Plant Biology: Specialized Roots
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Plant Biology: Specialized Roots

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Questions and Answers

What is the primary function of buttress roots in tropical trees?

  • Nutrient absorption
  • Photosynthesis
  • Water storage
  • Stabilization of the tree (correct)

    • Parasitic roots are capable of photosynthesis.

    False

    What are haustoria?

    Peg-like extensions produced by parasitic plants to attach to their host.

    Plants that grow on other plants but obtain nutrients from the environment are known as ______.

    <p>epiphytes</p> Signup and view all the answers

    Match the following types of roots with their descriptions:

    <p>Buttress Roots = Stabilizes tree in shallow soil Parasitic Roots = Depend on other plants for nutrition Mycorrhizae = Mutualistic association with plant roots Root Nodules = Contain nitrogen-fixing bacteria</p> Signup and view all the answers

    Which of the following benefits does mycorrhizae provide to plants?

    <p>Facilitating nutrient absorption</p> Signup and view all the answers

    What term describes the water remaining in the soil after it has drained away by gravity?

    <p>Field Capacity</p> Signup and view all the answers

    Fungi associated with mycorrhizae develop more root hairs than those without.

    <p>False</p> Signup and view all the answers

    Soil acidity can enhance the growth of nitrogen-fixing bacteria.

    <p>False</p> Signup and view all the answers

    What role do root nodules play in plants?

    <p>Root nodules house nitrogen-fixing bacteria that convert nitrogen into a usable form for plants.</p> Signup and view all the answers

    What can be added to counteract soil alkalinity?

    <p>sulfur</p> Signup and view all the answers

    The water held in soil between field capacity and the permanent wilting point is termed _____ water.

    <p>available</p> Signup and view all the answers

    Match the soil properties with their effects:

    <p>Field Capacity = Water retained after drainage Permanent Wilting Point = Insufficient water for plants Soil pH = Affects nutrient availability Adding Calcium or Magnesium = Counteracts soil acidity</p> Signup and view all the answers

    What is one of the primary functions of roots?

    <p>Absorbing water and minerals</p> Signup and view all the answers

    All roots develop from the radicle of the plant embryo.

    <p>False</p> Signup and view all the answers

    What type of growth stops after a plant reaches a certain size?

    <p>Determinate growth</p> Signup and view all the answers

    Name one type of specialized root.

    <p>Food-storage root</p> Signup and view all the answers

    Cork cambium arises in the endodermis outside of the vascular cambium.

    <p>False</p> Signup and view all the answers

    The ______ is responsible for the growth and protection of the root tip.

    <p>root cap</p> Signup and view all the answers

    Match the following root types with their functions:

    <p>Propagative Roots = Aids in vegetative reproduction Pneumatophores = Facilitates gas exchange Contractile Roots = Pulls the plant deeper into the soil Aerial Roots = Absorbs moisture from the air</p> Signup and view all the answers

    Name one function of water-storage roots.

    <p>To store water in arid regions.</p> Signup and view all the answers

    Which of the following best describes fibrous root systems?

    <p>Made up of numerous thin roots</p> Signup and view all the answers

    Sweet potatoes and yams store large amounts of ______ in their roots.

    <p>starch</p> Signup and view all the answers

    Match the following specialized roots with their functions:

    <p>Pneumatophores = Enhance gas exchange Contractile roots = Pull the plant deeper into the soil Fibrous roots = Absorb water and minerals Water-storage roots = Store water in arid regions</p> Signup and view all the answers

    Mycorrhizae are beneficial fungi that form a symbiotic relationship with plant roots.

    <p>True</p> Signup and view all the answers

    What modifies some roots for functions beyond just mineral and water absorption?

    <p>Specialization</p> Signup and view all the answers

    What is the role of soil structure for plants?

    <p>Soil structure influences root growth and water retention.</p> Signup and view all the answers

    Adventitious buds on roots develop into leaves.

    <p>False</p> Signup and view all the answers

    What is a common feature of aerial roots in orchids?

    <p>Velamen roots.</p> Signup and view all the answers

    Which of the following is NOT a source of food from roots?

    <p>Lettuce</p> Signup and view all the answers

    The B Horizon of the soil is known for having more organic material than the A Horizon.

    <p>False</p> Signup and view all the answers

    What are the three main types of rock that form parent material?

    <p>Igneous, Sedimentary, Metamorphic</p> Signup and view all the answers

    The _____ horizon of soil is characterized by being dark and rich in organic material.

    <p>A</p> Signup and view all the answers

    Match the following soil horizons with their characteristics:

    <p>A Horizon = Rich in organic material B Horizon = Subsoil, more clay C Horizon = Parent material E Horizon = Light colored, leached materials</p> Signup and view all the answers

    Which climate condition leads to poorly developed soils?

