Plant diseases

Question 1

Physical Defences:

Answer 1

Most plants have a waxy cuticle on their leaves and stems, acting as a barrier against pathogens and pests.

Cellulose cell walls provide another layer of protection, preventing pathogens from entering plant cells.

The waxy cuticle also prevents water accumulation, reducing infection risk from waterborne pathogens.

Question 2

Chemical Defences:

Answer 2

Plants produce antiseptic chemicals that kill bacteria and fungi.

They also create pest-deterring substances to prevent insects from feeding on them.

Some of these chemicals have medicinal uses—quinine (from cinchona tree bark) treats malaria, and aspirin (from willow tree bark & leaves) relieves pain and fever.

Question 3

Disease Detection:

Answer 3

Field methods
Environmental testing
Disease spread analysis
Lab-based diagnosis

Question 4

Field methods:

Answer 4

by observing symptoms

Question 5

Environmental testing:

Answer 5

Some plant symptoms (like yellow leaves) may stem from nutrient deficiencies rather than disease, so adjusting soil nutrients can clarify the cause.

Question 6

Disease spread analysis:

Answer 6

The distribution pattern of infected plants helps determine how a pathogen spreads (e.g. soil-borne pathogens cause patches of diseased plants, whereas airborne pathogens spread randomly).

Question 7

Lab-based diagnosis:

Answer 7

Antigen detection: Plants infected with pathogens contain unique surface molecules (antigens), which can be identified using monoclonal antibodies.

DNA detection: Scientists use genetic analysis to find pathogen DNA in plant tissue, allowing precise identification of infections.