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Chapter 1

Transport of Food and Minerals in Plants

Class 8 - Living Science Biology Ratna Sagar


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Question 1

Write true or false. Correct the false statements.

  1. Phloem carries water from the roots to the leaves in plants.
  2. Xylem parenchyma performs the function of storage.
  3. Water is absorbed by the root hair cells by a process called diffusion.
  4. Energy is required for active transport.

Answer

  1. False
    Correct Statement — Xylem carries water from the roots to the leaves in plants.

  2. False
    Correct Statement — Phloem parenchyma performs the function of storage (food).

  3. False
    Correct Statement — Water is absorbed by the root hair cells by a process called Osmosis.

  4. True

Tick the most appropriate answer

Question 1

Root hairs are found in the outermost layer of root called

  1. dermis
  2. epidermis
  3. cortex
  4. xylem

Answer

epidermis

Reason — Root hair cells are unicellular thin-walled outgrowths of the epidermis which is the outermost layer of a root.

Question 2

In phloem, the direction in which translocation of food takes place is

  1. downwards
  2. upwards
  3. both upwards and downwards
  4. none of these

Answer

both upwards and downwards

Reason — Food material moves through the phloem in both directions, upwards as well as downwards.

Question 3

Water is absorbed by the root hair cells through

  1. osmosis
  2. active transport
  3. transpiration
  4. ascent of sap

Answer

osmosis

Reason — The concentration of water in the root is lower than that of soil, thus water flows from soil to cell by Osmosis.

Question 4

The movement of salt or mineral molecules from a region of their higher concentration to a region of their lower concentration is called

  1. osmosis
  2. active transport
  3. diffusion
  4. blending

Answer

diffusion

Reason — Diffusion is the movement of salt or mineral molecules from a region of their higher concentration to a region of their lower concentration.

Question 5

The fluid containing mineral salts and water enclosed in a vacuole of a cell is called

  1. cytoplasm
  2. nucleoplasm
  3. cell sap
  4. tonoplast

Answer

cell sap

Reason — Cell Sap is the fluid containing mineral salts and water enclosed in the vacuole of a cell.

Question 6

The pressure developed in roots due to the continuous inflow of water which pushes the sap upwards is called

  1. root pressure
  2. sap pressure
  3. transpiration pull
  4. stem pressure

Answer

root pressure

Reason — The pressure developed in roots due to the continuous inflow of water which pushes the sap upwards is called Root Pressure.

Question 7

The loss of water vapour through the stomata of the leaves is called

  1. wilting
  2. translocation
  3. transpiration
  4. transportation

Answer

transpiration

Reason — The loss of water in the form of water vapour through the stomata of leaves and other aerial parts of a plant is called transpiration.

Question 8

Transpiration occurs through openings in leaves called

  1. pores
  2. guard cell
  3. stomata
  4. barks

Answer

stomata

Reason — Stomata are the openings present on lower side of leaves, through which transpiration as well as gaseous exchange occurs.

Fill in the blanks

Question 1

Water in xylem moves only in ............... direction.

Answer

Water in xylem moves only in one direction.

Question 2

............... is a plant tissue which conducts water and minerals from roots to upper parts of the plant.

Answer

Xylem is a plant tissue which conducts water and minerals from roots to upper parts of the plant.

Question 3

............... is the food-conducting tissue in plants.

Answer

Phloem is the food-conducting tissue in plants.

Question 4

............... are unicellular, thin-walled outgrowths of roots.

Answer

Root hairs are unicellular, thin-walled outgrowths of roots.

Question 5

Roots absorb minerals by ............... and ............... .

Answer

Roots absorb minerals by diffusion and active transport.

Question 6

The upward movement of sap through the xylem is called ............... .

Answer

The upward movement of sap through the xylem is called ascent of sap.

Question 7

There is a direct relationship between absorption and ............... .

Answer

There is a direct relationship between absorption and transpiration.

