Absorption

Plants need water and minerals for their survival. These are taken by plants from the soil through their roots.The process by which plants take-up these substances from soil is known as absorption.Water is vital to every function of a plant, from growth and photosynthesis to hydration.

Plants have root system for absorbing water from the soil.Root system of plants consists ofmain root andLateral (branch) roots.

Lateral roots bear large number of fine outgrowths; called root hair.Root hair are long protrusions of a root cell.They contain fluid (or sap), which is more concentrated than the surrounding soil water.Root hair are covered by a very thin, semi-permeable membrane. They provide a very large surface area for water absorption.

Absorption in plants involves movement of water molecules from the soil to root cells. Movement of water molecules occurs by three mechanisms: diffusion, osmosis and active transport.

Diffusion is a simple process of movement of molecules from a region of higher concentration to a region of lower concentration.Along with water, roots also absorb mineral salts. These mineral salts dissolve in water and form ions. If the concentration of ions in more in the soil, then they will move into the roots by the process of diffusion.

Osmosis can be defined as the movement of water (or solvent) molecules from the region of higher concentration to the region of lower concentration through a semi-permeable membrane.Water is absorbed by the roots from the surrounding soil by osmosis.

Active transport occurs in the opposite direction with respect to osmosis of water, i.e., from the region of lower concentration to the region of higher concentration.Active transport uses energy in the form of ATP to transport molecules.

Factors that affect water absorption in plants areavailability of water, temperature of water and soil (optimum being 20 to 35 degree celsius), concentration of soil water andaeration in soil.

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  • Q1

    A membrane that lets some particles to pass through is known as-

    Marks:1
    Answer:

    Semi-permeable membrane

    Explanation:

    Movement of fluid through a semipermeable membrane from a solution with a lower solute concentration to a solution with a higher solute concentration until there is an equal solute concentration on both sides of the membrane is called osmosis.

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  • Q2

    Selective permeability identifies the process of-

    Marks:1
    Answer:

    osmosis

    Explanation:

    The passage of a solvent through a semipermeable membrane from a less concentrated to a more concentrated solution until both solutions become of the same concentration.

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  • Q3

    In plants, water absorption occurs through-

    Marks:1
    Answer:

    Root hair

    Explanation:

    Plants absorb water from the soil by the process of osmosis. Root hair cells are adapted for this by having a large surface area to speed up osmosis. The absorbed water is transported through the roots to the different parts of the plant, where it is used for different purposes.

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  • Q4

    Active uptake of minerals by roots mainly depends on the-

    Marks:1
    Answer:

    Availability of O2

    Explanation:

    Active uptake of minerals by roots mainly depends on the Availability of O2.

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  • Q5

    If the marine animals are put in fresh water, they burst. It shows the process of

    Marks:1
    Answer:

    Endosmosis

    Explanation:

    Marine animals contain less water in their bloodstream and a higher content of salt in their tissues and organs. When placed in freshwater conditions, water will naturally diffuse from its high concentration to the area where it is of low concentration- the tissues and body of the fish. This process is known as endosmosis. As a result, the animal's body tissues and organs become engorged with water, resulting in rupture, hemorrhaging and the eventual 'bursting' of the creature's body.

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