Lesson Worksheet: Plant Defenses against Pathogens Biology

In this worksheet, we will practice describing plant structures that limit the entry of pathogens and different plant adaptations that limit the damage caused by infection.


Which plant structural defense feature is not preexisting and is only formed as a result of infection by a pathogen?

  • ATyloses
  • BWaxy cuticle
  • CThorns
  • DHairs
  • ECellulose cell walls


Some pathogens produce toxins that harm the plant. What chemicals does the plant produce to break down these toxins and limit the damage that they cause?

  • AGlycosides
  • BNonprotein amino acids
  • CPhenols
  • DEnzymes
  • EProtein receptors


How do receptors present in plant cells act as a defense mechanism?

  • AThey act as an insulator to stop the pathogen from spreading to other parts.
  • BThey bind to antimicrobial chemicals produced by the plant to increase their effectiveness.
  • CThey increase the exchange of materials between neighboring plant cells.
  • DThey bind to chemicals in the plant cell to make the cell walls stronger.
  • EThey bind to common molecules present on pathogens and initiate defense responses.


Farmers use different approaches to reduce crop damage caused by a pathogen:

  • Selective breeding
  • Spraying chemicals that are toxic to the pathogen
  • Genetic engineering

Which approaches lead to an increase in the immunity of the crop plant against disease?

  • ASelective breeding only
  • BSelective breeding and genetic engineering
  • CSelective breeding and spraying toxic chemicals
  • DSpraying toxic chemicals only
  • EGenetic engineering and spraying toxic chemicals


Which of the following would not be a plant response induced by infection?

  • AStrengthening of cell walls with lignin and callose
  • BIncreased shoot branching
  • CRelease of toxic molecules to attack the pathogen directly
  • DProduction of tyloses to block water transport in the xylem
  • ERelease of chemicals to alarm other cells that there is an infection


There are many causes of disease and death in plants. Which of the following is due to a pathogen?

  • ASoil mineral deficiency, leading to limited growth
  • BHeavy metal contamination from factory effluent
  • CHerbicide spraying to control weeds
  • DPotato blight, leading to a reduction in crop yield
  • ECattle grazing for dairy farming


Why do some plants produce gum or resins, as shown in the figure, in response to cutting or injury?

Resins - Gum
  • ATo bypass transport systems in the plant
  • BTo prevent the entry of microbes into the damaged area
  • CTo alert other parts of the plant to the infection
  • DTo allow gas exchange to continue after the cutting process


L-Canavanine is an amino acid produced by some species of plant. The figure shows that it is structurally similar to arginine.

How does the production of canavanine protect a plant from infection?

  • AIt prepares plant cells for future infections by the same pathogen.
  • BIt breaks down toxins that have been released by pathogens.
  • CIt is toxic to herbivores because it is incorporated into their proteins.
  • DIt causes the cell walls of epidermal cells to swell, preventing pathogen entry.
  • EIt promotes the lignification of cell walls, preventing pathogen entry.


Many species of willow, shown in the figure, make and distribute salicylic acid to all parts of the plant following an infection.

What is the role of salicylic acid in defending the willow against disease?

Weeping willow
  • AIt kills the infecting pathogen directly.
  • BIt increases the formation of food storage organs.
  • CIt promotes widespread cell death to limit the infection.
  • DIt alerts the whole plant that an infection has occurred.


Fill in the blank: The release of proteins with antitoxin properties in response to an infection is an example of .

  • Aa preexisting structural defense
  • Ban induced structural defense
  • Ca biochemical defense

This lesson includes 15 additional questions for subscribers.

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