plant grwz hormone

8/8/2019 Plant Grwz Hormone

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Chapter 6 The Plant Hormones

(Phytohormones) p309-366

Plant hormone

Plant growth substance

plant regulator

Plant hormones are naturally occurringorganic substance that can be transported from

the synthetic tissue to a specific target tissue

where, at low concentration,exert a profound

influence on physiological process.


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1gIAA/10000 tips.1mgIAA/1T leaf.

10mgBR/225kg of pollen.

5 putative plant hormonesIAAGACTKABA and Eth6BR.

Plant growth regulators () arenormally used to denote synthetic

compounds that exhibit plant hormonal

activity.


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Section 1 Auxins

1.1 Discover of auxin

Charles Darwin and Francis Darwin(1880, Phalaris

canariensis )

Boysen-

Jensson(1910)

F.W. Went(1928)----Avena curvature test.


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Went called it auxin.

Structure of IAA isIndole-3-acetic acid---IAA.

N

-CH2COOH

1.2 Distribution and transportation of IAA in

plant

All parts have auxins, but the highest concentrations locates in

meristematic regions and actively growing organ, such as


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0

0.1

0.2

0.3

0 20 40 60Distance form coleoptile apix to roottip(cm)

IAArelativecontents

coleoptile apices, root tips and the apical buds of

growing stems.

Fig 6-1 IAA concentrations in plant parts


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IAA Polar transportIAA is only one plant

hormone transported unidirectionally from

apical end to basal end.

IAA transport in root from basal to tip.


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Fig 6-2 IAA Polar transport controlled by IAA transport

protein (from Taiz and Zeiger 2006)


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Other transport: IAA synthesized in mature

leaf is transported in double-directionally alongthe phloem.


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1.3 Biosynthesis of IAA

1.3.1 Biosynthesis locationalmost parts of

plant. Especially in coleoptile, young leaf and

developing seed and fertilizing ovary

1.3.2 Steps of Biosynthesis

1Tryptophan pathway: The deficiency of Zn decreases IAA synthesis

due to decreasing in Trp synthesis.


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1 Pathway dependent on tryptophan

Tryptophan(Trp) CO2

-NH2

CO2

O2

-NH2

O2

+H2O

-2H

(IAA) Indole acetic acid

N

COOH

NH2

N

NH2

*Trp decarboxylase

*Trp

transaminase

N

COOH

O

Indole-3-pyruvic acid(IPA)

IAld reductase

Tol oxidaseN

O

N

OH

Trptamine

(TAM)

Amine oxidase

*IPAdecarboxylase

Indole-3-acetaldehyde(IAld)

N

COOH

IAld

dehydrogenase

Indole-3-ethanol

(tryptophol,TOL)

NNOH

Indole-3-acetaldoxime

N

N

Indole-3-acetonitrile

(IAN) *nitrilase

N

O

NH2

Indole-3-

acetamide

(IAM)

*Trp

monoxygenase

*IAM

hydrolase


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normal IAA-over

producing

plant

Fig 6-3 IAA-over producingplant grows worse


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Fig 6-4 Effects of indole-3-acetonitrile

and IAA on wild-type (wt) and nit1-3

mutant seedlings of Arabidopsis.

Eight-day-old seedlings grown in the presence

and absence of 30 M indole-3-actonitrile(B) or

1M IAA(C). (Control is shown[A].) Note that

wild-type plants show a typical auxin-like response

to both IAA and indole-3-acetonitrile.The nit1-3

motant responeds to IAA but does not exhibit an

auxin-like response to indole-3-acetonitrile. It

lacks nitrilase and cannot convert indole-3-acetonitrile to IAA

A

B

C

wt

wt

wt

Nit1-3

Nit1-3

Nit1-3

Nit1(nitrilase mutant) is

insensitive to indole-3-acetonitrile


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An orange pericarp (orp) maize cob showing the expected two-

gene recessive trait, the orange kernels carry both mutant genes

2 Pathway independent on tryptophanMutants for tryptophan nutrition deficient

Maize -orp mutant, trp synthase -subnuit point

mutant, 50 time high IAA-conjugate


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Arabidopsis-trp1,trp2 and trp3 cantsynthesize Trp but content 19-30 times as

higher as IAA-conjugates of wild type

N15-anthranilate(

N15-IAA 39%N15-Trp 13%


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N

N

anthranliate( Chorismate phenylalanine tyrosine() ( )

5-phosphoribosylanthranilate

1-(o-carboxyphenylamino)

-1-deoxyribulose-5-P

N

CH2

OP

0H

OH

N

N

COOH

NH2

N

COOH

O

N

COOH

IAASerine +indole

Indole-3-glyceral

phosphate

IGP synthase

Trp synthase

Trp synthase

Trp3

Trp2,orp

IGP

Trp

PR-anthranilate

isomerase

Anthranilate

PR-transferase

anthranilate synthase(Trp1,MTR)

IPA

IAN

Trp s

ynthas

e

aminotransferase

rty?

