August 8, 2007, the United States Environmental Protection
Agency issued a ruling that stated that existing data does not support a
conclusion that links human cancer to 2,4-D exposure. However, the
International Agency for Research on Cancer (IARC) has classified 2,4-D
among the phenoxy acid herbicides MCPA and 2,4,5-T as a class 2B
carcinogen - possibly carcinogenic to humans.[
A 1995 panel of 13 scientists
reviewing studies on the carcinogenicity of 2,4-D had divided opinions, but the
predominant opinion was that it is possible that 2,4-D causes cancer in
humans.
 Environmental behavior: Owing to the longevity and extent of use,
2,4-D is among the most thoroughly studied herbicides with respect to
environmental properties. 2,4-D applied at 1.16 lb/acre to bluegrass turf in a
laboratory experiment had a half-life of ten days. Other half-life figures for the
herbicide in soil are seven days (15-25 degree C with 65% moisture) and ten
days in non-sterile soil and 1.5 to 16 days in other studies. Soil microbes are

16. 14
primarily responsible for its disappearance in soil. Studies in Alaska and
Canada failed to detect leaching in 22 weeks or from spring to fall, but 2,4-D
has been included on the EPA list of compounds that are likely to leach from
soil.
In aquatic environments microorganisms readily degrade 2,4-D and breakdown by
sunlight is not a major reason for loss. Rates of breakdown increase with increased
nutrients, sediment load and dissolved organic carbon. Under oxygenated conditions
the half-life can be short, in the order of one week to several weeks. 2,4-D interferes
with normal plant growth processes. Uptake of the compound is through leaves, stems
and roots; however, it is, in general, nonpersistent. In one study when 2,4-D was
applied to grass, there were 80 ppm at day zero, 45 ppm at 14 days, and 6 ppm at 56
days. Breakdown in plants is by a variety of biological and chemical pathways.
A number of 2,4-D-degrading bacteria have been isolated and characterized from a
variety of environmental habitats[
. Metabolic pathways for the compound’s
degradation have been available for many years, and genes encoding 2,4-D catabolism
have been identified for several organisms. As a result of the extensive metadata on
environmental behavior, physiology and genetics, 2,4-D was the first herbicide for
which the bacteria actively responsible for in situ degradation was demonstrated. This
was accomplished using the technique of DNA-based stable isotope probing, which
enables a microbial function (activity), such as degrading a chemical, to be linked
with the organism’s identity without the need to culture the organism involved. This
advancement has been particularly beneficial for the study of soil microorganisms,
since only a very small fraction of the thousands of species present in highly diverse
soil bacterial communities can be isolated in pure culture.
b) α-Naphthalene acetic acid (α-NAA):
1-Naphthaleneacetic acid, commonly abbreviated NAA, is an organic compound with
the formula C10H7CH2CO2H. This colourless solid is soluble in organic solvents. It
features a carboxylmethyl group (CH2CO2H) linked to the "1-position" of
naphthalene. NAA is a plant hormone in the auxin family and is an ingredient in many
commercial plant rooting horticultural products; it is a rooting agent and used for the
vegetative propagation of plants from stem and leaf cutting. It is also used for plant
tissue culture.

17. 15
Properties:
Molecular formula C12H10O2
Molar mass 186.2066 g/mol
Appearance White powder
Melting point 135 °C
Solubility in water 0.38 g/L (17 °C)
Acidity (pKa) 4.24 (25 °C)
Appearance White crystals
Purity 98%
Melting point 130-134°C
Loss on drying 0.5%
Residue on ignition <0.1%
Toxicology:
Acute oral LD50 for rat 1000-5900mg/kg. Acute percutaneous LD50 for rabbit
>500mg/kg. Moderately irritating to rabbit skin, and strongly irritating to rabbit eyes
under prolonged exposure. Acute inhalation for rabbit LC50 (1hr)>2000ppm. Fish
LC50 (96hr): rainbow trout 57 mg a.i./l; bluegill 82 mg a.i./l; carp(48hs) 590mg/l;
water flea (48hs) 360mg/L. Non-toxic to bees at recommended dosage.
Application:
Plant growth regulator with auxin like activity. It can be absorbed via root, stem or
leaf. It is widely used in agriculture, forestry, vegetable, flower, fruit etc. It can
induce formation of adventitious root, improve cutting culture, promote fruit set, and
prevent prematuration of fruit.
c) 2-Methoxy-3,6-dichlorobenzoic acid (dicamba):
Dicamba (3,6-dichloro-2-methoxybenzoic acid) is an herbicide used to control annual
and perennial rose weeds in grain crops and highlands, and it is used to control brush

