ICSE Class 10 Biology Adsorption by roots Syllabus with Question Answer
Adsorption by Roots:
This topic covers how plants absorb water and minerals from the soil through their roots. It includes the concept of adsorption, which is the process by which the roots attract and hold water and mineral ions.
Importance of Adsorption:
You'll learn about why adsorption by roots is important for plant growth and how it contributes to the overall health and development of plants. Factors Affecting Adsorption: This section might cover the factors that influence the adsorption process, such as the surface area of the roots, the concentration of minerals in the soil, and the availability of water.
Role of Root Hairs:
Root hairs play a crucial role in adsorption by roots. You might study how root hairs increase the surface area of the roots, allowing for more efficient adsorption of water and minerals.
Experiments and Observations:
The syllabus might include practical experiments or observations related to adsorption by roots, where you can see the process in action and understand its significance better.
Make sure to refer to your specific textbook or syllabus for detailed information and any additional topics that might be included.
Chapter 3. Absorption by Roots
Short Questions
Question 1: How is root hair structurally adapted for absorption of water from the soil ?
Answer: (i) The root hair represents a large surface area in contact with the soil particle.
(ii) The minute root hair can penetrate between the soil particles and when it comes in
contact with soil water, the cell membrane allows efficient entry of water into the root.
(iii) The cytoplasm and the vacuoles also help in this water absorption by osmosis.
Question 2: Root hairs become flaccid, when fertilizers are added to the moist soil around
it. Explain.
Answer: When fertilizers are added to the moist soil around it, it will form hypertonic
solution, resulting the protoplasm to shrink and plasma membrane withdraw itself from the
cell wall. Hence, the root hairs also become limp or flaccid.
Question 3: What do you mean by transpiration pull ?
Answer: 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.
This phenomenon is known as transpiration pull.
Question 4: Define the Cohesive and Adhesive forces.
Answer: Cohesive Force: The force produced by the molecular attraction between water
particles.
Adhesive Force: The force of attraction between the molecules of unlike bodies that act to
hold them together is called adhesive force.
Question 5: Give at least three uses of water to green plants.
Answer: (i) Water is major component of protoplasm.
(ii) It is an important raw material for photosynthesis.
(iii) Most metabolic and enzymatic reactions take place in the presence of water.
Question 6: What is toxicity ?
Answer: It refers to the kind of external osmotic environment of a cell or it refers to the
type of solution outside the cell.
Question 7: “Grapes shrink when immersed in a very strong sugar solution.” Explain.
Answer: Very strong sugar solution is hypertonic to the grapes juice. Therefore, water
from inside the grapes moves to outside hypertonic solution. It results shrinkage of the
grapes.
Question 8: What is the significance of diffusion ?
Answer: Significance of Diffusion:
(i) It helps in the exchange of respiratory gases.
(ii) It helps in the transport of food molecules without the plant body.
Question 9: What is the water potential ?
Answer: Water potential is a measure of potential energy of water or the difference in
potential energy between a given water sample and pure water.
Question 10: A few RBC’s were kept in three test tubes containing isotonic, hypotonic and
hypertonic solutions. What will be the expected observations after a few hours ? Explain.
Answer: The shape and size of the cells will remain unchanged in isotonic solution,
because the cells will neither loose nor gain water in it.
Cells will swell up in hypotonic solution as water will enter in it due to endosmosis.
Cells will shrink in hypertonic solution as water will move out of the cell due to exosmosis.
Question 11: Explain why the grass in your lawn becomes greener if you add a little
fertilizer to it, but it dies if you add a lot of it.
Answer: If a little fertilizer is added, it provides minerals and other nutrients so the leaves
synthesize more chlorophyll and appear greener. If a lot of fertilizer is added, it forms a
hypertonic solution resulting in plasmolysis and consequently wilting of parts of the plant.
Ultimately the plant dies.
Give Reasons
Question 1: It is necessary to maintain a normal osmotic concentration of the blood.
Answer: Osmotic pressure is maintained in blood to prevent dehydration leading to
shrinkage of cells.
Question 2: Salt and sugar are used in preserving food.
Answer: Salt and sugar increase concentration of food, destroying bacteria by
plasmolysis.
Question 3: On sprinkling common salt on grass growing in a lawn, the grass is killed.
Answer: Sprinkling salt makes soil solution hypertonic hence grass lose water due to
exosmosis.
Question 4: The raising swell up in water.
Answer: The raisins are dry grapes. When these are kept in water, it enters into the
raisins by osmosis (endosmosis) and raisins swell up.
Question 5: We gargle with saline water in case of throat infection.
Answer: The salt solution (saline water) is hypertonic and when we gargle with it, comes
in contact of infection causing bacteria in the throat. The water present in the bacterial cell
comes out causing plasmolysis and they get killed giving us relief from infection.
Question 6: The leaves of wilted lettuce, if kept in cold water, become crisp.
Answer: The leaves of wilted lettuce are plasmolysed which when kept in the water get
deplasmolysed and become turgid. Hence the leaves become crisp.
Question 7: Bacteria and fungi do not grow in pickles, jams, jellies and squashes, etc.
Answer: Pickles, jams, jellies and squashes are kept in hypertonic solution of sugar or salt
which causes the plasmolysis of bacteria and fungi. So, they cannot grow in such an
unfavourable environment.
Question 8: Fresh water fish cannot survive in sea water.
Answer: The sea water is saline (having more concentration of salts) and acts as
hypertonic solution for the fresh water. So fresh water fish cannot survive in sea water as
it causes the plasmolysis of the cells of the fish and ultimately the fish will die.
Question 9: A closed can of dried seeds bursts open if some water enters it by accident.
Answer: If some water enters in a closed can of dried seeds, the seeds absorb water by
imbibition and osmosis and swell up. The swelling up of seeds exerts a force on the walls of
the can, and hence the can bursts open.
Question 10: Drops of water on a leaf of plant like peepal does not enter the leaf by
osmosis ?
Answer: Due to the presence of cuticle, which does not allow water molecules to pass
through it.
Question 11: Plants growing in fertilized soil are often found to wilt, if the soil is not
adequately watered. Why?
Answer: The concentration of water molecules being less outside, endosmosis takes place
resulting in the wilting of the plants.
Question 12: Plants begin to die when excess of soluble fertilizers are added to the soil ?
Answer: Excess application of soluble fertilizers in soil makes the soil solution hypertonic
than cell sap, hence exosmosis takes place and plants begin to die.
Differentiate
Question 1: Osmosis and Diffusion.
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