Role of Growth

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ROLE OF GROWTH

REGULATERS ON IN-VITRO

MORPHOGENESIS OF PLANT



GUIDED BY

DR.Swarnalata Mishra



CONTENTS

INTRODUCTION

WHAT IS IN-VITRO MORPHOGENESIS

WHAT IS GROWTH REGULATERS

TYPES OF GROWTH REGULATERS

AUXIN

CYTOKININS

GIBBERELLINS

ABSCISIC ACID

ETHYLENE

ROLE OF GROWTH REGULATERS

IN CASE OF INVITRO MORPHOGENESIS

CONCLUSION



INTRODUCTION

WHAT IS IN-VITRO MORPHOGENESIS

IN VITRO(Latin-With in the glass)

MORPHOGENESIS:-Formation of the structure of an organism or part;

differentiation & growth of tissues & organs during development.

IN VITRO MORPHOGENESIS:-Formation of the structure of an

organism or part ; differentiation & growth of tissues & organs during

development in an artificial environment i.e out side the living organism

that means within the glass.Modern tissue culture in case of plants & animals is a bright example of

invitro morphogenesis.



WHAT IS GROWTH REGULATERS

Internal and external signals that regulate growth are mediated, at least in

part , are known as Growth Regulaters.They are otherwise known as

growth hormones.

These are of two types:- Plant growth regulaters/Phytohormones

Animal growth regulaters /

Plant hormones differ from animal hormones in that:

No evidence that the fundamental actions of plant and animalhormones are the same.

Unlike animal hormones, plant hormones are not made in tissues

specialized for hormone production. (e.g., sex hormones made inthe gonads, human growth hormone - pituitary gland)

Unlike animal hormones, plant hormones do not have definite target areas (e.g.auxins can stimulate adventitious root development in a cut shoot, or shoot elongation or apical dominance, or differentiation of

vascular tissue etc).



PLANT GROWTH REGULATORSPLANT GROWTH REGULATORS

PLANT GROWTH REGULATORS ARE NECESSARY FOR,BUT DO NOT CONTROL, MANY ASPECTS OFPLANT GROWTH AND DEVELOPMENT. ² BETTER NAME IS GROWTH REGULATOR.

THE EFFECT ON PLANT PHYSIOLOGY IS DEPENDENON THE AMOUNT OF HORMONE PRESENT ANDTISSUE SENSITIVITY TO THE PLANT GROWTHREGULATOR.

Substances produced in small quantities by a plant, and thentransported elsewhere for use .

Have capacity to stimulate and/or inhibit physiological processes.

At least five major plant hormones or plant growth regulators:

ooauxins, cytokinins, gibberellins, ethylene and abscisic acidauxins, cytokinins, gibberellins, ethylene and abscisic acid



TYPES OF PLANT GROWTHTYPES OF PLANT GROWTH

REGULATERSREGULATERS

Auxins Auxins (cell elongation)

GibberellinsGibberellins(cell elongation + cell division - translated into

growth)

CytokininsCytokinins (cell division + inhibits senescence)

Abscisic acid Abscisic acid (abscission of leaves and fruits + dormancy induction of buds and seed)

EthyleneEthylene (promotes senescence, epinasty, and fruit ripening)



AUXIN

Auxin increases the plasticity of plant cell walls and is involved in

stem elongation.

Arpad Paal(1919):- Asymmetrical placement of cut tips on

coleoptiles resulted in a bending of the coleoptile away from the

side onto which the tips were placed (response mimicked the

response seen in phototropism).

Frits Went (1926) determined auxin enhanced cell elongation.



Demonstration of transported chemicalDemonstration of transported chemical



Auxin Auxin

Discovered as substance associated with phototropicresponse.

Occurs in very low concentrations.

Isolated from human urine, (40mg 33 gals

-1

)

In coleoptiles (1g 20,000 tons-1)

Differential response depending on dose.



