BACTERIA

1. WELCOME

2. R.V.S.K.V.V.
COLLEGE OF AGRICULTURE, INDORE
SUBJECT :- DISEASE RESISTANCE IN PLANTS
Dept. :- Genetics And Plant Breeding
Submitted to:- Submitted by :-
Dr. R.K. Singh Somya Arora
M.Sc Previous year

3. DEFENCE MECHANISMS IN
PLANTS

4. CONTENT
• INTRODUCTION
• TYPES OF DEFENCE MECHANISMS
• STRUCTURAL DEFENCE MECHANISM
• BIOCHEMICAL DEFENCE MECHANISM
• INHIBITORS RELEASED BY PLANTS
• INDUCED CHEMICAL DEFENCE

5. What is Defence Mechanism?
An automatic reaction of the body against
disease causing organisms
• Each plant species is affected by
approximately hundred different kinds
of Fungi, Bacteria, Mollicutes, Viruses
and Nematodes.

6. HOST:- A living organisms from which other
organisms derive its food.
PATHOGEN:- Any agent which can cause disease.
RESISTANCE:- The ability of an organism to exclude
or overcome completely or in some degree, the effect
of pathogens of other damaging factor.

8. STRUCTURAL DEFENCE
MECHANISM
The surface of the Plants or Hosts is first line of Defence
against the pathogen.
Structural Defence Mechanism are mainly of 2
types:-
Pre-existing structural defence mechanism.
Post-infectional or Induced structural defence mechanism.

9. Pre-existing structural defence
mechanism:-
The first line of defence in plants present in its surface.
If the pathogen is succeeds in penetration, it encounters
pre existing internal structural barriers.The external and
internal structural barrier existing before pathogen attack are
called pre existing defence structure or passive, static or
anti-infection structures.

10. Pre-existing structural defence
includes:-
Wax
Thick cuticle
Thickness and toughness of the outerwall of
epidermal cells
Stomata
Schlerenchyma cells
lenticels

11. Post-Infectional / Induced
structural defence mechanism
Even after the establishment of infection in plant cells, the
host defence system tries to create barriers for further
colonization of tissues.
Most pathogen manage to penetrate their host through
wounds and natural opening to produce various degree of
infection.

12. These may be regarded as:-
Histological defence barrier.
Cellular defence structures

13. Histological defence
structures:-
Even after the establishment of infection in plant cells,the host defence
system tries to create barriers for further colonization of tissues.
These are:-
Cork layer
Abscission layer
Tyloses
Gum deposition

14. Cellular defence structures :-
The cellular defence structures i.e. changes in
cell walls,have only limited role in defence.
Example:- Hyphal sheathing

15. Bio-chemical Defence
Mechanism
Although structural defence mechanisms do prevent the attack of
pathogen , the defence mechanism also include the chemical
substances produced in the plant cells before or after the infection
.
Types of Biochemical defence mechanism are:-
• Pre-existing chemical defence
• Induced chemical defence

16. Pre-existing chemical defence
1.Inhibitors:-
• Released by plants in its environment
• Present in plant cells before infection
2.Phenolics:-
• Tannins
• Glucanases
• Dienes
• Chitinase

17. Induced Chemical Defence
The induced biochemical changes in most plants are the last line of host
defence.This may condition a plant or plant tissue from susceptible to resistant
to immune status as per their genetic potential.
These are :-
Hypersensitivity response (HR)
Production of antimicrobial substances
Phytoalexins
Plantbodies

18. THANKYOU