Plant Hormones and Growth Regulators

 
PLANT
 
HORMONES
OR
PLANT
 
 
GROWTH
 
REGULATOR
 
C
ONTE
N
T
S
 
Introduction
Classification
Auxin
Cytokinins
Gibberellins
Abscisic
 
acid
Ethylene
Previously 
asked
 
questions
References
 
INTRODUCTION
 
Plant
 
growth
 
regulators
 
may
 be
 
defined
 
as
 any
 
organic
compounds,
 
which
 
are
 
active
 
at
 low
 
concentrations
 
in
promoting,
 
inhibiting or
 
modifying
 
growth
 
and
 
development.
The 
term 
Hormone 
is 
derived 
from 
a Greek 
root 
hormao
which
 
means
 
‘to
 
stimulate’
Thimann (1948) 
suggested 
using the 
term 
Phytohormone’
for
 
Hormones
 
of
 
plant.
The 
naturally occurring
 
growth substances 
are commonly
known as 
plant hormones, while 
the 
synthetic 
ones 
are called
growth
 
regulator.
Plant 
hormone is an 
organic 
compound synthesized 
in 
one
part of the plant and 
translocated to 
another part, 
where in
very
 
low
 
concentrations
 
it
 
causes
 
a
 
physiological
 
response.
The plant hormones are 
identified 
as promoters 
(
auxins,
gibberellin
 
and
 
cytokinin
),
 
inhibitors
 
(
abscissic
 
acid
 
and
ethylene
).
 
CLASSIFICATION
 
There
 
are
 
five
 
major
 
plant
 
growth
 
regulators 
 
which
includes:
1)
Auxin
2)
Cytokinins
3)
Gibberellins
4)
Abscisic
 
acid
 
(ABA)
5)
Ethylene
 
Growth promoters
 
Growth inhibitors
 
AU
X
IN
 
Types
 
 
TYPES OF
 
AU
X
INS
 
Indole
 
acids:
 
indole-3-propionic
 
acid
 
(
IPA
)
 
Naphthalene
 
acids
 
Naphthalene
 
acetic
 
Acid
 
(NAA)
 
β-Naphthoxyacetic
 
Acid
 
(NOA)
 
Chlorophenoxy
 
acids
 
2,4-Dichlorophenoxyacetic
acid
 
2,4,5-Trichlorophenoxyacetic
acid
 
Benzoic
 
acids
 
2,4,6-Trichlorobenzoic
 
acid
 
3,6-dichloro-2-methoxybenzoic
acid
 
ROLE OF
 
A
U
XIN
 
Development
 
of the
 
female sex organ
Auxins promotes development of female sex organ in flowers along
with ethylene.
Apical
 
dominance
Growth 
of
 
the shoot
 
apex
 
(terminal
 
shoot)
 
usually
 
inhibits
 
the
development 
of the lateral buds on the stem beneath. This
phenomenon is
 
called
 
apical
 
dominance.
Fruit
 
development
 
Pollination 
of the 
flowers 
of 
angiosperms 
initiates the 
formation 
of
seeds. 
As 
the 
seeds mature, 
they release auxin to the surrounding
flower
 
parts,
 
which develop
 
into
 
the
 
fruit that
 
covers
 
the 
seeds
 
Plant
 
B
 
has
 apical 
bud
 
removed
 
so
 
auxiliary
 
buds
 
grow.
 
A
 
B
 
Root
 initiation
 
and
 
development
The
 
localized
 
accumulation
 
of auxin
 
in
 
epidermal
 
cells
 
of the
 
root
initiates
 
the 
formation 
of
 
lateral
 
or
 
secondary
 
roots.
Auxin
 
also
 
stimulates
 
the 
formation 
of
 
adventitious
 
roots
 
in
 
many
species. 
Adventitious roots grow from 
stems 
or leaves rather than
from
 
the
 
regular
 
root
 
system
 
of
 
the
 
plant.
Phototropism
Plant
 
bend
 
towards
 
unilateral
 
light.
This
 
is
 
due
 
to
 
higher
 
concentration
 
of
 
auxin
 
on
 
the
 
shaded
 
side.
Partinocarpy
Induces parthinocarpy. i.e. direct Development of ovary in to fruit
without fertilization.
 
