Class 6 - Biology - The Leaf - Exercise And Solutions

EXERCISE

Multiple Choice questions:

1. Tick (√) the appropriate answer.

(i) Identify the plant which has compound leaves.

(a)    Banana                                  (b)    Banyan

(c)    Mango                                   (d)    Rose 

(ii) Which one of the following is not an insectivorous plant?

(a)    Pitcher plant                        (b)    Venus flytrap

(c)    Bladderwort                        (d)    Cactus

(iii) This leaf shows parallel venation.

(a)    Banana                                 (b)    Mango

(c)    Banyan                                (d)    Guava

(iv) The point on the stem from where the leaf arises is

(a)    Petiole                                 (b)    Lamina

(c)    Node                                   (d)    Trunk

(v) Which one of the following is essential for photosynthesis?

(a)    Carbon dioxide                 (b)    Nitrogen

(c)    Oxygen                               (d)    Soil

Short Answer questions

1. Name the following

(i) The part of the plant which grows under the ground: Root system

(ii) The part of the plant which grows above the soil: Shoot system

(iii) The wide flat portion of the leaf: Lamina

2. What are the four functions of roots?

a) Root fixes the plant in soil.

b) It absorbs water and minerals from soil for the growth of entire plant.

c) It binds the soil together and helps in soil conservation.

d) Some modified roots store foods. i.e, Radish and Carrot.

3. Mention the functions of the following:

i) Spines

Spines are modified leaves, which help to reduce water loss

ii) Tendril

In case of certain weak stemmed plants, the leaves or leaflets are modified

in to wiry, coiled structures. These are called tendrils. They are sensitive to

touch. As they touch any object they coil around it and support the plant to

climb up. Example: Sweet pea.

iii) Scale leaves

Some plants like onion, ginger have thin and dry or thick and fleshy scale

leaves. Their function is to protect the buds.

4. Define venation. What are the different types of venation found in leaves?

Arrangement of veins in a lamina is called venation. They are mainly of

Two types.

Reticulate venation: In this type venation, veins and veinlets are irregularly

distributed in the lamina and forms a network. e.g, dicot plants like Peepal,

mango and guava

Parallel venation: In this type venation veins run parallel to each other.

e.g, monocot plants like banana, grass, maize and wheat leaves.

5. Describe the modification of leaves in any one insectivorous plant.

The leaves of Venus flytrap plant have long hair. It is divided in to two

parts having a midrib in between like a hinge. When an insect visits the

leaf, it closes its two parts and trap the insect. The insect then digested

by the digestive juice secreted by the leaf.

6. Write the two main functions of leaves.

The two main functions of leaf are photosynthesis and transpiration.

7. Define: (i) Photosynthesis        (ii) Transpiration.

(i) Photosynthesis: The process by which a plant leaf prepares or

synthesizes food from water and carbon dioxide in the presence of

chlorophyll and sunlight is called photosynthesis.

Photosynthesis is represented as follows

                                          

(ii) Transpiration: This is the process by which water is lost in the form of

water vapour by evaporation from the surface of leaves and other

aerial parts of a plant. It has a cooling effect and it develops a

suction force to make the roots absorb more water and minerals

from soil.

Long answer questions:

1. Giving example differentiate between the following.

(i) Tap root and fibrous root  (ii) Simple leaf and compound leaf

(iii) Parallel venation and reticulate venation.

(i) Tap root and fibrous root

Tap root	Fibrous root
Tap root system has a thick main root called primary root and many side branches called secondary root.	Fibrous root system has a cluster of roots of the same thickness.
Tap root system found in dicot plants	Fibrous root system found in monocot plants.
Ex.- Plants such as gram, pea etc.	Ex.- Plants such as maize, grass, banana etc.

(ii) Simple leaf and compound leaf

Simple leaf	Compound leaf
In a simple leaf the lamina is undivided and is a single piece.	In a compound leaf the lamina is divided into smaller units called leaflets.
Ex.- Mango, banana, banyan	Ex.- Rose, and prickly poppy

(iii) Parallel venation and reticulate venation.

