Transport in Plants

Diffusion occurs when molecules move:

1. from lower concentration to higher concentration.
2. from higher concentration to lower concentration through a membrane.
3. from higher concentration to lower concentration.
4. 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.
Particles do not move from lower concentration to higher concentration by diffusion; that movement is opposite to diffusion. Diffusion does not always occur through a membrane. Diffusion is a passive process, so energy is not required.

Ascent of sap in plants takes place through.

1. Cortex
2. Epidermis
3. Xylem
4. Phloem

Answer

Xylem

Reason — Xylem is the vascular tissue responsible for the transport of water and minerals.
The cortex is the layer of cells between the epidermis and vascular tissues in roots and stems. It mainly helps in storage and transport of water inward, but it does not conduct sap upward. The epidermis is the outermost protective layer of the plant. It helps in protection and absorption (in roots via root hairs), but it does not transport sap. The phloem transports food (sugars) from leaves to other parts of the plant. It can move substances both upward and downward, but it does not carry water upward like xylem.

If the xylem vessels of a plant are plugged:

1. The leaves will turn yellow
2. No food will be made
3. The plant will wilt (shrivel)
4. The plant will continue to grow

Answer

The plant will wilt (shrivel)

Reason — The xylem vessels of the plant are responsible for the conduction of water and mineral salts in the plant body. So, if the xylem vessels of the plant are plugged, the transport of water will stop and the plant will wilt.
Yellowing of leaves (chlorosis) usually happens due to lack of nutrients like nitrogen or magnesium, not directly due to blockage of xylem. Food (glucose) is made in leaves by photosynthesis. While water is needed, xylem blockage does not immediately stop food production completely—it mainly affects water supply first. Without water transport, essential processes stop, so the plant cannot grow properly.

Force responsible for the ascent of sap is:

1. Capillary force
2. Root pressure
3. Transpirational pull
4. All the three

Answer

All the three

Reason — Ascent of sap takes place through xylem. Forces like capillary force, root pressure and transpirational pull help in this unidirectional movement of water.

Raisins swell when put in:

1. Rain water
2. Saline water
3. Mustard oil
4. Saturated sugar solution

Answer

Rain water

Reason — When raisins are placed in rain water, they absorb water through osmosis as rain water is a dilute solution in comparison to the contents of raisins. In saline water and saturated sugar solution, water moves out of the raisins by osmosis because these solutions are more concentrated; hence, the raisins do not swell and may shrink. Mustard oil is not absorbed by the raisins.

The root hairs are suited for absorbing water from the soil because:

1. They have a large surface area
2. They have a semi-permeable membrane
3. They contain a solution of higher concentration than the surrounding water.
4. All the three.

Answer

All the three

Reason — Root hairs are long and thin, so they can penetrate between soil particles. They have a large surface area for absorption of water, which increases the rate of absorption. Their cell membrane is semi-permeable, allowing water to enter by osmosis. The cell sap in the root hair cell is of a higher concentration as it contains more solutes compared to the surrounding soil water. This promotes water absorption.

Transpiration is defined as:

1. the rise of water up to the stem of a plant.
2. the elimination of water with dissolved water products.
3. the loss of water as water vapour from the aerial parts of a plant.
4. 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.
The rise of water through the stem of a plant describes ascent of sap, not transpiration. Water moves upward through xylem due to transpiration pull, but that is a different process. The elimination of water with dissolved waste products refers to excretion, not transpiration. Plants do not eliminate dissolved wastes through transpiration. Roots do not lose water by transpiration. Water loss mainly occurs from aerial parts only.

Which one of the following favours the fastest transpiration rate?

1. A cool, humid, windy day
2. A hot, humid, windy day
3. A hot, humid, still day
4. 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.
Cool temperature reduces evaporation, and high humidity reduces the diffusion of water vapour, resulting in slower transpiration. Hot temperature and wind increase transpiration, but high humidity slows it down by reducing the concentration gradient. Still air and high humidity greatly reduce transpiration, resulting in a very slow rate.

Vinay has kept a small herbaceous plant in a test tube containing water. The surface of the water is covered by a layer of oil. After three hours, he observed that the level of water in the test tube has decreased. This is due to:

1. Absorption
2. Transpiration
3. Wilting
4. Both (1) and (2)

Answer

Both (1) and (2)

Reason — The decrease in water level is due to both absorption by the plant and transpiration from the leaves.
Absorption is the uptake of water by roots, but here it is not the cause of water level decrease in the test tube alone—it is part of the process linked with transpiration. Wilting is a result of water loss, not the cause of water level decrease.

Root hairs are the epidermal outgrowths of the outermost layer of roots. They are well-suited for absorption of water from soil due to which of the following features ?

