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

Q1: How is a pinnately compound leaf different from a palmately compound leaf?
Ans:

Pinnately Compound Leaf:

• Leaflets: Pinnately compound leaves have leaflets arranged along a central axis called the rachis. The leaflets are attached in a feather-like or pinnate pattern.
• Arrangement: The leaflets of pinnately compound leaves are arranged on opposite sides of the rachis, forming pairs or sometimes in an odd number of leaflets.
• Example: Examples of plants with pinnately compound leaves include neem (Azadirachta indica) and rose (Rosa spp.).

Palmately Compound Leaf:

• Leaflets: Palmately compound leaves have leaflets attached to a common point at the tip of the petiole, resembling the fingers of a hand or a palm.
• Arrangement: The leaflets of palmately compound leaves radiate out from a central point, and their arrangement is similar to the spokes of a wheel.
• Example: Examples of plants with palmately compound leaves include horse chestnut (Aesculus hippocastanum) and umbrella plant (Schefflera spp.).

Q2: Explain with suitable examples the different types of Phyllotaxy?
Ans: Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is of three types:
(i) Alternate Arrangement of Leaves: In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sun flower plants.
(ii) Opposite Arrangement of Leaves: In opposite type, a pair of leaves arise at each node and lie opposite to each other as in Calotropis and guava plants.
(iii) Whorled Arrangement of Leaves: If more than two leaves arise at a node and form a whorl, it is called whorled, as in Alstonia.

Q3: Define the following terms:
(a) Aestivation
(b) Placentation
(c) Actinomorphic
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous flower
(g) Epipetalous Stamen
Ans:
(a) Aestivation: The mode of arrange¬ment of accessory floral organs (sepals and petals) in relation to one another in floral bud is known as aestivation. The main type of aestivation are valvate, twisted, imbricate, and vexillary.
(b) Placentation: The arrangement of ovules within the ovary is known as placentation. The placentation are of different types namely, marginal, axile, parietal, basal, and free central.
(c) Actinomorphic: When flower can be divided into equal radial halves in any radial plane passing through the centre, it is said to be actinomorphic, e.g., mustard, Datura etc.
(d) Zygomorphic: When a flower can be divided into two similar halves only in one particular vertical plane, it is said to be zygomorphic, e.g., pea, gulmohar, bean, Cassia.
(e) Superior ovary: In hypogynous flower, the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, brinjal.
(f) Perigynous flower: If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. Here ovary is half superior, e.g., peach, plum.
(g) Epipetalous stamen: When stamens are attached to the petals, they are called epipetalous stamens e.g., brinjal.

 
Q4: Differentiate between
(a) Racemose and cymose inflorescence
(b) Apocarpous and syncarpous ovary
Ans: 
(a)

(b)

Q5: Draw the labelled diagram of the following:
(i) Gram seed
(ii) V.S. of maize seed
Ans:
(i) Gram Seed:

 A Gram seed is typically an oval-shaped seed with a hard seed coat. It can be divided into the following parts:

• Seed coat: The outer protective covering of the seed.
• Hilum: The scar on the seed coat where it was attached to the plant.
• Micropyle: The small opening near the hilum through which water and air enter during germination.
• Embryo: The young plant inside the seed consisting of the epicotyl, hypocotyl, and cotyledons.

(ii) V.S. of Maize Seed:

A V.S. of a maize seed would typically show the following structures:

• Seed coat: The protective covering of the seed.
• Cotyledon: The part of the embryo that stores food for the developing plant.
• Embryo axis: The portion of the embryo consisting of the epicotyl (above the cotyledon) and hypocotyl (below the cotyledon).
• Plumule: The tiny shoot tip of the epicotyl that develops into the shoot system of the plant.
• Radicle: The embryonic root that develops into the root system of the plant.

Q6: Take one flower from each of the families Fabaceae and Solanaceae and write its semi-technical description. Also, draw their floral diagram after studying them.
Ans:
(a) Family Fabaceae/Papilionaceae (pea plant)

• Fabaceae/Papilionaceae is a sub-family of the Leguminoseae family.
  

Vegetative features:

• Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf base along folacious stipules.
• Root: Tap root system with root nodules.