Parallel venation	Reticulate venation
In this type of venation, vein runs parallel to each other.	In this type of venation, veins and veinlets are irregularly distributed in the lamina and forms a network.
This appears in monocot plants	This appears in dicot plants
Ex.- Peepal, mango, guava etc.	Ex.- banana, grass, wheat etc

2. What is the modification seen in Bryophyllum? Explain.

Bryophyllum is a plant whose leaves produce adventitious buds in their

margin. The buds grow in to new plant when they fall off from the

parent plant. It takes around 10 to12 days to grow tiny plantlets out

from these buds.

3. What purpose is served by the spines borne on the leaves of cactus?

Spines in the cactus plants help in reducing the water loss.

4. Explain why leaf survival is so important to the plant?

The survival of leaf is very important to the plant in many ways, such as

a) Leaves prepare food and a part of this food is needed by the plant

to survive. Photosynthesis is not possible without leaves.

b) The transpiration process is not possible without leaves. Hence

without leaves the transpiration pull will be affected and the plants

cannot absorb more water and minerals from the soil. This will affect

the growth of the plant.

5. Give an example of the following and draw generalized diagram for

the same:

(i) Simple leaf and compound leaf

(ii) Parallel venation and reticulate venation.

(i) Simple leaf: Example, Peepal          Compound leaf: example, Rose

(ii) Parallel venation: Example, banana     Reticulate venation, Peepal

6. Enlist some of the advantages of transpiration to green plants.

The advantage of transpiration to green plants are

Cooling effect: The water keeps on evaporating from the leaf surface

during transpiration. This helps the plant to cool itself when it is hot

outside.

Transpirational pull: As water continuously evaporates from the leaf

Surface, the roots pull up more water from the soil to make up this water

Loss during the transpiration. As a result, important mineral salts are also

Brought by the roots along with water from the soil. These minerals help

the plant to grow.

7. Why do some plants have to trap insects?

The soil in some areas are deficient in nitrates. So the plants are not able

to get necessary nitrates from the soil. Some plants develop their leaves

to trap insects to meet their nitrogen demand. These plants utilizes the

insect’s protein by converting it in to nitrate. Some example of such type

of plants are Pitcher plant, Venus flytrap and Bladderwort.

8. Explain some of the modifications of leaves found in plants.

Sometimes the complete leaf or a part of the leaf modified to perform a

special function. Some of these modification are Leaf tendril, Spines and

Scale leaves.

Leaf tendril: In case of certain weak stemmed plants, the leaves or

leaflets are modified in to wiry, coiled structures. These are called

tendrils. They are sensitive to touch. As they touch any object they coil

around it and support the plant to climb up. Example: Sweet pea.

Spines: Leaves are modified to spines to reduce water loss. Example

cactus and prickly puppy

Scale leaves: Some plants like onion, ginger have thin and dry or thick

and fleshy scale leaves. Their function is to protect the buds.

9. What is tendril? Explain its use to the plants.

In case of certain weak stemmed plants, the leaves or leaflets are

modified in to wiry, coiled structures. These are called tendrils. They

are sensitive to touch. As they touch any object they coil around it

and support the plant to climb up. Example: Sweet pea. 

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Extra Questions and Answers

A. Objective Questions

1. Fill in the blanks:

a) The underground part of the plant is called root system.

b) The part of the plant which grows above the soil is called shoot system.

c) Tap root system has a thick main root known as primary root.

d) The part of the stem between two successive nodes is called internode.

e) Buds in the top of the shoot is called apical buds

f) Apical buds are responsible for the vertical growth of the stem.

g) The angle between the upper side of the leaf and the stem is known as

the axil.

h) Buds found in the axil are called the axillary buds.

i) The basal part of the leaf is petiole.