P. Large surface area.
Q. Lower concentration of cell sap.
R. Semi permeable nature of the cell membrane.

1. Only P
2. Only Q
3. Only P and Q
4. Only P and R

Answer

Only P and R

Reason — The root hairs are well-suited for absorption of water from soil due to their large surface area, higher concentration of cell sap, and semi permeable nature of the cell membrane.
Lower concentration of cell sap is not a structural feature. In fact, root hair cell sap is more concentrated than soil water, which helps water move into the cell by osmosis.

Xylem tissue forms a tubular passage to transport water and mineral salts from the roots to the aerial parts of a plant. It consists of different types of cells.

P. Sieve tubes and companion cells
Q. Wood parenchyma and wood fibres
R. Tracheids and vessels

Which of the following are xylem components?

1. Only P
2. Only P and R
3. Only Q and R
4. All P, Q and R

Answer

Only Q and R

Reason — The Xylem tissue consists of tracheids, vessels, wood parenchyma and wood fibres. Sieve tubes and companion cells are part of phloem, the tissue responsible for transporting prepared food, not water.

Assertion (A): The food prepared by leaves is transported to all parts of the plant.

Reason (R): Roots are the underground parts of the plant which absorb food material from the soil.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is true but R is false.

Explanation — A is true as the food prepared by the leaves is transported to all parts of the plant including the roots.
R is false as roots absorb water and minerals from the soil. Water is the raw material used to prepare food (glucose) by photosynthesis.

Therefore, A is true but R is false is the correct option.

Assertion (A): In plants, transportation of water from roots to leaves is carried out by the conducting tissue called phloem.

Reason (R): Roots absorb water and minerals from the soil which are transported to leaves for various metabolic activities like photosynthesis, transpiration, respiration, etc.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is false and R is true.

Explanation — A is false as transportation of water in plants from roots to leaves is carried out by the conducting tissue xylem, not phloem. Phloem is responsible for transporting prepared food throughout the plant.
R is true as roots absorb water and minerals from soil and transport them to leaves for photosynthesis, respiration, etc.

Therefore, A is false and R is true is the correct option.

Assertion (A): The movement of molecules from their lower concentration to a higher concentration requires energy in the form of ATP.

Reason (R): Active transport is the process during which root hairs of a plant absorb minerals from the soil.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

Both A and R are true but R is not the correct explanation of A.

Explanation — A is true as movement of molecules from lower concentration to higher concentration occurs against the concentration gradient and requires energy in the form of ATP.
R is true as root hairs absorb minerals from the soil by active transport. However, R gives an example of active transport and does not directly explain why ATP is required.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

Assertion (A): Nitrogen is the main constituent of all proteins which helps in the growth and development of plants.

Reason (R): Nitrogen is micronutrient, which means it is required in very small amounts by the plants. It is absorbed from the soil as a nutrient element or mineral.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is true and R is false.

Explanation — Nitrogen is macronutrient, which means it is required in larger concentration by the plants.

Therefore, A is true and R is false is the correct option.

Assertion (A): Plants absorb water from the soil through a semi permeable membrane. The process is termed as osmosis.

Reason (R): The outermost layer of root hair cell is the cell wall which is semi permeable in nature, so it helps in the process of osmosis.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.

Answer

A is true and R is false.

Explanation — A is true as Water enters the root hair cells from soil by osmosis, which is movement of water through a semi-permeable membrane from higher water concentration (soil) to lower water concentration (cell sap). R is false as the cell wall is freely permeable, not semi-permeable. The cell membrane (plasma membrane) is the actual semi-permeable membrane responsible for osmosis.

Therefore, A is true and R is false is the correct option.

Fill in the blanks with suitable terms given below:

(fast, leaves, conducting, ascent, humid)

1. Transportation in plants is carried out by a ............... system.

2. The upward movement of sap that contains water and minerals is called ............... of the sap.

3. Transpiration is more when the wind is blowing ...............

4. Most water gets evaporated from the plant from its ...............

5. Transpiration is reduced if the air is ...............

Answer

1. Transportation in plants is carried out by a conducting system.

2. The upward movement of sap that contains water and minerals is called ascent of the sap.

3. Transpiration is more when the wind is blowing fast.

4. Most water gets evaporated from the plant from its leaves.

5. Transpiration is reduced if the air is humid.

Match the terms given in Column A with those given in Column B

Answer

State whether the following statements are True or False. Rewrite the false statements correctly.

1. Water absorption mainly occurs through the root-hair.

2. Water enters the root-hair by osmosis.

3. Water absorbed by the roots reaches the leaves and is used in producing food for the entire plant.

4. A semi-permeable membrane allows larger molecules to pass through but prevents the smaller ones.

5. Transpiration is the loss of water from the roots of the plant.

6. Transpiration cools the plant when it is hot outside.

Answer

1. True

2. True

3. True

4. False
   Corrected statement — A semi-permeable membrane allows smaller molecules to pass through but prevents the larger ones.