    <p>Desert conditions</p> Signup and view all the answers

    What is the role of bacteria and fungi in soil?

    <p>They decompose organic material.</p> Signup and view all the answers

    Rotenone is used as an insecticide derived from living organisms.

    <p>True</p> Signup and view all the answers

    What is the primary function of roots in plants?

    <p>To anchor plants into soil</p> Signup and view all the answers

    Which type of root system is characterized by a thick primary root and thinner branch roots?

    <p>Taproot system</p> Signup and view all the answers

    Which of the following roots develop from stems or leaves instead of other roots?

    <p>Adventitious roots</p> Signup and view all the answers

    What specialized function do water-storage roots primarily serve?

    <p>Storing water for dry periods</p> Signup and view all the answers

    Which type of roots are known for their ability to grow in air and absorb moisture from the environment?

    <p>Aerial roots</p> Signup and view all the answers

    Which zone of root development is responsible for the growth of new cells?

    <p>Region of cell division</p> Signup and view all the answers

    What is the primary role of mycorrhizae in relation to plant roots?

    <p>To enhance nutrient and water absorption</p> Signup and view all the answers

    Which of the following describes the function of root nodules?

    <p>Absorbing nitrogen from the air</p> Signup and view all the answers

    Which region of the root is responsible for the differentiation into various cell types?

    <p>Region of Maturation</p> Signup and view all the answers

    What is the primary function of the root cap?

    <p>To protect the root tip from damage</p> Signup and view all the answers

    Which type of cell gives rise to the epidermis in the root?

    <p>Protoderm</p> Signup and view all the answers

    In which region do root cells become elongated and merge their vacuoles?

    <p>Region of Elongation</p> Signup and view all the answers

    What is NOT a function of the root cap?

    <p>Regulating nutrient absorption</p> Signup and view all the answers

    What happens when root cells are located above the region of elongation?

    <p>No further increase in cell size takes place</p> Signup and view all the answers

    Which of the following components gives rise to the primary xylem in the root?

    <p>Procambium</p> Signup and view all the answers

    How does the presence of cambium affect root girth?

    <p>It allows for an increase in girth</p> Signup and view all the answers

    What is the primary advantage of mycorrhizae for plants?

    <p>They enhance the absorption of nutrients, particularly phosphorus.</p> Signup and view all the answers

    What is a characteristic of parasitic roots?

    <p>They have haustoria that attach to a host plant.</p> Signup and view all the answers

    Which plant type is classified as an epiphyte?

    <p>Orchids that grow on other plants but absorb nutrients from their environment.</p> Signup and view all the answers

    What is the role of root nodules in certain plants?

    <p>They contain bacteria that fix nitrogen into usable forms.</p> Signup and view all the answers

    What is a notable feature of epiparasites?

    <p>They derive some or all of their carbon from a fungus.</p> Signup and view all the answers

    How do buttress roots contribute to tropical trees?

    <p>By stabilizing the tree in shallow soil.</p> Signup and view all the answers

    Which structure allows parasitic plants to attach to their host?

    <p>Haustoria.</p> Signup and view all the answers

    What distinguishes saprophytes from other plant types?

    <p>They obtain nutrients from decaying organic matter.</p> Signup and view all the answers

    What type of growth continues indefinitely in plants?

    <p>Indeterminate growth</p> Signup and view all the answers

    Which type of roots primarily enhance gas exchange for plants growing in saturated conditions?

    <p>Pneumatophores</p> Signup and view all the answers

    What plant structure helps support plants during high winds?

    <p>Prop roots</p> Signup and view all the answers

    Which of the following roots is primarily involved in food storage?

    <p>Food-storage roots</p> Signup and view all the answers

    What is the main function of adventitious buds on roots?

    <p>Develop into suckers</p> Signup and view all the answers

    What characteristic of velamen roots in orchids helps reduce water loss?

    <p>Multiple epidermal layers</p> Signup and view all the answers

    Which root type is known to pull the plant deeper into the soil?

    <p>Contractile roots</p> Signup and view all the answers

    Which feature is common in water-storage roots found in arid conditions?

    <p>High carbohydrate content</p> Signup and view all the answers

    What is the primary role of the topsoil layer in soil horizons?

    <p>Rich in organic material and supports plant life</p> Signup and view all the answers

    Which type of rock does NOT contribute to parent material in soil formation?

    <p>Crystal rock</p> Signup and view all the answers

    In which climate condition are soils expected to be least developed?

    <p>Deserts or arid regions</p> Signup and view all the answers

    What key process do bacteria and fungi contribute to in soil?