Floral features:

• Inflorescence: Racemose, generally axial than terminal
• Flower: Zygomorphic and bisexual flowers are found
• Calyx: It contains five sepals which are gamosepalous while aestivation is imbricate.
• Corolla: It contains five petals (polypetalous) with vexillary aestivation.
• Androecium: It consists of ten anthers that are diadelphous with dithecous anthers.
• Gynoecium: Monocarpellary superior ovary which is unilocular with marginal placentation.
• Fruit: Legume pod with non-endospermic seeds
• Floral formula:
  

Economic importance: Peas are used as vegetables for making various culinary preparations.

(b) Flowers of Solanum nigrum Family Solanaceae

Vegetative features:

• Habit: Erect, herbaceous plant
• Leaves: Simple, exstipulate leaves with reticulate venation Stem: Erect stem with numerous branches.

Floral features:

• Inflorescence: Solitary and axillary
• Flowers: Actinomorphic, bisexual flowers
• Calyx: Calyx is composed of five sepals that are united and persistent. Aestivation is valvate.
• Corolla: Corolla consists of five united petals with valvate aestivation.
• Androecium: It consists of five epipetalous stamens.
• Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile placentation.
• Fruits: Berry
• Seeds: Numerous, endospermous

Floral formula: 

Economic importance: Used for medicinal purposes.

Q7: Describe the various types of placentations found in flowering plants.
Ans: Placentation: The arrangement of ovules within the ovary is known as placentation. The placentation are of different types namely, marginal, axile, parietal, basal, central and free central. The various types of placentations found in flowering plants are:
(a) Marginal placentation: The ovary in which the placenta forms a ridge along the ventral suture of the ovary and the ovules develop on two separate rows is known to have marginal placentation. This type of placentation is found in peas.

(b) Parietal placentation: When the ovules develop on the inner walls of the ovary, the ovary is said to have parietal placentation.

(c) Axile placentation: In axile placentation, the placenta is axial and ovules are attached to it. Examples include China rose, lemon, and tomato.

(d) Basal placentation: The ovary in which the placenta develops from its base and a single ovule is found attached to the base is said to have basal placentation. It is found in marigold and sunflower.

(e) Free central placentation: In free central placentation, the ovules develop on the central axis while the septa are absent. This type of placentation is found in Dianthus and primrose.

Q8: What is a flower? Describe the parts of a typical angiosperm flower.
Ans: The flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction. A flower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and gynoecium represent the male and female reproductive organs of a flower respectively. Parts of flower are:

• The calyx: The calyx is the outermost whorl of the flower and the members are called sepals. Generally, sepals are green, leaf like and protect the flower in the bud stage. When the sepals of a flower are free, they are called polysepalous, while fused sepals of a flower are called gamosepalous.
• Corolla: Corolla is composed of petals. Petals are usually brightly coloured to attract insects for pollination. When the petals are free, they are called polypetalous, while fused petals are called gamopetalous. Corolla may be tubular, bell-shaped, funnel-shaped or wheel-shaped.
• The androecium or the stamen is the male reproductive part of a flower. It consists of two parts, the filament and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen grains.
• Gynoecium represents the female reproductive part of a flower. It consists of an ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary bears numerous ovules attached to the placenta.

Q9: Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants.
Ans: 

• Inflorescence is the manner in which the flowers are arranged on the flowering axis. 
• During the flowering season, the vegetative apex of the stem gets converted into a floral meristem. 
• Based on whether the floral axis continues to grow or end in a flower, inflorescence is classified into racemose and cymose. 
• In racemose inflorescence, the floral axis continues to grow and produces flowers laterally. 
• On the other hand, in cymose inflorescence, the main axis terminates into a flower. Hence, it is limited in growth.

Q10: Describe the arrangement of floral members in relation to their insertion on thalamus?
Ans: Based on the position of the calyx, corolla, and androecium (with respect to the ovary on the thalamus), the flowers are described as hypognous, perigynous, and epigynous. 

• In hypogynous flowers, the ovary occupies the highest position on the thalamus while other floral parts are situated below it. In such flowers, the ovary is superior.
  Example: China rose, mustard, etc.
• In perigynous flowers, the ovary is situated at the centre and other floral parts are arranged on the rim of the thalamus. The ovary here is said to be half inferior.
  Example: plum, rose, peach. 
• In epigynous flowers, the thalamus grows around the ovary fusing with its wall. The other floral parts are present above the ovary. Hence, the ovary is said to be inferior.
  Example: flowers of guava and cucumber.

Old NCERT Syllabus 

Q. 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: Primarily, there are two types of root systems found in plants, namely the tap root system and fibrous root system. The main function of the roots is to absorb water and minerals from the soil. However, roots are also modified to perform various other functions. The roots of some plants act as storage sites for food, some provide support to massive plant structures, while others absorb oxygen from the atmosphere. 

