Defence Mechanisms in Plants Flashcards
Plant defense mechanisms are decided mainly to?
Structural Defence Mechanism and Biochemical Defence Mechanism
Structural defense mechanisms are mainly of two types:
Pre-existing structural defence
and Post-Infectional Structural defence
Biochemical Defense Mechanism are mainly of two types:
Pre-existing Biochemical Defence and Post-Infectional Biochemical Defence
EXAMPLES OF: Pre-existing structural defense mechanisms
Wax
Thick cuticle
Thickness and toughness of the outer wall of epidermal cells
Stomata
Sclerenchyma cells
Lenticels
Pre-existing structural defense that mixture of a long chained apolar lipid, protective jelly which coats the plant leaves and fruits synthetization of the epidermis.
and It is extremely hydro-phobic.
Wax
In linseeds, cuticle acts as a barrier against
Melampsora lini
Silicification and lignifications of epidermal cells offers protection against
Pyricularia oryzae and Streptomyces scabies in paddy and potato, respectively
cells are present in stem and leaf veins
Sclerenchyma Cells
Sclerenchyma Cells effectively block the spread of some fungal and bacterial pathogens that cause
angular leaf spot
Structures of Natural Openings are
Stomata and Lenticels
name of a pathogen that cause stem rust of wheat can enters its host only when the stomata are open.
Puccinia graminis f.sp. tritici
Small and suberized lenticels offer resistance to potato scab name the pathogen.
Streptomyces scabies
Post-Infectional Structural Defense are mainly of two types:
Cellular defense structure and Histological defense structure
Histological defense structure
Hyphal sheathing
Histological defense structure is mainly of four types:
Formation of cork layer
Formation of abscission layer
Formation of tyloses
Deposition of gums
defense structure that forms several layers of cells beyond the point of infection inhibits the further invasion by the pathogen beyond the initial lesion and also blocks the spread of toxic substances secreted by the pathogen.
Cork layers
example of infected protected with Cork layers
Potato tubers infected by Rhizoctonia
Prunus domestica leaves attacked by Coccomyces pruniphorae
defense structure consists of a gap formed between infected and healthy cells.
Abscission Layers
defense structure that overgrowths of the protoplast of adjacent living parenchymatous cells, which protrude into xylem vessels through pits.
Tyloses
defense structure secretion is most common in stone fruit trees but occurs in most plants.
Gum Deposition
the process in which gum produced by the plants and trees.
Gummosis
when can observed Hyphal sheathing in flax infected with?
Fusarium oxysporum f.sp. lini
Biochemical Defence Mechanism are mainly of two types:
Pre-existing chemical defence and Induced chemical defence
what are Pre-existing chemical defence
Inhibitors () and Phenolics
example of Inhibitors released by a Plant in it is Environment
Ex 1: Root exudates of marigold contain α-terthinyl which is inhibitory to nematodes.
Ex 2: In Cicer arietinum (chickpea), the Ascochyta blight resistant varieties have more glandular hairs which have maleic acid which inhibit spore germination.
Ex 3: Red scales of red onion contain the phenolic compounds; protocatechuic acid and catechol.
inhibitory compound present in the cell before infection
Phenolics: onion (catechol and protocatechuic acid ).
Tannins :
-Dienes: fatty acid-like compound
- Chlorogenic acid: in potato inhibits common scab bacteria
Saponins
-Tomatine in tomato and Avenacin in oats
Chemical defenses
ricin: from Castor oil beans Just 0.2mg would be fatal if
Citronella: from lemon grass Insect repellents
pyrethrins: made by chrysanthemums and act as insect neurotoxins.
caffeine: toxic to insects and fungi
Antibacterial compounds –cotton
antibacterial glossypol
organelles containing enzymes that break down bacterial cell walls.
Lysosomes
enzymes that break down the chitin in fungal cell walls
Chitinases
Gluconates (Anti-oomycetes)
enzymes made by some plants that break down glucans; polymers found in the cell walls of oomycetes (e.g. P. infestans)
species of Sambucus (elderberry) toxins produce
produce chemicals that can be metabolized (broken down) to form cyanide compounds. cyanide-inducing glycoside
