Effect of pathogens on plants

Effect of pathogens on plants

What is Pathogen?

  • A pathogen or infectious agent is a biological agent that causes disease or illness to its host.
  • The term is most often used for the agent that disturb the normal physiology.
  • The main pathogen are the virus, bacteria, and fungi.

The physiological function includes:

  • Pathogenesis
  • Respiration
  • Permeability of cell membrane
  • Translocation of water and nutrient
  • Transcription and translation


  • Pathogenesis is a basic function of plant
  • It transforms light energy into chemical energy which is utilized by cellular activities
  • Any pathogen that interferes with it will cause disease that may appear as chlorosis (yellowing) and necrosis (burring and death) of leaves and stem.
  • Reduce the amount of photosynthesis surface.

Effect of pathogens on plants

Image Source: https://doi.org/10.1016/j.pbi.2016.06.012

Effect of virus infection

  • Reduce chloroplast amount
  • Reduce chlorophyll and sucrose amount
  • Cause chloroplast abnormalities.

Effect of bacterial infection

  • Decrease in chloroplast
  • Suppress CO2 fixation

Effect of fungal infection

  • Reduce chloroplast content
  • Loss of chlorophyll
  • Reduce photophosphorylation coupling mechanism
  • Suppress CO2 fixation


  • Respiration increase during pathogen attack
  • Rate continuous to rise during multiplication and sporulation of the pathogen
  • Decline to normal or below the normal level
  • Increased respiration decrease in plant reserve
  • Change metabolism

Effect of virus

  • Slightly increase respiration rate in leaves

Effect of fungi

  • Respiration rate is usually increased in diseased plants.
  • In the early stage of disease synthetic process-induced high rate of respiration.
  • In late-stage, injury and decomposition lead to increase respiration.

Mechanism of permeability

Pathogen change the permeability by

  • Mechanical injury
  • Enzymatic degradation
  • Toxins
  • Cause leakage of electrolytes.

Translocation water and nutrient

  • Affect the function of root
  • Roots absorb less water
  • Interfere with water economy of plant by causing excessive transpiration.

Effect of bacteria

  • Enter the vascular system in both xylem and phloem through the wound

Effect of fungi

  • Decrease water absorption
  • Vascular Wilt disease
  • Decrease water flow

Effect of virus

  • Death of phloem
  • Inhibit enzymes that break down starch into smaller into translatable molecules.

Transcription and Translation

  • Disturbance in any of above both process may effect the following
  • Expression of genes
  • Cause a drastic unfavorable change in the structure and function of affected cells.


  1. https://www.cram.com/flashcards/effects-of-plant-pathogens-on-plant-physiological-functions-401789
  2. http://www.davidmoore.org.uk/21st_Century_Guidebook_to_Fungi_PLATINUM/Ch14_11.htm
  3. https://academic.oup.com/jxb/article/58/15-16/4019/454268
  4. https://www.ncbi.nlm.nih.gov/pubmed/18182420.

Effect of pathogens on plants

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