 
Evidence
 
for
 
the
 
role
 
of
 
auxin
 
in
 
adventitious
 
root
 
formation
 
With
 
synthetic
 
auxin
 
Without
 
synthetic
auxin
 
Adventitious
roots
 
growing
from 
stem
tissue
 
 
Saintpaulia
 
(
Gesneriaceae
 
family)
(African
 
violets)
 
Phototropism
 
CYTOKININS
 
This 
was 
discovered in the course of 
studies involved 
in
identifying
 
factors
 
that stimulate
 
plant cells to
 
divide.
Cytokinins
 
were 
discovered
 
by
 
Folke
 
Skoog,
 
Carlos
Miller
 
and 
co-workers
 
in
 
1955.
F.
 
skoog
 
discovered
 
that
 
degraded
 
DNA
 
after
 
autoclaving
was able to
 
induce
 
cell
 division
 
in
 
Tobacco
 
pitch
 
tissue.
After 
thorough 
analysis of the degeaded 
product 
of 
DNA 
it
was 
found
 that
 
the
 
active component was
 
6-fufuryl amino
 
purine
 
(6-furfuryladenine)
,
 
and it
 
was 
named
 
as
 
kinetin.
The
 
naturally
 
occurring
 
cytokinins
 
are
 
cis-
 
trans-zeatin
(ZEA),
 
dihydrozeatin,
 
isopentenyladenine(IPA)
 
etc.
The 
synthetic
 
Cytokinins
 
are
 
kinetin,
 
N-N
 
diphenylurea,
6-benzylaminoprine(BAP)
 
etc.
 
naturally
 
occurring
 
cytokinins
 
Synthetic
 
Cytokinins
 
ROLE
 
OF
 
CYTOKININS
 
Regulates the cell cycle/cell
 
division
 
(hence,the 
name
"cytokinins)
 
 
especially
 
by 
controlling
 
the
 
transition
 
from
G2
 
to
 
mitosis.
Control
 
morphogenesis
In plant 
tissue 
cultures, 
cytokinin 
is required 
for 
the
growth of 
a callus (an undifferentiated, tumor-like 
mass
of
 
cells).
Greening
Promotes
 
the 
light-induced
 
formation
 of
 
chlorophyll.
Bud
 
development
Direct
 
application
 
of
 
cytokinin
 
promotes
 
the
 
growth
 
of
axillary
 
buds.
 
Delay
 
senescence
senescence is 
the 
programmed aging process that occurs in
plants (and other
 organisms
 
for
 
that
 
matter).
loss
 
of
 
chlorophyll,
 
RNA,
 
protein
 
and 
lipids.
cytokinin 
application to 
an 
intact leaf markedly reduces 
the
extent and
 
rate of
 
chlorophyll
 
and
 
protein degradation
 
and
leaf
 
drop.
It
 
delays
 
the
 
ageing
 
of
 
the plant.
 
Transgenic
SAG12-IPT
 
plant
 
Nicotiana
 
(Solanaceae
 
family)
(Tobacco
 
plant)
 
 
Comparison
 
of
 
a transgenic
 
SAG12-IPT
 
plant
 
with
 the
 
wild
 
type,
 
Note
 
the
significantly
 
delayed
 
leaf
 
senescence
 
in
 
the
 
transgenic
 
plant.
 
GIBB
E
RELLINS
 
Gibberellins (GAs) were first isolated from 
the 
fungus
Gibberella fujikuroi 
in 1926 by Japanese scientist 
E.
Kurosawa
G. 
fujikuroi 
causes 
baka’nae 
(foolish 
seedling) disease in
rice,
 
causing
Excessive
 
shoot
 
elongation,
Yellowish
 
green
 
leaves
taller
 
plants
 
with
 
absent or
 
poorly
 
developed
 
grains
Frequent
 
lodging
 
due
 
to
 
long stature
Chemical was extracted & 
purified 
and 
named 
as
Gibberellic
 
A
c
id
 
(GA).
Now
 
80
 
different
 
Gibberellins
 
are
 available-
 
GA1
 
to
 
GA80
is
 
available.
The
 
most
 
commonly
 
occurring
 
gibberellins
 
is
 
GA3.
 
Gibberellic
 
acid(GA
3
)
 
ROLE
 
OF
 
GIBBERELLINS
 
Promotes
 
stem
 
elongation
When
 
applied
 
to
 
intact
 
plants,
 
GA
 
usually
 
causes
 
an
 
increase,
 
unlike
auxin.
It
 
overcomes
 
dwarfism
 
in
 
mutants
 
.
 