18. 16
and bracken in pastures. It will kill broadleaf weeds before and after they sprout.
Legumes will be killed by dicamba. In combination with a phenoxyalkanoic acid or
another herbicide, dicamba is used in pastures, range land, and noncrop areas (fence
rows, roadways and wastage) to control weeds. Brand names for formulations of this
herbicide include Banvel, Oracle and Vanquish. It is a light tan, slightly phenolic,
crystalline liquid. It is stable to oxidation and hydrolysis, and melts at temperatures
between 90 and 100 °C (194 and 212 °F). Dicamba is nonflammable and does not
present any unusual handling hazards.
Properties:
Molecular formula C8H6Cl2O3
Molar mass 221.04 g/mol
Appearance White crystalline solid
Density 1.57
Melting point 114-116 °C
Solubility in water 500,000 µg/ml
Solubility in ethanol 922 g/L
Mode of action:
Dicamba acts by increasing plant growth rate. At sufficient concentrations, the plant
outgrows its nutrient supplies and dies.
Toxicological effects:
Dicamba is moderately toxic by ingestion and slightly toxic by inhalation or dermal
exposure (oral LD50 in rats: 757 mg/kg body weight, dermal LD502,000 mg/kg,

19. 17
inhalation LC50200 mg/L). Symptoms of poisoning with dicamba include loss of
appetite, vomiting, muscle weakness, slowed heart rate, shortness of breath, central
nervous system effects (victim may become excited or depressed), benzoic acid in the
urine, incontinence, cyanosis (bluing of the skin and gums), and exhaustion following
repeated muscle spasms. In addition to these symptoms, inhalation can cause irritation
of the linings of the nasal passages and the lungs, and loss of voice. Most individuals
who have survived severe poisoning from dicamba have recovered within 2 to 3 days
with no permanent effects.
Dicamba is very irritating and corrosive and can cause severe and permanent damage
to the eyes. The eyes should be flushed with running water for at least 15 minutes if
any dicamba is splashed into them. The eyelids may swell and the cornea may be
cloudy for a week after dicamba is splashed in the eyes. Dermal and inhalation
exposure to humans may occur during application, particularly via splashing during
dilution, mixing, and loading. Application by aircraft increases the potential for
exposure of humans, livestock, and wildlife due to spray drift and ventilation. Chronic
exposure can lead to the development of the same symptoms as described above. Most
of the available data on potential human health effects come from laboratory animal
studies. These data are evaluated and used to make inferences about potential effects
on human health.
Environmental impact:
 Soil: Dicamba is released directly to the environment by its application as a
herbicide for the control of annual broadleaf weeds. It may cause damage to
plants as a result of its absorption from the soil by plant roots. Dicamba is very
mobile in most soils and significant leaching is possible. The adsorption of
dicamba to organo-clay soil is influenced by soil pH with the greatest
adsorption to soil occurring in acidic soils. Dicamba is moderately persistent in
soil. Its reported half-life in soil ranges from 1 to 6 weeks. Dicamba is likely to
be more rapidly degraded in soils with high microbial populations, but
dissipates more slowly in hardwood forests and wetlands than would be
expected from the results of laboratory studies. At a level of 10 mg/kg in sandy
loam soil, dicamba caused a transient decrease in nitrification after two but not
three weeks of incubation. The investigator determined that the decrease in
nitrification is not substantial and does not suggest the potential for a prolonged
impact on microbial activity. In the same study, dicamba did not affect
ammonia formation or sulfur oxidation.

