THE ROLE OF NEW GENERATION PHYTO HORMONES: AN OVERVIEW

ABOUT AUTHORS:
Lohithasu Duppala*, Santhosh naidu Matsa, Manikumar Kothakota,
GITAM Institute of Pharmacy, GITAM University, visakhapatnam, Andhra Pradesh, India-530045.
lohithasu@gmail.com, +91-9491894432

ABSTRACT:
Generally, almost all communication in higher plants was thought to be mediated by the five classes of classical plant hormones i.e. auxins, cytokinins, gibberellins, abscisic acid and ethylene. The plant hormone action thus appeared to be basically different from that in animals. This article discusses the general role for new generation of plant hormones includes Brassinosteriods, Salicylic acid. Peptides,Polyaminesand Jasmonates.

REFERENCE ID: PHARMATUTOR-ART-1687

INTRODUCTION:
Plant Hormones(Plant growth regulators):
These are small organic substances, which are synthesized in minute quantities by specific plant cells/tissues (one part of plant body) and transported to another part where they influence specific physiologic processes(promote or inhibit growth and development), active in low concentration. Hormones are synthesized or stored in regions of transduction. Hormones travel within phloem or from cell to cell after reception of appropriate stimulus. The term HORMONE was first used by Starling in 1906s.

Plant hormones-categories:

Based on function or chemical structure ,they can categorized into

1.Auxins- Natural (Indole -3-acetic acid) ;Synthetic (Indole -3-butyric acid, 2-methyl-4-chlorophenoxy acetic acid, Indole -3-propionicacid,2,4-dichlorophenoxy acetic acid)

2.Gibberllins-GA₁ …..GA_nin order of discovery

3.Cytokinins- kinetin, Zeatin, dihydrozeatin ,tricanthene, isopentenyl adenine etc.,

4.Growth inhibitors- Ethylene ,Abscisic acid(stress hormone) ,Chlorochine chloride, Morphactins, Maleic hydrazide

5.Other new generations- Brassinosteriods ,Salicylic acid,Peptides,Polyamines,Jasmonates and others.

Brassinosteriods
Salicylic acid
Peptides
Polyamines
Jasmonates

1.Brassinosteriods :

Brassinolide structure

Chemically similar to animal steroid hormones.In contrast to animal steroid signal molecules,Brassinosteriods are perceived by a plasma memberane localized receptor kinase.These are the polyhydrxylated steroid hormones of plants. Studied in Arabidopsis.Brassinolide, is the most bio-active form from 70 naturally occurring Brassinosteriods.
Brassinolide was the first isolated brassinosteroid , when pollen from Brassica napus .The Brassinosteroids , biosynthesised from campesterol. Brassinosteroids are recognized at the cell membrane, although they are membrane-soluble.^1,2
Extract from the plant Lychnis viscaria contains a relatively high amount of Brassinosteroids. Lychnis viscaria increases the disease resistance of surrounding plants.
Brassinosteroids have been reported to counteract both abiotic and biotic stress in plants. Brassinosteroids increased tolerance to high temperature in Brassica juncea L.
These were first isolated from pollen of the mustard family and extensively.Over 70 naturally occurring Brassinosteriods are known.Effective at low concentrations.

Brassinosteriods stimulate^3-12

Cell division ,stem elongation and cell elongation .
Cell wall loosening and cell wall regeneration.
Differentiation of xylem tissues and inhibit leaf abscission.
Plants found deficient in Brassinosteriods suffer from Dwarfism.
Regulate the growth and differentiation of plants throught their life cycle
Promotion of Vascular differentiation.
some protection to plants during chilling and drought stress.
Ethylene biosynthesis.
Required for fertility-Is necessary for pollen elongation for pollen tube formation.
Inhibit root development and growth.

2.Salicylic Acid:

Salicylicacid structure

· Salicylic acid, synthesized from phenylalanine. It is a monohydroxybenzoic acid, a type of phenolic acid and a beta hydroxy acid. It is found in plants with roles in plant growth and development, photosynthesis, transpiration, ion uptake and transport¹³.
· Promotes production of pathogenesis related proteins.
· Can reverse effects of ABA in some cases. SA also induces specific changes in leaf anatomy and chloroplast structure. SA is involved in endogenous signaling, mediating in plant defense against pathogens.

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3.Signaling Peptides^14-18:

These are small molecules that can be transported throughout the plant and effect development and involved in defense response.These are involved in self-incompatibilityand helps to determine cell fate.
Involved in nodule formation in legumes.These are also involved in wound signal transduction, in cell proliferation, and in the regulation of salt/water homeostasis.

Eg: Systemin , Rapid Alkalinization Factor , enod40,Polaris , Phytosulfokines ,natriuretic peptides etc.,

4.Polyamines^19-20:

Spermidine structure Putrescine structure

These are mostly aliphatic amines,having two or more primary amino groups –NH₂.
These are ubiquitous in living organisms and have been implicated in a wide range of biological processes, including plant growth, development and response to stress.
These are involved in somatic embryogenesis ,stem elongation and flowering,root growth,tuber development ,fruit ripening ,abiotic stresses .These are also involved DNA replication, transcription of genes, cell division, organ development, fruit development and ripening, leaf senescence and abiotic stresses.These are ffective at low concentrations.Mutants have abberant development

Eg: Putrescine, spermidine and spermine are most common.

5.Jasmonates:

Methyl jasmonate structure

Jasmonic acid is most common of Jasmonate.
These are methyl esters,Scented

Jasmonate function

Induce tuberization
Important in plant defense
Inhibit growth
Inhibit germination
Promote senescence
Promote pigmentation

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