Absorption By Roots

Question 1

Functions of Roots

Answer 1

• Anchoring the Plant
• Absorption of minerals and water
• Storage of foods

Question 2

Need of Water for Plant

Answer 2

• Photosynthesis
• Transpiration
• Transportation of mineral salts, sugars
• mechanical stiffness

Question 3

Need of Minerals

Answer 3

• constituents of cell organelles
• synthesis of various compounds or enzymes

Question 4

Characteristics of Roots for absorption of water

Answer 4

• Large surface area provided by root hairs
• More concentration of cell sap than that of surrounding water, which aids in osmosis
• Thin cell wall and cell membrane.

Question 5

Summarise the entire mechanism of absorbing water into 5 steps.

Answer 5

1. Imbibition
2. Diffusion
3. Osmosis
4. Active Transport
5. Turgidity and Flexibility

Question 6

Define Imbibition

Answer 6

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

Question 7

How does imbibition help plants?

Answer 7

• Due to imbibition, seed coat ruptures in case of germinating seeds.
• It is also an important force in the ascent of sap.

Question 8

Define Diffusion

Answer 8

Diffusion is the free movement of molecules of a substance from the region of their higher concentration to a region of their lower concentration, when the two are in direct contact

Question 9

Define Osmosis

Answer 9

Osmosis is the movement of water molecules from the region of their higher concentration to a region of lower concentration through a semipermeable membrane

Question 10

What is endomosis?

Answer 10

The osmotic inflow of water into a cell when it is placed in water or dilute solution whose concentration of water is more than the cell sap.
It causes swelling of cell

Question 11

What is exosmosis?

Answer 11

The osmotic outflow of water into a cell when it is placed in water or dilute solution whose concentration of water is less than that of the cell sap. It causes cell shrinkage

Question 12

How long can osmosis continue?

Answer 12

• Theoretically: Osmosis can continue indefinitely as long as there is a concentration gradient and a semi-permeable membrane present.
• Practically, in a vertical column, osmosis can only continue until the height and weight of the liquid column balance the osmotic pressure

Question 13

Define osmotic pressure.

Answer 13

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

Question 14

Define Tonicity

Answer 14

Tonicity is the relative concentration of the solution that determines the direction and extent of diffusion.

Question 15

What are the three types of tonicity possible?

Answer 15

Hypertonic, Hypotonic and Isotonic

Question 16

Define Isotonic solution

Answer 16

Isotonic solution is the kind of solution in which the relative concentration of the water molecules and the solute on either side of the cell membrane is the same.

Question 17

Define Hypotonic Solution

Answer 17

A hypotonic solution is a type of solution where the relative concentration of water molecules is higher outside the cell compared to inside, resulting in a lower concentration of solute outside the cell compared to inside.

Question 18

Define Hypertonic Soln

Answer 18

A hypertonic solution is a type of solution where the relative concentration of water molecules is lower outside the cell compared to inside, resulting in a higher concentration of solute outside the cell compared to inside.

Question 19

Define Active Transport

Answer 19

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

Question 20

Need and use of active transport in plants.

Answer 20

Active transport in plants is essential due to the higher mineral concentration in the root sap compared to the surrounding soil solution. This concentration gradient facilitates osmosis, allowing water and essential minerals to move into the roots against the concentration gradient. Mechanisms such as proton pumps and ion channels are employed to actively transport minerals into root cells, ensuring efficient nutrient uptake and supporting optimal plant growth.

Question 21

When is a cell said to be turgid? What is Turgidity?

Answer 21

When a cell reaches a state where it cannot accommodate any more water, i.e, when it is fully distended, it is called turgid and the condition is called turgidity

Question 22

Define Turgor Pressure

Answer 22

• Pressure exerted by cell contents on cell wall in a turgid condition.

Question 23

Plasmolysis

Answer 23

It is the shrinkage of protoplasm on placement in a hypertonic solution.