20. 18
 Water: Dicamba salts used in some herbicides are highly soluble in water. A
recent study conducted by the U.S. Geologic Survey (USGS 1998) found
dicamba in 0.11%-0.15% of the ground waters surveyed. The maximum level
detected was 0.0025 mg/L. There was no apparent correlation between the
prevalence of dicamba in groundwater from agricultural areas (0.11%)
compared with nonagricultural urban areas (0.35%).
 Air: Dicamba is relatively volatile, and this process may be a significant factor
in the dispersion of dicamba in the environment. Brown-and-burn operations
may result in the formation of considerable quantities of combustion products.
The combustion products of dicamba are not identified.
 Environmental fate: In soil, dicamba breaks down to very simple
substances like carbon dioxide and water. The soil bacterium Pseudomonas
maltophilia (strain DI-6) converts dicamba to 3,6-dichlorosalicylic acid (3,6-
DCSA), which is adsorbed to soil much more strongly than is dicamba and
lacks herbicidal activity. Very little information is available on the toxicity of
these breakdown intermediates. The enzymes responsible for this first
breakdown step is a three-component system called dicamba O-demethylase.
One component of the three has recently been incorporated into the genome of
a variety of crop plants making them resistant to dicamba (Behrens et al.,
Science, 2007, 316, 1185-1188). Dicamba is toxic to many terrestrial broadleaf
and conifer species, but is generally less toxic to grasses, and is relatively toxic
to some species of cacti. Dicamba was tested for acute toxicity in a variety of
aquatic animals.
d) 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T):
Some of the most widely-used weed killers are synthetic auxins. These include 2,4-
dichlorophenoxy acetic acid (2,4-D) and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T).
2,4-D and its many variants are popular because they are selective herbicides, killing
broad-leaved plants but not grasses . It turns out that the auxin influx transporter
works fine for 2,4-D, but that 2,4-D cannot leave the cell through the efflux
transporters. Perhaps it is the resulting accumulation of 2,4-D within the cell that kills
it. A mixture of 2,4,-D and 2,4,5-T was the "agent orange" used by the U.S. military to
defoliate the forest in parts of South Vietnam. Because of health concerns, 2,4,5-T is
no longer used in the U.S.

21. 19
Effect of synthetic cytokinins
Nature of Cytokinins
Cytokinins are compounds with a structure resembling adenine which promote cell
division and have other similar functions to kinetin. Kinetin was the first cytokinin
discovered and so named because of the compounds ability to promote cytokinesis
(cell division). Though it is a natural compound, It is not made in plants, and is
therefore usually considered a "synthetic" cytokinin (meaning that the hormone is
synthesized somewhere other than in a plant). The most common form of naturally
occurring cytokinin in plants today is called zeatin which was isolated from corn (Zea
mays).
Cytokinins
Cytokinin Functions:
A list of some of the known physiological effects caused by cytokinins are listed
below. The response will vary depending on the type of cytokinin and plant species
(Davies, 1995; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992).
 Stimulates cell division.
 Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.
 Stimulates the growth of lateral buds-release of apical dominance.
 Stimulates leaf expansion resulting from cell enlargement.
 May enhance stomatal opening in some species.
 Promotes the conversion of etioplasts into chloroplasts via stimulation of
chlorophyll synthesis.

22. 20
Kinetin (N6-furfuryladenine):
Kinetin, or N6-furfuryladenine, is a relative newcomer to the field of anti aging skin
care products. Very little research has been done on this compound, but clinical
evidence seems to show that kinetin is a powerful natural antioxidant that helps
protect DNA and proteins from oxidative damage caused by free radicals. Kinetin isn't
a widely used antioxidant but you may see more of it in the years to come.
Kinetin( 6-Furfurylaminopurine)
N6-furfuryladenine, or kinetin, is a plant hormone. Technically, it belongs to the
group of compounds known as cytokinins, which are a class of growth regulators in
plants. In plants, kinetin and the other cytokinins promote cell division and are active
in the processes of cellular growth and differentiation. Some research seems to
indicate that kinetin also helps to prevent the decline and degeneration of leaves. At
least in plants, kinetin is a true anti aging hormone.
Properties:
Appearance White crystals
Purity 99%
Melting point 266-269°C
Loss on drying 0.5%
Residue on ignition 0.05%
Uses of Kinetin:
Kinetin functions as an essential growth hormone, which can influence cell growth
and differentiation. It can delay and offset aging characteristics such as cell growth
rate and size. It is claimed to reduce wrinkles and improve skin texture, telangiectasia,
and mottled hyper pigmentation, although there is limited information to support this.

