ICSE BIOLOGY · 2021. 3. 5. · Instagram: @icse.study.mate, Telegram: t.me/icsestudymatetalks...

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ICSE BIOLOGY

CHAPTER 3 : ABSORPTION BY

ROOTS – THE PROCESSES

INVOLVED

UNIT 2 :PLANT PHYSIOLOGY

1




ICSE BIOLOGY

➢ Need of Mineral Nutrients for plants:

1)These elements are required as constituents of cell and cell

organelles as well as in the synthesis of a variety of compounds or

enzymes within the cell.

BASIC CONCEPTS

➢ Need of water for plants:

1)Constituent of protoplasm.

2)Photosynthesis.

3)Transpiration.

4)Transportation.

5)Mechanical stiffness to plant tissues.

CHARACTERISTICS OF ROOTS FOR ABSORBING

WATER➢

SURFACE AREA

OF ROOT IS

ENORMOUS FOR

EFFECTIVE

ABSORPTION

ROOT HAIRS CONTAIN

CELL SAP, OF A HIGHER

CONCENTRATION THAN

THAT OF SURROUNDING

WATER.(Osmosis)

ROOT HAIRS

HAVE THIN

WALLS.

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Y

PHENOMENA OF ABSORPTION AND CONDUCTION OF

WATER AND MINERALS

➢

IMBIBITION

DIFFUSION

OSMOSIS

ACTIVE TRANSPORT

TURGIDITY AND FLACCIDITY ( Plasmolysis )

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1) IMBIBITION : Imbibition is a phenomenon by which the living or

dead plant cells absorb water by surface attraction.

Example ;

Wooden doors swell up on contact with water or on exposure to moist air.

This generally occurs during monsoon when the surrounding atmosphere

have high moisture content or with direct splash of rain water on wooden

doors and windows. The windows generally swell up because wood is

made up of cellulose so it has a high affinity of water.

2) DIFFUSION : Diffusion is the free movement of molecules of a

substance (solute or solvent, gas, liquid) from the region of their higher

concentration to the region of their lower concentration when two are in a

direct contact.

Example ;

Fig 1: Diffusion of the molecules of a certain dye in water

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3) OSMOSIS : Osmosis is the movement of water molecules from their

region of higher concentration to their region of lower concentration

through a semi-permeable membrane.(Only water molecules move from

their higher concentration to their lower concentration through the semi

permeable membrane as it only allow solvent molecules to pass.)

ENDOMOSIS EXOSMOSIS

*) ENDOSMOSIS – It is the inward diffusion of water trough a semi-

permeable membrane when the surrounding solution is less

concentrated.(Tip: The cell swells up and water moves into it)

*) EXOSMOSIS – It is the outward diffusion of water through a semi-

permeable membrane when the surrounding solution is more

concentrated.(Tip : The protoplasm of cell shrinks as water moves

outwards)

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➢ TONICITY – Relative Concentration of the solutions that determine the

direction and extent of diffusion is called tonicity.

ISOTONICHYPERTONIC HYPOTONIC

*) ISOTONIC SOLUTION – (iso : same) The relative concentration of

water molecules and the solute on either side of the cell membrane is the

same . In such a solution, there is no net movement of water molecules

across the cell membrane i.e. no osmosis. The shape and size of cell

remains same.

*) HYPERTONIC SOLUTION – (hyper : higher) In this condition, the

solution outside the cell has a higher solute concentration than the fluids

inside the cell. Consequently, the water molecules from the interior of the

cell will move out i.e. exosmosis. The Cell shrinks and loses shape.

*) HYPOTONIC SOLUTION – (hypo : lower) In this condition, the solution

outside the cell has a lower solute concentration than the fluids inside the

cell. As a result, the water molecules from outside will move into the cell

i.e. endosmosis. Cell enlarges or even bursts.

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4) ACTIVE TRANSPORT – Active transport is the passage of a

substance ( salt or ion) from its lower to higher concentration through

a living cell membrane ‘forcibly’ using energy from cell in the form of

ATP. (Tip: Active transport is in a direction opposite to that of diffusion)

5) TURGIDITY AND FLACCIDITY ( PLASMOLYSIS) -

❖ TURGIDITY – When a cell reaches a state where it cannot

accommodate any more water i.e., it is fully distended, is called turgid

and the condition is called turgidity.