    <p>Decomposition of organic material</p> Signup and view all the answers

    How does excessive water flow through soil impact soil minerals?

    <p>It leaches important minerals out of the soil</p> Signup and view all the answers

    Which characteristic is true of the C horizon in soil layers?

    <p>Varies in depth and is the source of parent material</p> Signup and view all the answers

    Which of the following plants is noted as a source of food from roots?

    <p>Yams</p> Signup and view all the answers

    What is primarily found in the subsoil B horizon compared to topsoil?

    <p>Lighter color and increased clay content</p> Signup and view all the answers

    Study Notes

    Introduction

    • Roots anchor plants, absorb water and minerals, store food or water, and perform other specialized functions.
    • Upon germination, the embryo’s radicle grows into the first root, which can develop into a thick taproot with thinner branch roots.
    • Adventitious roots can arise from a stem or leaf.
    • In woody plants, the cork cambium arises in the pericycle outside of the vascular cambium.

    Specialized Roots

    • Food-Storage Roots: Plants like sweet potatoes and yams store large amounts of carbohydrates in their roots.
    • Water-Storage Roots: Some members of the Pumpkin family, particularly in arid regions, produce massive water-storage roots.
    • Propagative Roots: Adventitious buds on roots develop into suckers (aerial stems), common in fruit trees.
    • Pneumatophores: Spongy roots, extending above the water's surface in plants with roots in water, enhance gas exchange.
    • Aerial Roots: Orchids have Velamen roots with a multi-layered epidermis to reduce water loss; Corn has prop roots for support in high wind. Ivies utilize aerial roots for climbing.

    Mycorrhizae & Root Nodules

    • Mycorrhizae are fungi forming mutualistic associations with plant roots, both benefiting from the association. Fungi aid in nutrient absorption, especially phosphorus, while the plant provides sugars and amino acids.
    • Plants with mycorrhizae have fewer root hairs compared to those without.
    • Root nodules contain nitrogen-fixing bacteria. Plants cannot convert free nitrogen into usable form, but these bacteria produce enzymes that convert nitrogen into nitrates and other nitrogenous substances easily absorbed by roots.

    Human Relevance of Roots & Soils

    • Roots are a source of food (carrots, sugar beets, turnips, etc.), spices, dyes, drugs, and insecticides.
    • Soils are formed through the interaction of climate, parent material, topography, vegetation, living organisms, and time.
    • The solid portion of soil consists of minerals and organic matter.
    • Pore spaces between solid particles are filled with air or water.

    Soil Horizons

    • Soils are divided into horizons:
      • Topsoil (10-20cm): A Horizon (dark, with more organic material) and E Horizon (light)
      • B Horizon (0.3-0.9m): Subsoil, containing more clay and a lighter color than topsoil.
      • C Horizon (varies): Parent material that extends to bedrock.

    Parent Material, Climate, and Living Organisms

    • Parent Material: Rock that has not been broken down into smaller particles, categorized as Igneous (volcanic), Sedimentary (deposited by glaciers, water, or wind), or Metamorphic (changes in igneous or sedimentary rocks from pressure or heat).
    • Climate: Significant influence on weathering of rocks.
      • Deserts have little weathering by rain and poorly developed soils.
      • Moderate rainfall areas have well-developed soils.
      • High rainfall areas have excessive water flow, leaching out important minerals.
    • Living Organisms & Organic Composition: Soil contains a vast population of organisms, including roots, bacteria, and fungi that decompose organic material.

    Terminology for Water in the Soil

    • Field Capacity: Water remaining in soil after drainage by gravity, affected by texture, structure, and organic content.
    • Permanent Wilting Point: Insufficient water absorption for plant needs, leading to permanent wilting.
    • Available Water: Soil water between field capacity and permanent wilting point.

    Soil pH

    • Soil pH affects nutrient availability.
    • Alkalinity reduces the availability of minerals like copper, iron, and manganese, countered by adding sulfur or nitrogenous fertilizers.
    • Acidity inhibits nitrogen-fixing bacteria, countered by adding calcium or magnesium compounds (liming).

    Introduction to Roots and Soils

    • Roots anchor plants into the soil, absorb water & minerals, store food or water, and serve other specialized functions.

    Root structure and development

    • Upon germination, the embryo's radicle grows out and develops into the first root.
    • Radicle may develop into a thick taproot with thinner branch roots.
    • Dicotyledonous plants (dicots) have taproot systems.
    • Adventitious roots can arise from stems or leaves and develop into a fibrous root system.
    • Adventitious roots do not develop from another root.
    • Fibrous roots consist of a large number of fine roots with similar diameters.
    • Monocotyledonous plants (monocots) and some dicots have fibrous roots.