23. 21
Kinetin Dosing:
There is no available information on appropriate human doses of this plant growth
hormone.
Contraindications:
Contraindications have not yet been identified.
Pregnancy/Lactation:
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Kinetin Interactions:
None well documented.
Kinetin Adverse Reactions:
There is a very low incidence of side effects when used topically. Common side
effects include erythema, peeling, burning, and stinging.
Toxicology:
Research reveals little or no information regarding toxicology with the use of this
product. Acute transperitoneal toxicity for mouse, LD50 =450mg/Kg.
Cosmetic effects:
The skin care product Kinerase claims to be a “nature-identical” plant growth factor,
which “delays and improves unwanted changes in appearance and texture of
photodamaged skin.” It allegedly reduces wrinkles and improves skin texture,
telangiectasia, and mottled hyperpigmentation.
Animal data:
Single-celled yeast, Saccharomyces cerevisiae , used as a model, demonstrated spore
formation at micromolar concentrations of kinetin. Another report finds kinetin to
delay aging and prolong lifespan of the fruitfly Zaprionus paravittiger . Addition of
kinetin in a culture medium of human cells can delay and offset aging characteristics
such as growth rate and cell size. The amount of DNA in the nuclei of the fibroblast
cells increased in the presence of kinetin from human skin.
Clinical data:
Results are typically seen in 4 to 6 weeks. Product literature compares Kinerase with
the prescription cream Renova (0.05% tretinoin), finding Kinerase to be superior to
Renova parameters by patient self-assessment at a 24-week period. There was an
incidence of side effects using Kinerase vs Renova (eg, erythema, peeling, burning,
and stinging).
Application:
Kinetin is a cytokinin type plant growth regulator. It can promote cell division,
differentiation and growth, and thus enhance germination and fruit set, induce callus

24. 22
initiation, reduce apical dominance, break lateral bud dormancy, retard aging. It is
used in agriculture
4-Chlorophenoxyacetic acid (4-CPA):
Product Name 4-Chlorophenoxyacetic acid(4-CPA)
Content 98%
Melting Point 155-159 ° C
Appearance White powder
Loss on drying <1.0%
Residue on ignition <0.1%
Chemcial Name: 4-chlorophenoxyacetic acid p-chlorophenoxy acetic acid
Toxicology:
Acute oral LD50 for rats 2200mg/Kg; acute dermal LD50 >2200mg/Kg. Irritating to
skin and eyes. LC50 for fish: carp 3-6ppm loach (48hr) 2.5ppm,water flea>40ppm.
Application:
Auxin like plant growth regulator, absorbed by plant via root, stem, leaf, bloom and
fruit. It is used to prevent abscission of bloom and fruit, inhibit rooting of beans,
promote fruit set, induce formation of seedless fruit. Also used for ripening and fruit
thinning. It performs better when used in combination with 0.1% mono potassium
phosphate. It also has herbicidal effect at high dosage.

25. 23
6-Benzylaminopurine (6-BA):
Chemical name 6-Benzylaminopurine(6-BA),6-benzyladenine
Purity 99%
Melting Point 230-233°C
Appearance White crystals
Loss on drying 0.5%
Residue on ignition <0.05%
Toxicology:
Acute oral toxicity(LD50 ): male rat 2125mg/Kg, female rat 2130mg/Kg; mouse
(male & female), 1300mg/Kg. Acute percutaneous toxicity, LD50 >5000mg/Kg for
mouse (male & female). Median tolerance limit(TLm) for carp, 400ppm, 48hr.
Irritative and harmful to eyes.
Application:
6-BA is the first synthetic cytokinin. It can inhibit degradation of chlorophyll, nucleic
acid and protein, promote delivery of amino acid, inorganic salt and growth regulators
to applied ositions. It helps plant to keep green and retard aging. It can be used in
agriculture, horticulture, for plants at different stages, from germination to harvest.

26. 24
Thidiazuron:
Thidiazuron
Thidiazuron exceeds 98% purity, it is the highest specification available.
► Thidiazuron is a plant growth regulator.
► Formula: C9H8N4OS
► MW 220.25
► Assay min. 98 %.
Common name: thidiazuron (BSI, E-ISO, (m) F-ISO, ANSI)
IUPAC name: 1-phenyl-3-(1,2,3-thiadiazol-5-yl)urea
Chemical Abstracts name: N-phenyl-N'-1,2,3-thiadiazol-5-ylurea
Applications:
Biochemistry Cytokinin activity. Mode of action Plant growth regulator, absorbed by
the leaves, which stimulates formation of an abscission layer between the plant stem
and the leaf petioles, causing the dropping of entire green leaves. Uses Used for
defoliation of cotton, in order to facilitate harvesting. Formulation types EC; WP;
Oily flowable.
Mammalian toxicology:
Oral Acute oral LD50 for mice >5000, rats >4000 mg/kg. Skin and eye Acute
percutaneous LD50 for rats >1000, rabbits >4000 mg/kg. Mild eye irritant; non-
irritating to skin (rabbits). No skin sensitisation (guinea pigs). Inhalation LC50 (4 h)
for rats >2.3 mg/l air. NOEL (90 d) for rats 200 mg/kg diet; (1 y) for dogs 100 mg/kg
diet. No significant effects observed in a 2 y carcinogenicity study in mice and a 3-

