Abiotic And Biotic Stresses

Question 1

Define stress

Answer 1

Certain factors in the environment may have a potentially adverse effects on a plants’ survival, growth and reproduction.

Question 2

State 2 types of stresses and define them

Answer 2

1. Abiotic stress
   ( due to non living factors in env such as drought cold and salt stress )
2. Biotic stress
   ( due to living factors such as pest and pathogen attack)

Question 3

State 3 types of abiotic stress

Answer 3

1. Drought stress
2. Cold stress
3. Salt stress

Question 4

State 2 types of defense mechanisms found in plants to overcome biotic stress

Answer 4

Preexisting structural and chemical defense mechanisms

Induced structural and chemical defense mechanisms

Question 5

Examples for Induced structural and chemical defense mechanisms

Answer 5

• Morphological changes in the cell wall
• Formation of cork and abscission layers
• Phenolic compounds
• Toxic compounds
• Enzymes that can degrade fungal cell walls or damage insect organs

Question 6

Give examples for Preexisting structural and chemical defense mechanisms

Answer 6

• Amount and quality of wax and cuticle that cover the epidermal cells
• The structure of the epidermal cell walls and thickness
• The size, location and shapes of stomata
• Toxic compounds
• Thorns, pricks, trichomes

Question 7

State some toxic compounds found in plants as their pre existing defense mechanism

Answer 7

alkaloids (eg. Nicotine)
phenolics (eg. Flavonoids, lignin & tannins)
terpenoids (eg. Azadirachtin)
lectin