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Questions and Answers
What is the primary cause of symptom expression in host plants infected by pathogens?
What is the primary cause of symptom expression in host plants infected by pathogens?
Which physiological function is primarily affected by foliar pathogens?
Which physiological function is primarily affected by foliar pathogens?
What is the result of pathogens establishing themselves in the host plant?
What is the result of pathogens establishing themselves in the host plant?
Which of the following is NOT a harmful effect of infection on plant physiology?
Which of the following is NOT a harmful effect of infection on plant physiology?
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What occurs as a result of root pathogens affecting translocation?
What occurs as a result of root pathogens affecting translocation?
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Which process is maintained by the chlorophyll in plants during photosynthesis?
Which process is maintained by the chlorophyll in plants during photosynthesis?
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What effect does tissue destruction from pathogens have on photosynthesis?
What effect does tissue destruction from pathogens have on photosynthesis?
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Which physiological function does NOT share a direct link to pathogen effects on the host plant?
Which physiological function does NOT share a direct link to pathogen effects on the host plant?
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What is the primary consequence of obligate fungal parasites on plant metabolism?
What is the primary consequence of obligate fungal parasites on plant metabolism?
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How do viruses that cause leaf-curling affect plant physiology?
How do viruses that cause leaf-curling affect plant physiology?
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What effect does an increase in respiratory rate have on infected plant tissues compared to healthy ones?
What effect does an increase in respiratory rate have on infected plant tissues compared to healthy ones?
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Which of the following is NOT an effect of pathogens on plant transpiration?
Which of the following is NOT an effect of pathogens on plant transpiration?
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What happens to the permeability of a plant cell's membrane when disrupted by pathogens?
What happens to the permeability of a plant cell's membrane when disrupted by pathogens?
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Which pathogen is associated with the leaf spot of barley?
Which pathogen is associated with the leaf spot of barley?
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Which pathogen produces fusicoccin that affects membrane ATPase?
Which pathogen produces fusicoccin that affects membrane ATPase?
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Which of the following results from a decrease in chlorophyll due to vascular pathogens?
Which of the following results from a decrease in chlorophyll due to vascular pathogens?
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What is the primary output of aerobic respiration in plants?
What is the primary output of aerobic respiration in plants?
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What is a consequence of powdery mildew invading epidermal cells?
What is a consequence of powdery mildew invading epidermal cells?
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Which of the following molecules can flow through the cell membrane due to its permeability?
Which of the following molecules can flow through the cell membrane due to its permeability?
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How does respiration in resistant plants compare to that in susceptible plants following infection?
How does respiration in resistant plants compare to that in susceptible plants following infection?
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What is one strategy pathogens may use to disturb membrane integrity?
What is one strategy pathogens may use to disturb membrane integrity?
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What role do toxins like tentoxin play in plant disease?
What role do toxins like tentoxin play in plant disease?
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Which virus is responsible for yellowing and stunting in rice?
Which virus is responsible for yellowing and stunting in rice?
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What is a common characteristic of disease-affected plants' respiration levels?
What is a common characteristic of disease-affected plants' respiration levels?
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What is the role of transcription in protein synthesis?
What is the role of transcription in protein synthesis?
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How do pathogens affect transcription in host plants?
How do pathogens affect transcription in host plants?
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What happens to resistant plants shortly after infection?
What happens to resistant plants shortly after infection?
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How do pathogens primarily interfere with the translocation of water in plants?
How do pathogens primarily interfere with the translocation of water in plants?
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What is one mechanism by which damping-off fungi cause damage to plant roots?
What is one mechanism by which damping-off fungi cause damage to plant roots?
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What is likely to happen to the energy needs of infected plants?
What is likely to happen to the energy needs of infected plants?
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What is a common physiological change in infected plants?
What is a common physiological change in infected plants?
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What effect does xylem clogging by pathogens have on a plant?
What effect does xylem clogging by pathogens have on a plant?
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How do pathogens contribute to crop economy?
How do pathogens contribute to crop economy?
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How do plants respond to vascular wilt pathogens, according to the text?
How do plants respond to vascular wilt pathogens, according to the text?
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What happens to carbohydrates during the attack of pathogens on phloem elements?
What happens to carbohydrates during the attack of pathogens on phloem elements?
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What may result from disturbances in the biochemical pathways of plants?
What may result from disturbances in the biochemical pathways of plants?
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What role do enzymes breaking down RNA play during pathogen infection?
What role do enzymes breaking down RNA play during pathogen infection?
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Which pathogens are known to cause significant damage by clogging the xylem?
Which pathogens are known to cause significant damage by clogging the xylem?
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What is one effect of the disease in plant tissues caused by pathogens?
What is one effect of the disease in plant tissues caused by pathogens?