27. 25
generation reproduction study in rats. Other Acute i.p. LD50 for rats 4200 mg/kg.
Non-mutagenic. Toxicity class WHO (a.i.) III (Table 5); EPA (formulation) III.
Ecotoxicology:
Birds Acute oral LD50 for Japanese quail >3160 mg/kg. Dietary LC50 (8 d) for
bobwhite quail and mallard ducks >5000 mg/kg diet. Fish LC50 (96 h) for rainbow
trout, bluegill sunfish, and catfish >1000 mg/l. Daphnia LC50 (48 h) >10 mg/l. Bees
Non-toxic to honeybees. Worms LC50 (14 d) for earthworms >1400 mg/kg.
Environmental fate:
Animals In rats and goats, metabolism involves hydroxylation of the phenyl group,
followed by formation of water-soluble conjugates. Following oral administration, the
compound is excreted in the urine and faeces within 96 hours. Plants Only small
amounts of residue (normally <0.1 mg/kg) are likely in cottonseed. Soil/Environment
Strongly adsorbed by soil. DT50 in soil c. 26-144 d (aerobic), 28 d (anaerobic).
Essential soil microbial processes are only temporarily influenced, if at all.
Abscisic acid:
Abscisic acid
Formula C15H20O4.
MOL WT 264.32
Physical state white to light yellow crystalline powder
Melting point 189 - 1910
C
Solubility in water Slightly soluble
PH
4 - 5 (1% aq. solution)
Stability Stable under ordinary conditions. Light/air sensitive.
Toxicity:

28. 26
SYNONYMS (±)-Abscisic acid; ABA; 2-cis-4-trans-Abscisic acid; Dormin;
(S-(Z,E))-5-(1-Hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl)-3-methylpenta-2,
4-dienoic acid; (2-cis,4-trans)-5-(1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-
yl)-3-methyl-2,4-pentadienoic acid; Abscisin II; cis-trans-(+)-Abscissic acid.
Applications:
Abscisic acid is one of five (or more) major plant hormones (Auxin, Cytokinins,
Gibberellins, Ethylene and Abscisic acid). It can be classified as a shock hormone
which are produced in response to rapid developing stress situations. Abscisic acid is
ubiquitous in higher plants. The the highest levels are found in young leaves and
developing fruits and seeds at the beginning of the winter season. Auxin and cytokinin
are growth hormones. Gibberellins and ethylene are known as stress hormones.
Though each plant hormone evokes many different specific biochemical,
physiological, or morphological responses, the effects of different hormones overlap
and may be stimulatory or inhibitory to regulate plant development and growth.
Abscisic tends to disrupt various aspects of plant growth to develop fruits and
augment sugar content. Accordingly, it can be classified as the growth retardants,
which can be sub-classified as gibberellin biosynthesis inhibitors or compounds which
are not involved in inhibiting gibberellin biosynthesis.
Effect of ethephon :
A flammable, colorless, Gas with a characteristic sweet odor. Ethylene (IUPAC name:
ethene) is a gaseous organic compound with the formula C2H4. It is the simplest
alkene (older name: olefin from its oil-forming property). Because it contains a
carbon-carbon double bond, ethylene is classified as an unsaturated hydrocarbon.
Ethylene is widely used in industry and is also a plant hormone. Ethylene is the most
produced organic compound in the world; global production of ethylene exceeded 107
million tonnes in 2005.To meet the ever increasing demand for ethylene, sharp
increases in production facilities have been added globally, particularly in the Persian
Gulf countries.
Ethephone

29. 27
Common name: ethephon (ANSI, Canada); chorethephon (New Zealand)
IUPAC name: 2-chloroethylphosphonic acid
Chemical Abstracts name: (2-chloroethyl) phosphonic acid

