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Questions and Answers
What is a significant consequence of anaerobiosis in plants?
What is a significant consequence of anaerobiosis in plants?
What symptom is NOT typical of drought stress in plants?
What symptom is NOT typical of drought stress in plants?
How does salt stress primarily affect plants?
How does salt stress primarily affect plants?
What is the ideal temperature range for most crops to grow normally?
What is the ideal temperature range for most crops to grow normally?
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What effect can climate change have on salt stress in plants?
What effect can climate change have on salt stress in plants?
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What characteristic helps roots adapt to drought conditions?
What characteristic helps roots adapt to drought conditions?
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Which factor does NOT contribute to salt stress in plants?
Which factor does NOT contribute to salt stress in plants?
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What is a common response of plants to flooding stress?
What is a common response of plants to flooding stress?
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What type of metabolic adaptation allows aquatic plants to survive anaerobic conditions during winter?
What type of metabolic adaptation allows aquatic plants to survive anaerobic conditions during winter?
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Which of the following enzymes is NOT mentioned as being formed after 5 hours of anaerobiosis?
Which of the following enzymes is NOT mentioned as being formed after 5 hours of anaerobiosis?
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How do Reactive Oxygen Species (ROS) influence physiological processes in plants?
How do Reactive Oxygen Species (ROS) influence physiological processes in plants?
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What are the macromolecules that Reactive Oxygen Species (ROS) can interact with?
What are the macromolecules that Reactive Oxygen Species (ROS) can interact with?
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What triggers enhanced shoot elongation in aquatic and amphibious species?
What triggers enhanced shoot elongation in aquatic and amphibious species?
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Which of the following processes can be negatively impacted by oxidative stress?
Which of the following processes can be negatively impacted by oxidative stress?
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What is a characteristic of rhizomes in temperate aquatic and wetland plants?
What is a characteristic of rhizomes in temperate aquatic and wetland plants?
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Which aspect does NOT define the properties of Reactive Oxygen Species (ROS)?
Which aspect does NOT define the properties of Reactive Oxygen Species (ROS)?
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What contributes to cell rupture in plants under cold stress?
What contributes to cell rupture in plants under cold stress?
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Which process is triggered by receptor proteins during cold stress in plants?
Which process is triggered by receptor proteins during cold stress in plants?
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What is the primary characteristic of resistance in plants against environmental stresses?
What is the primary characteristic of resistance in plants against environmental stresses?
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Which type of stress involves saturation of soil pores with water?
Which type of stress involves saturation of soil pores with water?
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What is the role of the CBF protein in cold stress tolerance?
What is the role of the CBF protein in cold stress tolerance?
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How does adaptation differ from avoidance in plants under stress?
How does adaptation differ from avoidance in plants under stress?
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How do simple sugars contribute to cold stress tolerance in plants?
How do simple sugars contribute to cold stress tolerance in plants?
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What is the role of aerenchyma in hydrophytes?
What is the role of aerenchyma in hydrophytes?
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What are the potential effects of cold stress on plants?
What are the potential effects of cold stress on plants?
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What does cold acclimation involve in terms of biochemical changes?
What does cold acclimation involve in terms of biochemical changes?
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What is meant by the term 'hardening' in plants dealing with stress?
What is meant by the term 'hardening' in plants dealing with stress?
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What is a common type of defense response plants use against pathogen attack?
What is a common type of defense response plants use against pathogen attack?
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Which process is characterized by a plant's response to adverse conditions through reduced injury and repair mechanisms?
Which process is characterized by a plant's response to adverse conditions through reduced injury and repair mechanisms?
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What is a common physiological change in plants facing drought stress?
What is a common physiological change in plants facing drought stress?
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Which of the following is NOT a response of plants to cold stress?
Which of the following is NOT a response of plants to cold stress?
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What type of stress is associated with the presence of heavy metals in the soil?
What type of stress is associated with the presence of heavy metals in the soil?
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What is the main effect of UV-C radiation on microorganisms?
What is the main effect of UV-C radiation on microorganisms?
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How can UV radiation affect photosynthesis in plants?
How can UV radiation affect photosynthesis in plants?
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What is the primary biochemical response in plants to avoid self-poisoning during anaerobiosis?
What is the primary biochemical response in plants to avoid self-poisoning during anaerobiosis?
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What morphological change in plants can result from UV radiation exposure?
What morphological change in plants can result from UV radiation exposure?
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Which of the following is a consequence of anaerobic conditions in plant roots?
Which of the following is a consequence of anaerobic conditions in plant roots?
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What occurs to the ATP yield from glucose during fermentation in the absence of oxygen?
What occurs to the ATP yield from glucose during fermentation in the absence of oxygen?
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How does UV radiation impact flowering times in plants?
How does UV radiation impact flowering times in plants?
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What effect does UV radiation have on plant growth regulators?
What effect does UV radiation have on plant growth regulators?
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What is one of the proposed mechanisms by which heavy metals exert toxicity in plants?
What is one of the proposed mechanisms by which heavy metals exert toxicity in plants?
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Which heavy metal is mentioned as competing with phosphorus in plant absorption?
Which heavy metal is mentioned as competing with phosphorus in plant absorption?
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Which of the following is a consequence of heavy metal accumulation in soil?
Which of the following is a consequence of heavy metal accumulation in soil?
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What alteration in plant growth is associated with exposure to radiation?
What alteration in plant growth is associated with exposure to radiation?
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How does UV-A radiation affect plant biomass?
How does UV-A radiation affect plant biomass?
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What effect does UV-B radiation have on photosynthesis?
