Botany Quiz: Xylem Transport and Cavitation
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Questions and Answers

What is the consequence of the buildup of solutes in the xylem sap?

  • An increase in xylem osmotic potential
  • A decrease in root pressure
  • An increase in transpiration rate
  • A decrease in xylem water potential (correct)

    • What is the term for the positive hydrostatic pressure in the xylem?

  • Root suction
  • Transpiration pull
  • Xylem tension
  • Root pressure (correct)

    • What is the term for the liquid droplets produced on the edges of leaves?

  • Sweating
  • Transpiration
  • Respiration
  • Guttation (correct)

    • What are the specialized pores through which xylem cell sap exudes?

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

    What happens to water vapor and gases when transpiration is low and ψp increases?

    <p>They dissolve back into the xylem solution</p> Signup and view all the answers

    What is the phenomenon that plants minimize the consequences of in xylem transport of water in trees?

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

    What is a characteristic of organisms within the biological kingdom Plantae?

    <p>Non motility</p> Signup and view all the answers

    What is the primary function of terrestrial plants' mechanisms for moving water and minerals from soil?

    <p>To support photosynthesis and growth</p> Signup and view all the answers

    What is the primary source of water available to plants?

    <p>Rainfall or irrigation</p> Signup and view all the answers

    What is the primary source of energy for plants?

    <p>Solar energy</p> Signup and view all the answers

    What is a characteristic of cell structure in plants?

    <p>Cell walls containing cellulose</p> Signup and view all the answers

    What is the main topic of the text?

    <p>The affiliation of Dr. Kwadwo Ayeh</p> Signup and view all the answers

    What happens to the spaces between soil particles after a heavy rainfall?

    <p>The smaller spaces are filled first</p> Signup and view all the answers

    What is an example of a physiological process in plants?

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

    What percentage of water is retained by sandy soils after a heavy rainfall?

    <p>15%</p> Signup and view all the answers

    What is the term for the movement of water through the soil in response to a pressure gradient?

    <p>Bulk flow</p> Signup and view all the answers

    What is the term for the exchange of substances between a cell or organism and its environment?

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

    What is the result of plants absorbing water from the soil?

    <p>The soil is depleted of water near the surface of the roots</p> Signup and view all the answers

    What is an example of a metabolic change in plants?

    <p>Synthesis of lipids</p> Signup and view all the answers

    What is the term for the study of physiological processes in plants?

    <p>Plant Physiology</p> Signup and view all the answers

    What type of soil retains more water after a heavy rainfall?

    <p>Clay soil</p> Signup and view all the answers

    How do roots of plants interact with the soil?

    <p>They permeate the soil in the immediate surroundings</p> Signup and view all the answers

    What is the term for the attraction that pulls water into spaces between soil particles?

    <p>Capillary attraction</p> Signup and view all the answers

    What is the direction of water movement in the soil due to the depletion of ψp near the root surface?

    <p>Down the pressure gradient</p> Signup and view all the answers

    Which pathway does not involve crossing a membrane?

    <p>Apoplast pathway</p> Signup and view all the answers

    What is the purpose of plasmodesmata in the Symplast pathway?

    <p>To connect cytoplasm of adjacent cells</p> Signup and view all the answers

    What is the route by which water enters the cell on one side and leaves the cell on the other side of the same cell?

    <p>Transmembrane pathway</p> Signup and view all the answers

    What is the result of the depletion of ψp near the root surface?

    <p>Establishment of a pressure gradient away from the root surface</p> Signup and view all the answers

    What is the name of the pathway that involves movement of water through the cell wall and the extracellular air spaces?

    <p>Apoplast pathway</p> Signup and view all the answers

    Study Notes

    Physical Challenges Associated with Xylem Transport of Water in Trees

    • Plants minimize the consequences of xylem cavitation, which occurs when transpiration is low, and water vapor and gases may dissolve back into the xylem solution.
    • Root pressure is built up by the accumulation of solutes in the xylem sap, leading to a decrease in the xylem osmotic potential (ψs) and a decrease in the xylem water potential (ψp).
    • This provides a driving force for water absorption, resulting in a positive hydrostatic pressure in the xylem, which is likely to occur when soil water potentials are high and transpiration is low.
    • Guttation occurs when plants produce liquid droplets on the edges of their leaves.
    • Hydathodes are specialized pores through which xylem cell sap exudes.

    What are Plants?

    • A plant is any one of the vast number of organisms within the biological kingdom Plantae.
    • Plants are Earth's primary producers and ultimate collectors of solar energy, converting it into chemical energy, which is stored as bonds when they synthesize carbohydrates.
    • Plants are non-motile, but have evolved to reach towards what they need, such as water, mineral nutrients, and light.
    • Terrestrial plants have elaborate mechanisms for moving water and minerals from soil to the sites of photosynthesis and growth.
    • Terrestrial plants continuously lose water through evaporation and have evolved mechanisms to avoid desiccation.

    Whole Plant Physiology

    • Physiological processes include any chemical or physical change occurring within a cell or organism, and any exchange of substances between the cell or organism and its environment.
    • Examples of physiological processes include diffusion, osmosis, gas diffusion, transpiration, water conduction, solute absorption, and radiant energy transport.
    • Metabolic changes, such as those concerned with respiration, photosynthesis, synthesis, and degradation of lipids, amino acids, proteins, etc., are also considered physiological processes.

    Water Absorption by Roots

    • Water absorption by roots depends on the soil type and structure.
    • Roots of plants permeate the soil in the immediate surroundings, and lateral roots and root hairs penetrate the soil, where aggregates or soil crumbs may be found.
    • Rainfall or irrigation is the main source of water available to plants.
    • Water percolates downward by gravity through spaces between soil particles.

    Water Movement through Soil

    • Bulk flow is the concerted movement of molecules en masse, often in response to a pressure gradient.
    • Water moves through the soil by bulk flow, which is the predominant mechanism.
    • As plants absorb water from the soil, they deplete the soil of water near the surface of the roots, reducing the ψp in the water near the root surface and establishing a pressure gradient with respect to neighboring regions of soil that have a higher ψp.
    • Water-filled pore spaces are interconnected, and water moves down the pressure gradient towards the root surface by bulk flow.

    Root Water Uptake

    • The apoplast is the continuous system of cell walls, intercellular air spaces, and the lumens of non-living cells (e.g., xylem conduits and fibers).
    • Water moves through the cell wall and the extracellular air spaces without crossing any membrane as it travels across the root hairs.
    • The symplast is made up of cytoplasm interconnected via plasmodesmata.
    • Water travels across the root cortex via plasmodesmata.
    • The transmembrane pathway is the route by which water enters the cell on one side and leaves the cell on the other side of the same cell.

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    Description

    This quiz covers the physical challenges associated with xylem transport of water in trees and the phenomenon of cavitation in plants.

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