❖ TURGOR PRESSURE – When a cell is turgid, its wall is stretched

under pressure from inside, and in its turn, it presses the cell contents

towards the centre of the cell. The pressure of the cell contents on the

cell wall is called turgor pressure and the pressure exerted by the

cell wall on the cell content is called wall pressure.

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❖ PLASMOLYSIS – It is the contraction of cytoplasm from the cell wall

caused due to withdrawal of water when placed in hypertonic solution .

(The recovery or the reversal of Plasmolysis is called deplasmolyisis.)

For example :

When some salt is sprinkled over a leech, The blood and fluids inside the

leech come out (exosmosis) and the leech dies. This happens because

the water content in salt is less than that of leech. So, blood moves from

leech towards salt. Hence, the leech gets Plasmolysis.

❖ FLACCIDITY – It is the condition in which the cell content is shrunken

and the cell is no more “ tight". The cell is said to be flaccid.

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➢ USES OF TURGIDITY TO PLANTS :

1. Turgidity provides rigidity to soft tissues such as leaves. –

Wilting of leaves during day time as rate of transpiration is

more than the water absorbed, In the evening transpiration is reduced, The amount of water absorbed exceeds the turgidity

returns.

2. Turgor pressure helps to push through the hard ground

3. Turgity of guard cells helps in opening and closing of stomata

4. Turgor Pressure in root cells builds up root pressure(Root

pressure is the pressure developed in the roots due to

continued inward movement of water through cell-to-cell osmosis which helps in the ascent os cell sap upwards

through the stem.)

{Note: Just read the experiments on absorption and conduction of water in plants from Text book}

➢ Root pressure, Capillarity and transpiration pull Contributes in the ascent of sap up to the topmost regions.

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IMPORTANT REVISION QUESTIONS

1. Why Plants require water & minerals?

2. What is Imbibition?

3. Why wood gets swelled up during Monsoon?

4. What is Diffusion?

5. Define Osmosis?

6. Suppose You through common salt on a grass growing in your

garden, You see the grass gets killed, Why?

7. If you Uproot a plant from the soil its leaves immediately wilts, Why?

8. What is a Semi-Permeable membrane, Give some examples.

9. What is osmotic pressure?

10. What is Tonicity?

11. What is Active transport?

12. When a cell is said to be…i)flaccid, ii)Turgid ?

13. State some uses of Turgidity to plants?

14. What is root Pressure?

15. Differentiate Between:-

i) Endosmosis and Exosmosis

ii)Active Transport and passive transport.

iii)Isotonic, Hypertonic and Hypotonic

iv) Diffusion and Osmosis

16.

{Answers in the end}

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The diagram above represents an experimental set-up to demonstrate a

certain process. Study the same and answer the questions that follow:

a)Name the process.

b)Define the above named process.

c)Observations after an hour.

d)What control experiment can be set-up for comparison?

e)Keeping in mind the root-hair, cell and its surroundings, name the parts

that correspond to i) Concentrated sugar solution, ii)Parchment paper,

iii)water in the beaker.

f)Name any other substance that can be used as a alternative for

parchment paper.

17)

From the above Diagram; A complete ring of bark was removed from a

tree in spring. The tree continued to live trough summer but a swelling

appeared on the bark above the ring while the bark below shriveled up.

a)Account for the swelling in the bark above the ring.

b)Account for the shrinking of the bark below the ring.

c)Name the tissue that distributes food in plant.

d)Name the tissue that distributes water in plants.

e)What is the role of a bark in a plant.

Shrinked/shrivelledbark

{Study all objectives From text book}

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NAME THE FOLLOWING :-

1. The term given to osmosis in which water from the living cell diffuse

out. -- Exosmosis.

2. Pressure through which water can rise up to a few feet. – Root

Pressure.

3. The process in Which water absorption needs metabolic energy. –

Active Transport.