30. 28
The areas of an ethylene plant are:
1. steam cracking furnaces:
2. primary and secondary heat recovery with quench;
3. a dilution steam recycle system between the furnaces and the quench system;
4. primary compression of the cracked gas (3 stages of compression);
5. hydrogen sulfide and carbon dioxide removal (acid gas removal);
6. secondary compression (1 or 2 stages);
7. drying of the cracked gas;
8. cryogenic treatment;
9. The entire cold cracked gas stream goes to the demethanizer tower. The
overhead stream from the demethanizer tower consists of all the hydrogen and
methane that was in the cracked gas stream. Cryogenically (−250 °F (−157 °C))
treating this overhead stream separates hydrogen from methane. Methane
recovery is critical to the economical operation of an ethylene plant.
10.The bottom stream from the demethanizer tower goes to the deethanizer tower.
The overhead stream from the deethanizer tower consists of all the C2,'s that
were in the cracked gas stream. The C2 stream contains acetylene, which is
explosive above 200 kPa (29 psi). If the partial pressure of acetylene is
expected to exceed these values, the C2 stream is partially hydrogenated. The
C2's then proceed to a C2 splitter. The product ethylene is taken from the
overhead of the tower and the ethane coming from the bottom of the splitter is
recycled to the furnaces to be cracked again;
11.The bottom stream from the de-ethanizer tower goes to the depropanizer tower.
The overhead stream from the depropanizer tower consists of all the C3's that
were in the cracked gas stream. Before feeding the C3's to the C3 splitter, the
stream is hydrogenated to convert the methylacetylene and propadiene (allene)
mix. This stream is then sent to the C3 splitter. The overhead stream from the
C3 splitter is product propylene and the bottom stream is propane which is sent
back to the furnaces for cracking or used as fuel.
12.The bottom stream from the depropanizer tower is fed to the debutanizer tower.
The overhead stream from the debutanizer is all of the C4's that were in the
cracked gas stream. The bottom stream from the debutanizer (light pyrolysis
gasoline) consists of everything in the cracked gas stream that is C5 or heavier.

31. 29
Since ethylene production is energy intensive, much effort has been dedicated to
recovering heat from the gas leaving the furnaces. Most of the energy recovered from
the cracked gas is used to make high pressure (1200 psig) steam. This steam is in turn
used to drive the turbines for compressing cracked gas, the propylene refrigeration
compressor, and the ethylene refrigeration compressor. An ethylene plant, once
running, does not need to import steam to drive its steam turbines. A typical world
scale ethylene plant (about 1.5 billion pounds of ethylene per year) uses a
45,000 horsepower (34,000 kW) cracked gas compressor, a 30,000 horsepower
(22,000 kW) propylene compressor, and a 15,000 horsepower (11,000 kW) ethylene
compressor.
Laboratory aspects:
Ethylene can be produced in the laboratory by heating absolute ethanol with
concentrated sulfuric acid. Interestingly for such a useful compound, ethylene is rarely
used in organic synthesis in the laboratory. Being a simple molecule, ethylene is
spectroscopically simple. Its UV-vis spectrum is still used as a test of theoretical
methods.
Ethylene as a plant hormone:
Ethylene serves as a hormone in plants. It acts at trace levels throughout the life of the
plant by stimulating or regulating the ripening of fruit, the opening of flowers, and the
abscission (or shedding) of leaves. Commercial ripening rooms use "catalytic
generators", to make ethylene gas, from a liquid supply of ethanol. Typically, a
gassing level of 500 ppm to 2,000 ppm is used, for 24 to 48 hours. Care must be taken
to control carbon dioxide levels in ripening rooms when gassing, as high temperature
ripening (68F) has been seen to produce CO2 levels of 10% in 24 hours.
Ethylene perception in plants:
Ethylene could be perceived by a transmembrane protein dimer complex. The gene
encoding an ethylene receptor has been cloned in Arabidopsis thaliana and then in
tomato. Ethylene receptors are encoded by multiple genes in the Arabidopsis and
tomato genomes. The gene family comprises five receptors in Arabidopsis and at least
six in tomato, most of which have been shown to bind ethylene. DNA sequences for
ethylene receptors have also been identified in many other plant species and an
ethylene binding protein has even been identified in Cyanobacteria.