Nitrilasenit1

N

COOH

Indole-3-butyric acid(IBA)

IBA sythase

IBA-conjugates

IAA-conjugates


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1.4 Inactive and degradation ofIAA

1.4.1 IAA-conjugate:

IAA-Amide

IAA-Sugar


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Function of IAA-conjugates

(1)Storage form.

(2)Easy transport form.

(3)Anti oxidation form.

(4)Level control and detoxification.


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1.4.2 IAA oxidation

Two enzymes: IAA oxidase and peroxidase


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1.5 Physiological effects and application

of IAA (1)Enhancing elongation of cell and

organ.

Control


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-12-10-8-6-4-202468

10

0 1 2 3 4 5 6 7 8 9 10 11 12

-Relativegrowthrate

+

10-11 10-9 10- 7 10- 5 10- 3 10- 1

IAA concentrationmol/L)

Root

Bud Stem

Fig 6-5 Effect of IAA concentration on elongation of root,

bud and stem. The growth-optimum concentration is for

stem higher than for bud, then for root. The root growth is

most sensitive to IAA.


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Mechanism for elongation by IAA 1

IAA activates genesmRNA andprotein synthesisSlow reaction.

IAAmRNA

protein

Elongation

+IAA

+IAA+actinomycinD

CK

+IAA

+IAA+cycloheximide

CKElongation

andmR

NA

Elongation

andPro

tein


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BAcid growth theory () .

rapid reactionIAA activates ATPasepH , cell wallacidification enzyme activation cell wall dehydration andloosening water absorption

Fig6-12 IAA as an effector activates ATPase (H+-pump) in

plasmic membrane

H+ H+

Microfiber of cellulose

Pentosan

other cell wall polysaccharide

Hydrogen bound

Inactive EIAA

Active EATP

ADP+Pi


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Plant hormone receptors are a group ofproteins which first bind plant hormones

and make the hormone play a serious

role in physiological functions.


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(2) Enhancing cell division and organogenesis

Cutting-shoot rooting () Cambium cell division and root primordial cell

division in the early spring.

IAACK

The rooting with 10-100 mgL-1 or 0.5-1% of powder.


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(3) Enhancing fruit setting and parthenocarpy

()production of seedless fruit

Watermelon, popper, tomato, egg plant etc aresprayed with 24-D (dichlorophenoxyacetic acid)

of 10 mgL-1 to produce seedless fruit by

parthenocarpy in early spring time or greenhouse

cultivation.


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Lateral bud develops

after removing apical

bud.

Lateral bud poorly

develops afterremoving apical bud,

then putting IAA in the

part

Lateral bud

(4) Maintaining apical dominance


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(5) Enhancing abscissionflower and fruitthinning ()Apple with NAA (naphthalene acetic acid)520 mgL-1

or NAD (naphthalene acetamide)2550 mgL-1.

(6) Inhibiting sprouting ofpotato .

1% of NAA powder


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(7) Enhancing flowering and controlling

sexual differentiation.

14 months old pineapple with 2.4D 50-100mgL-1 or NAA 1520 mgL-1 ( 30ml per plant)

Cucumber .

(8) As a herbicide to kill dicot with 24-D(1000 mgL-1 .


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Conclusion of IAA functions: (1)Enhancing elongation of cell and organ

(2)Enhancing cell division and organogenesis

(3)Enhancing fruit setting and parthenocarpy

(4) Maintaining apical dominance

(5) Enhancing abscission (6) Inhibiting sprouting

(7) flowering and sexual differentiation.

(8) As a herbicide


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Section 2 Gibberellic acid (GA) 2.1 Discover of GA

Rice foolish seedling infected by Gibberellia

fujikuroi. A large family of more than 125members.

12

3 54

18

20

CH3

CH3

CH3

6

8

7

10 9

19 CH3HH

11 12

13

14

15

16 17

CH3

HH

gibberellane

1

2

3 54

18CH3

O

6

8

7

10 9

COOHH

H

11 12

13

14

15

16 17

CH2

OHH

19CO

GA3

GA is diterpenes constituting with 4 isopentenal groups

HO


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C19 --GA is higher activity than 20C GA. Those with both

3-OH and 1,2 unsaturation exhibit the highest activity.

