NCERT Solutions for Class 11 Biology Chapter 5 - Morphology of Flowering Plants

Precisely in chapter 2 and meticulously in chapter 3, the classification of the plant kingdom has been discussed based on morphology and other characteristics. So, this chapter is a sub-part of the third chapter, and the morphology of flowering plants has been discussed here. To correctly understand the biology of any higher plant (or any other living organism) and to successfully classify them, appropriate knowledge about the standard technical/biological terms and definitions is a must.

It is also written that awareness about the plants' potential variants in different parts that are seen as altered or modified versions of the plants to their environments is crucial. For example, transformation to various habitats, for protection, storage, or climbing. Other topics included in this chapter are stem, roots, inflorescence, leaf, fruit, seed, flower, description of a stereotype flowering plant in a semi-technical language, and a description of some significant plant families and a few more. All the stated topics have been shortly elucidated below.

• The Root
• The Stem
• The Leaf
• The Inflorescence
• The Flower
• The Fruit
• The Seed
• Not so technical Explanation of a Typical Flowering Plant
• Elaboration on some important flowering plant families

The above subtopics make chapter 5 of class 11 Biology syllabus complete where extensive knowledge about different parts of the flowering plants has been provided for students' comprehensive learning. Through this chapter, students will come across many variations of a flowering plant in terms of size, shape, mode of nutrition, structure, habit, habitat, and life span. It also peaches about the well-developed root and shoot systems of the flowering plant, particularly about the root system, which is either fibrous or taproot in nature.

Also presented are details on stem modifications and various terms linked with the morphology of flowering plants. The chapter also discusses ovules, which, after undergoing fertilization, grows into a seed. After this, the focus of the chapter moves to the types of seed and their structure. The important families of the flowering plant discussed here are Fabaceae, Liliaceae, and Solanaceae where the families' floral & vegetative characters and economic significance have been explained.

Q1. What is meant by modification of root? What type of modification of root is found in the:
(a)Banyan tree
(b)Turnip
(c)Mangrove trees
Answer:
Roots of the plants are involved in absorbing underground water and minerals. Apart from the function of water and mineral absorption, the roots of some plants often modify to perform various other functions such as storage, nitrogen fixation, aeration, and support, etc. These are called root modifications.
The modification of roots is found in:
(a)Banyan tree- In banyan tree roots modify to provide support to the tree. The banyan tree possesses pillar-like adventitious roots that arise from the aerial part of the stem. These roots grow towards the ground and provide support to the tree. Such roots are called prop roots.
(b)Turnip- The roots of turnip are called napiform roots and they help in the storage of food.
(c)Mangrove tree- These possess roots that modify for the absorption of oxygen by growing vertically upwards from the soil. These types of roots are called pneumatophores.
 

Q2.Justify the following statements on the basis of external features
(1)Underground parts of flower are not always root.
Answer:
The roots of a plant are generally underground while the stem is present above the ground. However, it is not necessary that the root is the only part of the plant to be found underground. In some specific conditions, stems are also found to be present in underground regions. For example, The stems in ginger and banana are underground and swollen due to the storage of food. They are called rhizomes. Similarly, the corm is an underground stem in Colocasia. Similarly, in peanuts, the flower after fertilization gets pushed inside the soil by growing a flower stalk. Hence, by this information, we can conclude that the underground parts of a plant are not always roots.

(2)The flower is a modified shoot.
Answer:
After a certain period of growth, the apical meristem of a stem gives rise to the floral meristem. While the formation of the floral meristem, the axis of the stem gets condensed, and the internodes lie near each other. Various floral appendages arise from the node. A flower can be said to be a modified shoot because of the presence of nodes.

