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

• 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.

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

• 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.

References

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