NCERT Solutions Class 11 Biology Chapter 5 Morphology of Flowering Plants

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

1. 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: The root performs two major functions in plant namely

a. Absorption of nutrient from the soil and its conduction to the aerial parts of plants, and
b. Provide mechanical support to plant by anchoring the plant tightly with soil.

But in some cases, depending on the environmental conditions and physiological needs of the plants, the root gets modified to perform other functions apart from the above two mentioned functions. This change in the root structure and function is known as root modification.

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.

Answer:

(i) Underground parts of a plant are not always roots.

During the course of evolution, plants modified their external morphologies according to the environmental condition of their ecological niches for better adaptability. There are several examples where the stem, which is generally the aerial part of plant, get modified in a way that they remain under the soil. Such stem modification can easily be recognized by the presence of node and internodes on them. The main reason for such modification is to protect the plant from unfavorable environmental condition. For example, the underground part of ginger, turmeric, jimikand, and Colocasia all have distinct node and internodes, thus they are stem modifications. Similarly in banana, pineapple and Chrysanthemum, the stem remains underground and grows beneath the soil. In case of onion and garlic, the leaves become fleshy, remain under ground and stores food. Thus from the above examples, it is clear that both stem and leaves in some cases have modified themselves and grow beneath the ground. Thus underground parts of plants are not always roots.

(ii) Flower is a modified shoot.

During flowering season, the apical shoot meristem gets transformed to flowering meristem. The close anatomical study of a flower reveals presence of node and internodes. The main axis gets highly condense as the internodes do not undergo further elongation. From the nodes, arise various floral appendages such as calyx, corolla, androecium and gynoecium. Thus is can be said that a flower is a modified shoot.

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

Answer:

4. Explain with suitable examples the different types of phyllotaxy.

Answer: The term phyllotaxy originated from Greek word where phyllon is “leaf" and “taxis” stands for arrangement. Thus number and order (pattern) of arrangement of leaves around the stem is called phyllotaxy.

Broadly, it is of three types:

 Alternate: When each node of the axis bears a single leaves it is called alternate phyllotaxy. Examples are china rose, mustard and sun flower plants.

 Opposite: When each node of the axis bears a pair of leaf facing in opposite direction, it is called opposite phyllotaxy. Examples are Calotropis and guava plants.

 Whorled: When more than two leaves arise from each node, it is called whorled phyllotaxy. Example is Alstonia.

5. Define the following terms:

(a) aestivation (b) placentation (c) actinomorphic (d) zygomorphic (e) superior ovary (f) perigynous flower(g) epipetalous stamen

Answer:

(a) Aestivation: The positional arrangement of sepals or petals in floral bud with respect to the other sepals or petals in same whorl within a flower bud is known as aestivation. The four different types of aestivation known are valvate, twisted, imbricate and vexillary.

(b) Placentation: The arrangement of ovules in wall of ovary is called placentation. Depending on the mode of arrangement, placentation is categorized into five different types, namely marginal, axile, parietal, basal and free central.

(c) Actinomorphic: The flowers that can be divided into equal halves in any of the radial plane passing through the center of the flower are called actinomorphic flower. They show radial symmetry. Examples: Flowers of datura, chilli and mustard.

(d) Zygomorphic: The flowers that of can be divided into two equal halves only in one particular vertical plane are called Zygomorphic flowers. Examples: Flowers of gulmohur, bean and Cassia.

(e) Superior ovary: The flower where gynoecium is present above calyx, corolla and androecium, the ovary occupies the upper part of the thalamus. Such an ovary is called superior ovary. Example: mustard, china rose and brinjal.

(f) Perigynous flower: When the ovary (gynoecium) is located at the center of the thalamus and the other floral appendages are located at the rim of thalamus at the level of ovary, such flower are called perigynous flower. Example plum, rose, peach.

(g) Epipetalous stamen: The stamen when connected with petals of the flower is known as epipetalous stamen. Example Brinjal.

6. Differentiate between

(a) Racemose and cymose inflorescence (b) Fibrous root and adventitious root (c) Apocarpous and syncarpous ovary

Answer:

(a) Racemose and cymose inflorescence

(b) Fibrous root and adventitious root

(c) Apocarpous and syncarpous ovary

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

Answer:

(i) Gram seed

Figure: Gram seed showing cotyledon (Ref: NCERT Biology, Textbook for Class XI, Chapter No. 5, Morphology of Flowering Plants, Page no. 77)

(ii) Vertical section (V.S.) of maize seeds

Figure: Vertical section of maize seeds. (Ref: NCERT Biology, Textbook for Class XI, Chapter No. 5, Morphology of Flowering Plants, Page no. 77)

8. Describe modifications of stem with suitable examples.

Answer: Stems are the aerial part of plant which originate from the plumule of the embryo and bear branches, leaves, flowers and fruits. The main functions of stem are as follows:

 Form an axis to support the lateral branches, flower and fruits.

 Conduction of water and nutrients through vascular tissue.

 Bear leaves.

Apart from above mentioned functions, stems sometimes get modified into structure and function to perform several other specialized functions such as those mentioned below:

(a) Storage: In case of potato, jimikand, Colocasia, ginger, and turmeric the stem gets modified into an underground structure to protect the plant from unfavorable conditions and also acts as a storage organ.

(b) Support: In some creepers, such as cucumber, pumpkin and watermelon, the stem gets modified into a slender, spirally coiled structure called tendrils which by getting coiled around the wall or rope help the plant in climbing up.

(c) Protection: In Bougainvillea and all Citrus plants, the axillary bud of stem gets modified to a straight and pointed woody structure called thorn, which protects the plants from being eaten up by herbivorous animals.