    Regions of a root

    • Root cap: Thimble-shaped mass of parenchyma cells covering the root tip.
      • Protects root tissues from damage as it grows.
      • Secretes mucilage, acting as a lubricant.
      • Functions in perceiving gravity.
    • Region of cell division: Composed of the apical meristem in the center of the root tip.
      • Three meristematic areas:
        • Protoderm - gives rise to the epidermis
        • Ground meristem - gives rise to the cortex and pith
        • Procambium - gives rise to the primary xylem and primary phloem.
    • Region of elongation: Cells become several times their original length. Vacuoles merge.
    • Region of maturation: Cells differentiate into various cell types. Root hairs form.
      • In woody plants: cork cambium arises in the pericycle outside of the vascular cambium.

    Specialized Roots

    • Most plants produce either a fibrous root system, a taproot system, or a combination of both.
    • Some plants have roots modified for functions beyond mineral and water absorption.

    Food-Storage Roots

    • Sweet potatoes and yams: Extra cambial cells develop in parts of the xylem.
      • This produces large numbers of parenchyma cells.
      • Organs swell and provide storage areas for carbohydrates.

    Water-Storage Roots

    • Some members of the Pumpkin family, particularly in arid regions, produce huge water-storage roots.

    Propagative Roots

    • Adventitious buds on roots develop into suckers (aerial stems).
      • This is common in fruit trees.

    Pneumatophores

    • Plants with roots growing in water can develop spongy roots that extend above the water's surface.
      • This enhances gas exchange between the atmosphere and subsurface roots.

    Aerial Roots

    • Orchids have velamen roots, with an epidermis several layers thick to reduce water loss.
    • Corn prop roots support plants in high winds.
    • Ivies (English ivy, Virginia creeper) have aerial roots that aid in climbing.

    Contractile roots

    • Found in some herbaceous dicots and monocots.
    • Pull the plant deeper into the soil.
    • Lily bulbs are pulled deeper into the soil each year.

    Buttress Roots

    • Some tropical trees growing in shallow soil produce buttress roots to stabilize the tree.

    Parasitic Roots

    • These are produced by plants like dodders, broomrapes, and pinedrops.
    • Most lack chlorophyll and depend on chlorophyll-bearing plants for nutrition.
    • Haustoria are peg-like extensions that allow them to parasitize a host.

    Mycorrhizae

    • Fungi that form a mutualistic association with plant roots.
      • Mutualistic association: Both fungus and root benefit and are dependent on the association for normal development.
      • Fungi facilitate absorption and concentration of nutrients, specifically phosphorus, for roots.
      • Plants provide sugars and amino acids to the fungus.
      • Plants with mycorrhizae have fewer root hairs compared to those without an associated fungus.
      • Particularly susceptible to acid rain.

    Root Nodules

    • Plants cannot convert free nitrogen to usable forms.
    • Some species of bacteria produce enzymes that convert nitrogen into nitrates and other nitrogenous substances readily absorbed by roots.
    • Root nodules contain a large number of nitrogen-fixing bacteria.

    Human Relevance of Roots

    • Sources of food: Carrots, sugar beets, turnips, horseradishes, cassava (tapioca), yams, sweet potatoes.
    • Spices: Sassafras, sarsaparilla, licorice.
    • Dyes.
    • Drugs: Aconite, ipecac, gentian, reserpine.
    • Insecticide: Rotenone.

    Soils

    • Soil is formed through the interaction of climate, parent material, topography, vegetation, living organisms, and time.
    • The solid portion of soil consists of minerals and organic matter.
    • Pore spaces between solid particles are filled with air or water.

    Soil Horizons

    • Topsoil (10-20cm)
      • A-horizon: Dark, with more organic material than lower layers.
      • E-horizon: Light.
    • B-horizon (0.3-0.9m): Subsoil
      • More clay, lighter in color than topsoil.
    • C-horizon (varies): Parent material which extends to bedrock.

    Parent Material

    • Parent material: Rock that has not been broken down into smaller particles.
      • Rock types:
        • Igneous: Volcanic
        • Sedimentary: Deposited by glaciers, water, or wind
        • Metamorphic: Changes in igneous or sedimentary rocks from pressure or heat

    Climate

    • Climate varies throughout the globe, as does its role in weathering rocks.
      • Deserts: Little weathering by rain, and soils are poorly developed.
      • Moderate rainfall: Well-developed soils.
      • High rainfall: Water flow through soil leaches out important minerals.

    Living Organisms and Organic Composition

    • Many kinds of organisms, roots, and other plant parts can be found in soil.
    • Bacteria and fungi decompose organic material from dead leaves, plants, and animals.

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