What effect does UV-B radiation have on photosynthesis?
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Which of the following processes can lead to the accumulation of heavy metals in soil?
Which of the following processes can lead to the accumulation of heavy metals in soil?
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What is a possible adaptive mechanism of plants surviving in radioactive environments?
What is a possible adaptive mechanism of plants surviving in radioactive environments?
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Study Notes
LS302 Defense Mechanisms in Plants and Animals
- LS302 is a course on defense mechanisms in plants and animals.
- Unit 3 topics include: plant stress metabolism (environmental stresses), salinity, water stress, heat, chilling, anaerobiosis, pathogenesis, heavy metals, radiation, and their effect on plant growth and metabolism; criteria of stress tolerance; antioxidative defense systems in plants, reactive oxygen species (ROS) and their generation, enzymic and non-enzymic components of antioxidative defense mechanisms.
Stress Physiology
- Stress is any change in environmental conditions that reduces or changes plant growth or development.
- Examples of stresses include: freeze, chill, heat, drought, flood, salinity, pest and air pollution.
- Resistance is the ability to adapt or tolerate stresses.
Environmental Stresses
- Water stress
- Salinity stress
- Heat stress
- Chilling stress
- Anaerobiosis (lack of oxygen)
- Pathogenesis (diseases)
- Heavy metals
- Radiation
Plant Metabolism
- Abiotic stresses include UV radiation, temperature, soil salinity, water stress, wounding, and atmospheric changes.
- Biotic stresses include pests, diseases, and allelopathic interactions.
- Defense related components include polyphenols, alkaloids, terpenes, phytoalexins, and polyamines.
- Health related components include polyphenols (antioxidants), terpenes (antioxidants and vitamin precursors).
- Organoleptic related components include polyphenols (bitterness, color, firmness) and terpenes (odor, color).
Plant Adaptations
- Resistance includes adaptation, avoidance and tolerance.
- Adaptation involves permanent stress resistance in morphology, structure, physiology, and biochemistry under long-term stress.
- Avoidance is a way to avoid encountering stress using neither metabolic processes nor energy.
- Examples of avoidance include very short lifecycles in desert plants and dormancy during harsh conditions.
- Tolerance is a plant's resistant reaction to reduce or repair stress-related injury with morphology, structure, physiology, biochemistry or molecular biology when the plant faces stress.
- Hardening is a gradual adaptation to stress when plants are located in a stressful environment.
Water Stress (Flooding/Waterlogging)
- Flooding: water layer above the soil surface (partial or complete submergence).
- Waterlogging: soil pores saturated with water.
- Plants with flooding/waterlogging adapted conditions experience: soil compaction, phytotoxic byproducts, changes in pH and Eh, O2 deficiency, leading to hypoxia/anoxia.
Waterlogging/Flooding Responses
- Energetic status alteration (inhibition of mitochondrial respiration, ATP synthesis, photosynthesis)
- Physiological modifications (internal water deficit, inhibition of stomatal aperture, reduced root permeability).
- Morphological and anatomical changes (suberized exodermis, aerenchyma, hypertrophied lenticels, adventitious roots).
Anaerobiosis
- Flooding stress or oxygen stress conditions from flooding
- Decreased oxygen supply limits respiration, nutrient uptake and other root functions.
Drought Stress
- Water scarcity; low soil moisture content; low water potential; leaves lose water faster than roots can absorb it.
- Roots expand to uptake more water when stress is present.
- Drought symptoms: leaf rolling, stunting, yellowing, scorching, permanent wilting.
Salt Stress
- Improper use of water resources in irrigation with high salt content.
- Faulty agricultural practices like improper fertilization.
- Climate change aggravates the problem.
- High Na+ and Cl- ions in the soil lead to hyperosmotic and hyperionic conditions and hinder water absorption.
Salinity Stress Effects
- Decreased growth in roots and shoots.
- Reduced crop yield.
- Nutritional disorders (low K/Na ratio).
- Changes in physiological and biochemical attributes (decrease chlorophyll content).
- ROS generation increase.
- Increased proline accumulation to help adapt to salinity.
Temperature Stress (Heat/Cold)
- Heat stress: periods of high temperatures; ideal temperature range for crops is 68-86°F (20-30°C). Temperatures outside this range can be harmful to plants.
- Cold stress: low temperature conditions causing plant damage from freezes, chills, etc.
- Cold and freeze: Reactive oxygen species (ROS) contribute to membrane damage, ice forms adhesions with membranes leading to cell rupture and protein denaturation.
Stress Due to Infection and Wounding
- Pathogen attacks cause various responses. Constitutive defenses include morphological and structural barriers, chemical compounds, proteins and enzymes. Plants produce toxic chemicals and/or pathogen degrading enzymes.
- Wounding is stress imposed on plants via injury.
Heavy Metal Stress
- Heavy metals reduce plant growth and productivity and impact plant development due to their toxicity and non-degradability. Sources include industrial waste, auto emissions, fertilizer use and more.
Radiation and Plant Growth and Metabolism
- Differences in leaf characters based on radiation exposure.
- Radiation exposure results in reduced viability and reproductive success.
- Plants adapt by replacing cancerous cells and adjusting growth.
- Some plants may exhibit different characteristics under radiation.
Other
- Videos and websites for further learning about plant adaptations.
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Description
This quiz covers Unit 3 of the LS302 course, focusing on the defense mechanisms in plants and animals against various environmental stresses. Topics include stress metabolism, criteria of stress tolerance, and antioxidative defense systems related to water, salinity, heat, and more. Test your understanding of how these factors influence plant growth and metabolism.