Overcomes
 
dormancy
 
in
 
seeds
Dormancy 
is a period in an 
organism's 
life cycle when growth,
development, and (in 
animals) 
physical 
activity 
are 
temporarily
stopped.
Gibberellins also have a fundamental role in breaking seed
dormancy
 
and
 
stimulating
 
germination.
Many forms of dormancy are broken by 
GA. 
These include
seed 
dormancy, 
dormancy of 
potato tubers 
and dormancy 
of
shoot
 
internodes
 
and 
buds.
GA
 
can
 
induce
 
fruit enlargement
External 
application 
of gibberellins 
can also 
enlarge 
fruit 
size
in
 
grapes
 
Sex
 
expression
In
 
plants
 
with
 
separate
 
male
 
and
 
female
 
flowers,
 
GA
application
 
can
 determine sex.
 
For
 
example, in
 
cucumber
 
and
 
spinach,
 
GA
 
treatment
increases
 
the
 
proportion
 
of
 
male 
flowers.
In
 
maize,
 
GA
 
treatment
 
causes
 
female
 
flower
 
development.
Involved
 
in
 
parthenocarpic
 
fruit
 
development
Development of 
fruit 
without fertilization . The 
fruit
resembles
 
a normal 
fruit,
 
but
 
it
 
is
 
seedless
GA
 
causes
 ovaries
 
to mature
 
without
 
fertilization
 
and
produces
 
bigger
 
fruits.
 
Germination
Gibberellins are 
involved 
in the natural process of
germination.
Before 
the 
photosynthetic apparatus develops sufficiently in
the
 
early
 
stages
 
of
 
germination, the
 
stored
 
energy
 
reserve
of starch
 
nourish
 
the
 
seedling.
Flowering
Exogenous GA
 
application
 
can
 
induce
 
flowering
 
in
 
species
that
 
ordinarily
 
require cold
 
treatment to
 
bloom.
 
ABS
C
ISIC
 
AC
I
D(
A
BA)
 
ABA plays a major role in adaptation to abiotic
environmental stresses, seed
 
development,
 
and
 
germination.
Abscisic
 
acid
 
is
 
an
 
important
 
growth 
regulator
 
for
 
induction
of
 
embryogenesis.
This
 
is
 
a
 
growth
 inhibitor.
 
ROLE 
O
F
 
ABSCISIC
 
ACID
 
Seed
 
Dormancy
ABA
 
plays
 
a
 
major
 
role
 
in
 
seed
 
dormancy
D
u
ring
 
se
e
d mat
u
ration,
 
ABA
 
le
v
els
 
inc
r
e
a
se
dramatically.
This inhibits germination and turns on the
production
 
of
 
proteins
 
that enable
 
the
 
embryo
 
to
survive
 
dehydration
 
during
 
seed
 
maturation.
 
ABA
 
induces
 
stomatal
 
closure
 
Solutes 
(
e.g. 
potassium 
and
chloride 
ions) 
accumulate 
in
guard 
cells 
causing 
water 
to
accumulate 
in 
guard 
cells,
making them 
turgid(swollen
from
 
water
 
uptake.)
 
ABA 
is 
one
 
signal
 
that
 
causes
guard 
cells 
to 
release 
solutes 
and
thus
 release
 
water,
 making
 
them
flaccid(compressed/shrink)
 
and
closing the 
stoma (pore) between
them
 
Drought
 
resistance
Abscisic 
acid 
is 
the 
key internal 
signal 
that facilitates
drought
 
resistance
 
in
 
plants
Un
d
er
 
wat
e
r
 
st
r
ess
 
con
d
iti
o
n
s
,
 
ABA
 
a
c
cu
m
u
l
ates in
leaves 
and 
causes stomata to close 
rapidly, 
reducing
transpiration
 
and preventing
 
further
 water
 
loss.
ABA causes the opening of 
efflux 
K+ channels in guard
cell plasma membranes, leading to a 
huge loss 
of this ion
from
 
the
 
cytoplasm.
The simultaneous osmotic loss of water leads to a
decrease in 
guard 
cell’s 
turgidity, 
with 
consequent
closure
 
of
 
stomata.
 
Inhibition
 
of
 
bud growth
 
and 
shoot
 
formation.
Abscisic 
acid 
owes 
its 
names 
to its 
role in 
the 
abscission
of
 
plant
 
leaves.
In
 
preparation 
for
 
winter,
 
ABA
 
is
 
produced
 
in
 
terminal
buds.
 
This 
slows 
plant 
growth 
and directs leaf primordia to
develop scales to protect 
the 
dormant buds 
during the
cold
 
season.
 