32. 30
Environmental and biological triggers of ethylene:
Environmental cues can induce the biosynthesis of the plant hormone. Flooding,
drought, chilling, wounding, and pathogen attack can induce ethylene formation in the
plant. In flooding, root suffers from lack of oxygen, or anoxia, which leads to the
synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC). ACC is transported
upwards in the plant and then oxidized in leaves. The product, the ethylene causes
epinasty of the leaves.
One speculation recently put forth for epinasty is the downward pointing leaves may
act as pump handles in the wind. The ethylene may or may not additionally induce the
growth of a valve in the xylem, but the idea would be that the plant would harness the
power of the wind to pump out more water from the roots of the plants than would
normally happen with transpiration.
Physiological responses of plants:
Like the other plant hormones, ethylene is considered to have pleiotropic effects. This
essentially means that it is thought that at least some of the effects of the hormone are
unrelated. What is actually caused by the gas may depend on the tissue affected as
well as environmental conditions. In the evolution of plants, ethylene would simply be
a message that was coopted for unrelated uses by plants during different periods of the
evolutionary development.
List of plant responses to ethylene:
 Seedling triple response, thickening and shortening of hypocotyl with
pronounced apical hook.
 In pollination, when the pollen reaches the stigma, the precursor of the
ethylene, ACC, is secreted to the petal, the ACC releases ethylene with ACC
oxidase.
 Stimulates leaf and flower senescence
 Stimulates senescence of mature xylem cells in preparation for plant use
 Induces leaf abscission
 Induces seed germination
 Induces root hair growth – increasing the efficiency of water and mineral
absorption

33. 31
 Induces the growth of adventitious roots during flooding
 Stimulates epinasty – leaf petiole grows out, leaf hangs down and curls into
itself
 Stimulates fruit ripening
 Induces a climacteric rise in respiration in some fruit which causes a release of
additional ethylene.
Affects gravitropism
 Stimulates nutational bending
 Inhibits stem growth and stimulates stem and cell broadening and lateral
branch growth outside of seedling stage
 Interference with auxin transport (with high auxin concentrations)
 Inhibits shoot growth and stomatal closing except in some water plants or
habitually flooded ones such as some rice varieties, where the opposite occurs
(conserving CO2 and O2)
 Induces flowering in pineapples
 Inhibits short day induced flower initiation in Pharbitus nil and
Chrysanthemum morifolium
Commercial issues:
Ethylene shortens the shelf life of many fruits by hastening fruit ripening and floral
senescence. Tomatoes, bananas and apples will ripen faster in the presence of
ethylene. Bananas placed next to other fruits will produce enough ethylene to cause
accelerated fruit ripening. Ethylene will shorten the shelf life of cut flowers and potted
plants by accelerating floral senescence and floral abscission. Flowers and plants
which are subjected to stress during shipping, handling, or storage produce ethylene
causing a significant reduction in floral display. Flowers affected by ethylene include
carnation, geranium, petunia, rose, and many others.
Ethylene can cause significant economic losses for florists, markets, suppliers, and
growers. Researchers have developed several ways to inhibit ethylene, including
inhibiting ethylene synthesis and inhibiting ethylene perception.
Aminoethoxyvinylglycine (AVG), Aminooxyacetic acid (AOA), and silver ions are
ethylene inhibitors. Inhibiting ethylene synthesis is less effective for reducing post-
harvest losses since ethylene from other sources can still have an effect. By inhibiting