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What role do plasmodesmata play in nutrient translocation in phloem?
What role do plasmodesmata play in nutrient translocation in phloem?
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Study Notes
Pathogen Effect on Host Plant Physiology
- Plant physiology studies the life processes of plants, including cell, tissue, and organ functions.
- Plant disease arises from interactions between the host plant and a pathogen.
- Pathogen infection begins with physical contact, and effects remain localized until host tissues are penetrated.
- Pathogens disrupt various physiological functions depending on the plant organ and tissue they infect.
Harmful Effects of Infection
- The primary cause of plant symptoms, damage, and loss is the harmful effects of pathogens on host physiology.
- These effects include tissue disintegration, hormonal imbalance affecting growth, reduced photosynthesis, and abnormal respiration.
- Pathogens infecting flowers can impair seed production.
- Root pathogens affect translocation, leading to plant wilting and death.
Foliar Pathogen Effects
- Foliar pathogens infect leaves, stems, petioles, and other aerial parts.
- Pathogens destroy chlorophyll production, reducing photosynthesis.
- Pathogen infection affects plant growth and yield.
- Changes in cell biology include a striking increase in protoplasm, movement of the nucleus at the penetration site, and granulation of cytoplasmic particles.
- Cell contents turn yellow, then dark brown, leading to cell death.
Effect of Pathogens on Plant Physiological Functions
- Photosynthesis:
- Pathogens interfere with photosynthesis, resulting in plant disease.
- Pathogens redirect host nutrients for their use, creating a 'metabolic sink'.
- Reduced photosynthetic surface, chlorophyll degeneration, and the production of toxins (e.g., tentoxin, tabtoxin) by pathogens affect photosynthesis rate.
- Respiration:
- Pathogens increase respiration rate in infected plants.
- Respiration rises to peak during fungal sporulation before returning to normal (or subnormal) levels.
- Differences occur between resistant and susceptible plants (rate of rise and duration).
- Increased respiration affects metabolism and protoplasmic streaming in infected plants.
- Diseases like cereal rusts, powdery mildews, rice blast, and potato late blight show increased respiration.
- Translocation of Water and Nutrients (Xylem):
- Pathogens obstruct water and mineral absorption and translocation via the xylem.
- Pathogens can damage roots, inhibiting root hair production or altering root cell permeability.
- Pathogens can cause rot, canker, gall formation, or clog xylem, impeding transport.
- Examples include pathogens like Sclerotium rolfsii, Agrobacterium tumefaciens, and Meloidogyne spp.
- Translocation of Water & Nutrients (Phloem):
- Pathogens damage phloem elements, hindering downward nutrient transport.
- Starch accumulation in leaves is a consequence of phloem degeneration, often observed in leaf-curling viruses or fungal parasites like rust and mildew.
- Viruses sometimes inhibit starch breakdown enzymes in the phloem, hindering nutrient movement.
- Transpiration:
- Pathogens disrupt the plant cuticle and increase transpiration.
- Pathogens affect leaf cell permeability, leading to collapsing vessels and tylose formation.
- Diseases like powdery mildew and rust cause exposed leaf surfaces, leading to unchecked water loss.
- Blight conditions reduce healthy cell count in plants, lowering transport through the plant's xylem.
Effect on Cell Membrane
- Pathogens disrupt cell membranes, leading to uncontrolled loss of useful substances and increased permeability.
- This is often the initial detectable response of cells to infection.
- Pathogen strategies include stimulating enzymes to actively transport molecules in or out, interfering with membrane repair processes, and degrading membrane components.
- Examples of pathogen-produced toxins include fusicoccin and lipid-degrading enzymes.
Effect on Transcription and Translation
- Pathogens can alter chromatin composition, structure, and function, affecting DNA.
- For example, viruses may utilize host machinery to create their RNA.
- Pathogen action may result in elevated levels of RNA in infected plants, particularly in resistant strains.
- RNA elevation is likely due to the synthesis of substances contributing to a defense mechanism.
Effect of Pathogens on Plant Biotrophic Infections
- In certain infections (e.g., Plasmodiophora brassicae, certain rust, mildew types), pathogen activity causes host nuclei and nucleoli to enlarge.
Conclusion
- Plant growth is crucial for human and animal survival, supporting agriculture.
- Highly integrated biochemical pathways in plants are susceptible to disruption by pathogens.
- Localized pathogen effects can have severe consequences for the entire plant.
- The resulting symptoms and diseases lead to a reduction in crop quality and quantity.
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Description
Explore the intricate relationship between pathogens and host plants in this quiz. Understand how infections impact plant physiology, leading to various symptoms and detrimental effects on growth and reproduction. Test your knowledge on the ways pathogens disrupt essential plant functions.