ETHYLENE
 
It is
 
the
 
only
 
gaseous
 
hormone
 of
 plants.
It is produced naturally by higher plants 
and 
is able to
diffuse 
readily, 
via intercellular spaces, 
throughout 
the
entire
 
plant
 
body
In
 
1934,
 
Gane
 
identified
 
that
 
plants
 
could
 
synthesise
ethylene and in 1935 Crocker 
proposed 
ethylene to be the
hormone 
responsible for fruit 
ripening and senescence of
vegetative
 
tissues.
Apples
 
and
 
pears
 
are
 
examples
 
of fruit
 that
 
produce
ethylene
 
with
 
ripening.
 
Ethylene is 
responsible for the 
changes in texture,
softening,
 
color,
 
and
 
other
 
processes
 
involved
 
in
 
ripenining.
 
ROLE
 
OF
 
ETHYLENE
 
Fruit
 
ripening
Under natural 
conditions, fruits 
undergo 
a series of changes,
including changes in 
colour, 
declines in 
organic 
acid 
content
and
 
increases
 
in
 sugar
 
content.
In
 
many
 
fruits, 
these
 
metabolic processes
 
often
 
coincide
with a period 
of 
increased respiration, 
the 
respiratory
climacteric
 
.
During
 
the climacteric there is
 
also a
 
dramatic increase in
ethylene
 
production.
Ethylene 
can 
initiate 
the climacteric in a number of 
fruits
and
 
is used
 
commercially
 
to
 
ripen
 
tomatoes,
 
avocados,
melons,
 
kiwi 
fruit
 
and bananas.
 
Shoot
 
Growth
Applied ethylene has 
the 
capacity to influence 
shoot
growth.
Application of ethylene to 
dark-grown seedlings 
can
cause reduced elongation of the stem, bending of the
stem
 
and swelling
 
of
 
the
 
epicotyl
 
or
 
hypocotyl.
Ethylene 
treatment 
of
seedlings 
promotes
hook 
closure 
and stem
thickening rather than
elongation. These
etiolated pea 
seedlings
were
 
treated
 
with
 
0,
 
0.1
and 1 ppm ethylene
(left
 
to
 
right)
 
Flowering
The
 
ability
 
of
 
ethylene
 
to
 
affect
 
flowering
 
in
 
pineapples
 
has
important
 
commercial
 
applications
 
.
Growth
 
effects
Inhibits
 
logitudinal but
 promotes
 
horizontal
 
growth.
Breaks
 dormancy
 
REFERENCES
 
Chawla H.S(2009 ) , 
Introduction 
to 
plant
biotechnology(3
rd 
edition), Science 
publishers, 
22-
23
Edwin 
F. 
George, Edwin 
F. 
George, Michael A.
Hall, Geert-Jan De Klerk (2007) - Plant
Propagation
 
by
 
Tissue
 
Culture.The
 
Background,
Volume
 
1,Springer,175-282
 
Thank
 
you
Slide Note
Embed
Share

Plant growth regulators, also known as plant hormones, play a crucial role in regulating growth and development in plants. They are organic compounds that act at low concentrations to promote, inhibit, or modify growth processes. The main plant hormones include auxins, cytokinins, gibberellins, abscisic acid, and ethylene. Each hormone has specific functions such as promoting female sex organ development, influencing apical dominance, and regulating fruit development. Understanding these hormones is essential for improving plant growth and productivity.

  • Plant hormones
  • Growth regulators
  • Auxins
  • Cytokinins
  • Gibberellins

Uploaded on Sep 13, 2024 | 1 Views


Download Presentation

Please find below an Image/Link to download the presentation.

The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.

E N D

Presentation Transcript


  1. PLANTHORMONES OR PLANT GROWTH REGULATOR

  2. CONTENTS Introduction Classification Auxin Cytokinins Gibberellins Abscisic acid Ethylene Previously asked questions References

  3. INTRODUCTION Plant growth regulators may be defined as any organic compounds, which are active at low concentrations in promoting, inhibiting or modifying growth and development. The term Hormone is derived from a Greek root hormao which means to stimulate Thimann (1948) suggested using the term Phytohormone for Hormones of plant. The naturally occurring growth substances are commonly known as plant hormones, while the synthetic ones are called growth regulator. Plant hormone is an organic compound synthesized in one part of the plant and translocated to another part, where in very low concentrations it causes a physiological response. The plant hormones are identified as promoters (auxins, gibberellin and cytokinin), inhibitors (abscissic acid and ethylene).

