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Plant Defences (PHYSICAL (Cellulose Cell Wall - acts as barrier and…
Plant Defences
PHYSICAL
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Waxy Cuticle - prevent water collecting on the cell surface. Pathogens cannot survive without water.
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Stomatal Closure - possible points of entry for pathogens which close when pathogenic organisms are detected.
Callose - large polysaccharide, deposited at the end of sieve tubes. Blocks the flow through the sieve tubes so pathogen cannot travel through the plant.
Tylose Formation - swelling that fills xylem vessel. It plugs the vessel so pathogen cannot be transported.
As the production of chemicals requires a lot of energy, many chemicals are not produced until after the infection.
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Callose Deposition - Callose deposits polysaccharide polymers that impede cellular penetration at the site of infection. Strengthens cell wall and blocks plasmodesmata.
Oxidative bursts - produce highly reactive oxygen molecules which are capable of damaging cells of invading pathogens.
CHEMICAL
Chemicals such as Terpenoids, Phenols, alkaloids and hydrolytic enzymes.
Chemicals such as terpenoids, phenols, alkaloids, defensins and hydrolytic enzymes - most are already present in the plant in bark etc. so are passive but production is increased when the plant is under attack so is active
Necrosis - active only, deliberate cell suicide in order to limit pathogens access to nutrients, brought about by intracellular enzymes
P/C] Tylose - passive only, creates a balloon like swelling that blocks the xylem vessels, it also contains chemicals such as terpines that are toxic to pathogens
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