ABSORPTION BY ROOTS

Question 1

Why do plants need water and minerals?

Answer 1

1. photosynthesis
2. transpiration
3. transportation
4. mechanical stiffness

Question 2

What are the characteristics of roots to absorb more water?

Answer 2

1. large surface area
2. higher concentration of cell sap
3. thin walls

Question 3

Define imbibition

Answer 3

Imbibition is a phenomenon by which living or dead plant cells absorb water by surface attraction

Question 4

What are two hydrophilic substances?

Answer 4

substances made of
1. cellulose
2. proteins
are hydrophilic
- have a strong affinity for water

Question 5

Why do wooden doors swell up on exposure to water?

Answer 5

Due to imbibition

Question 6

What pressure causes seed coats to rupture in germinating seeds?

Answer 6

Imbibitional pressure

Question 7

Define diffusion

Answer 7

The free movement of molecules from their region of lower concentration to their region of higher concentration when the two are in direct contact

Question 8

Define osmosis

Answer 8

The movement of water molecules from their region of higher concentration to their region of lower concentration through a semi permeable membrane

Question 9

What are the two types of osmosis?

Answer 9

1. endosmosis
2. exosmosis

Question 10

Define endosmosis

Answer 10

inward diffusion of water from its region of higher concentration to lower concentration through a semi permeable membrane

Question 11

Define exosmosis

Answer 11

The outward movement of water molecules from higher concentration to lower concentration through a semi permeable membrane

Question 12

Name an impermeable membrane

Answer 12

rubber sheet

Question 13

Name 3 semi permeable membranes

Answer 13

1. visking bag
2. animal bladder
3. celophane paper

Question 14

Name a freely permeable membrane

Answer 14

Muslin cloth

Question 15

Theoretically, how long should osmosis continue?

Answer 15

Until both solutions become isotonic

Question 16

Define osmotic pressure

Answer 16

The minimum pressure that must be exerted to prevent the passage of pure solvent into the solution when the two are separated by a semi permeable membrane

Question 17

Define tonicity

Answer 17

The relative concentration of the solutions that determines the direction and extent of diffusion

Question 18

What are the three types of solutions based on tonicity?

Answer 18

1. isotonic
2. hypertonic
3. hypotonic

Question 19

What is an isotonic solution?

Answer 19

A condition where the concentration of the solutes is the same and no osmosis takes place
No change in size or shape of cell

Question 20

What is a hypotonic solution?

Answer 20

The solution in which endosmosis takes place due to higher concentration of solute
Cell size increases and cells may even burst

Question 21

What is a hypertonic solution?

Answer 21

The solution in which exosmosis takes place due to the increased concentration of solute outside the cell
Cell size decreases and loses shape

Question 22

Define active transport.

Answer 22

The passage of salts or ions from its region of lower concentration to higher concentration through a living cell membrane by using energy from the cell as ATP

Question 23

Why can’t certain ions pass through the cell membrane easily?

Answer 23

Due to the higher concentration of ions maintained inside the cell to develop osmotic pressure to absorb water
These ions are forcibly transported into the cell by active transport using energy from the cell as ATP

Question 24

Define passive transport

Answer 24

The free movement of ions or salts from their state of higher concentration to their state of lower concentration without the supply of energy from the cell

Question 25

What is turgidity?

Answer 25

It is the state of the cell where the cell wall is rigid and stretched due to the increase in the volume of vacuoles due to absorption of water

Question 26

What is turgor pressure?

Answer 26

The pressure of the cell contents on the cell wall

Question 27

What is wall pressure?

Answer 27

The pressure exerted by the cell wall on the cell contents

Question 28

Why is the cell in a state of balance when it is turgid?

Answer 28

As no more water enters or leaves the cell as the turgor pressure counter balances the wall pressure.
No absorption takes place even if there is a higher concentration of solute within the cell

Question 29

What is flacidity?

Answer 29

The state of the cell where it is no longer tight and is shrunken, caused due to the loss of water

Question 30

What is plasmolysis?

Answer 30

The contraction of cytoplasm from the cell wall caused due to the loss of water when the cell is placed in a hypertonic solution
The state of the cell is flaccid

Question 31

What is deplasmolysis?

Answer 31

The swelling up of cytoplasm when placed in a hypotonic solution caused due to the absorption of water
It is the reversal of plasmolysis

Question 32

Define root pressure

Answer 32

The pressure developed in the roots due to continuous inward movement of water through cell to cell osmosis.

It helps in the ascent of sap

Question 33

Define bleeding

Answer 33

The loss of water or sap through a cut or injured stem

Question 34

Define guttation

Answer 34

The loss of excessive water through the margins or tips of leaves

Question 35

What are the forces contributing to the ascent of sap?

Answer 35

1. root pressure
2. capillarity - narrow diameter - capillary force
3. transpirational pull - cohesion
4. adhesion - suction force

Question 36

Name the force contributing to ascent of sap that is important in tall trees such as pines

Answer 36

Adhesion