  4. CLASSIFICATION There are five major plant growth regulators which includes: 1)Auxin 2) Cytokinins 3) Gibberellins 4)Abscisic acid (ABA) 5) Ethylene Growth promoters Growth inhibitors

  5. AUXIN

  6. Types

  7. TYPES OFAUXINS Indole acids: indole-3-propionicacid (IPA)

  8. Naphthalene acids Naphthalene aceticAcid (NAA) -Naphthoxyacetic Acid (NOA)

  9. Chlorophenoxy acids 2,4-Dichlorophenoxyacetic acid 2,4,5-Trichlorophenoxyacetic acid

  10. Benzoic acids 2,4,6-Trichlorobenzoicacid 3,6-dichloro-2-methoxybenzoic acid

  11. ROLE OFAUXIN Development of the female sex organ Auxins promotes development of female sex organ in flowers along with ethylene. Apical dominance Growth of the shoot apex (terminal shoot) usually inhibits the development of the lateral buds on the stem beneath. This phenomenon is called apical dominance. Fruit development Pollination of the flowers of angiosperms initiates the formation of seeds. As the seeds mature, they release auxin to the surrounding flower parts, which develop into the fruit that covers the seeds

  12. A B Plant B has apical bud removed so auxiliary buds grow.

  13. Root initiation and development The localized accumulation of auxin in epidermal cells of the root initiates the formation of lateral or secondary roots. Auxin also stimulates the formation of adventitious roots in many species. Adventitious roots grow from stems or leaves rather than from the regular root system of the plant. Phototropism Plant bend towards unilateral light. This is due to higher concentration of auxin on the shaded side. Partinocarpy Induces parthinocarpy. i.e. direct Development of ovary in to fruit without fertilization.

  14. Evidence for the role of auxin in adventitious root formation Withsynthetic auxin Withoutsynthetic auxin Adventitious rootsgrowing from stem tissue Saintpaulia(Gesneriaceae family) (African violets)

  15. Phototropism

  16. CYTOKININS This was discovered in the course of studies involved in identifying factors that stimulate plant cells to divide. Cytokinins were discovered by Folke Skoog, Carlos Miller and co-workers in 1955. F. skoog discovered that degraded DNA after autoclaving was able to induce cell division in Tobacco pitch tissue. After thorough analysis of the degeaded product of DNA it was found that the active component was 6-fufuryl amino purine (6-furfuryladenine), and it was named as kinetin. The naturally occurring cytokinins are cis- trans-zeatin (ZEA), dihydrozeatin, isopentenyladenine(IPA) etc. The synthetic Cytokinins are kinetin, N-N diphenylurea, 6-benzylaminoprine(BAP) etc.

  17. naturally occurring cytokinins

  18. Synthetic Cytokinins

  19. ROLE OF CYTOKININS Regulates the cell cycle/cell division (hence,the name "cytokinins) especially by controlling the transition from G2 to mitosis. Control morphogenesis In plant tissue cultures, cytokinin is required for the growth of a callus (an undifferentiated, tumor-like mass of cells). Greening Promotes the light-induced formation of chlorophyll. Bud development Direct application of cytokinin promotes the growth of axillary buds.

  20. Delay senescence senescence is the programmed aging process that occurs in plants (and other organisms for that matter). loss of chlorophyll, RNA, protein and lipids. cytokinin application to an intact leaf markedly reduces the extent and rate of chlorophyll and protein degradation and leaf drop. It delays the ageing of the plant.

  21. Transgenic SAG12-IPT plant Nicotiana (Solanaceae family) (Tobaccoplant) Comparison of a transgenic SAG12-IPTplant with the wild type, Note the significantly delayed leaf senescence in the transgenic plant.

  22. GIBBERELLINS Gibberellins (GAs) were first isolated from the fungus Gibberella fujikuroi in 1926 by Japanese scientist E. Kurosawa G. fujikuroi causes baka nae (foolish seedling) disease in rice, causing Excessive shoot elongation, Yellowish green leaves taller plants with absent or poorly developed grains Frequent lodging due to long stature Chemical was extracted & purified and named as GibberellicAcid (GA). Now 80 different Gibberellins are available- GA1 to GA80 is available. The most commonly occurring gibberellins is GA3.

