BIOL 459 - FINAL EXAM QUESTIONS WITH CORRECT ANSWERS LATEST 2025-2026
Biotic vs Abiotic - Answers living vs nonliving
What bacterial species is responsible for frost damage to crops? - Answers Pseudomonas
syringae, a plant pathogen
Fungal/plant pathogen - Answers biotic stress where an organism that, to complete a part or all
of its life cycle, grows inside the plant and, in doing so, has a detrimental effect on the plant
What are 4 ways microbial pathogens have evolved ways to invade plants? - Answers 1.
mechanical pressure on surface layers
2. enzymatic attack
3. natural openings (stomata, lenticels)
4. use of previously wounded tissue
Where do microbial pathogens attach to a plant? - Answers Most microbes attach only to a
specific part of the plant and produce characteristic disease symptoms
Pathogenic fungi produce what? - Answers produce host-selective toxins that are active in only
a few plant species
How does fungal infection of a plant occur? - Answers 1. fungi secrete HC-toxin and other
fungal elicitors that trigger plant defense responses
1. HC-toxin enters cell and interferes with expression of plant defense genes
3. resistant plants produce HC-toxin reductase which detoxifies HC-toxin
Gray mold fungus - Answers secretes many cell-wall degrading enzymes and destroys the plant
tissues before fungal hyphae multiply
What are the 2 broad categories of herbivorous insects which are recognized? - Answers
chewing and sap sucking
How does feeding arthropods damage plants? - Answers not only damages plants directly but
facilitates colonization by viral, bacterial , and fungal pathogens
What is a major example of the biotic stress, herbivorous arthropods as vectors of fungal
pathogens? - Answers symbiotic relationship between bark beetles and fungi has devastated
many forest stands all over the world, interaction between the bark beetles and the symbiotic
fungi eventually leads to death of the tree
what are the 2 plant defense systems? - Answers 1. secondary metabolites
,2. genes for disease resistance
What are the 2 classes of secondary metabolites? - Answers 1. alkaloids
2. terpenoids
3. phenolics
what are major functions of secondary compounds? - Answers deter herbivores, attract
herbivore enemies, insect feeding deterrent, toxic to fungi, photosynthetic co-factors
Terpenoid defenses are protective against what? - Answers protective terpenoid defenses in
pines effective against arthropods and fungi
What are plant genes for disease resistance? - Answers pathogen molecules (PAMPS) interact
with PRR receptors at cell membrane. Pathogen effectors interact with R proteins within the
plant cell.
How does PRR reception occur? - Answers 1. PRR receptor binding allows for PAMP recognition
2. signaling pathway named PAMP-triggered-immunity (PTI) is activated
3. Basal defense is activated resulting in cell wall strengthening & anti-microbial compounds
Type III Secretion System - Answers Bacteria have a type III system allowing them to inject
proteins called "effectors" directly into plant cells, these effectors can suppress host basal
defense
Effector-triggered-immunity (ETI) - Answers ETI pathway activated in response to effector
proteins by bacteria
Resistance proteins (R) - Answers proteins plant cells have which can recognize effectors and
are specific to only one effector
IF ETI is activated, what response occurs? - Answers Hypersensitive Response occurs (HR) and
stops bacterial growth. The plant is then resistant to bacterium
Biotrophic organisms - Answers bacteria, fungi, viruses
Necrotrophic organisms - Answers herbivores, insects, other animals, fungi
What is the hormonal response to biographic organisms? - Answers salicylic acid
What is the hormonal response to necrotrophic organisms? - Answers Jasmonates
Jasmonates - Answers •Response to necrotrophic pathogens
•Induction of anti-herbivory responses
, •Production of herbivore-induced volatiles to prime other tissues and attract predatory insects
Mutants without JA - Answers have low defense against herbivory and have low rates of
survival
cannot induce expression of anti-herbivory which allows for wound-induced signals and
protease inhibitors which are feeding inhibitors
How do systemic defense responses work in jasmonates? - Answers Jasmonates are triggered
by necrotrophics and defense responses are activated in distant tissues. they stimulate the
production of volatile signaling in other tissues
Salycylate synthesis is induced upon - Answers pathogen attack;
isochorismate synthase (ICS) is induced upon pathogen infection.
SA accumulation induces pathogenesis related (PR) and other defense genes
SAR - systemic altered resistance - Answers SA is necessary in systemic tissue for SAR. It is
likely that multiple signals contribute to SAR
**methyl salicylate MeSA produces SA
Flagellin - Answers PAMP bacterial protein which triggers a set of immune responses that are
mediated by salicylic acid
The interaction of an R protein with an effector protein from a pathogen promotes - Answers a
stronger immune response, including the hypersensitive response
The hypersensitive response involves - Answers stops bacterial growth and involves cell death.
