狠狠撸

REVIEW ON
PLANT
SECONDARY
METABOLITES IN
PLANTS AND
THEIR
SIGNIFICANCE
Submitted By:-
Hemlata
Ph.D scholar
Deptt. of Entomology

SECONDARY METABOLITES
? Plants synthesize different
organic molecules called
secondary metabolites.
? These compounds often differ
between individuals from the
same population of plants.
?They are involved in the normal
growth, development, or
reproduction of an organism.
?They protect plants against
stresses, both biotic and abiotic.

Significance of Secondary Metabolites
? Secondary metabolites attract animals
for pollination and seed dispersal.
? The plants used in their defence
against herbivores and pathogens.
? They act as agents of plant-plant
competition.
? They are used in making drugs,
insecticides, flavours, pigments,
scents, rubber, spices and other
industrial materials like gums, resins
for human welfare.

Types of Secondary Metabolites
? These are highly numerous in number, chemically diverse in
nature and belong to three groups.
? Isoprenoids or Terpenes, e.g., rubber, steroids, essential
oils, carotenoid pigments.
? Nitrogen containing compounds, e.g., alkaloids,
glucosinolates, glycosides, non-protein amino acids.
? Phenolic compounds, e.g., lignin, tannins, coumarins,
aflatoxins, flavonoids .

1.TERPENES
? Terpenes are involved in defense as toxins and feeding
deterrents to a large number of plant feeding insects.
? Terpenes are divided into :
a) Monoterpenes
b) Sesquiterpenes
c) Diterpene
d) Triterpenes
e) Polyterpenes

Monoterpenes(C10)
? This pyrethroid occur in the leaves
and flowers of Chrysanthemum
species.
? It has a low persistence in the
environment and low mammalian
toxicity.
?In Gymnosperms (conifers) á-
pinene, ?-pinene, limonene and
myrecene are found.

Sesquiterpenes(C15)
? It plays an important role in plant defense.
? Such as costunolides are antiherbivore agents having
strong feeding repellence to many herbivorous, insects and
mammals.
? ABA is also a sesquiterpene.
? It plays a roles in:
o Initation and maintenance of seed and bud dormancy.
o Plants response to water stress.

Diterpenes(C20)
? Abietic acid is a diterpene found in pines and leguminous
tress.
? It is present in resin canals of the tree trunk.
?Phorbol found in euphorbiaceae work as skin irritants and
internal toxins to mammals.

Triterpenes(C30)
? They are important component of plant cell
membranes, especially in the plasma membrane.
?Milkweeds produce glucosides that protect them
against herbivores by most
insects and even cattle.

?Limnoid, a group of bitter substances in citrus fruits
and act as antiherbivore compounds.
?Azadirechtin acts as a feeding deterrent to some
insects like insects in order Lepidoptera and diptera.

Polyterpenes(C5)n
? These polyterpenes occur in plants.
? Tetraterpenes are carotenoids family of
pigments.
? Rubber is found in long vessels called
laticifers, provide protection as a mechanism
for wound healing and as a defense against
herbivores.

2.Nitrogen containing compounds
? They include alkaloids, cyanogenic glucosides, and
non-protein amino acids.
? Most of them are biosynthesized from common
amino acids.
? They play a great role in the antiherbivore defense
and toxicity to humans.

Alkaloids
? Alkaloids are a group of naturally occurring chemical
compounds.
? Most alkaloids are believed to function as defensive
elements against predators, especially mammals because of
their general toxicity and deterrence capability.

Cyanogenic glucosides
? They constitute a group of N-containing protective
compounds usually occur in members of families
viz., Graminae, Rosaceae and Leguminosae.
? The presence of cyanogenic glycosides deters
feeding by insects and other herbivores such as
snails and slugs.

?Amygdalin, the common cyanogenic
glucoside found in the seeds of
almonds, apricot, cherries and
peaches.
?Lima bean is inducible indirect
antiherbivore defences including the
production of volatile organic
compounds (VOCs).

Non-protein amino acids
? Many plants also contain unusual amino acids called
non- protein amino acids.
? They are present in free forms and act as protective
defensive substances.
?Canavanine and azetidine is a non-functional
proteins its catalytic site is disrupted.

3.Phenolic compounds
? A hydroxyl functional group on an aromatic ring
called Phenol.
? These is an important part of the plants defence
system against pests and disease including root
parasitic nematodes.