Roots and its modifications in various plants:

(a) Banyan tree

• The banyan tree (Ficus benghalensis) has massive pillar-like adventitious roots arising 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.
  Prop Roots

(b) Turnip

• The roots of turnip (Brassica rape) help in the storage of food. Similar food-storing roots are found in radishes, carrots, and sweet potatoes.
  Roots of Turnip

(c) Mangrove tree

• The roots of mangrove plants grow vertically upwards from the soil for the absorption of oxygen from the atmosphere as the soil is poorly aerated. These types of roots are called pneumatophores.
  pneumatophores

Q. Justify the following statements on the basis of external features:
(i) Underground parts of a plant are not always roots
(ii) Flower is a modified shoot
Answer: (i) Various parts of plants are modified into underground structures to perform various functions such as stems, leaves, and even fruits.

• The stems in ginger and banana are underground and swollen due to the storage of food. They are called rhizomes. 
• Similarly, corn is an underground stem in Colocasia and Zamin-khand. 
• The tips of the underground stem in potato become swollen due to the accumulation of food and forms tuber. Tubers bear eyes, which are subtended by a leaf scar. 
• Basal leaves in onions become fleshy because of the accumulation of food. 
• In peanuts, the flower after fertilization gets pushed inside the soil by growing a flower stalk. The formation of fruits and seeds takes place inside the soil.

(ii) During the flowering season, the apical meristem gives rise to the floral meristem. The axis of the stem gets condensed, while the internodes lie near each other. Instead of leaves, various floral appendages arise from the node. Therefore, it can be said that the flower is a modified shoot.

Q. Describe modifications of Stem with suitable examples.
Answer: Stems of various plants have undergone modifications to perform different functions. Examples: Rhizomes, Corms, tubers.

Underground stems or storage stems: 

• In ginger and banana, the underground stem is called a rhizome. The underground stem in Colocasia (arvi) is known as corm. 
• Rhizomes and corms are underground stems, modified for the storage of food. Also, these stems help in vegetative reproduction of these plants. 
• The tips of the underground stem in potato plants become swollen due to the accumulation of food. 
• The potato is a tuber that helps in the storage of food and bears eyes on it. Subtended by a leaf scar, these eyes bear buds that give rise to new plants.

(a) Supportive stems 

Example: tendril

• The stem in some weak plants bear thin, slender, and spirally-coiled structures called tendrils that help the plant get attached to nearby structures for support. Tendrils are found in cucumbers, melons, and other members of the family Cucurbitaceae. 

(b) Protective stems 

Example: Thorns

• The stem in bougainvillea and citrus plants (like lemon and orange) bear sharp, pointed structures called thorns, which provide protection to the plant from herbivores.

(c) Photosynthetic stems 

Example: Opuntia

• The stem in the Opuntia is green. It carries out the process of photosynthesis in the absence of leaves. 

Others stem modifications:
In some plants, underground stems such as grasses spread in the soil and help in perenation. These stems are called runners. The short lateral stem called the offset in some aquatic plants (such as Eichhornia) bears leaves and tufts of roots at the node and gives rise to new plants.

Q. How do the various leaf modifications help plants?

Answer: The main function of the leaves is to carry out the process of photosynthesis. However, in a few plants, leaves are modified to perform different functions.
(a) Tendrils: The leaves of a pea plant are modified into tendrils that help the plant in climbing.
(b) Spines: The leaves in cactus are modified into sharp spines that act as an organ of defence.
(c) Phyllode: The leaves of some Australian acacia are short-lived and soon replaced by flattened, green structures called phyllodes that arise from the petiole of the leaves. The petioles in these plants synthesize food.
(d) Pitcher: The leaves of the pitcher plant are modified into pitcher-like structures, which contain digestive juices and help in trapping and digesting insects.

Q. Write the floral formula of an actinomorphic bisexual, hypogynous flower with five united sepals, five free petals. Five free stamens and two united carpals with superior ovary and axile placentation.

Answer:
The floral formula of the described flower is represented as:

• Actinomorphic flowers are represented by the symbol. 
• A bisexual flower is indicated by.
• The calyx contains five united sepals which can be represented as K_(5).
• The corolla consists of five free petals and it represented as C_5.
• The androecium consists of five free stamens and is represented by A_5.
• The gynoecium consists of a superior ovary with two united carpels and axile placentations, which can be represented as G(2).