Lesson 17: Plant Defenses, Nutrition, and Soil Vocabulary Study Guide

Lesson 17: Plant Defenses, Nutrition, and Soil

Key Vocabulary and Concepts

This lesson covers essential terms related to plant defense mechanisms, nutrition, and soil interactions. Understanding these terms is crucial for grasping how plants protect themselves, acquire nutrients, and interact with their environment.

• Allelopathy: The chemical inhibition of one plant by another, due to the release of toxic substances into the environment.

• Auxin: A class of plant hormones that regulate growth and developmental processes.

• Bedrock: The solid rock layer beneath soil, which influences soil formation and mineral content.

• Carnivorous plants: Plants that derive some or most of their nutrients by trapping and consuming animals, typically insects.

• Cation exchange: The process by which plants obtain mineral nutrients from soil particles through the exchange of cations (positively charged ions).

• Defenses: Mechanisms by which plants protect themselves from herbivores, pathogens, and environmental stress.

• Gene-for-gene hypothesis: A model describing the genetic interaction between a plant and a pathogen, where resistance depends on specific gene pairs.

• Humus: The organic component of soil formed by the decomposition of leaves and other plant material.

• Hypersensitive Response (HR): A rapid, localized cell death at the site of pathogen infection to prevent its spread.

• Inducible Plant Defenses: Defense mechanisms activated in response to attack or stress, rather than being constantly present.

• Jasmonic acid: A plant hormone involved in regulating defense responses against herbivores and pathogens.

• Legume: A family of plants (e.g., beans, peas) that often form symbiotic relationships with nitrogen-fixing bacteria.

• Macronutrients: Essential elements required by plants in large amounts, such as nitrogen, phosphorus, and potassium.

• Micronutrients: Essential elements required in small amounts, such as iron, zinc, and copper.

• Nitrogen fixation: The conversion of atmospheric nitrogen ($N_2$) into a form usable by plants, typically by bacteria in root nodules.

• Mycorrhizae: Symbiotic associations between fungi and plant roots that enhance nutrient uptake.

• Parasitic plant: Plants that obtain nutrients by attaching to and feeding off other plants.

• Photosystem inhibitors: Chemicals that disrupt the photosynthetic process in plants.

• Pi protein: Proteins involved in plant defense, often produced in response to pathogen attack.

• Rhizobium: A genus of bacteria that forms symbiotic relationships with legumes, facilitating nitrogen fixation.

• Root hair: Extensions of root epidermal cells that increase surface area for water and nutrient absorption.

• Root nodule: Specialized structures on legume roots housing nitrogen-fixing bacteria.

• Salinity: The concentration of salts in soil, which can affect plant growth and nutrient uptake.

• Salicylic acid: A plant hormone involved in systemic acquired resistance and defense signaling.

• Secondary metabolism: The production of compounds not directly involved in growth, development, or reproduction, often for defense.

• Static plant defense: Defense mechanisms that are always present, such as thorns or toxic chemicals.

• Soil: The upper layer of earth where plants grow, composed of minerals, organic matter, water, and air.

• Subsoil: The layer of soil beneath the topsoil, containing fewer organic materials but more minerals.

• Suberin: A waxy substance found in plant cell walls, providing a barrier to water and pathogens.

• Systemin: A peptide hormone involved in plant defense signaling, especially in response to wounding.

• Systemic Acquired Resistance (SAR): A whole-plant resistance response that occurs following an earlier localized exposure to a pathogen.

• Topsoil: The uppermost layer of soil, rich in organic material and nutrients.

• Wound response: The activation of defense mechanisms following physical damage to plant tissues.

Additional Info

• Example: Rhizobium bacteria in root nodules of legumes convert atmospheric nitrogen into ammonia, which plants can use for growth.

• Application: Understanding plant defense mechanisms is essential for agriculture, as it helps in developing disease-resistant crops.

• Equation: Nitrogen fixation can be represented as: $N_2 + 8H^+ + 8e^- ightarrow 2NH_3 + H_2$