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Morphology of Flowering Plant

NCERT Textual Exercise (Solved)

1. What is meant by modification of root ? What type of modification of root is found in the:

(a) Banyan tree (b) Turnip (c) Mangroove trees. Ans. When roots are modified to carry out some additional functions, they represent

modification of roots. (a) In banyan trees adventitious roots are modified into hanging,

supporting roots for giant Banyan tree. These are known as modification of roots.

(b) Tap roots of turnip get swollened and modified for storage of food. Such roots are called napiform roots.

(c) In mangrove, tree roots come out from ground and grow vertically. Such roots are called pneumatophores or respiratory roots. They help to get oxygen for respiration.

2. 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. Ans. (i) Underground parts of a plant are not always roots as some perennial

herbs develop their stems underground for the purpose of perennation during unfavourable conditions. The stem produces aerial branches every year when conditions become favourable. The underground stems act as storage organs and also help in vegetative propagation by means of their buds. These stems are non-green and leafless like roots but differ from them on the basis of

(a) presence of nodes and internodes, scale-leaves, and axillary and terminals buds

(b) absence of root hair and root cap. (ii) Flower is a highly modified and condensed shoot meant essentially

for the sexual reproduction of the plant. Flower as a modified shoot can be explained with the structure of thalamus or receptacle.. Thalamus represents three internodes and four nodes. The elongated internode between the calyx and corolla is termed anthophore between corolla and androecium is known as androphore or gonophore and between androecium and gynoecium is known as gynophore. The flower usually develops as a branch from a bud, growing in the axil of a small leaf- like structure known as bract.

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3. How is a pinnately compound leaf different from a palmately compound leaf?

Ans. In pinnately compound leaf, a number of leaflets are present on rachis (e.g., neem) whereas in palmately compound leaf, leaflets are attached at a common point i.e., at the tip of petiole e.g., silk cotton.

4. Explain with suitable examples the different types of phyllotaxy. Ans. Phyllotaxy is the pattern of arrangement, of leaves on the stem or branch.

This is usually of three types : (i) Alternate: In this arrangement a single leaf arises on each node in

alternate manner e.g., in China rose. (ii) Opposite: A pair of leaves arises on node in the manner that these

seems to be arranged in a whorl, e.g., Alitonia. 5. Define the following terms: (a) Aestivation (b) Placentation (c) Actinomorphic (d) Zygomorphic (e) Superior ovary (f) Perigynous flower (g) Epipetalous stamen. Ans. (a) Aestivation: It is the arrangement of sepals/petals in relation to one

another in a floral bud. (b) Placentation: The manner of arrangement of placentae inside the

cavity of the ovary is called placentation. (c) Actinomorphic: A flower that can be vertically divided in two equal

halves by any vertical division passing through a centre. Such flowers are radially symmetrical.

(d) Zygomorphic: A flower that can be vertically divided in two equal halves in one plane only. Such flowers are bilaterally symmetrical.

(e) Superior ovary: When the flower is hypogynous e.g., Cruciferae. (f) Perigynous: When the sepals, petals and stamens appear to be arising

from middle of the ovary, the flower is described as perigynous. In these flowers, the ovary is semi-inferior, e.g., Saxifraga.

(g) Epipetalous stamen: Stamen are attached with petals. 6. Differentiate between (a) Racemose and cymose inflorescence (b) Fibrous root and adventitious root (c) Apocarpous and syncarpous ovary

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Ans.

Racemose Inflorescence Cymose InflorescenceThe main axis of racemose inflorescence has indefinite growth because there is no terminal flower.The flowers are borne laterally in acropetal succession, i.e., oldest flowers are borne at the base and younger ones are borne near the tip. The order of opening of flowers is centripetal.

The growth of the main axis is definite because the growing point of peduncle is used up in the formation of a flower.The flowers are borne in a basipetal succession i.e. the oldest flower is borne at the top and the younger ones are lateral. The order of opening of the flowers is basipetal or centrifugal.

Fibrous root Adventitious rootThese roots arise due to repeated branching of radicle.They appear from base of stem.e.g., wheat plant

These roots do not arise from radicle.They may appear from parts like stem or leaves.e.g., grass, banyan

Apocarpous ovary Syncarpous ovaryThere are two or more carpels in the gynoecium which are free from each other.