34. 32
ethylene perception, fruits, plants and flowers don't respond to ethylene produced
endogenously or from exogenous sources. Inhibitors of ethylene perception include
compounds that have a similar shape to ethylene, but do not elicit the ethylene
response. One example of an ethylene perception inhibitor is 1-methylcyclopropene
(1-MCP). Commercial growers of bromeliads, including pineapple plants, use
ethylene to induce flowering. Plants can be induced to flower either by treatment with
the gas in a chamber, or by placing a banana peel next to the plant in an enclosed area.
Applications:
Mode of action Plant growth regulator with systemic properties. Penetrates into the
plant tissues, and is decomposed to ethylene, which affects the growth processes.
Uses To promote pre-harvest ripening in apples, currants, blackberries, blueberries,
cranberries, morello cherries, citrus fruit, figs, tomatoes, sugar beet and fodder beet
seed crops, coffee, capsicums, etc.; to accelerate post-harvest ripening in bananas,
mangoes, and citrus fruit; to facilitate harvesting by loosening of the fruit in currants,
gooseberries, cherries, and apples; to increase flower bud development in young apple
trees; to prevent lodging in cereals, maize, and flax; to induce flowering of
Bromeliads; to stimulate lateral branching in azaleas, geraniums, and roses; to shorten
the stem length in forced daffodils; to induce flowering and regulate ripening in
pineapples; to accelerate boll opening in cotton; to modify sex expression in
cucumbers and squash; to increase fruit setting and yield in cucumbers; to improve the
sturdiness of onion seed crops; to hasten the yellowing of mature tobacco leaves; to
stimulate latex flow in rubber trees, and resin flow in pine trees; to stimulate early
uniform hull split in walnuts.
Mammalian toxicology:
Reviews FAO/WHO 80 (see part 2 of the Bibliography). G. Hennighausen et al.,
Pharmazie, 32, 181 (1977). Oral Acute oral LD50 for rats 3030 mg/kg (tech.). Skin
and eye Acute percutaneous LD50 for rabbits 1560 mg/kg (tech.). Irritating to skin and
eyes. Inhalation LC50 (4 h) for rats 6.26 mg/l (tech.). NOEL (2 y) for rats 3000 ppm
diet. ADI (JMPR) 0.05 mg/kg b.w. [1997]. Toxicity class WHO (a.i.) III (Table 5);
EPA (formulation) I (tech.) EC hazard Xn; R20/21| C; R34| R52, R53: for
preparations containing ≥25%, C; R20/21, R34: for 25%>concn.≥10%,C; R34: for
10%>concn.≥5%, Xi; R36/37/38.
Ecotoxicology:
Birds Acute oral LD50 for bobwhite quail 1072 mg/kg (tech.). Dietary LC50 (8 d) for
bobwhite quail >7000 ppm in diet (tech.). Fish LC50 (96 h) for carp >140, rainbow

35. 33
trout 720 mg/l (tech.). Daphnia EC50 (48 h) 577.4 mg/l. Algae EC50 (24-48 h) for
Chlorella vulgaris 32 mg/l. Other aquatic spp. Low toxicity. Bees Not toxic to bees.
Worms Not toxic to earthworms.
Environmental fate:
Animals In animals, ethephon is rapidly excreted intact via the urine, and as ethylene
via the expired air. Plants In plants, ethephon rapidly undergoes degradation to
ethylene. Soil/Environment Rapidly degraded in soil, and strongly adsorbed; unlikely
to leach.

36. 34
Conclusion
As plants grow their genotype is expressed in the phenotype which is modified by the
environmental conditions that they experience. Somehow the rates of growth and
differentiation of cells in different parts of the plant are coordinated in response to
these inputs. Hormones in animals coordinate body functions by being produced in
one place and acting in another. Plants do not have a circulatory system and "action at
a distance" may not be a feature of plant hormones. They are molecules that are not
directly involved in metabolic or developmental processes but they act at low
concentrations to modify those processes. There are five generally recognized classes
of plant hormone; some of the classes are represented by only one compound, others
by several different compounds. They are all organic compounds, they may resemble
molecules which turn up elsewhere in plant structure or function, but they are not
directly involved as nutrients or metabolites. Interactions between a plant's genome
and its environment controls the characteristics (phenotype)of that plant. Plant
hormones play an integral role in the phenotype which is expressed by a plant by
acting as a messenger between the environment and the genome. If the plant is
exposed to arid conditions with low soil moisture (drought), Synthesis of abscisic acid
is stimulated. Abscisic acid will then turn on particular genes (drought resistance
genes) which will express a given phenotype (drought resistance). Agriculture,
horticulture and plant sciences in general are being revolutionized by the development
of genetic engineering (DNA recombination). This technology is providing plant
biologists with the ability to transfer genes along with their traits from very different
organisms. One step back in the genetic engineering of hormonally regulated genes is
that the hormone will produce one effect in a particular part of the plant or at a
specific stage of development and a totally different response at another location or
stage of development. Research on promoter sites and their interaction with chemical
messengers is an important area of research which may lead to the development of
engineering hormonally regulated genes. A promoter is the region of a gene which
regulates the activation of that gene. The idea behind studying promoters is that
certain promoters will only turn on a gene at a particular stage of development or in a
particular location of the plant. Attachment of the gene of interest to the promoter of
interest makes it possible to express a particular gene in a particular location or at a
particular stage of development. We presently have much to learn about plant
hormones but with the aid of genetic engineering, the plant science fields will be
advancing at an astonishing pace in the near future.

37. 35
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