2.2 Synthesis and transport of GA

GAs exist universally in plant kingdom and fast

growing parts are higher ontent

GAs are synthesized in shoot,root, flower and fruit.


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Fig 6-13 Histochemical localization of GA1promoter activity indicating CPS expression during

the development of transgenic Arabidopsis

containing the GA1 promoter-GUS gene fusion

pGA1-103.


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In plant

Copalylpyrophosphate CPP

CHO

GA127aldehyde

3CH2C-OCoA

OCH2COOH

HOCCH2

CH2CH2OH

OH OH

H3C-C=CH-CH2- O- P -O-P-OH

CH2

O O

4 molecules

Geranylgeranylpyrophosphate

GGP

OPP

Kaurene

Kaurenoic acid

various

GA

-CCC

-AMO-1618

-Phosphor-D

OPP

In microbe

Biosynthesis pathway of GA and several retardants (inhibitors for

GA biosynthesis)

COOH COOH

Mevalonic acid Isopentenyl pyrophospha(IPP)


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Fig 6-14 Inactive form:

2-hydroxylation and

GA-conjugate: GA-glucoside.


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2.3 Physiological role and application of GA

(1) Promoting elongation of stem anddivision of cell.

Function in subapices and promote

elongation of whole plant, especially ofmutants and physiological draft.


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Fig 6-15 Effect of

GA3 on stemelongation of

Progress No.9 dwarf

pea seedlings:(left)

control plants, (right)plants seven days

after treatment with 5

g GA3

.

physiological draft


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CK 100pg 1ng

Fig 6-16 Promotion of leaf sheath elongation of

Tanginbozu dwarf rice three days after treatment with

GA3.


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Application in stem or leaf-harvested

plants such as celery, lettuce, tea etc with 1-5mgL-1 .

20-40 mgL-1 of GA3 can accelerates heading

of late season rice or hybrid rice.

Mechanisms:

(1) Cell division ---shorten cell division cycle,

especial interphase in which DNA synthesis.

(2) Cell elongation increasing in IAA level


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(2) Cell elongation---increasing in IAA level(synthesis, antioxidation and conjugate

dehydration)---Increasing in cell wall plasticity and

extensibility

0

20

40

60

80

0 10 20 30

+GA-GA

02

468

10121416

0 10 20 30

+GA-GA

Plasticity

%

E

longation%

Fig 6-17 Cell wall plasticity and elongation induced by GA


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Fig 6-18 GA signal transduction


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(2) Breaking dormancy and promoting

germination of seed.

GA3 0.5-1mg/L for GA-dependant mutants

and GA3100mg.L-1

can substitute red lightfor seed germination.

Mechnisminduction to -amylase inaleurone.


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Application Beer production. Breaking bud dormancy of potato with 0.5-

1.0 mgL-1 GA3.

(3) P ti b lti d fl i


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Normal T GA3 Low T

(3) Promoting bolting and flowering

GA substitutes low temperature andlong daytime.


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Fig 6-20 GA and flower (after Taiz &zeiger 2006)


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Grape, apple and pear are sprayed with GA3 10-20

mgL-1 during flowering stage.

Grape is sprayed

with GA3 200-500

mgL-1 for seedless fruits


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(5) Controlling sexual differentiation

GA3 1000 mgL-1 4-5 leaf old to form male

flower in cucumber but female flower in some tree.


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Conclusion of GA function: (1) Promoting elongation of stem and division of

cell

(2) Breaking dormancy and promotinggermination of seed

(3) Promoting bolting and flowering


(5) Controlling sexual differentiation

S ti 3 C t ki iCTK


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Section3 CytokininCTK3.1 Discover of CTK

1950s, Skoog and co-workers found

extracts of vascular tissue, coconut milk,and yeast stimulated cell division---kinetin.

---cytokinin(1965).

1963, Letham reported the isolation of

purine with kinetin like properties from

young, developing maize seed--- Zeatin.

S l CTK t t


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Several CTK structures

H-N-R1

N

N

N

N

R2

R3

N6-substituted

derivatives of

nitrigenous purineN

N

N

N

HH

H-N-CH2-C=C

CH3

CH3

H

N

N

N

N

HH

H-N-CH2-C=C

CH3

CH2OH

H

N

N

N

N

HH

H-N-CH2-C- CH

CH3

CH2OH

H

H

Isopentenyl

adenine

ZeatinDihydrozeatin

6


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3.2 Transportation and Biosynthesis of CTK

(1) Transportation of CTK

CTK synthesized in root can be transported

up along with xylem. CTK applied in leaf orbud surface does not move but that is

injected into phloem can be transported in

double directions.

