Class 11 Biology Chapter 5 Morphology of Flowering Plants
Chapter 5
Morphology of Flowering Plants
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: In some plants, roots change their structure and shape and become modified to perform functions other than absorption and conduction of minerals and water. They are modified for support storage of food and respiration. This is known as modification of root.
The type of modification of root found in the -
a. Banyan tree - prop roots
b. Turnip – tap roots
c. Mangrove trees – pneumatophores.
Q2. 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. Underground parts of a plant are not always roots: In some plants like ginger and potato are the underground stems which are modified for food storage. They also act as organs of perennation to tide over conditions unfavourable for growth.
ii. Flower is a modified shoot: Flower is form on a stem and thus it is a shoot. It is meant for sexual reproduction. So, it is known as modified shoot.
Q3. How is a pinnately compound leaf different from a palmately compound leaf?
Answer:
In pinnately compound leaf, a number of leaflets are present on a common axis i.e., the rachis whereas in palmately compound leaf, the leaflets are attached at a common point i.e., at the tip of petiole.
Q4. Explain with suitable examples the different types of phyllotaxy.
Answer: Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. Phyllotaxy is three types – alternate, opposite, and whorled. Alternate type of phyllotaxy is seen in plants like China rose, mustard, and sunflower, where a single leaf arises at each node in alternate manner. Opposite type of phyllotaxy is seen in plants like Calotropis and guava, where a pair of leaves arise at each node and lie opposite to each other. The whorled type is seen in plants like Alstonia, where more than two leaves arise at a node and form a whorl.
Q5. Define the following terms:
a. Aestivation
b. Placentation
c. Actinomorphic
d. Zygomorphic
e. Superior ovary
f. Perigynous flower
g. Epipetalous stamen
Answer:
a. The mode of arrangement of petals or sepals in floral bud with respect to the other members of the same whorl is known as aestivation.
b. The arrangement of ovules within the ovary is known as placentation.
c. When a flower can be divided into two equal radial halves in any radial plane passing through the centre, it is known as actinomorphic.
d. When a flower can be divided into two similar halves only in one particular vertical plane, it is said as zygomorphic.
e. When the ovary occupies the highest position while the other floral parts are situated below it. The ovary in such flower is known as superior.
f. When the ovary is situated in the centre and the other parts of the flower are located on the rim of the thalamus almost at the same level, such flower is known as perigynous.
g. When the stamens are attached to the petals, they are known as epipetalous.
Q6. Differentiate between
a. Racemose and cymose inflorescence
b. Fibrous root and adventitious root
c. Apocarpous and syncarpous ovary
Answer:
a. In racemous inflorescence the main axis continues to grow, the flowers are borne laterally in an acropetal succession whereas in cymose inflorescence, the main axis terminates in a flower and limited in growth, the flowers are borne in a basipetal order.
b. Fibrous root are seen in monocotyledonous plants where primary root is short lived and replaced by a large number of roots which are said as fibrous root and it originated from the base of the stem whereas adventitious roots are seen in plants like grass, banyan tree where these roots arise from parts of the plant other than the radical.
c. In apocarpus ovary, the carpels are free whereas in syncarpous ovary, the carpels are fused.
Q7. Draw the labelled diagram of the following:
i. gram seed
ii. V.S. of maize seed.
Answer:
i.Gram seed
ii.V.S of maize seed
Q8. Describe modification of stem with suitable examples.
Answer:
In some plants like ginger and potato are the underground stems which are modified for food storage. They also act as organs of perennation to tide over conditions unfavourable for growth.
In some plants like pumpkin, cucumber, watermelon, stem tendrils are developed form axillary buds. They are slender and spirally coiled and help plants to climb.
In some plants like Citrus, Bougainvillea, the axillary buds are modified into woody, straight and pointed thorns. They protect plants from browsing animals.
In some plants like Opuntia and Euphorbia, modify their stem into flattened structure in Opuntia, and fleshy cylindrical structure in Euphorbia. They contain chlorophyll and carried out photosynthesis.
