12.4 Flashcards
(15 cards)
What are the initial physical barriers plants have to prevent pathogen entry?
Waxy cuticle, bark, and cellulose cell walls of individual cells act as physical barriers to prevent pathogens from entering.
Why don’t plants heal diseased tissues like animals do?
Plants seal off and sacrifice infected tissues because they can continuously replace damaged parts by growing from meristems.
How do plants recognize a pathogen attack?
- Receptors in cells detect molecules from pathogens or breakdown products of the cell wall.
- This activates signaling molecules that switch on genes in the nucleus.
- Cellular responses are triggered, including chemical defenses and strengthening cell walls.
What happens immediately after a pathogen attack in terms of cell wall strengthening?
Callose is synthesized and deposited between cell walls and membranes of adjacent cells, forming barriers to block pathogen entry.
What is the role of lignin in plant defense?
Lignin is added to cell walls along with callose, creating a thicker and stronger mechanical barrier against invasion.
How does callose help in stopping pathogen spread within the plant vascular system?
- Callose blocks sieve plates in the phloem, sealing off infected parts.
- It is also deposited in plasmodesmata to isolate infected cells from neighbors.
What are the main cellular responses triggered by pathogen recognition in plants?
Dumb cells scream loudly
Dumb = Defensive chemicals (produced to fight pathogens)
Cells = Cell signaling (alerts nearby/uninfected cells)
Scream = Strengthening of cell walls
Loudly = Lignin and callose are added for reinforcement
What are the beta-linkages found in callose and what do they link?
Callose contains β-1,3 and β-1,6 glycosidic linkages between glucose monomers.
What are insect repellents in plant chemical defenses, and give examples?
Chemicals that repel insect vectors, e.g., pine resin and citronella (from lemongrass).
Name two plant-derived insecticides and their actions.
- Pyrethrins (from chrysanthemums): act as insect neurotoxins.
- Caffeine: toxic to insects
What are three antibacterial compounds made by plants?
Please dont linger
- Phenols: act as antiseptics.
- Defensins: plant proteins that disrupt microbial membranes.
- Lysosymes: enzymes that break down bacterial cell walls.
List four antifungal chemical defenses produced by plants.
- Phenols (general antifungals)
- Gossypol (from cotton)
- Saponins (disrupt fungal membranes)
- Chitinases (enzymes breaking down chitin in fungal walls)
Summarize three roles of callose in plant defenses.
- Forms physical barriers between infected and neighboring cells.
- Blocks sieve plates in phloem to limit pathogen spread.
- Seals plasmodesmata to isolate infected cells.
What enzyme do plants use to defend against oomycetes, and how does it work?
Some plants produce compounds that can be converted into cyanide, which is toxic to most living organisms when cells are attacked.
What is the overall significance of signaling molecules in plant immunity?
They trigger gene activation in the nucleus, leading to defensive chemical production and physical defenses in both infected and nearby cells.