J) Leaves directly attached to the stem without a petiole is called sessile

leaves.

k) The green flat and board part of the leaf is called lamina.

l) Petiole continues to the lamina as the midrib.

m) Veins provide a skeleton or supportive framework to the leaves.

n) During photosynthesis water is combined with carbon dioxide to

produce glucose and oxygen.

o) Plants which trap insects to meet their nitrogen demand are called

insectivorous plant.

p) Leaves of Bryophyllum and Begonia produces buds along their margin.

q) Size of the pitcher varies from 10-20 cm.

r) At the bottom of the pitcher, enzymatic juices are secreted.

s) Pitcher plants found in Garo and Khasi hills in Meghalaya.

2. Give one word for the following.

a) The outer age of leaf – Margin.

b) The flat and green part of the shoot, that grows laterally from the

nodes of the stem are called – Leaves.

c) The arrangement of leaves on a stem is called – Phyllotaxy.

d) Young tiny plants – Plantlets.

e) plant that bears buds in leaves for propagation – Bryophyllum.

B. Short Questions And Answers.

Define the following

a) Autotrophic nutrition: All green plants prepare their own food. They

themselves prepare the nutrition for their use. This method of nutrition is

called autotrophic nutrition.

b) Vegetative propagation: Some new plants can be produced from the

vegetative parts of the plant such as roots, stems and leaves. This type

of reproduction is called vegetative propagation.

c) Bladderwort: Bladderwort has highly segmented leaves. Some of the

segments of these leaves form small bladder like structures. The bladder

has an entry point which can be closed. The insects enter in to it but

cannot come out and are digested inside.

d) The shoot system: The part of the plant which grows above the soil is

called the shoot system. It is made up of Stem, Buds, Leaves, Flowers

and Fruits.

C. Long Questions And Answers.

Answer the following:

1. What are the functions of stem?

The functions of stem are

a) Stem bears all aerial parts of the plant, buds, leaves, flowers and

fruits.

b) Stem helps in the upward movement of water and minerals absorb

by the root and transport them up to the leaves, flowers and fruits.

c) Food prepared by the leaves is conducted downwards to the roots

and other non-green parts by the stem.

d) Stem also manufactures food when green and young.

2. Mention the types of leave on the basis of shape with example.

On the basis of shape the leaves are classified as

i) Needle shaped, e.g, pine, onion

ii) Oval, e.g, guava, apple

iii) Heart shaped, e.g, Peepal

iv) Oblong, e.g, banana

v) Circular, e.g, lotus, nasturtium

vi) Tapering, e.g, eucalyptus, ashoka

3. Mention the types of leave on the basis of margin with example.

On the basis of margin the leaves are classified as

i) Complete or entire margin, e.g, peepal

ii) Toothed or serrated margin, e.g, china rose, rose

iii) Wavy margin, e.g, ashoka, mango

iv) Spinous margin, e.g, prickly puppy

4. Describe the different types of arrangement of leaves with example.

The different types of arrangement of leaves are Alternate arrangement,

Opposite arrangement, Whorled arrangement.

Alternate arrangement: In this type arrangement only one leaf arises from

each node. The next leaf arises from the successive node in opposite

direction. Example: mint, Peepal, china rose.

 Opposite arrangement: In this type of arrangement two leaves arise from

each node opposite to each other. Example: guava and jasmine.

 Whorled arrangement: In this arrangement more than two leaves are

attached in each node. Example: oleander.

5. Draw the structure of a leaf and describe its different parts.

A leaf has three main parts. Petiole,

Lamina or leaf blade and Midrib.

Petiole: This is the basal part of the leaf. It

is attached to the stem at the node.

Leaf blade or lamina: The green, flat and

broad part of the leaf is known as lamina

or leaf blade. The outer age of leaf

blade is called leaf margin.

Midrib: Petiole continues to the lamina as

midrib. This laterally gives out fine branches called veins. Petiole, midrib

and veins conduct water and food.

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