4. The loss of water in the form of droplets through leaves of an intact

plant – Guttation.

5. Outer layer of root hair is made up of pectin and inner layer is made

up of __________. – Cellulose.

6. The condition when there is no osmotic movement in either direction –

Isotonic.7. It refers to the Relative concentrations of solutes of two fluids. –

Tonicity.

8. Water tends to move from _______ fluids to _______ fluids. –

Hypotonic , Hypertonic.

9. The condition of a cell placed in a hypotonic solution. – Turgid.

10. Food conducting tissue. – Phloem.

11. Water conducting tissue --- Xylem.

12. The process by which molecules distribute themselves evenly within

the space they occupy. – Diffusion.

13. Pressure exerted by the cell contents on the cell wall. – Turgor

pressure.

14. The condition in which the cell contents are shrunken. –

Plasmolysed.

15. Loss of water through a cut stem. – Bleeding.

16. The pressure under which water passes from the living cells of a root

into xylem . – Root pressure.

17. The state of a plasmolysed cell after the re-entry of water –

Deplasmolysis.

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GIVE REASONS:-

1. Fresh water fish cannot survive in sea water.

Answer> freshwater fish can't survive in the ocean or saltwater because

the seawater is too salty for them. The water inside their bodies would

flow out their cells, and they will die of dehydration. processes are

called Osmosis.

2. A closed can of dried seeds Bursts open if some water enters it by

accident.

Answers> If some water enters in a closed can of dried seeds,

the seeds absorb water by imbibition and osmosis and swell up. As

the water content of seeds are lesser so it intakes the water and

swells up or even bursts.

3. Plants growing in well fertilized soil wilt if the soil is not adequately

watered.

Answers> Plants growing in fertilized soil are often formed to wilt, if the

soil is not adequately watered because of flaccidity or a decrease in

turgor pressure exerted by the absorbed water on the cell wall

of plants. As the fertilizers take up water content of soil, so it needed

adequate water to comply this loss of water.

4. Potato cubes when placed in water become firm and increase in size.

Answers> Endosmosis is a process in which a solvents molecules travels

through a semi-permeable membrane, making their way to a more

concentrated solution from a less concentrated one. The potato cells have

cell sap of higher concentration than the surrounding water. As a result,

endosmosis occurs in which water molecules travel to the inside of the

potato cells, making them firm.

Due to the inflow of water, the cells become turgid, so the potato cube

becomes firm and increased in size.

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ANSWERS

1. Plants require water for four purposes:- Photosynthesis, transpiration,

transportation and Mechanical stiffness.

plants require minerals elements as constituents of cell and cell

organelle as well as in the synthesis of a variety of compounds or

enzymes within the cell.

2. Imbibition is a phenomenon by which the living or dead plant cells

absorb water by surface attraction.

3. Woods are dry and composed of cellulose and dead cells,this makes

wood to have high affinity for water . Wooden doors swell up on

contact with water or on exposure to moist air. This generally occurs

during monsoon when the surrounding atmosphere have high

moisture content or with direct splash of rain water on wooden doors

and windows. The windows generally swell up because wood is made

up of cellulose so it has a high affinity of water.

4. Diffusion is the free movement of molecules of a substance (solute or

solvent, gas, liquid) from the region of their higher concentration to the

region of their lower concentration when two are in a direct contact.

5. Osmosis is the movement of water molecules from their region of

higher concentration to their region of lower concentration through a

semi-permeable membrane

6. If we throw salt on a grass growing in the garden it gets killed

because the salt have lesser concentration and the grass has higher

concentration of water does with direct contact the water moves from

grass to salt thus resulting in insufficient water for the survival of

plants, Therefore, The grass dies

7. If we uproot a plant from soil , its leaves soon wilts because the roots

can’t absorb water from soil and the rate of loss of water through

transpiration exceeds the rate of absorption of water so, leaves losses

its turgidity and the leaves wilt down.

8. A semi-permeable membrane is a natural or artificial membrane that

allows only certain molecules of a solution to pass through its pores.

for example:-Parchment paper,goat’s bladder, cellophane paper.

