Diffusion occurs when molecules move:
- from lower concentration to higher concentration.
- from higher concentration to lower concentration through a membrane.
- from higher concentration to lower concentration.
- when energy is used.
Answer
from higher concentration to lower concentration.
Reason — The movement of molecules (gas, liquid or solid) from higher concentration to lower concentration is called diffusion.
Ascent of sap in plants takes place through.
- Cortex
- Epidermis
- Xylem
- Phloem
Answer
Xylem
Reason — Xylem the vascular tissue is responsible for the transport of water and minerals.
If the xylem vessels of a plant are plugged:
- The leaves will turn yellow
- No food will be made
- The plant will wilt (shrivel)
- The plant will continue to grow
Answer
The plant will wilt (shrivel)
Reason — The xylem vessel of the plant is responsible for the conduction of the water and mineral salt in the plant body. So if the xylem vessels of the plant are plugged then the conduction of water will be stopped and then the plant will wilt.
Force responsible for the ascent of sap is:
- Capillary force
- Root pressure
- Transpirational pull
- All the three
Answer
All the three
Reason — Ascent of sap takes place through xylem. Forces like capillary force, root pressure, transpirational pull helps in this unidirectional movement of water.
Raisins swell when put in:
- Rain water
- Saline water
- Mustard oil
- Saturated sugar solution
Answer
Rain water
Reason — When raisins are placed in rain water, they absorb water through Osmosis as rain water serves as a dilute solution in comparison to the contents of raisins. In case of saline water and saturated sugar solution, they are more concentrated than the raisins hence Osmosis doesn't take place. As Mustard oil is not water, so it is not absorbed by the raisins.
The root hairs are suited for absorbing water from the soil because:
- They have a large surface area
- They have a semi-permeable membrane
- They contain a solution of higher concentration than the surrounding water.
- All the three.
Answer
All the three
Reason — Root hairs are long and thin so they can penetrate between soil particles and they have a large surface area for absorption of water which in return, increases the speed at which water and nutrients can be absorbed. The cell sap in the root hair cell is said to be of a high concentration as it contains more solutes compared to the surrounding soil water. This promotes water absorption.
Transpiration is defined as:
- the rise of water up to the stem of a plant.
- the elimination of water with dissolved water products.
- the loss of water as water vapour from the aerial parts of a plant.
- the loss of water as water vapour from the roots as well as the leaves of the plant.
Answer
the loss of water as water vapour from the aerial parts of a plant.
Reason — Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant.
Which one of the following favours the fastest transpiration rate?
- A cool, humid, windy day,
- A hot, humid, windy day,
- A hot, humid, still day,
- A hot, dry, windy day.
Answer
A hot, dry, windy day.
Reason — Transpiration is mainly affected by the temperature, humidity, and wind speed. On a hot, dry, windy day transpiration increases.
Fill in the blanks with suitable terms given below:
(fast, leaves, conducting, ascent, humid)
(a) Transportation in plants is carried out by a ............... system.
(b) The upward movement of sap that contains water and minerals is called ............... of the sap.
(c) Transpiration is more when the wind is blowing ...............
(d) Most water gets evaporated from the plant from its ...............
(e) Transpiration is reduced if the air is ...............
Answer
(a) Transportation in plants is carried out by a conducting system.
(b) The upward movement of sap that contains water and minerals is called ascent of the sap.
(c) Transpiration is more when the wind is blowing fast.
(d) Most water gets evaporated from the plant from its leaves.
(e) Transpiration is reduced if the air is humid.
Match the terms given in Column A with those given in Column B
| Column A | Column B |
|---|---|
| (a) Phloem parenchyma | (i) Cylindrical cells devoid of a nucleaus |
| (b) Tracheids | (ii) Tubular cells forming long channels |
| (c) Xylem vessels | (iii) Cells attached to sieve tubes |
| (d) Sieve tubes | (iv) Elongated dead cells |
| (e) Companion cells | (v) Cells storing food |
Answer
| Column A | Column B |
|---|---|
| (a) Phloem parenchyma | (v) Cells storing food |
| (b) Tracheids | (iv) Elongated dead cells |
| (c) Xylem vessels | (ii) Tubular cells forming long channels |
| (d) Sieve tubes | (i) Cylindrical cells devoid of a nucleaus |
| (e) Companion cells | (iii) Cells attached to sieve tubes |
State whether the following statements are True or False. Rewrite the false statements correctly.
(a) Water absorption mainly occurs through the root-hair.
(b) Water enters the root-hair by osmosis.
(c) Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.
(d) A semi-permeable membrane allows larger molecules to pass through but prevents the smaller ones.
(e) Transpiration is the loss of water from the roots of the plant.
(f) Transpiration cools the plant when it is hot outside.