Q3. How is a pinnately compound leaf different from a palmately compound leaf?
Answer:

Q4. Explain with suitable examples the different types of phyllotaxy.
Answer:
The pattern or arrangement of leaves on the stem or branch is called Phyllotaxy. There are three types of phyllotaxy found in plants.
(1)Alternate phyllotaxy- On a branch, a single leaf arises at each node. E.g China rose.
(2)Opposite phyllotaxy- At one node, two leaves arise, opposite to each other. E.g guava plant.
(3)Whorled phyllotaxy- More than two leaves arise at a node and form a whorl in a whorled phyllotaxy. E.g Alstonia

Q5. Define the following terms:
(a)Aestivation
Answer:
-Aestivation- The mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl is called aestivation. Aestivation in plants can be valvate, twisted, imbricate, and vexillary.

(b)Placentation
Answer:
-Placentation- The arrangement of ovules within the ovary is called placentation. There are five types of placentation found in plants including marginal, basal, parietal, axile, and free central placentation.

(c)Actinomorphic
Answer:
Actinomorphic- The flowers which can be divided into two radial halves by any radial plane passing through its center are called actinomorphic flowers. E.g. chilly and mustard.


(d)Zygomorphic
Answer:
-Zygomorphic- The flowers which can be divided into two similar halves by a single vertical plane only are known as zygomorphic flowers. E.g. peas and beans.

(e)Superior ovary
Answer:
-Superior ovary- When the gynoecium is present at the highest position, while other floral parts are arranged below it, the ovary is said to be a superior ovary. A flower with this arrangement is described as hypogynous. Examples include brinjal and mustard.

(f)Perigynous flower

Answer:
-Perigynous flower- When the gynoecium is present in the center while the rest of the floral parts are present at the rim of the thalamus at the same level as gynoecium, the flower is called perigynous flower. E.g. plum and rose.

(g)Epipetalous stamens
Answer:
-Epipetalous stamen- The stamen which remains attached to the petals are called epipetalous stamens. E.g brinjal.
 

Q6. Differentiate between

(a)Racemose and cymose inflorescence
Answer:

(b)Apocarpous and syncarpous ovary
Answer:

Q7. Draw the labeled diagram of the following:
(i) gram seed
Answer:
Structure of gram seed-

(ii). V.S. of maize seed
Answer:

V.S. of maize seed-
 

Q8. Describe modifications of the stem with suitable examples.
Answer:

The major types of stem modifications are as follows:-
(1)Rhizome- It is a fleshy, non-green underground stem having distinct nodes and internodes. The nodes bear dry scale leaves with axillary buds. Adventitious roots arise from the lower side. e.g., Alocasia, Dryopteris, Banana, Ginger, turmeric, Canna, etc.
(2)Bulb- It is an underground pyriform to spherical structure bearing a reduced convex or slightly conical disc-shaped stem and several fleshy scales enclosing a terminal bud. e.g, Lily, onion, etc.
(3)Corm- It is a condensed form of rhizome growing in the vertical direction. It is more or less spherical with a flat base. Adventitious roots arise either from its base or all over the body. Examples- Colocasia, Amorphophallus.
(4)Tuber- Stem tuber is a swollen tip of an underground stem. It possesses a number of small depressions called eyes. These eyes represent nodes. Adventitious roots are usually absent e.g., Potato.
(5)Runner- These are special, narrow, green, above-ground horizontal or prostrate branches that develop at the bases of erect shoots called crowns. E.g. Centella, Oxalis, doob grass etc.
(6)Stolon- These are elongated horizontal runners which can cross over small obstacles. The tip of the stolon generally grows above the level of the ground. E.g. Jasmine, peppermint, wild strawberry, etc.
(7)Offset- They are one internode long small runners which are found in rosette plants at the ground level. E.g Pistia, Eichhornia etc.
(8)Stem- tendrils- These are thread-like sensitive structures that coil around support and help the plant in climbing. E.g. grapevine.
(9)Stem thorns- These are hard, stiff, and sharp structures that protect the plants. e.g. Citrus, Bougainvillea, Duranta etc.
(10)Phylloclade- They are flattened or cylindrical green stems of unlimited growth which have taken over the function of photosynthesis. The formation of phylloclades helps the plants to grow in dry habitats. e.g. Opuntia, Casuarina etc.
(11)Cladode- These are the green stem of limited growth that has taken over the function of photosynthesis from the leaves. The true leaves are reduced to scales or spines. E.g. Ruscus.