can make plant resistant to bacterium by sealing the pathogen in a tomb of dead cells which
prevents the pathogen from spreading
phytohormones - Answers hormones produced by pathogens which can exploit connections
between growth hormones and pathogen-response hormones to their own advantage
What are the major abiotic stress responses? - Answers 1. water-logging
2. drought
3. high or low temperatures
4. excessive soil salinity
5. inadequate mineral in the soil
6. too much or too little light
Biotic vs Abiotic - Answers living vs nonliving
What bacterial species is responsible for frost damage to crops? - Answers Pseudomonas
syringae, a plant pathogen
Fungal/plant pathogen - Answers biotic stress where an organism that, to complete a part or all
of its life cycle, grows inside the plant and, in doing so, has a detrimental effect on the plant
What are 4 ways microbial pathogens have evolved ways to invade plants? - Answers 1.
mechanical pressure on surface layers
2. enzymatic attack
3. natural openings (stomata, lenticels)
4. use of previously wounded tissue
Where do microbial pathogens attach to a plant? - Answers Most microbes attach only to a
specific part of the plant and produce characteristic disease symptoms
Pathogenic fungi produce what? - Answers produce host-selective toxins that are active in only
a few plant species
How does fungal infection of a plant occur? - Answers 1. fungi secrete HC-toxin and other
fungal elicitors that trigger plant defense responses
1. HC-toxin enters cell and interferes with expression of plant defense genes
3. resistant plants produce HC-toxin reductase which detoxifies HC-toxin
Gray mold fungus - Answers secretes many cell-wall degrading enzymes and destroys the plant
tissues before fungal hyphae multiply
What are the 2 broad categories of herbivorous insects which are recognized? - Answers
chewing and sap sucking
How does feeding arthropods damage plants? - Answers not only damages plants directly but
facilitates colonization by viral, bacterial , and fungal pathogens
What is a major example of the biotic stress, herbivorous arthropods as vectors of fungal
pathogens? - Answers symbiotic relationship between bark beetles and fungi has devastated
many forest stands all over the world, interaction between the bark beetles and the symbiotic
fungi eventually leads to death of the tree
what are the 2 plant defense systems? - Answers 1. secondary metabolites
,2. genes for disease resistance
What are the 2 classes of secondary metabolites? - Answers 1. alkaloids
2. terpenoids
3. phenolics
what are major functions of secondary compounds? - Answers deter herbivores, attract
herbivore enemies, insect feeding deterrent, toxic to fungi, photosynthetic co-factors
Terpenoid defenses are protective against what? - Answers protective terpenoid defenses in
pines effective against arthropods and fungi
What are plant genes for disease resistance? - Answers pathogen molecules (PAMPS) interact
with PRR receptors at cell membrane. Pathogen effectors interact with R proteins within the
plant cell.
How does PRR reception occur? - Answers 1. PRR receptor binding allows for PAMP recognition
2. signaling pathway named PAMP-triggered-immunity (PTI) is activated
3. Basal defense is activated resulting in cell wall strengthening & anti-microbial compounds
Type III Secretion System - Answers Bacteria have a type III system allowing them to inject
proteins called "effectors" directly into plant cells, these effectors can suppress host basal
defense
Effector-triggered-immunity (ETI) - Answers ETI pathway activated in response to effector
proteins by bacteria
Resistance proteins (R) - Answers proteins plant cells have which can recognize effectors and
are specific to only one effector
IF ETI is activated, what response occurs? - Answers Hypersensitive Response occurs (HR) and
stops bacterial growth. The plant is then resistant to bacterium
Biotrophic organisms - Answers bacteria, fungi, viruses
Necrotrophic organisms - Answers herbivores, insects, other animals, fungi
What is the hormonal response to biographic organisms? - Answers salicylic acid
What is the hormonal response to necrotrophic organisms? - Answers Jasmonates
Jasmonates - Answers •Response to necrotrophic pathogens
•Induction of anti-herbivory responses
, •Production of herbivore-induced volatiles to prime other tissues and attract predatory insects
Mutants without JA - Answers have low defense against herbivory and have low rates of
survival
cannot induce expression of anti-herbivory which allows for wound-induced signals and
protease inhibitors which are feeding inhibitors
How do systemic defense responses work in jasmonates? - Answers Jasmonates are triggered
by necrotrophics and defense responses are activated in distant tissues. they stimulate the
production of volatile signaling in other tissues
Salycylate synthesis is induced upon - Answers pathogen attack;
isochorismate synthase (ICS) is induced upon pathogen infection.
SA accumulation induces pathogenesis related (PR) and other defense genes
SAR - systemic altered resistance - Answers SA is necessary in systemic tissue for SAR. It is
likely that multiple signals contribute to SAR
**methyl salicylate MeSA produces SA
Flagellin - Answers PAMP bacterial protein which triggers a set of immune responses that are
mediated by salicylic acid
The interaction of an R protein with an effector protein from a pathogen promotes - Answers a
stronger immune response, including the hypersensitive response
The hypersensitive response involves - Answers stops bacterial growth and involves cell death.
can make plant resistant to bacterium by sealing the pathogen in a tomb of dead cells which
prevents the pathogen from spreading
phytohormones - Answers hormones produced by pathogens which can exploit connections
between growth hormones and pathogen-response hormones to their own advantage
What are the major abiotic stress responses? - Answers 1. water-logging
2. drought
3. high or low temperatures
4. excessive soil salinity
5. inadequate mineral in the soil
6. too much or too little light
