NCERT Solutions for Class 11 Biology Chapter 5

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Class:11
Subject:Biology
Chapter 5:Morphology of Flowering Plants

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Morphology of Flowering Plants: Solutions




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Important Terms on  Morphology of Flowering Plants

  • The Root: The root is underground part of the plant and develops from elongation of radicle of t he embryo.
Main functions of root system
  1. Absorption of water and minerals from the soil.
  2. Provides anchorage to plant parts.
  3. Stores reserve food material and synthesises plant growth regulators (cytokinins).



Regions of Roots
  • Root Cap: The root is covered at the apex by the thimble-like structure which protect the tender apical part.
  • Region of meristematic activity: Cells of this region have the capability to divide; cells are small, thin walled with dense protoplasm.
  • Region of elongation: Cell of this region are elongated and enlarged. This region is responsible for the growth of root in length.
  • Region of Maturation: This region has differnentiated and matured cells.
    Some epidermal cells form very fine and delicate thread like structures called root hairs.
  • Modifications of Root: Roots are modified for support, storage of food, respiration.




Modifications of Stem
  • In some plants the stems are modified to perform the function of storage of food, support, protection and vegetative propagation.
  • For food storage: Rhizome (ginger, turmeric), Tuber (potato), Bulb (onion), Corm (Colocasia, Amorphophallus/Zamin-kand)
  • For support: Stem tendrils of wawtermelon, grapevine, cucumber, pumpkins.
  • For protection: Axilliary buds of stem of Citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.
  • For vegetative propagation: Underground stems of grass (runner), strawberry (stolons), leateral branches of mint and jasmine, Eichhornia (offsets).
  • For assimilation of food: Flattened stem of Opuntia and cylindrical stem of Euphorbia contains chlorophyll and performs photosynthesis.



Types of aestivation
  1. Valvate: Sepals or petals just touch one another at the margin, without overlapping. e.g., Calotropis
  2. Twisted: Sepals or petals overlap the next sepal or petal e.g., China rose, Cotton, lady’s finger.
  3. Imbricate: The margins of sepals or petals overlap one another but not in any definite direction, e.g., Cassia, Gulmohar.
  4. Vexillary: The largest petal overlaps the two lateral petals which in turn overlap two smallest anterior petals, e.g., Bean, Pea.

What is meant by modification of root? What type of modification of root is found in the Banyan tree.

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 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.

Justify the following statements on the basis of external features Underground parts of a plant are not always roots.

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 storage of food. They are called rhizomes. Similarly, corm 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.

Explain with suitable examples the different types of phyllotaxy?

Phyllotaxy refers to the pattern or arrangement of leaves on the stem or branch of a plant. It is of three types, alternate, opposite, and whorled phyllotaxy.
In alternate phyllotaxy, a single leaf arises from the node of a branch. This type of phyllotaxy is observed in the sunflower, mustard, and peepal. Plants with opposite phyllotaxy have two leaves arising from the node in opposite directions. It is found in guava and jamun plants. Plants with whorled phyllotaxy have three or more leaves arising from the node. It is found in Alstonia.

Define the term Aestivation.

Aestivation:
The term ‘aestivation’ refers to the mode in which sepals or petals are arranged in a floral bud with respect to other floral members. There are four types of aestivation in plants i.e., valvate, twisted, imbricate, and vexillary.

Take one flower each of families Fabaceae and Solanaceae and write its semitechnical description.

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

How do the various leaf modifications help plants?

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.

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

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.

Describe the arrangement of floral members in relation to their insertion on thalamus?

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
e.g., 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 e.g., 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
e.g., flowers of guava and cucumber.