Answer
(a) True
(b) True
(c) True
(d) False
Corrected statement — A semi-permeable membrane allows smaller molecules to pass through but prevents the larger ones.
(e) False
Corrected statement — Transpiration is the loss of water from the aerial parts of the plant.
(f) True
Name the plant tissue which helps in carrying the food to different parts of a plant.
Answer
Phloem carries the food to different parts of the plant.
Name the two conducting tissues of the plants.
Answer
Two conducting tissues of the plants are:
- Xylem
- Phloem
Name the four components of Xylem tissue
Answer
The four components of Xylem tissue are:
- Tracheids
- Vessels
- Xylem Parenchyma
- Xylem Sclerenchyma
Name the four components of Phloem tissue
Answer
The four components of Phloem tissue are:
- Sieve Tubes
- Companion Cells
- Phloem Fibres
- Phloem Parenchyma
Name the three factors which increase the rate of transpiration
Answer
The three factors which increase the rate of transpiration are:
- Light intensity
- Wind speed
- High Temperature
Name the three macro-nutrients
Answer
Three macro-nutrients are:
- Nitrogen
- Phosphorus
- Potassium
Name the three micro-nutrients
Answer
Three micro-nutrients are:
- Zinc (Zn)
- Iron (Fe)
- Manganese (Mn)
Define Semi-permeable membrane.
Answer
A semi-permeable membrane is a membrane which allows the passage of molecules selectively. It allows a solvent such as water molecules to pass through it freely but prevents the passage of the solute (sugar or salt molecules in solution).
Define Osmosis.
Answer
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.
Define Diffusion.
Answer
Diffusion is defined as 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 direct contact.
Define Transpiration.
Answer
Transpiration is the loss of water in the form of water vapour from the aerial parts (leaves and stem) of the plant.
Define Ascent of sap.
Answer
The upward movement of water and dissolved inorganic particles from the roots to the leaves through the xylem tissue against gravity is called ascent of sap.
Define Translocation of food.
Answer
Translocation of food refers to the movement of food and other nutrients from one part of a plant to another.
Define Root hairs.
Answer
A root hair is a long protuberance (extension) of an epidermal cell of the root that helps in increasing the surface area for absorption of water and nutrients from soil.
Write two important functions of Xylem.
Answer
Two functions of Xylem are:
- Transportation of water and minerals from roots to the aerial parts.
- Tracheids, vessels and xylem sclerenchyma provide physical support.
Write two important functions of Phloem.
Answer
Two functions of Phloem are:
- Transportation of food prepared by leaves to all parts of plant.
- Storage of food by phloem parenchyma.
Write two important functions of Root.
Answer
Two functions of Root are:
- Absorption of Water and Nutrients from the soil.
- Roots anchor the plant firmly to the ground, providing stability.
How are roots useful to the plants? Give any two points.
Answer
Roots are useful to the plants in the following ways:
- Roots absorb water and minerals from the soil.
- Roots fix the plant firmly in the ground.
What do xylem vessels carry?
Answer
Xylem vessels carry water and mineral salts from the roots to the aerial parts of the plant.
Under what conditions do plant transpire (a) more quickly and (b) most slowly?
Answer
(a) Plants transpire more quickly on hot, dry, windy days as Sunlight, higher temperatures, fast winds and low humidity increase the rate of transpiration.
(b) Transpiration is most slow on cool, humid, still days as lower temperatures, still winds and high humidity decrease the rate of transpiration.
Mention two ways in which transpiration helps the plants.
Answer
Two ways in which transpiration helps the plants:
- Cooling effect — Transpiration from the aerial parts of the plant, cools down the plant surface.
- Ascent of sap and distribution of minerals — Transpiration results in the development of low water potential in the leaf tissues. Thus, water moves from the xylem tissue to the leaf cells and helps in the ascent of sap. Mineral ions also move up along with water due to the transpiration pull.
Write three important uses of water in the plants.
Answer
Three important uses of water in the plants are:
- Transportation of food/sugars or minerals occur in solution form.
- Food production/photosynthesis cannot occur without water.
- Transpiration of water helps to keep the plant cool.
What are the three special features of root hairs which make then suitable for the absorption of water from the soil?
Answer
The three special features of root hairs which make then suitable for the absorption of water from the soil are:
- The numerous root hairs provide a large surface area. More the surface area, greater is the absorption.
- Root hairs contain cell sap which is of a higher concentration than the surrounding soil water.
- The cell wall is freely permeable, i.e., permits movements of all types of substances. But the cell membrane is semi-permeable. It allows only some substances to pass through it.
Give reasons — Transpiration is reduced if the air is humid.
Answer
On a humid day, air already contains moisture. This reduces the concentration gradient between the leaf's internal air spaces and the external environment. Therefore, transpiration is reduced if the air is humid.
