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

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    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

    Ans. The main function of roots in plants is water and mineral absorption. Apart from this main function, roots of some plants are modified to perform various other functions such as storage, nitrogen fixation, aeration and support, etc.
    These are called root modifications.

    The roots are modified 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. These roots are modified to store food.

    (c) Mangrove tree: These trees grow in water logged soil, so oxygen is not easily available to their roots. Therefore their roots are modified to absorb oxygen by growing vertically upwards from the soil. This is the reason these roots are also called breathing roots or pneumatophores.

    2. Justify the following statements on the basis of external features:

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

    (b) Flower is a modified shoot.

    Ans. (a) Underground parts of a plant are not always roots: In some plants, stems remain underground to carry out some additional functions, like food storage and vegetative propagation. For example, Potatoes are modified form of underground stem. Stems of ginger remain underground for vegetative reproduction and food storage.

    (b) A flower is a modified shoot: Flower comes out of stem hence it is a shoot. It serves the special purpose of sexual reproduction. Hence, flower is called a modified shoot.

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

    Ans. In case of pinnately compound leaves, the leaflets are present on a common axis while in palmately compound leaves, the leaflets originate from the apex of the midrib.

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

    Ans. The arrangement of leaves on the stem or branch is called phyllotaxy. There are three types of phyllotaxy, which are as follows:

    Alternate: In this type of leaf arrangement, a single leaf arises at each node in alternate manner. For example, China rose, mustard,
    sunflower, etc.

    Opposite: In this type of leaf arrangement, a pair of leaves arise at each node. The leaves lie opposite to each other in this case. For example,
    Calotropis, guava, etc.

    Whorled: In this type of leaf arrangement, more than two leaves arise at a node. For example, Alstonia.

    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: The mode of arrangement of
    sepals or petals in floral buds with respect to the other members of the same whorl is
    called aestivation.

    (b) Placentation: The arrangement of ovules in
    the ovary is called placentation.

    (c) Actinomorphic: When a flower shows radial
    symmetry, it is called an actinomorphic flower, e.g., mustard, chilli, etc.

    (d) Zygomorphic: When a flower shows bilateral symmetry, it is called a zygomorphic flower, e.g., pea, gulmohar, bean, etc.

    (e) Superior Ovary or Hypogynous Flower: When the ovary occupies the highest position and other floral parts are below it, the flower is called hypogynous. In this case, the ovary is said to be superior, e.g., mustard, China rose, brinjal, etc.

    (f) Perigynous Flower: When the ovary and other parts of the flower are situated at the same level, the flower is called perigynous. In this case, the ovary is said to be half-inferior, e.g., rose, peach, etc.

    (g) Epipetalous Stamens: When stamens are attached to the petals, this arrangement is called epipetalous, e.g., brinjal.

    6. Differentiate between:

    (a) Racemose and cymose inflorescence

    (b) Fibrous root and adventitious root

    (c) Apocarpous and syncarpous ovary

    Ans. (a) Differences between racemose and cymose inflorescence:

    Racemose Inflorescence Cymose Inflorescence
    It is indefinite type of inflorescence in which flowers are arranged acropetally. It means the arrangement has younger flowers at the centre and older flowers at the base.
    Examples: pea, wheat, etc.
    It is definite inflorescence. In this arrangement, younger flowers are at the base and the older flowers are at the centre.
    Examples: petunia, chilli, etc.

    (b) Differences between fibrous root and adventitious root:

    Fibrous root Adventitious root
    These roots arise from the base of the stem.
    Examples: wheat, rice, etc.
    These roots arise from the parts of plant other than radicle.
    Examples: grasses, banyan trees, etc.

    (c) Differences between apocarpous ovary and syncarpous ovary:

    Apocarpous Ovary Syncarpous Ovary
    In this ovary, more than one carpel is present in the flower, but these carpels are distinct.
    Examples: lotus, rose, etc.
    In this ovary, more than one carpel is present in the flower, but these carpels are fused.
    Examples: mustard, tomato, etc.

    7. Draw the labelled diagram of the following:

    (a) Gram seed

    (b) V.S. of maize seed

    Ans. (a) Gram seed

    Morphology of Flowering Plantsans7

    8. Describe modifications of stem with suitable examples.

    Ans. Stems are modified into different types for the following functions:

    (a) Food storage: The underground stems of potato, ginger, turmeric, zamikand, Colocasia, etc., are modified for food storage. Such modifications are the tools of perenation to tide over unfavourable conditions.

    (b) Photosynthesis: In some plants of dry regions, the stems are modified into flattened or fleshy cylindrical structures. The flattened structure can be seen in Opuntia and the cylindrical structure can be seen in Euphorbia. Such structures contain chlorophyll and photosynthesis can take place in them.

    (c) Climbing: In some plants, stem tendrils develop from axillary buds. These are slender and spirally coiled structures. A tendril helps the plant to climb to a support, e.g., cucumber, pumpkin, grapevine, etc.

    (d) Defence: In some plants, the axillary buds are modified into woody, straight and pointed thorns. Such thorns protect the plant from browsing animals, e.g., Citrus, Bougainvillea.

    (e) Vegetative propagation: Stems are modified for vegetative propagation in many plants, e.g., grass, berry, dahlia, etc.

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

    Ans. Characters of family Fabaceae and family Solanaceae:

    Characters of Family Fabaceae:
    (a) They are trees, shrubs, and herbs with nodules on their roots.

    (b) Erect or climber stems.