In some plants like strawberry, grass etc has underground stems which spread niches and when their older parts die new plants are formed.
Q9. Take one flower each of the families Fabaceae and Solanaceae and write its semi-technical description. Also draw their floral diagram after studying them.
Answer:
Fabaceae:
Vegetative characters: Shrubs, trees, herbs; root with root nodules; stem is erect or climber; leaves are alternate, pinnately compound or simple; leaf base, pulvinate; stipulate; venation reticulate.
Floral characters:
Inflorescence: racemose
Flower: bisexual, zygomorphic
Calyx: sepals five, gamosepalous; imbricate aestivation
Corolla: petals five with vexillary aestivation
Androecium: ten, diadelphous, anther dithecous
Gynoecium: ovary superior, mono carpellary, unilocular with many ovules, style single
Fruit: legume; seed: one to many, non-endospermic
Floral formula:
Economic importance: Peas are used as vegetables.
Floral diagram of Pisum sativum
Solanaceae:
Vegetative characters: herbs, shrubs and small trees
Stem: herbaceous rarely woody, aerial; erect, cylindrical, branched, solid or hollow, hairy or glabrous, underground stem in potato
Leaves: alternate, simple, rarely pinnately compound , exstipulate; venation reticulate
Floral characters:
Inflorescence: cymose
Flower: bisexual, actinomorphic
Calyx: sepals five, united, persistent, valvate aestivation
Corolla: petals five, united; valvate aestivation
Androecium: stamens five, epipetalous
Gynoecium: bicarpellary, syncarpous; ovary superior, bilocular
Fruits: capsule or berry
Seeds: many, endospermous
Floral formula:
Economic importance: used for medicinal purposes
Floral diagram of Solanum nigrum
Q10. Describe the various types of placentations found in flowering plants.
Answer: The arrangement of ovules within the ovary is known as placentation and they are different types:
• In marginal placentation, the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea.
• In axile placentation, the placenta is axial and the ovules are attached to it in a multilocular ovary, as in tomato, lemon, and china rose.
• In parietal placentation, the ovules formed on the inner wall of the ovary or on peripheral part.
• In free central placentation, the ovules are borne on central axis and septa are absent, as in Dianthus and Primrose.
• In basal placentation, the placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.
Q11. What is a flower? Describe the parts of a typical angiosperm flower.
Answer: Flower is form on a stem and thus it is a shoot. It is meant for sexual reproduction. So, it is known as modified shoot.
The parts of a typical angiosperm flower are:
• Calyx is the outermost whorl of the flower and the members are called sepals which are green leaf like and protect the flower in the bud stage.
• Corolla is made of petals which are usually brightly coloured to attract insects for pollination.
• Androecium is composed of stamens which represents the male reproductive organ consists of a stalk or a filament and an anther.
• Gynoecium is the female reproductive part of the flower and is made up of one or more carpels which consist of three parts stigma, ovary, and style.
Q12. How do the various leaf modifications help plants?
Answer: Leaves are generally modified to perform functions other than photosynthesis. They are converted to form tendrils for climbing as in peas or into spines for defence as in cacti. In some plant like onion and garlic, leaves are modified to store food.
Q13. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.
Answer: The arrangement of flowers on the floral axis is known as inflorescence. Inflorescence is of two types:
In racemous inflorescence the main axis continues to grow, the flowers are borne laterally in an acropetal succession whereas in cymose inflorescence, the main axis terminates in a flower and limited in growth, the flowers are borne in a basipetal order.
Q14. Write the floral formula of a 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: 
Q15. Describe the arrangement of floral members in relation to their insertion on thalamus.
Answer: The flowers are described as hypognous, perigynous, and epigynous based on the position of the calyx, corolla, and androceium.
In hypogynous flower, the ovary occupies the highest position while the other floral parts are situated below it. The ovary in such flower is known as superior.
In perigynous flower, the ovary is situated in the centre and the other parts of the flower are located on the rim of the thalamus almost at the same level.
In epigynous flower, the margin of thalamus grows upward enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. In here the ovary is said to be inferior.
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