(2) Biosynthesis of CTK Root tip about1mm


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Fig 6-18 Crown gall

tumor on a tomato plant.

The stem of a one-month-old

tomato seedling was wounded

with a needle carrying a cultureof wild-type Agrobacterium

tumefaciens. The crown gall

tumor was photographed one

month later.

Pathway of CTK biosynthesis


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Pathway of CTK biosynthesis

N

N

N

N

H

H-N-H

OP-O-CH2

OH OH

Isopentenyl pyrophosphate

AMP

Isopentenyl

AMP synthase

-3O4P2-O-CH2-C=C

CH3

CH3

HCH2-C=C

CH3

CH3

H

N

N

N

N

H

H-N-

OP-O-CH2

OH OH

IsopentenylAMP

CH2-C=C

CH3

CH3

H

H-N-

N

N

N

NH

HIsopentenyl adenine

CH2-C=C

CH2

CH3

H

H-N-

N

N

N

NH

H

-OH

Zeatin


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CTK degradation

by conjugates

3 3 Physiological role and application of


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3.3 Physiological role and application of

CTK(1) Enhancing cell division and enlargement

CTKcallus

Cotyledon

CK

Why? Gene expression


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(2) Inducing organ differentiation.


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Root and bud differentiation depending onCTK/IAA ratio

CTK/IAA

ratio higherCTK/IAA

ratio lower

CTK/IAA

ratio middle

CTK/IAA ratio from higher to lower

(3) Delaying senescence


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(3) Delaying senescenceH2O

CTK

Keep flesh

Strawberry10 mg L-1 KT

orange400 mg L-1 6-BA

mushroom100 mg L-1 6-BA

P IPT CK CK Th f


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PSAG12-IPT

PSAG12-IPT

CK CK

CK

The senescence of

IPT transgene plantand wild parent

7d storage

(4)Inhibiting dominance and enhancing lateral sprout .


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Fig 6-20 Transgenic tobacoexpressing the Agrobacterium

tumefaciens iptgene under the

control of the strong CaMV

35S promoter.

Retard leaf senescence and

early release of lateral buds

(5) Enhancing germination

of light-favored seed


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Conclusion of CTK function: (1) Enhancing cell division and enlargement

(2) Inducing organ differentiation

(3) Delaying senescence

(4)Inhibiting dominance and enhancing lateral

sprout

(5) Enhancing germination of light-favored

seed

Section 4 Abscisic acid (ABA)


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Section 4 Abscisic acid (ABA)

4.1 Discover of ABA

1963, Addicott --abscisin, Wareing --- dormin.

CH3

COOH

CH3CH3

CH3

OH

O

Sesquiterpene-C15

ABA extensively exists in

plant organs, especially in

dormant or abscising parts.


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4.3Physiological role and application of


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ABA(1) Inducing stomata closureDrought signal and anti-transpiration substance,10-100

lL-1

control ABA

ABACa2+permeable

K+in channelABA

i d


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Ca2+

Ca2+

p

channel

Vacuole

Depolarize

K+

K+out channel

A-

S-type

anion channelR-type

anion channel

pH

Ca2+H

+

ATP

ADP+Pi

Fig 6-21 A guard cell model, illustrating the proposed

functions of ion channels in ABA signaling and stomatalclosing. The right of the stomatal shows ion channels and regulators thatmediate ABA-induced stomatal closing. The left cell shows the parallel

effects of ABA-induced [Ca2+]cyt increases that inhibit stomatal opening

mechamisms.

induces

stomatal

closure

(2) Inducing bud dormancy and inhibiting

seed germination


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seed germination

anti-function to GA.

(3) Enhancing organ abscission andsenescence.

Chlorophyll degradation

(4) Increase in resistance as a stress hormone

Induction osmotin, dehydorin and Lea protein during

maturation or drought stress.


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Section 5 EthyleneEth


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A gaseous hormone 5.1 Biosynthesis of Eth

Synthesis in all part, especially in rolling

apices, ripened fruit, wounding or flooding

plants.

Auto-catalyze feather.