Auxins Auxins



Auxin Auxin

Auxin promotes activity of the vascular cambium and vascular

tissues.

o plays key role in fruit development.

Cell Elongation: Acid growth hypothesisCell Elongation: Acid growth hypothesis

auxin works by causing responsive cells to actively transport

hydrogen ions from the cytoplasm into the cell wall space.



SignalSignal--transduction pathways in plantstransduction pathways in plants

Auxin interacts with calcium ions which in turn

calmodulin, a protein, which regulates many processes

in plants, animals, and microbes.



Loosening of cell wallLoosening of cell wall



Polar transport of AuxinPolar transport of Auxin



Auxin

Synthetic auxins :- widely used in agriculture and horticulture

prevent leaf abscission

prevent fruit drop promote flowering and fruiting

control weeds

Agent Orange: - 1:1 ratio of 2,4-D and 2,4,5-T used to

defoliate trees in Vietnam War.



Additional responses to auxin Additional responses to auxin

Abscission :- loss of leaves

Flower initiation

Sex determination

Fruit development Apical dominance



Control of abscission by auxinControl of abscission by auxin



Apical Dominance

Lateral branchgrowth are inhibitednear the shoot apex,

but less so fartherfrom the tip.

Apical dominance

is disrupted in someplants by removing the shoot tip, causing the plant to become

bushy.



GibberellinGibberellin



Gibberellins

Gibberellins are named after the fungus Gibberella

fujikuroi which causes rice plants to grow abnormally

tall.

synthesized in apical portions of stems and roots

important effects on stem elongation

in some cases, hastens seed germination



Effects of GibberellinsEffects of Gibberellins

Cell elongation.

GA induces cellular division and cellular elongation; auxininduces cellular elongation alone.

GA-stimulated elongation does not involve the cell wallacidification characteristic of auxin- induced elongation

Breaking of dormancy in buds and seeds.

Seed Germination - Especially in cereal grasses, like

barley. Not necessarily as critical in dicot seeds.Promotion of flowering.

Transport is non-polar, bidirectional

producing general responses.



Gibberellins and Fruit Size

Fruit Formation - "Thompson Seedless" grapes grown

in California are treated with GA to increase size anddecrease packing



Mobilization of reservesMobilization of reserves



CytokininsCytokinins



Discovery of cytokininsDiscovery of cytokinins

Gottlieb Haberlandt in 1913 reported an unknowncompound that stimulated cellular division.

In the 1940s, Johannes van Overbeek, noted that plant embryos grew faster when they were supplied withcoconut milk (liquid endosperm) , which is rich in nucleicacids.

In the 1950s, Folke Skoog and Carlos Miller studying theinfluence of auxin on the growth of tobacco in tissueculture. When auxin was added to artificial medium, thcells enlarged but did not divide.

Miller took herrin -s erm DNA. Miller knew of



Discovery of cytokininsDiscovery of cytokinins

Adenine or adenine-like compounds induce cell divisionin plant tissue culture. Miller, Skoog and their coworkersisolated the growth factor responsible for cellular divisionfrom a DNA preparation calling it kinetin which belongsto a class of compounds called cytokinins.

In 1964, the first naturally occurring cytokinin wasisolated from corn called zeatin. Zeatin and zeatinriboside are found in coconut milk. All cytokinins(artificial or natural) are chemically similar to adenine.

Cytokinins move nonpolarly in xylem, phloem, andparenchyma cells.

Cytokinins are found in angiosperms, gymnosperms,

mosses, and ferns. In angiosperms, cytokinins areroduced in the roots seeds fruits.




Cytokinins, in combination with auxin, stimulate cell

division and differentiation. most cytokinin produced in root apical meristems

and transported throughout plant

inhibit formation of lateral roots

auxins promote their formation



Function of cytokininsFunction of cytokinins

Promotes cell division.

Morphogenesis.

Lateral bud development.