    (c) Leaves are alternating, pinnately compound or simple, and pulvinate at the base; venation is reticulate.

    Morphology of Flowering Plantsans9

    Floral characters:

    Inflorescence: Racemose

    Flower: Bisexual, zygomorphic

    Calyx: Sepals five, gamosepalous; valvate/imbricate aestivation

    Corolla: Petals five, polypetalous, papilionace-ous, consisting of a posterior standard, two lateral wings, two anterior ones forming a keel (enclosing stamens and pistil), vexillary aestivation.

    Androecium: Stamens ten in number, diadelphous, anther dithecous.

    Gynoecium: Ovary superior, monocarpellary, unilocular with many ovules, style short.

    Fruit: Legume; seed: one to many, non-endospermic.

    Economic importance:
    Plants of these families are pulses used as fodder and sweet pea.
    Ex: Peas, trifolium.

    Floral formula:

    Characters of Family Solanaceae:

    (a) The Solanaceae family, also known as the potato family, consists primarily of herbs, shrubs, and small trees.

    (b) Stems are herbaceous, rarely woody and aerial; they are erect, cylindrical, branching, solid or hollow, hairy or glabrous, and underground in potatoes.

    (c) Leaves are exstipulate with reticulate venation, alternating, simple, rarely pinnately compound.

    Morphology of Flowering Plantsans9(ii)

    Floral Characters:

    Inflorescence: Solitary, axillary or cymose as in Solanum.

    Flower: Bisexual, actinomorphic.

    Calyx: Sepals five, united, persistent, valvate aestivation.
    Corolla: Petals five, united; valvate aestivation.

    Androecium: Stamens five, epipetalous.

    Gynoecium: Bicarpellary obligately placed, syncarpous; ovary superior, bilocular, placenta is swollen with many ovules, axile.

    Fruits: Berry or capsule.
    Seeds: Numerous, endospermous.
    Economic importance:
    Plants belonging to this family are used as food, spices, medicines and ornamentals plants.

    Floral diagram:

    Ex: Brinjal, chilli, ashwagandha, petunia.

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

    Ans. Placentation of flowering plants is the distribution of ovule-bearing cushions or placentae inside the ovary. It is of the following types:

    (a) Marginal: A monocarpellary unilocular ovary bears ovules longitudinally along the ventral suture in one or two alternate rows.
    For example, Pea.

    (b) Parietal: A syncarpous, unilocular ovary bears two or more placentae longitudinally along the wall. For example, Viola. A false septum or replum occurs between two parietal placentae in Mustard. It makes the ovary falsely bilocular. In cucurbits, the three parietal placentae grow inwardly, meet in the centre and bend outwardly. The ovary becomes trilocular. In Poppy and Prickly Poppy, the ovule-bearing parietal placentae grow inwardly to form incomplete septa.

    (c) Axile: A syncarpous bilocular to multilocular ovary bears ovules on the central axile column where the septa meet. For example, Petunia.

    (d) Free Central: Polycarpellary syncarpous but unilocular, ovary bears ovules around a central column which is not connected to ovary wall. For example, Primrose.

    (e) Basal: Unilocular ovary bears a single ovule from the basal region. For example, Sunflower.

    (f) Apical: Unilocular ovary bears a single ovule from the apical region. For example, Cannabis.

    (g) Superficial: Ovules are borne along the inner surface of ovary including the septa if present. For example, Nymphaea (multilocular).

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

    Ans. Flower is the reproductive part of angiospermic plants for sexual means of reproduction. A typical flower has four whorls arranged on a swollen end of stalk or pedicel called thalamus. They are Calyx, Corolla, Androecium and Gynoecium.

    (a) Calyx: It is the outermost whorl of a flower. It is made up of units called sepals. It is generally green in colour and protective in function.

    (b) Corolla: It is the whorl present inner to the calyx. It consists of petals. The petals are brightly coloured to attract the insects.

    (c) Androecium: It is the whorl present next to the corolla. The androecium mainly consists of stamens which are the male reproductive units 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 filament. Inside the anther, pollen grains are formed.

    (d) 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.

    Morphology of Flowering Plantsans11

    12. How do the various leaf modifications help plants?

    Ans. 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 as 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.

    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. A flower is a modified shoot wherein internodes do not elongate and the axis gets condensed. The apex produces different kinds of floral appendages laterally at successive nodes instead of leaves. When a shoot tip transforms into a flower, it is always solitary. Depending on whether the apex gets converted into a flower or continues to grow. There are two major types of inflorescence—racemose inflorescence and cymose inflorescence.

    (a) In racemose type of inflorescence the main axis continues to grow, the flowers are borne laterally in acropetal succession.

    (b) 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 a actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and axile placentation.

    Ans. The floral formula of the described flower is represented as:

    (a) Actinomorphic flowers are represented by the symbol ⊕.

    (b) A bisexual flower is indicated by .

    (c) The calyx contains five united sepals which can be represented as K(5).

    (d) The corolla consists of five free petals and it represented as C5.

    (e) The androecium consists of five free stamens and is represented by A5.

    (f ) The gynoecium consists of a superior ovary with two united carpels and axile placentation, which can be represented as G(2). 

    15. 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 hypogynous, perigynous and epigynous.
    (a) Hypogynous: 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, e.g., China rose, mustard, etc.
    (b) Perigynous: 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, e.g., plum, rose, peach, etc.
    (c) Epigynous: 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, e.g., flowers of guava and cucumber, etc.

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