Question 8

............... is an example of a macro-nutrient.

Answer

Nitrogen is an example of a macro-nutrient.

Define the following terms

Question 1

Osmosis

Answer

Osmosis — The movement of water through a semi-permeable membrane from an area of its higher concentration to an area of its lower concentration is called Osmosis.

Question 2

Diffusion

Answer

Diffusion — The movement of salt or mineral molecules from a region of their higher concentration to a region of their lower concentration is called diffusion.

Question 3

Active transport

Answer

Active transport — The movement of minerals ions from a region of their lower concentration to a region of their higher concentration by using energy (ATP) is called Active transport.

Question 4

Transpiration

Answer

Transpiration — The loss of water in the form of water vapour through the stomata of the leaves and other aerial parts of a plant is called transpiration.

Question 5

Transpiration pull

Answer

Transpiration pull — The process by which water is sucked up through the xylem as a result of water loss by transpiration is called transpiration pull.

Differentiate between

Question 1

Xylem and Phloem

Answer

Sl.
No.
XylemPhloem
1.It transports water and minerals from roots to aerial parts of the plant.It transports food materials from the leaves to other parts of the plant.
2.It is mostly made up of dead cells.It is mostly made up of living cells.
3.It forms vascular bundles with phloem. It is located towards the inner side of the vascular bundle.It forms vascular bundles with the xylem. It is located on the outer side of the vascular bundle.
4.There are four types of cells in xylem: xylem vessels, tracheids, xylem fibres and xylem parenchyma.Four elements of Phloem are: sieve tubes, companion cells, phloem parenchyma and phloem fibres.

Question 2

Osmosis and Diffusion

Answer

Sl.
No.
OsmosisDiffusion
1.The movement of water molecules through a semi-permeable membrane from an area of its higher concentration to an area of its lower concentration is called Osmosis.The movement of salt or mineral molecules from a region of their higher concentration to a region of their lower concentration is called Diffusion.
2.It takes place only in a liquid medium.It takes place in any medium such as solid, liquid and gas.
3.It requires a semi-permeable membrane.It does not require any semi-permeable membrane.
4.It is a slow process.It is comparatively a faster process in gases, slow in liquids.

Question 3

Diffusion and Active transport.

Answer

Sl.
No.
DiffusionActive transport
1.It is the movement of molecules or ions of a substance from a region of their higher concentration to a region of their lower concentration.It is the movement of ions of a substance from their lower concentration region to their higher concentration region using energy.
2.It is the movement of solute or solvent molecules.It is the movement of ions only (no water).
3.No cell energy is needed.Cell energy is needed in the form of ATP.
4.It occurs through a non-living permeable membrane.It occurs through a living selectively permeable membrane.

Answer the following in short

Question 1

What are root hair?

Answer

Root hairs cells are unicellular thin-walled outgrowths of the epidermis, which is the outermost layer of a root. They increase the surface area for absorption of water and nutrients from soil.

Question 2

What do you know about root pressure?

Answer

The pressure developed in roots due to the continuous inflow of water which pushes the plant sap upwards is called root pressure.

Question 3

Define transpiration.

Answer

The loss of water in the form of water vapour through the stomata of the leaves and other aerial parts of a plant is called transpiration.

Question 4

What is wilting?

Answer

If water is lost through transpiration more quickly than it is absorbed by the root hair cells, the plant cells tend to lose water. As a result, the leaves, stem and flowers droop. This is called wilting.

Question 5

What is translocation?

Answer

The transport of soluble products of photosynthesis, that is the sugar molecules is called translocation.

Question 6

Name any two micro-nutrients.

Answer

Boron and manganese are examples of two micro-nutrients.

Question 7

Name a disease in plants caused by the deficiency of zinc.

Answer

Chlorosis is a disease in plants caused by the deficiency of zinc.

Answer the following in detail

Question 1

How do the roots of plants absorb water?