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Fig 6-21 pathway of ethylene synthesis

Regulation of Eth biosynthesis


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MACCACC

SAM

AVG (aminoethoxyvinylglycine)

AOA (aminooxyacetic acid)

inhibitor

Ripening, senescing,

over-IAA, wounding,

chilling, flooding etc

stimuli

CH2=CH2

O2

CO2+HCN+H2O

Ripening anaerobicuncouple Co2+ ,

high temperature >35oC,

scavengers

ACC

oxidase

ACC

synthase

H2C

H2C

CNH3

+

COO-H2C

H2C

CNH

COO-

COO-

CH2

-C=O

5.2 Physiological role and application of Eth


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(1) Triple responses (): A typical reaction of plant to ethylene

represents inhibition and swelling ofhypocotyl, inhibition of elongation , and

exaggeration of the curvature (leaf epinasty).

Fig6-22 The triple response to

ethylene of six-day-old


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y y

etiolated pea seedlings andfour-day-old etiolated mung

bean seedlings

Fig 6-23 Screen foretr1


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mutant of Arabidopsis


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Fig 6-24 ethylene receptor

Fig 6-25 ethylene signal


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transduction

Epinasty () : the downward


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curvature of leaves occurs as the upper side ofpetiole grows faster than the lower side.

Normal plantPlant under flood or ethylene

(2) fruit ripening: a regulator, (, 2-


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) ClCH2CH2OP (OH)2 (water soluble)releases ethylene when pH is larger than 4.

Ethylene treatment

500-1000 mgL-1,

CK

(3) Inducing abscission


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Eth increases in the activities ofPectinase,peroxidase and cellulase in abscission zone.

Application: 600-800 mgL-1 as a defoliant for

cotton. Thinning fruit or flower in tea, grape and

Carya illinoensis().(4) Enhancing female flower formation

1-4 leaf old cucumber treated with 100-200 mgL-1.

(5) Enhancing secretion of secondary products

Oak etc treated with 5% of ethylene solution.

Inhibition of growth,

CO2 assimilation,

Increased

root water

uptake

Inhibition of

cell elongation,

cell division


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Cytokininat high

concentration

Auxinat high concentration

activity (auxin herbicides)

Stressconditions

Ethylene

ABAStress condition(loss of turgor)

Developmental

signals

Senescence Stomatal closure

Root,shootgravitropism

Inhibition of axillary bud

growth in apical dominance

Promotion of dormancy

transpirationp

?

?

Intereaction among IAA,CTK,ethylene and ABA

Section 6 Other plant growth substance


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in brief 6.1 BR ( Brassinosteroids or

Brassinolide,.

Promote growth for section or whole


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plant delaying senescence, increaseresistance and yield. 0.001-0.1mg/L .

6.2 Polyamine()


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Polyamines in plants Put() NH2(CH2)4NH2 Cad() NH2(CH2)5NH2 Spd() NH2(CH2)3NH (CH2)4NH2 Hspd() NH2(CH2)4NH (CH2)4NH2

Spm() NH2(CH2)3NH (CH2)4NH(CH2)3NH2 Agm() NH2(CH2)5NH C (NH) NH2

Promote Growth delaying senescence

6.3 JA (Jasmonic acid )(Me-JA)


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O

COOH

O

COOH

O

COOH

O

COOH

+JA -JA

-7-iso-JA +7-iso-JA

Inhibit growthpromote senescence and

tuberization

6.4 SASalicylic acid,


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-COOH

-OH

Signal transduction in resistance to diseases of

plant PRPs-pathogenesis-relative proteins

Enhance male flower .

Section 7 Plant growth regulators


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7.1 Plant growth-promoters

Indole derivatives :IPAIBA,

naphthalene derivatives :NAANOA, chlorophenol derivatives: 2.4-D2.4.5-D,

2.4.6- Trichlorophenoxyacetic acid,

2.3.6- Trichlorobenzoid acid .

Cytokinin-like :KTDiphenylurea 6BA


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8.3 Plant growth retardants

C d i t t t GA i f ti d


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Compounds resistant to GAs in function andinhibit the growth of the subapical meristem.The inhibitory effect can be reversed by GA,

but not by IAA.

8.3.1 B9 (dimathyl aminosuccinamic acid)

To prevent plant branch from overgrowing andto increase flower differentiation.

8.3.2 CCCChlorochdine chloride ). To prevent wheat from logding. 0.15-0.3% in

primary elongation stage.

8.3.3 Pix1. 1-dimethypiperidinium chloride,

)


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). Cotton plant with 25-150 mgL-1 during flower stage.

8.3.4 PP333 Paclobutrazol,) .

Drafting culture for fruit trees. Prevent late-season rice seedling from overgrowingwith 200 mgL-1 150Kg/mu at 1leaf stage.


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plant grwz hormone

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