What are Plant Defenses? Biology Definition and Examples

📚 Quick Study Guide

• 🛡️ Plant defenses are adaptations that help plants survive against herbivores, pathogens, and environmental stressors.
• 🌿 These defenses can be structural (e.g., thorns, thick cuticles) or chemical (e.g., toxins, repellents).
• 🐛 Herbivore-induced plant defenses are triggered by herbivore feeding and can attract predators of the herbivores.
• 🦠 Plants also have defense mechanisms against pathogens, including the production of antimicrobial compounds and the hypersensitive response (HR).
• ☀️ Environmental stressors like UV radiation can induce the production of protective pigments like anthocyanins.

🧪 Practice Quiz

1. Which of the following is an example of a structural plant defense?
   1. A. Production of toxins
   2. B. Presence of thorns
   3. C. Release of volatile organic compounds
   4. D. Activation of the hypersensitive response
2. What is the function of the hypersensitive response (HR) in plants?
   1. A. To attract herbivores
   2. B. To prevent pathogen spread by localized cell death
   3. C. To enhance photosynthesis
   4. D. To increase water uptake
3. Which type of plant defense is activated only after an herbivore attack?
   1. A. Constitutive defense
   2. B. Induced defense
   3. C. Passive defense
   4. D. Physical defense
4. What role do volatile organic compounds (VOCs) play in plant defense?
   1. A. They provide structural support
   2. B. They attract pollinators
   3. C. They attract predators of herbivores
   4. D. They increase water retention
5. Which of the following chemicals is commonly used by plants for defense?
   1. A. Glucose
   2. B. Cellulose
   3. C. Alkaloids
   4. D. Lignin
6. What is the primary function of a plant's cuticle?
   1. A. To attract insects
   2. B. To prevent water loss and pathogen entry
   3. C. To enhance nutrient absorption
   4. D. To increase photosynthesis
7. How do plants defend against UV radiation?
   1. A. By producing more chlorophyll
   2. B. By developing thicker leaves
   3. C. By synthesizing protective pigments like anthocyanins
   4. D. By increasing water uptake