(d) Photosynthesis: In arid region, to prevent high water loss through transpiration, plants modify their stem into flattened or fleshy cylindrical structure. These structures also develop chlorophyll and perform photosynthesis. Examples are Opuntia and Euphorbia.

(e) Vegetative Propagation: In many cases, the underground stem when spread to new niches develops into new plants, like in grasses and strawberry. In mint and jasmine, lateral branches after growing for certain length, arch down to ground and form a new plant.In some aquatic plants like Pistia and Eichhornia, each node bears rosette of leaves and tuff of roots, when get detached from parent plant, give rise to new plant.

9. Take one flower each of the families Fabaceae and Solanaceae and write its Semi-technical descripti Also draw their floral diagram after studying them.

Answer:

10. Describe the various types of placentations found in flowering plants.

Answer: The arrangement of ovules in wall of ovary is called placentation. Depending on the mode of arrangement, placentation is of five types as described below:

(a) Marginal Placenta: This type of placenta is observed in flowers where gynoecium is monocarpellary, apocarpous and unilocular as in pea. At the ventral surface of the ovary a ridge is formed by the placenta and ovule are borne in the ridge.

(b) Axile placentation: This type of placenta is observed when gynoecium is multicarpellary, syncarpous and multilocular. Here the placenta is axial and ovules are attached to it in the multilocular ovary. Examples: china rose, tomato and lemon.

(c) Parietal placentation: This type of placenta is observed when gynoecium is multicarpellary, syncarpous and unilocular. Here ovules develop on the periphery of the ovary. Example: mustard and Argemone.

(d) Free central placentation: Here the gynoecium is multicarpellary, syncarpous and unilocular and the ovules are born on the central axis without any septa. Example: Dianthus and primrose.

(e) Basal placentation: Here the gynoecium is unilocular with single ovule arising from the base of ovary. Example: sunflower and marigold.

Figure: Types of placentation: (a) Marginal (b) Axile (c) Parietal (d) Free central and (e) Basal

(Ref: NCERT Biology, Textbook for Class XI, Chapter No. 5, Morphology of Flowering Plants, Page no. 75)

11. What is a flower? Describe the parts of a typical angiosperm flo

Answer: The reproductive unit of angiosperm plant, bearing male or female or both gametes, responsible for sexual reproduction is called flower. A flower is a modified stem with highly condensed axis.

Figure: Flower and its parts (Ref: NCERT Biology, Textbook for Class XI, Chapter No. 5, Morphology of Flowering Plants, Page no. 74)

A typical angiospermic flower consists of four whorls, namely calyx, corolla, androecium and gynoecium. When the flower contains all these four whorls, it is called complete flower.The complete flower is also a bisexual flower as both male and female gametes forming organs are present. The various parts of the flower are described below:

Calyx: It is the outermost whorl of the flower. It consists

of individual units called sepals. Generally sepals are green in color. Its main function is to protect the plants during bud stage from adverse environmental condition. If the sepals are free it is called polysepalous but sometimes sepals are fused giving rise to gamosepalous condition.

Corolla: Next to calyx is corolla, which consists of individual petals. Petals are beautifully colorful to attract insect to increase the chances of pollination. Androecium: The male gamete producing part of plant is called androecium. Its individual units are called stamens. Individual stamen consists of filament and anther.

Gynoecium: It is the female reproductive organ of plant. It consists of carpels. Each carpel is made up of three parts, ovary, style and stigma.

12. How do the various leaf modifications help plants?

Answer: Leaves are the photosynthetic sites of the plant, however in some cases, they get modified to provide support, protection, storage or nutrient to the plants.

(a) Support: In case of pea plant, the leaves get converted to spiral structure called tendrils that help the plant to climb on other plant or wall.

(b) Protection: In cactus and Australian Acacia, the leaves get reduced to spines to protect the plant from animals as well as to reduce water loss through stomata. (c) Storage: The fleshy underground leaves of garlic and onion help in storage of food and ensure survival of plant under unfavorable conditions.

(d) Nutrient: The carnivorous plants such as venus-fly trap, growing in nitrogen deficient soil, leaves get modified into pitcher to capture insect and thus provide required nutrient to plants.

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

Answer: The arrangement of flowers on the flower axis is called inflorescence.

During the flowering season of a fully developed plant, the apical meristem gives rise to floral meristem which in turn develops the floral axis. Floral axis contains laterally developed flowers.On the basis of type of growth of floral axis, inflorescence is of two types:

Cymose or determinate inflorescence: When the floral axis terminates with a flower bud, it is known as cymose inflorescence.

Racemose or Indeterminate inflorescence: When the floral axis keeps on growing without terminating as a flower bud, it is known as racemose inflorescence.

15. Describe the arrangement of floral members in relation to their insertion on thalam

Answer: The floral appendages are arranged on thalamus. On the basis of location of ovary in respect to that of other floral appendages (calyx, corolla and androecium) flower can be broadly classified into three categories

Hypogynous flower: In some plants like, mustard, China rose and brinjal, gynoecium occupies the highest position compare to calyx, corolla and androecium. Such flowers are called hypogynous flowers. Here the ovary is located at the uppermost part of thalamus. Such an ovary is called superior ovary.

Perigynous flower: Here the gynoecium is at the center of thalamus and other floral whorls are at the rim of the thalamus with ovary situated at the same level. Such flowers are called perigynous flowers. Example: rose.

Epigynous flower: Here the margin of thalamus completely covers the ovary and other floral whorl arises above ovary. Such flowers are called epigynous flowers. Example: Guava.

Figure 13 Position of floral parts on thalamus : (a) Hypogynous (b) and (c) Perigynous (d) Epigynous(Ref: NCERT Biology, Textbook for Class XI, Chapter No. 5, Morphology of Flowering Plants, Page no. 73)