  23. Gibberellic acid(GA3)

  24. ROLE OF GIBBERELLINS Promotes stem elongation When applied to intact plants, GAusually causes an increase, unlike auxin. It overcomes dwarfism in mutants .

  25. Overcomes dormancy in seeds Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. Gibberellins also have a fundamental role in breaking seed dormancy and stimulating germination. Many forms of dormancy are broken by GA. These include seed dormancy, dormancy of potato tubers and dormancy of shoot internodes and buds. GAcan induce fruit enlargement External application of gibberellins can also enlarge fruit size in grapes

  26. Sex expression In plants with separate male and female flowers, GA application can determine sex. For example, in cucumber and spinach, GAtreatment increases the proportion of male flowers. In maize, GAtreatment causes female flower development. Involved in parthenocarpic fruit development Development of fruit without fertilization . The fruit resembles a normal fruit, but it is seedless GAcauses ovaries to mature without fertilization and produces bigger fruits.

  27. Germination Gibberellins are involved in the natural process of germination. Before the photosynthetic apparatus develops sufficiently in the early stages of germination, the stored energy reserve of starch nourish the seedling. Flowering Exogenous GAapplication can induce flowering in species that ordinarily require cold treatment to bloom.

  28. ABSCISICACID(ABA) ABA plays a major role in adaptation to abiotic environmental stresses, seed development, and germination. Abscisic acid is an important growth regulator for induction of embryogenesis. This is a growth inhibitor.

  29. ROLE OFABSCISICACID Seed Dormancy ABAplays a major role in seed dormancy During seed maturation,ABAlevels increase dramatically. This inhibits germination and turns on the production of proteins that enable the embryo to survive dehydration during seed maturation.

  30. ABA induces stomatal closure ABA is one signal that causes guard cells to release solutes and thus release water, makingthem flaccid(compressed/shrink) and closing the stoma (pore) between them Solutes (e.g. potassium and chloride ions) accumulate in guard cells causing water to accumulate in guard cells, making them turgid(swollen from water uptake.)

  31. Drought resistance Abscisic acid is the key internal signal that facilitates drought resistance in plants Under water stress conditions, ABA accumulates in leaves and causes stomata to close rapidly, reducing transpiration and preventing further water loss. ABA causes the opening of efflux K+ channels in guard cell plasma membranes, leading to a huge loss of this ion from the cytoplasm. The simultaneous osmotic loss of water leads to a decrease in guard cell s turgidity, with consequent closure of stomata.

  32. Inhibition of bud growth and shoot formation. Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in terminal buds. This slows plant growth and directs leaf primordia to develop scales to protect the dormant buds during the cold season.

  33. ETHYLENE It is the only gaseous hormone of plants. It is produced naturally by higher plants and is able to diffuse readily, via intercellular spaces, throughout the entire plant body In 1934, Gane identified that plants could synthesise ethylene and in 1935 Crocker proposed ethylene to be the hormone responsible for fruit ripening and senescence of vegetative tissues. Apples and pears are examples of fruit that produce ethylene with ripening. Ethylene is responsible for the changes in texture, softening, color, and other processes involved in ripenining.

  34. ROLE OF ETHYLENE Fruit ripening Under natural conditions, fruits undergo a series of changes, including changes in colour, declines in organic acid content and increases in sugar content. In many fruits, these metabolic processes often coincide with a period of increased respiration, the respiratory climacteric . During the climacteric there is also a dramatic increase in ethylene production. Ethylene can initiate the climacteric in a number of fruits and is used commercially to ripen tomatoes, avocados, melons, kiwi fruit and bananas.

  35. Shoot Growth Applied ethylene has the capacity to influence shoot growth. Application of ethylene to dark-grown seedlings can cause reduced elongation of the stem, bending of the stem and swelling of the epicotyl or hypocotyl. Ethylene treatment of seedlings promotes hook closure and stem thickening rather than elongation. These etiolated pea seedlings were treated with 0, 0.1 and 1 ppm ethylene (left to right)

  36. Flowering The ability of ethylene to affect flowering in pineapples has important commercial applications . Growth effects Inhibits logitudinal but promotes horizontal growth. Breaks dormancy

  37. REFERENCES Chawla H.S(2009 ) , Introduction to plant biotechnology(3rd edition), Science publishers, 22- 23 Edwin F. George, Edwin F. George, Michael A. Hall, Geert-Jan De Klerk (2007) - Plant Propagation by Tissue Culture.The Background, Volume 1,Springer,175-282

  38. Thank you

More Related Content

giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#giItT1WQy@!-/#