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Ascent of xylem sap, caused due to trans...

Ascent of xylem sap, caused due to transpiration, depends mainly on three physical properties of water, These properties result in

A

low tensile strength but high capillarity

B

low tensile strength as well as low capilarity

C

high tensile strength as well as high capilarity.

D

high tensile strength but low capilarity.

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To solve the question regarding the ascent of xylem sap due to transpiration and its dependence on the physical properties of water, we can break down the solution into clear steps. ### Step-by-Step Solution: 1. **Understanding the Ascent of Xylem Sap**: - The ascent of xylem sap refers to the upward movement of water and dissolved minerals from the roots to the leaves in plants. This process is primarily driven by transpiration, which is the loss of water vapor from plant surfaces. 2. **Identifying the Key Physical Properties of Water**: - The ascent of xylem sap depends on three main physical properties of water: - **Cohesion**: This is the mutual attraction between water molecules. It allows water molecules to stick together, forming a continuous column of water in the xylem vessels. - **Adhesion**: This refers to the attraction of water molecules to polar surfaces, such as the walls of the xylem vessels. This property helps water molecules to cling to the xylem walls, aiding in their upward movement. - **Surface Tension**: This property arises due to the cohesive forces between water molecules at the surface. It allows water to resist external forces and contributes to the ability of water to rise in narrow tubes (capillarity). 3. **Explaining the Mechanism of Water Movement**: - The combination of cohesion and adhesion results in a high tensile strength of water, allowing it to resist breaking under tension. When water evaporates from the leaves (transpiration), it creates a negative pressure in the xylem. This negative pressure pulls the water column upward. - As one water molecule moves up due to this pull, it drags the next water molecule along with it due to cohesion. This process continues, allowing water to rise molecule by molecule. 4. **Conclusion**: - Therefore, the ascent of xylem sap is primarily dependent on the properties of cohesion, adhesion, and surface tension, which together facilitate the movement of water against gravity.
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Give two physical properties of water.

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Knowledge Check

  • What is the effect on chemical properties and physical properties of water when temperature is changed ?

    A
    Chemical properties of water remain same but the physical state changes with change in temperature.
    B
    Chemical properties of water change with change in temperature but physical properties remain same.
    C
    There is no effect on chemical or physical properties of water when temperature is changed.
    D
    Both chemical and physical properties of water change with change in temperature.

  • The transpiration-driven ascent of xylem sap depends mainly upon "______" property of water.

    A
    cohesion
    B
    adhesion
    C
    surface tension
    D
    all of these.

  • Assertion : Secondary treatement of sewage is also called biological treatment while primary treatment is called physical treatment. Reason : Primary sewage treatment depends only upon sedimentation properties of materials present in sewage and filtration.

    A
    If both assertion and reason are true and reason is the correct explanation of assertion
    B
    If both assertion and reason are true but reason is not the correct explanation of assertion
    C
    If assertion is true but reason is false
    D
    If both assertion and reason are false

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