Answer

The roots have thin layered, unicellular outgrowths of the epidermis; which are called root hairs. They increase the surface area for absorption of water from the soil. Following are the steps of absorption of water:

  • Water is absorbed by the root hairs by the process of Osmosis. The concentration of water molecules is more in soil as compared to the cell. This causes osmosis to occur, and so water is absorbed by the root hair cells from outside as shown in the given diagram.
  • Water molecules move through osmosis from root hair cells to adjacent cells of the inner tissue.
  • This process continues until water reaches the xylem tissue in the root. Thus, water moves from root hair cells through the root cortex to the xylem in the root.
  • Inside the xylem, water travels upwards from one cell to another against the force of gravity.

Below diagrams shows the absorption and movement of water in root cells:

How do the roots of plants absorb water? Transport of Food and Minerals in Plants, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Question 2

What do you understand by active transportation of minerals?

Answer

Mineral molecules are more concentrated inside the root hair cells than in the soil outside. Still, root hair cells absorb them. For this, they use the process of active transport. The movement of minerals ions from a region of their lower concentration to a region of their higher concentration is called active transport. This process involves the use of energy in the form of ATP.

Question 3

Explain the relationship between absorption and transpiration.

Answer

There is a direct relationship between absorption and transpiration. As water is lost through transpiration, more water is absorbed as more water is required. This creates a suction pressure which pulls up water from the xylem of the roots to the stem and then to the leaves. It is called transpiration pull. Thus, the amount of water in the roots gets reduced. In turn, water from the surrounding soil passes on to the root hair cells by the process of osmosis. Thus, the cycle of absorption and transpiration continues.

Question 4

How does the food manufactured in the leaves reach different parts of the plant?

Answer

The sugar molecules manufactured by the leaves by photosynthesis are transported throughout the plant by phloem. The transport of soluble products of photosynthesis is called translocation. Phloem has cells called sieve tubes which are placed one above the other to form long tubes through which food is transported.

Question 5

Give two points of importance of transpiration in plants.

Answer

Two points of importance of transpiration in plants are:

  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.

Question 6

Differentiate between macro-nutrients and micro-nutrients with examples.

Answer

Sl.
No.
Macro-nutrientsMicro-nutrients
1.The minerals that are required in large quantities are called Macro-nutrients.The minerals that are required in small quantities are called Micro-nutrients.
2.Their requirement is 0.2 to 0.4% of dry weight of the plant.Their requirement is 0.1 to 0.02% of dry weight of the plant.
3.Nitrogen, phosphorous, potassium, sulphur, calcium and magnesium are examples of macro-nutrients.Boron, manganese, chlorine, iron, zinc, copper, nickel and molybdenum are examples of micro-nutrients.

Identify the figure

Question 1

Identify the figure and label parts a, b, c.

Identify the figure and label parts a, b, c. Transport of Food and Minerals in Plants, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Answer

The figure shows a root hair. The parts labelled a, b, c are:

a → Nucleus

b → Cell Membrane

c → Cytoplasm

Think and Answer

Question 1

If vegetables such as brinjals or lady's fingers become somewhat dry and shrivelled, they are put in water. They start looking fresh again, because water enters inside them. In the absence of any opening, how does water enter the vegetables?

Answer

The shrivelled vegetables start looking fresh again when kept in water because the concentration of water is more outside the vegetable and the semipermeable cell membrane allows osmosis to take place. By the process of osmosis, slowly the vegetable absorbs water, in absence of any opening.

Question 2

In xylem, tracheids and xylem vessels are placed end to end like tubes. How does this help plants?

Answer

In xylem, tracheids and xylem vessels are placed end to end like tubes. These cells are dead that means they don't have protoplasm. Thus it makes a clear straw-like passage for the easy movement of water and minerals in the plant. Also, these cells have lignified walls, which make their walls stiff, provide structural support and prevent the walls from collapsing during water transport.

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