Delay of senescence.






Abscisic acid Abscisic acid

In 1940s, scientists started searching for hormones that would

inhibit growth and development,what Hemberg called dormins.

n the early 1960s.Philip Wareing confirmed that application of

a dormin to a bud would induce dormancy ..T. Addicott discovered that this substance stimulated abscission

f cotton fruit . He named this substance abscisin(Subsequent

esearch showed that ethylene and not abscisin controls abscissiobscisin is made from carotenoids and moves nonpolarly

hrough plant tissue.





Abscisic Acid

Abscisic acid is produced chiefly in mature green leave

in fruits.

Suppresses bud growth and promotes leaf senescence. Also plays important role in controlling stomatal openin

closing.



Functions of abscisic acidFunctions of abscisic acid

General growth inhibitor.

Causes stomatal closure.

Produced in response to stress.



Discovery of ethyleneDiscovery of ethylene

In the 1800s,it was recognized that street lights that burned

gas, could cause neighboring plants to develop short,thick

stems and cause the leaves to fall off. In 1901, Dimitry

Neljubow identified that a byproduct of gas combustionwas

ethylene gas and that this gas could affect plant growth.

In R.Gane showed that this same gas was naturally produc

by plants and that it caused faster ripening of many fruits.

Synthesis of ethylene is inhibited by carbon dioxide and

requires oxygen.



EthyleneEthylene

H H

\ /

C = C

/ \

H H



Functions of ethyleneFunctions of ethylene

aseous in form and rapidly diffusing.

Gas produced by one plant will affect nearby plants.

Fruit ripening.

Epinasty ² downward curvature of leaves.

Encourages senescence and abscission.

Initiation of stem elongation and bud development.

Flowering - Ethylene inhibits flowering in most species, but

promotes it in a few plants such as pineapple,bromeliads andmango.

Sex Expression - Cucumber buds treated with ethylene

become carpellate (female) flowers, whereas those treated

with gibberellins become staminate (male) flowers.



LE OF GROWTH REGULATER

IN CASE OF IN VITRO MORPHOGENESIS PLANTS:-

The in vitro growth of the plant cells occurs in a suitable medium

containing all the requisite elements.

The ingradients of medium effect the growth & metabolism of cell.Effect of growth regulaters on different parts of same plant or on

different species in relation to metabolite formation are variable.

There are some examples , where growth regulaters like;

Auxin,Cytokinin,gibberellins,ABA,Ethylene etc. shows various role in

growth induction/inhibition on different parts of same plant or

on different species .

Cytokinin & Auxin affect organogenesis.



IN EX-PLANT CULTURE

An excised pieces of differentiated tissue or organ isregarded as an ex-plant. The ex-plant may be taken from

any part of the body. e.g.root,steam,leaves.

Shoot formation in in vitro morphogenesis is a part of

ex-plant culture. Shoot formation in plant is induced by the

combine action of cytokinin & auxin (low/no auxin+ high

cytokinin).

Root formation in vitro morphogenesis is induced by (hig auxin + low/no cytokinin) concentration.

Leaf culture in vitro morphogenesis is induced by (high aux

+ low/no cytokinin) concentration.



IN EX-PLANT CULTURE

Callus culture:-Callus is the undifferentiated and unorganised

mass of plant cells.

Callus culture in vitro morphogenesis is induced by (high

auxin + low/no cytokinin).Seed germination is induced by the effect of growth regulater

gibberellin .

Somaclonal variation:-The genetic heterogeneity of cells in a

population represents continuity of genotypes,whereasphenotypically the population is represented as a dicrete sum

of subclones.Somaclonal variation is induced when the

concentration of auxin & cytokinin is same.



(undifferentiated plant cells) tissue(undifferentiated plant cells) tissue



Callus culture in Sorghum



LUS & SHOOT INITIATION IN TOM



CONCLUSION



THANK YOU

Role of Growth

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