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What is the consequence of the buildup of solutes in the xylem sap?
What is the term for the positive hydrostatic pressure in the xylem?
What is the term for the liquid droplets produced on the edges of leaves?
What are the specialized pores through which xylem cell sap exudes?
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What happens to water vapor and gases when transpiration is low and ψp increases?
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What is the phenomenon that plants minimize the consequences of in xylem transport of water in trees?
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What is a characteristic of organisms within the biological kingdom Plantae?
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What is the primary function of terrestrial plants' mechanisms for moving water and minerals from soil?
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What is the primary source of water available to plants?
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What is the primary source of energy for plants?
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What is a characteristic of cell structure in plants?
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What is the main topic of the text?
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What happens to the spaces between soil particles after a heavy rainfall?
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What is an example of a physiological process in plants?
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What percentage of water is retained by sandy soils after a heavy rainfall?
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What is the term for the movement of water through the soil in response to a pressure gradient?
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What is the term for the exchange of substances between a cell or organism and its environment?
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What is the result of plants absorbing water from the soil?
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What is an example of a metabolic change in plants?
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What is the term for the study of physiological processes in plants?
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What type of soil retains more water after a heavy rainfall?
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How do roots of plants interact with the soil?
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What is the term for the attraction that pulls water into spaces between soil particles?
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What is the direction of water movement in the soil due to the depletion of ψp near the root surface?
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Which pathway does not involve crossing a membrane?
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What is the purpose of plasmodesmata in the Symplast pathway?
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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?
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What is the result of the depletion of ψp near the root surface?
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What is the name of the pathway that involves movement of water through the cell wall and the extracellular air spaces?
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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.