Coumarin
? These phenolic compounds are present in vascular
plants.
? They have a wide range of anti-microbial activity
against both fungi and bacteria.
? It behave as natural pesticidal defense compounds
for plants.

? Halogenated coumarin derivatives inhibit fungal growth.
?7-hydroxylated simple coumarins may play a defensive role
against parasitism of Orobanche cernua.

Lignin
? Lignin vary among species, plant organs and even
layers of a single cell wall.
? Its chemical durability makes it relatively
indigestible to herbivores and insects pathogens.
? Lignifications block the growth of pathogens and are
a frequent response to infection or wounding.

Flavonoids
? Flavonoids have different functions in plant system
including pigmentation and defense.
? They are ubiquitous in photosynthesizing cells.
? Flavonoids protect plants from different biotic and
abiotic stress.

It act as:
1. Phytoalexins
2. Unique UV- filter
3.Detoxifying agents
4. Allelopathic compounds
5. Function as signal
molecules
6.Antimicrobial defensive
compounds

Isoflavonoids
? Isoflavonoids are ubiquitously present in plants.
? They play a critical role in plant development and
defense response.
? It promotes the formation of nitrogen-fixing nodules
by symbiotic rhizobia.

Tannins
? Tannins reduce the growth and survivorship of many
herbivores.
? It act as feeding repellents to a great diversity of
animals.
? In mammalian herbivores, they cause a astringent
sensation in the mouth.
? Protocatechllic and chlorogenic acids have a special
function in disease resistance.

? They prevent smudge in onions, a disease caused by
the fungus Colletotrichum circinans.
? Proanthocyanidins act as feeding deterrents against
some insects such as, Lymantria dispar (L.),
Euproctis chrysorrhoea (L.) and O. brumata.

4.Sulphur containing secondary
metabolites
? They include:
? GSH
? GSL
? Phytoalexins
? Thionins
? Defensins
? Allinin
They linked with the
defence of plants against
microbial pathogens.

GSH
? The major forms of organic S in the soluble fraction
of plants.
? It reduces S in the regulation of plant growth and
development.
? Ascorbic acid is the integral weapon in the defense
against ROS generated by O3.

GSL
? A group of N and S containing glucosides that increase their
resistance against the unfavourable effects of predators,
competitors and parasites.
? They release volatiles defensive substances exhibiting toxic or
repellent effects.
?Mustard oil glucosides in cruciferae and
allyl cys sulfoxides in allium.
?Isothiocyanates and nitriles, function in defense as
herbivorous toxins and feeding repellent.

Phytoalexins
? Phytoalexins are synthesized in response to bacterial
or fungal infection.
? They help in limiting the spread of the invading
pathogens by accumulating around the site of
infection.

? There are multiple responses involving
several related derivatives such as:
1. Orchinol in orchid tubers
2. Trifolirhizin in red clover
3. Glyceollins in Glycine max
4. Wyerone forms in Vicia fava
5. Pistin in Pisum sativum pods

Defensins, thionins and lectins
? Defensins genes are partly pathogen-inducible are
involved in resistance.
? Accumulation of thionins in the cell wall of wheat
involved in defense responses to infections and in
spreading of Fusarium culmorum.
? Plant produce lectins as defensive proteins that bind
to epithelial cell lining of the digestive tracts and
interfere with nutrient absorption.

CONCLUSIONS
? The potential roles of Plant secondary metabolites in
defence mechanisms and ecological adaptation.
? The N and S containing secondary metabolites enhance the
capability of a plant to cope with biotic and abiotic stress.
? Additional research in area of natural pesticides
development is needed in current scenario.
? This will improve their resistance against herbivores and
microbial pathogens as well as various environmental
stresses.

PLANT SECONDARY METABOLITES IN PLANTS AND THEIR SIGNIFICANCE

狠狠撸

PLANT SECONDARY METABOLITES IN PLANTS AND THEIR SIGNIFICANCE

Recommended

More Related Content

Similar to PLANT SECONDARY METABOLITES IN PLANTS AND THEIR SIGNIFICANCE (20)

More from Hemlata (8)

Recently uploaded (20)

PLANT SECONDARY METABOLITES IN PLANTS AND THEIR SIGNIFICANCE