Q10. Describe the various types of placentations found in flowering plants.
Answer:
Placentation refers to the arrangement of ovules within the ovary of a flower. There can be five types of placentation in plants. These are as follows:
1.Marginal placentation: The placenta forms a ridge along the ventral suture of the ovary and the ovules develop on two separate rows in marginal placentation e.g. peas.
2.Parietal placentation: When the ovules develop on the inner walls of the ovary, the ovary is said to have parietal placentation.
3.Axile placentation: In axile placentation, the placenta is axial and ovules are attached to it e.g. China rose, lemon, and tomato.
4.Basal placentation: In basal placentation, the placenta develops from its base and a single ovule is found attached to the base. It is found in marigolds and sunflowers.
5.Free central placentation: The ovules develop on the central axis while the septa are absent in the free central placentation. This type of placentation is found in Dianthus and primrose

.

Q11. What is a flower? Describe the parts of a typical angiosperm flower.
Answer:
The flower is the reproductive part of angiospermous plants for sexual means of reproduction. A typical flower has four whorls arranged on a swollen end of stalk or pedicel called the thalamus. They are Calyx, Corolla, Androecium, and Gynoecium.
1. Calyx- It is the outermost whorl of a flower. It is made up of units called sepals. It is generally green in color and protective in function.
2. Corolla- It is the whorl present inner to the corolla. It consists of petals. The petals are brightly colored to attract insects.
3. Androecium- It is the whorl present next to the corolla. The androecium mainly consists of stamens which are the male reproductive unit of a flower. A stamen is composed of two parts i.e. anther and filament. The anther is the bilobed structure with a stalk called a filament. Inside the anther, pollen grains are formed.
4. Gynoecium- The innermost whorl of a flower is called gynoecium. It consists of pistils. A pistil is composed of three parts stigma, style, and ovary. Pistils are the female reproductive units of a flower.




Q12. How do the various leaf modifications help plants?
Answer:
The leaf is a green, lateral, and flattened outgrowth that is borne on the node of a stem or its branches is specialized to perform photosynthesis. Apart from photosynthesis, leaves often modify to perform several other functions also. Some of the modifications of leaves in plants that help the plants are as follows:

1.Tendrils- The leaves of the plants may modify into tendrils that help the plants in climbing
2.Spines- These are hard and stiff structures that act as organs of defense. e.g. cactus
3.Phyllode- The leaves of some plants are short-lived and they are soon replaced by flattened, green structures called phyllodes. These arise from the petiole of the leaves and are involved in synthesizing the food.
4.Pitcher- The leaves of the pitcher plant are modified into pitcher-like structures. These contain digestive juices and help in trapping and digesting insects.

Q13. Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants?
Answer:
The arrangement of flowers on the floral axis is termed an inflorescence. There can be two types of inflorescence i.e. racemose and cymose on the basis of whether the floral axis continues to grow or end in a flower. In racemose inflorescence, the floral axis continuous to grow and bear flowers whereas in cymose inflorescence the floral axis stopped growing and terminates into a flower.
 

Q14. Write the floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens, and two united carpels with superior ovary and axile placentation.
Answer:
The floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens, and two united carpels with the superior ovary and axile placentation is as follows:

Q15. Describe the arrangement of floral members in relation to their insertion on the thalamus.
Answer:
There can be three types of arrangements of floral members in relation to their insertion on the thalamus. These are as follows:

1.Hypogynous – Ovary occupies the highest position while the other parts are situated below the ovary. The ovary in such a case is called superior. Eg. Mustard, brinjal, and China rose. Flowers with this arrangement are called hypogynous flowers.
2.Perigynous -In this arrangement, the gynoecium is situated at the center and other parts are on the rim at the same height. Such ovary is called half-inferior and flowers are called perigynous flowers.
3.Epigynous- In this arrangement, the ovary is situated below all the other parts. The ovary, in this case, is said to be inferior while the flower is called epigynous flower.