5. False
   Corrected statement — Transpiration is the loss of water from the aerial parts of the plant.

6. 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:

1. Xylem
2. Phloem

Name the four components of Xylem tissue

Answer

The four components of Xylem tissue are:

1. Tracheids
2. Vessels
3. Xylem parenchyma
4. Xylem fibres / wood fibres

Name the four components of Phloem tissue

Answer

The four components of Phloem tissue are:

1. Sieve Tubes
2. Companion Cells
3. Phloem Fibres
4. Phloem Parenchyma

Name the three factors which increase the rate of transpiration

Answer

The three factors which increase the rate of transpiration are:

1. Light intensity
2. Wind speed
3. High Temperature

Name the three macro-nutrients

Answer

Three macro-nutrients are:

1. Nitrogen
2. Phosphorus
3. Potassium

Name the three micro-nutrients

Answer

Three micro-nutrients are:

1. Zinc (Zn)
2. Iron (Fe)
3. 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:

1. Transportation of water and minerals from roots to the aerial parts.
2. Tracheids, vessels and xylem sclerenchyma provide physical support.

Write two important functions of Phloem.

Answer

Two functions of Phloem are:

1. Transportation of food prepared by leaves to all parts of plant.
2. Storage of food by phloem parenchyma.

Write two important functions of Root.

Answer

Two functions of Root are:

1. Absorption of Water and Nutrients from the soil.
2. 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:

1. Roots absorb water and minerals from the soil.
2. 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 slowest 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:

1. Cooling effect — Transpiration from the aerial parts of the plant, cools down the plant surface.
2. 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:

1. Transportation of food/sugars or minerals occurs in solution form.
2. Water is required for photosynthesis.
3. Transpiration of water helps to keep the plant cool.

What are the three special features of root hairs which make them suitable for the absorption of water from the soil?

Answer

The three special features of root hairs which make them suitable for the absorption of water from the soil are:

1. The numerous root hairs provide a large surface area. More the surface area, greater is the absorption.
2. Root hairs contain cell sap which is of a higher concentration than the surrounding soil water.
3. 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:

1. Transpiration provides cooling effect helping the plant to cool itself when it is hot outside.
2. Transpiration helps in maintaining the concentration of the sap inside the plant body.
3. 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

Distinguish between the following pairs on the basis of words indicated in the brackets:

Nitrogen and Potassium (role in plants)

Answer

Distinguish between the following pairs on the basis of words indicated in the brackets:

Xylem and Phloem (direction of conduction)

Answer

An experiment was set up as shown in the figure below. 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 a 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 from evaporating. In test tube B, the water level remains the same because there is no plant present and the oil prevents the water from evaporating.

Given below 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 below kept was 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. This force pulls water upward from the roots through the stem to the leaves. It also helps the roots absorb more water from the soil. This pulling force is called transpirational pull.

How does temperature, light intensity and wind affect transpiration?

Answer

1. Temperature — Higher temperatures increase the rate of transpiration due to faster evaporation of water.
2. 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.
3. 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 — Epidermis / epidermal cells of the root

(b) Unicellular outgrowth — Root Hair / Epidermal cell

(c) Part that is freely permeable — Cell wall

(d) Part that is semi-permeable — Cell membrane

After playing outside on a hot sunny afternoon, Aarav came home sweating and drank a lot of water. Later in the evening, he noticed that the plant on his study table looked dull and droopy. Wondering if plants also "get hot" in summer, he asked his mother what was wrong. She told him that just like humans sweat to cool down, plants also lose water through a process that helps them stay cool. But when too much water is lost, the plant starts to droop.

(a) What is the process by which plants lose water through their leaves?

(b) Through which part of the leaf does this water loss mainly happen?

(c) Besides cooling the plant, how else does transpiration help the plant?

(d) In transpiration, water is lost from the plant in the form of ............ (water vapour /water droplets).

(e) Draw a simple flow chart showing water movement from roots to leaves and then out of the plant.

(f) Aarav's mother said that once he waters the plant, it will look fresh again. What is the process by which roots absorb water from the soil?

Answer

(a) The process by which plants lose water through their leaves is called transpiration.

(b) Water loss mainly happens through stomata.

(c) Besides cooling, transpiration also helps in upward movement of water and minerals from roots to leaves (transpiration pull). It maintains turgidity and helps in distribution of minerals throughout the plant.

(d) In transpiration, water is lost from the plant in the form of water vapour (water vapour /water droplets).

(e)

(f) The process by which roots absorb water from the soil is called osmosis.