Fungal Pathogens 7.2

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Inquiry Question 2: How does a plant or animal respond to infection?

Content Descriptor: Investigate the response of a named Australian plant to a named pathogen through practical and/or secondary-sourced investigation, for example:

Fungal pathogens: (7.2.1)


The waratah is a native Australian plant, with characteristic bright red flowers. It uses these flowers and large quantities of nectar, attracting birds and pollinators. The curved shape of the individual flower’s brushes honey eaters with nectar, with its seeds also being dispersed by birds. Adaptations to the environment include:

  • Lignotuberswhich can re-sprout after bushfires
  • Thickwaxy leaves

Fungal pathogens:

  • Dampingoff refers to the fungal infection of the root and crown
  • Onefungal pathogen is Phytophtora cinnamomi
  • Symptomsinclude:
  • Yellowleaves
  • Wilting
  • Dieback
  • Blackeningand death of stem and roots
  • Thiscan be artificially prevented by the use of fungicides

Waratah response:

  • Secretionof anti-fungal enzymes making an inhospitable environment for fungi
  • Jettisoninfected leaves or stems
  • Strengtheningof cell wall to deter further penetration

Viral pathogens: (7.2.2)


A large flowering plant which has been genetically bred so that no bananas have seeds. Bananas now reproduce via asexual methods

Viral pathogens:

  • BBTV (banana bunchy top virus) is a single stranded viral pathogen transmitted by the insectvector of aphids.
  • Thiscauses stunted leaf growth:
  • Artificialcontrol measures include control of the aphid vector

Banana response:

  • A technique known as RNA silencing is employed by plants, where plants recognize the viralgenetic material and copy it so other cells can respond to the virus

Content Descriptor: Analyse responses to the presence of pathogens by assessing the physical and chemical changes that occur in the host animal’s cells and tissues: (7.2.3) Physical Changes:

Inflammation and its subsequent signs, caused by chemical responses to the pathogen:

  • Redness
  • Swelling
  • Lossof function
  • Pain
  • Heat

Chemical changes:

  • Someintracellular bacteria take over protein synthesis
  • Apoptosis(cell death) to seal off a pathogen
  • Infected cells release cytokines and chemokines, which stimulate lymphocytes andchemotaxis
  • Interferonsstimulate the release of antivirals
  • Seriesof chemicals which cause inflammation:
  • Heparin– prevents blood clotting to maintain blood supply
  • Histamine– increased permeability of blood vessels
  • Serotonin– cause vasoconstriction and increased permeability of blood vessels
  • Prostaglandins – made from cell membranes. May stimulate fever, pain,vasoconstriction and vasodilation, increased permeability

Inquiry Question Review: How does a plant or animal respond to infection? (7.2.4)

You should be able to:

  • Describethe plant responses to viral and fungal pathogens
  • Describethe physical and chemical changes as a result of pathogens