There are two or more carpels in the gynoecium which are fused to form a single compound ovary.

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

Ans. (i)

(ii)

8. Describe modifications of stem with suitable examples. Ans. Refet to studymate book for the answer

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9. 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. Fabaceae: This family was earlier called papilonoidal, a subfamily of family Leguminosal. It is distributed all over the world. Example: Semitechnical description of Pisum sativum.

Habit: An annual herb. Root: Nodulated tap root. Stem: Climber, leaflet tendrils Leaves: Alternate, pinnately compound or simple; leaf base, pulvinate,

stipulate, venation reticulate. Inflorescence: Racemose Flower: Bisexual, zygomorphic, complete, irregular, hypogynous Calyx: Sepal 5, gamosapalous, valvate acitivation. Corolla: Petals 5, polypetalous, rapilionaceous consisting of a posterior

standard, two lateral wings, two anterior ones forming a keel. Thus, flower becomes zygomorphic, descending imbricate aestivation.

Androcium: Stamen 10, diadelphous [1 + (9)], anther dithecous, introrse. Gynoecium: Ovary superior, mono carpillary, unilocular with many ovules,

marginal placentation. Fruit: Legume Floral formula: Solanaceae: It is large family, commonly called as the potato family.

It is widely distributed in tropics, subtropics and temperate zone, e.g. semitechnical description of datura metel.

Habit: Stout annual harb. Stem: Erect, cylindrical, hairy slightly fistular. Leaves: Alternate, simple, petiolate, ovate with acute apex. Venation

reticulate. Floral characters Inflorescence: Solitary, axillary Flower: Ebracteate, active morphic, hypogynous Calyx: Sepals 5, gamosepalous, persistent, valvate aestivation. Corolla: Petals 5, gamopetalous, valvate aestivation Androecium: Stamen 5, epipetalous

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Gynoecium: Bicarpellary, syncarpous, ovary superior, four-celled by formation of false septum in placenta swollen with many ovules.

Fruit: Spinous capsule with septifragal defiscence.

Floral formula: 10. Describe the various types of placentations found in flowering plant. Ans. The arrangement of ovules within the ovary is known as placentation, basal

central and free central. In marginal placentation, the placenta form a ridge along the ventral structure of the ovary and the ovules are borne on this ridge forming two rows, as in pea. When the placenta is on central axis and ovary is several chambered it is called axile. e.g., China rose, tomato, lemon. In parental placentation, the ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of false septum e.g., mustard. In free central type, the ovules are borne or central axis and septa are absent of primrose. In basal placentation, placenta develops at the base of ovary and single ovule attached to it, e.g., sunflower, marigold.

11. What is flower? Describe the parts of a typical angiosperm flower. Ans. Refer text. 12. How do the various leaf modifications help plants? Ans. Leaves are often modified to perform functions other than photosynthesis.

They are converted into tendrils for climbing as in peas or into spines for defence as in cacti. The fleshy leaves of onion and garlic store food. In some plants, such as Australian acacia, the leaves are small and short-lived. The petioles in these plants expand, become green and synthesise food. Leaves of certain insectivorous plants such as pitcher plant, venus-fly trap are also modified leaves.

13. Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.

Ans. The arrangement of flowers on the floral axis is termed as inflorescence. Depending on whether the apex gets converted into a flower or continues to grow, two major types of inflorescences are defined–racemose and cymose. In racemose type of inflorescence the main axis continues to grow, the flowers are borne laterally in an acropetal succession.

In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipetal order.

14. Write the floral formula of actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carpels

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with superior ovary and axile placentation. Floral formula : 15. Describe the arrangement of floral members in relation to their insertion on

thalamus. Calyx, corolla, androcium and gynoecium. Ans. Based on the position of calyx, corolla and androecium in respect of the

ovary on thalamus, the flowers are described as hypognous, perigynous and epigynous. In the hypogynous flower, the gynoecium occupies the highest position while the other parts are suited below it. The ovary in such flowers is said to be superior e.g. mustard, China rose etc. If gynoecium is situated in the centre and other parts of the flower are located on the rim of thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior e.g. thalamus grows upwards enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber and the ray florets of sunflower.

b/9w øãç 9ø Ù ò€¦ · 10. describe the various types of placentations found in flowering...

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