Give reasons — Transpiration, despite resulting in loss of water from the plant, remains a crucial process for its overall well-being.
Answer
Despite resulting in loss of water, transpiration remains a crucial process for the overall well-being of the plant because:
- Transpiration provides cooling effect helping the plant to cool itself when it is hot outside.
- Transpiration helps in maintaining the concentration of the sap inside the plant body.
- Transpiration creates the suction force called transpirational pull that is necessary for ascent of sap.
Distinguish between the following pairs on the basis of words indicated in the brackets:
Diffusion and active transport (concentration gradient)
Answer
| Property | Diffusion | Active transport |
|---|---|---|
| Concentration gradient | Movement of molecules occur from their higher concentration to lower concentration. | Movement of molecules occur from their lower concentration to a higher concentration at the expense of plant's energy. |
Distinguish between the following pairs on the basis of words indicated in the brackets:
Nitrogen and Potassium (role in plants)
Answer
| Property | Nitrogen | Potassium |
|---|---|---|
| Role in plants | Major constituent of all proteins. | More abundant in growing tissues, involved in the opening and closing of stomata. |
Distinguish between the following pairs on the basis of words indicated in the brackets:
Xylem and Phloem (direction of conduction)
Answer
| Property | Xylem | Phloem |
|---|---|---|
| Direction of conduction | Upwards i.e., from roots to aerial parts of plant. | Downwards i.e., from leaves towards roots and other parts. |
An experiment was set up as shown in the figure alongside. After some time, the water level in test tube A fell down but not in test tube B. Why was there a fall in the water level of test tube A and not in that of test-tube B?
Answer
Test tube A contains plant, therefore, the water level in test tube A falls because the water is absorbed by the plant through the roots dipped in the water. Since the test tube contains oil, no water loss occurred due to evaporation because oil prevents water molecules from evaporating. In test-tube B the water level remains the same because there is no plant present as well as oil refrains the water to evaporate.
Given alongside is an experimental set up. Study the figure and answer the following questions:
(a) What is the main objective of the experiment?
(b) Name the tissue which is responsible for the process shown in the figure.
(c) Name two dyes which can be used in the above experiment to make a coloured solution.
Answer
(a) The main objective of the given experiment is to show how the water is transported in plants.
(b) The tissue which is responsible for the process shown in the figure is xylem.
(c) Two dyes which can be used in the above experiment to make a coloured solution are Eosin and Red ink.
The set up shown alongside was kept in sunlight for an hour. It was observed that drops of water appeared on the inside surface of the polythene bag.
(a) Name the process which is being demonstrated.
(b) Why was the pot with its soil left uncovered by the polythene bag?
(c) Why was the pot left in sunlight?
(d) Suppose that the pot in this experiment was placed inside a dark room instead of placing it in sunlight for some time. What difference would be noticed?
Answer
(a) Transpiration is being demonstrated here.
(b) The pot and its soil were left uncovered by the polythene bag because in the experiment we need to observe the loss of water occurred by plants. If the pot is covered, the water from the soil may also get evaporated and we will not get accurate results.
(c) In sunlight, the rate of transpiration is faster as the stomata are open to allow inward diffusion of carbon dioxide for photosynthesis. Hence, the plant was left in sunlight.
(d) If the pot was placed inside a dark room, transpiration will hardly occur as the stomata of the plant are closed. Hence, negligible water droplets will get condensed on the inner side of polythene bag.
Briefly explain, how transpiration helps in the upward conduction of water in plants?
Answer
As water evaporates from the leaves during transpiration, it creates a suction force or tension in the xylem vessels. As a result of transpiration, a suction force is created in the xylem vessel. This force causes the water to be pulled up from the xylem in the roots to the stem and then to the leaves. This suction force helps draw more water up through the stem, which in turn causes the roots to absorb more water from the soil. This pulling force is called transpirational pull.
How does temperature, light intensity and wind affect transpiration?
Answer
- Temperature — Higher temperatures increase the rate of transpiration due to faster evaporation of water.
- Light intensity — With Sunlight the rate of transpiration is faster as stomata are open to allow inward diffusion of carbon dioxide for photosynthesis. During night time, the stomata remain closed and hence transpiration hardly occurs.
- Wind — Transpiration is more when the wind is blowing faster as water vapour moves away faster from the surface of leaves.
Draw a magnified view of the root hair and label all its parts neatly. From the parts labelled by you, name the parts matching the description given below:
(a) Outermost layer of the root
(b) Unicellular outgrowth
(c) Part that is freely permeable
(d) Part that is semi-permeable
Answer
Magnified view of the root hair with its parts labelled is shown below:
(a) Outermost layer of the root — Cell wall
(b) Unicellular outgrowth — Root Hair / Epidermal cell
(c) Part that is freely permeable — Cell wall
(d) Part that is semi-permeable — Cell membrane