Plant Stress Part 2 Flashcards
What is salt stress in plants?
An excess of salts in soil lowers the water potential of soil, reducing water uptake by roots.
High salinity in soil is toxic to plants.
How do some plants respond to moderate soil salinity?
By producing solutes that are well tolerated at high concentrations.
These solutes keep the water potential of the cell more negative than that of the soil solution.
What are halophytes?
Plants that are salt-tolerant and have developed salt glands to secrete excess salts.
Examples include many mangrove plants.
What is biotic stress in plants?
The stress caused by pest and pathogen attacks.
What are the two categories of plant defense mechanisms?
Preexisting and induced mechanisms.
What are preexisting structural defense mechanisms in plants?
- Amount and quality of wax and cuticle covering epidermal cells
- Structure and thickness of epidermal cell walls
- Size, location, and shapes of stomata
- Thorns, pricks, trichomes
What are some chemical defense mechanisms in plants?
- Toxic compounds such as cyanogenic glycosides
- Alkaloids like nicotine
- Phenolics such as flavonoids, lignin, and tannins
- Terpenoids including Azadirachtin and Lectin
What are induced structural defense mechanisms in plants?
- Morphological changes in the cell wall
- Formation of cork and abscission layers
- Production of phenolic compounds
- Production of toxic compounds
- Production of enzymes that degrade fungal cell walls or damage insect organs
True or False: Induced defense mechanisms are present before infection or pest attack.
False
Fill in the blank: The amount and quality of _______ that cover the epidermal cells are part of the preexisting defense mechanisms.
[wax and cuticle]