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9. Osmotic pressure is the minimum pressure that must be exerted to prevent the passage of pure solvent into the solution when the two are separated by semi-permeable membrane.

10. Relative concentration of the solution that determine the direction and extent of diffusion is called tonicity.

11. Active transport is the passage of a substance from its lower to higher concentration through a living cell membrane using energy from the cell in the form of ATP.

12. i)It is the state of a cell in which the cell wall is rigid and stretched by an increase in the volume of vacuoles due to the absorption of water, then the cell is said to be turgid. Ii)The condition in which the cell content is shrunken and the cell is no longer “tight”. Then the cell is said to be flaccid.

13. Some uses of turgidity to plants are:-i. Turgidity provides rigidity to soft tissues such as leaves. –

Wilting of leaves during day time as rate of transpiration is

more than the water absorbed, In the evening transpiration is

reduced, The amount of water absorbed exceeds the turgidity

returns.

ii. Turgor pressure helps to push through the hard ground

iii. Turgity of guard cells helps in opening and closing of stomata

iv. Turgor Pressure in root cells builds up root pressure(Root pressure is the pressure developed in the roots due to

continued inward movement of water through cell-to-cell

osmosis which helps in the ascent os cell sap upwards

through the stem.)

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14. Root Pressure is the pressure developed in the roots due to

continued inward movement of water through cell to cell osmosis which

helps in the ascent of cell sap upwards through the stem.

15. i)

Endosmosis Exosmosis

• The inward diffusion of

solvent through a semi

permeable membrane when

the surrounding solution s less

concentrated, is known as

endosmosis.

• This tends to swell up the

cell.

• The Outward diffusion of

solvent through a semi

permeable membrane when

the surrounding solution is

more concentrated, is known

as exosmosis.

•This tends to shrinkage of

cell.

ii)

Active Transport Passive transport

• Active transport is the

passage of a substance from

its lower to higher

concentration through a living

membrane.

• Requires Energy in the form

of ATP.

• Passive transport is the

passage of a substance from

its higher to lower

concentration through a living

membrane

• Does not require Energy.

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iii)

Isotonic Hypotonic Hypertonic

• The relative

concentration of

water molecules

and the solute on

either side of the

cell membrane is

the same .

• In such a

solution, there is

no net movement

of water

molecules across

the cell

membrane i.e. no

osmosis.

• The shape and

size of cell

remains same.

• In this condition,

the solution outside

the cell has a lower

solute concentration

than the fluids inside

the cell.

• As a result, the

water molecules

from outside will

move into the cell

i.e. endosmosis.

• Cell enlarges or

even bursts.

• In this condition,

the solution outside

the cell has a

higher solute

concentration than

the fluids inside the

cell.

• the water

molecules from the

interior of the cell

will move out i.e.

exosmosis

• The Cell shrinks

and loses shape.

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iv) Diffusion Osmosis

• Diffusion is the transport of

gases or dissolved

substances in solution from a

region of higher concentration

to a region of lower

concentration when two in

direct contact.

• Rapid in gases, slow in

solutions.

• Can occur without a Semi

permeable membrane.

• Osmosis is the transport of

water through a semi-permeable

membrane from a solution of low

concentration to a Solution of

high concentration.

• Slow process

• A semi permeable membrane is

must.

16. a) Osmosis.

b) Osmosis is the transport of water through a semi-permeable

membrane from a solution of low concentration to a Solution of high

concentration.

c)The initial level of the thistle funnel will increase.

d)Another thistle funnel with plain water.

e) i)protoplasm ,ii)cell membrane ,iii)Soil

f)Cellophane paper.

17. a) because the food produced in the leaves will move down the stem,

as the phloem is cut so Food cannot move down, does it gets stored

above the cut ring and it grows in diameter due to accumulation of

food thus it gets swelled.

b) the below portion as not getting food so its starts shrinking up.

c) Phloem

d)Xylem

e) Bark contains the phloem tissues which are food conducting

tissues and also serves for protection and support.

ICSE BIOLOGY · 2021. 3. 5. · Instagram: @icse.study.mate, Telegram: t.me/icsestudymatetalks...

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