Absorption by Root Class 10 Concise Descriptive Type Ans ICSE Biology Selina Solutions Ch-4 Questions. In this article you will get the solutions of Descriptive Type Questions as council latest syllabus. Visit official website CISCE for detail information about ICSE Board Class-10 Biology.
Absorption by Root Class 10 Concise Descriptive Type Ans Selina Solutions Ch-4
| Board | ICSE |
| Subject | Biology |
| Class | 10 |
| Book | Selina Concise |
| Chapter-4 | Absorption by Root– The Process Involved |
| Topics | Solutions of Descriptive Type Questions |
| Session | 2024-25 |
Solutions of Descriptive Type Questions
(Absorption by Root Class 10 Concise ICSE Biology Selina Solutions Ch-4 Questions)
Que-1: Give two examples of turgor movements in plants
Sol:
(i) insectivorous plants– whose leaves close up to entrap a living prey. When the insect comes in contact with the leaf, it loses its turgor hence closing the leaves of the plant.
(ii) Mimosa pudica,– If one of the leaves is touched, even lightly, the leaflets fold up and within 2 to 3 seconds, the entire leaf droops. If the leaf is touched somewhat strongly, the wave of folding and drooping spreads from the stimulated leaf to all neighbouring leaves.
Que-2: Define the following terms:
(a) Imbibition
(b) Diffusion
(c) Osmosis
(d) Osmotic pressure
(e) Active transport
(f) Tonicity
(g) Root pressure
Sol:
a) Imbibition — Imbibition is a phenomenon by which the living or dead plant cells absorb water by surface attraction. Its the passive absorption of water by substances such as cellulose (in cell wall) and starch.
(b) 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 the two are in a direct contact.
(c) Osmosis — Osmosis is the movement of water molecules from their region of higher concentration (dilute solution or with a lower solute concentration) to their region of lower concentration (concentrated solution or with a higher solute concentration) through a semi permeable membrane.
(d) Osmotic pressure — 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.
(e) Active transport — Active transport is the passage of a substance from its lower to higher concentration through a living cell membrane using energy from the cell.
(f) Tonicity — Relative concentration of the solutions that determine the direction and extent of diffusion is called tonicity.
(g) Root pressure — The upward flow of water due to heavy pressure from the roots is called root pressure. Thus, it is one of the forces to raise water up through the stem into the leaves.
Que-3: Give reasons for the following:
(a) If you sprinkle some common salt on grass growing on a lawn, it is killed at that spot.
(b) If you uproot a plant from the soil, its leaves soon wilt.
(c) It is better to transplant seedlings in a flower-bed in the evening and not in the morning.
(d) A plant cell when kept in a hypertonic salt solution for about 30 minutes turns flaccid.
(e) Potato cubes when placed in water become firm and increase in size.
Sol:
(a) the common salt acts as a hypertonic solution for the grass. The cells of grass start losing water, grass becomes flaccid and Plasmolysis occurs causing the protoplasm to go away from the cell wall. This creates gaps between the membrane and the cell wall. Grass cells shrink completely and ultimately get killed
(b) there is no more water absorbed by the roots. This does not allow the compensation for the loss of water by transpiration hence the leaves of the uprooted plant wilt soon.
(c) in the evening helps the seedlings to adjust for a longer time during the night (cooler temperatures) because the quantity of water absorbed exceeds the loss of water through transpiration. Therefore, it is better to transplant seedling in a flower bed in the evening and not in the morning.
(d) in a hypertonic salt solution, plant starts losing water due to Plasmolysis. As the solution outside the cell has higher solute concentration than the fluids inside the cell so exosmosis occurs. In 30 minutes, the plant cell will lose its distended appearance, the cytoplasm will shrink and the plasma membrane will withdraw from the cell wall causing the plant cell to turn flaccid.
(e) Potato cubes in the water due to endosmosis, water from the surrounding enters the potato cubes making them firm and increasing their size.
Que-4: What are the four main forces which contribute to the ascent of sap (upward movement of water and minerals) ? Name them and explain in short.
Sol:
- Adhesion — It causes the water to stick to the surface of cells thus drawing more water molecules from below when the leaf cells lose water during transpiration. This pulling force (or suction force) provided by the leaves is important for tall trees.
- Root pressure — Root pressure builds up sufficient force to push the sap in the xylem vessels up to a certain height and may be enough for herbaceous plants.
- Capillary force — Capillarity (narrow diameter) of xylem vessels causes the water from a lower level to rise to fill up the vacuum created by the loss of water due to transpiration from the leaves. Narrower the diameter of a tube, greater will be the height of water rising in it exerting a force called capillary force.
- Transpiration pull — As the water is lost from the leaf surface by transpiration, more water molecules are pulled up due to the tendency of water molecules to remain joined (cohesion), and thus to produce a continuous column of water through the stem.
Que-5: What is transpirational pull? How is it caused?
Sol: As water is lost from the leaf surface by transpiration, more water molecules are pulled up due to the tendency of water molecules to remain joined i.e. cohesion. This produces a continuous column of water throughout the stem which is known as ‘transpiration pull’. A negative pressure or tension is produced in the xylem that pulls the water from the roots and soil. Transpirational pull is an important force which causes the ascent of sap.
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