CH-5 (MORPHOLOGY OF FLOWERING PLANTS) BIOLOGY CLASS -XI, CBSE NCERT EXAM NOTES

Chapter-5
Morphology of Flowering Plants

Table of Contents []

• Morphology
• External Morphology
• Internal Morphology
• Anatomy
• Histology
• Adaptation
• The Root
• Characteristics
• Regions of Roosts
  • Root Cap
  • Region of meristematic activity
  • Region of elongation
  • Region of Maturaction
  • Modifications of Root
  • The Stem
  • Function of Stem
• Modifications of Stem
• Function of Leaf
• Modifications of Leaves
• Types of Aestivation
  • Valvate
  • Twisted
  • Imbricate
  • Vexillary
• Types of Placentation
  • Marginal
  • Axile
  • Perietal
  • Free central
  • Basal
  • Placenta
  • The fruit

Points to Remember

1. Morphology : The study of various external features, forms and relative position of different organs of the organism is know as morphology. It may be further divided into internal and external morphology.

2. External Morphology : It deals with external forms like shape, size, colour, structure and relative position of different organs.

3. Internal Morphology : Further divided into anatomy and histology.

4. Anatomy : It deals with the study of internal structure exposed after dissection and opening of various parts of an organ.

5. Histology : The study of tissues, their composition and structure.

6. Adaptation : Any alteration in the structure or function of an organism or any of its part that results from natural selection and by which the organism becomoes better fitted to survive and multiply in its environment.

7. The Root : The root is underground part of the plant and develops from elongation of radicle of the embryo.

8. Characteristics : It is inside the soil, chlorophyll is absent, absence of nodes, internodes, leaves and buds; positive geotropic and hydrotropic and negative phototropic.

Main function 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 Roosts :

1. Root Cap : The root is covered at the apex by the thimble-like structure which protect the tender apical part.


2. Region of meristematic activity : Cells of this region have the capability to divide; cells are small, thin walled with dense protoplasm.


3. Region of elongation : Cells of this region are elongated and enlarged. This region is responsible for the growth of root in length.


4. Region of Maturaction : This region has differentiated and matured cells. Some epideremal cells form very fine and delicate thread like structures called root hairs.


5. Modifications of Root : Roots are modified for support, storage of food, respiration.


• For support : Prop roots in banyan tree, stilt roots in maize and sugarcane.
• For respiration : Pneumatophores in Rhizophora (Mangrove).
• For storage of food : Fusiform (radish), Napiform (turnip), Conical (carrot), Fasisculated fleshy roots (Asparagus).


6. The Stem : Stem is the aerial part of the plant and develops from plumule of the embryo. It bears nodes and internodes.


7. Function of Stem : Exposure of leaves, Conduction of water and minerals, translocation of food, exposure of flowers and fruits.

Modifications of Stem :

In some plants the stems are modified to perform the function of storage of food, support, protection and vegetative propagation.

• Food food storage : Rhizome (ginger, turmeric), Tuber (potato), Bulb (onion), Corm (Colocasia, Amorphohallus/ Zamin-kand)
• For Support : Stem tenderils of watermelon, grapevine, cucumber, pumpkins, into pointed thorns. They protect the plants from animals.
• For vegetative propagation : Underground stems of grass (runner), strawberry (stolons), lateral branches of mint and jasmine, Eichhorina (offsets).
• For assimilation of food : Flattened stem of Opuntia and cylinderical stem of Euphorbia contains chlorophyll and performs photosynthesis.

The Leaf : Develops from shoot apcial meristem, flattened, green structure acropetally arranged manufacture the food by photosynthesis. It has bud in axil. A typical leaf base, petiole and lamina (leaf blade). In some leguminous plants the leaf base may become swollen which is called as pulvinus.

Venation : The arrangement of veins and veinlets in the lamina of leaf.
Types of Venation :
1. Reticulate : Veinlets form a network as in leaves of dicotyledonous plants (China rose, peepal).
2. Parallel : Veins are parallel to each other as in leaves of monocotyledonous plants (grass, maize, sugarcane).

Function of Leaf :
Photosynthesis, gaseous exhange, transpiration, protection of buds and conduction.

Modifications of Leaves :

Inflorescene : The arrangement of flowers on the floral axia (Peduncle)

Main types of Inflorescene

Special Inflorescene type -- Ficus, Salvia, Euphorbia, Sunflower

Flower -- Modified shoot meant for reproductionn

Bract -- Reduced leaf base found at the base of peficel. Flowers with bracts are called bracteale and without bracts are called ebracteate.

Perianth : If calyx and corolla are not distinguishable, they are called perianth.  "Example : Lily"

Aestivation : The mode of arrangement of sepals or petals infloral bud.

Types of Aestivation :

1. Valvate : Sepals or petals just touch one another at the margin, withut 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 overlap the two lateral petals which in turn overlap two smallest anterior of ovules within the ovary.

Types of Placentation :

1. Marginal : Placenta forms a ridge along the ventral suture of ovary, e.g., Pea.

2. Axile : Margins of carpels fuse to form central axis, e.g., China rose, Tomato, Lemon

3. Perietal : Ovules develop on inner wall of ovary, e.g., Mustard, Argemone

4. Free central : Ovules borne on central axis, lacking septa, e.g., Dianthus, Primrose

5. Basal : Placenta develop at the base of ovary e.g., Sunflower, Marigold

6. Placenta : Parenchymatou flattened cushion inside ovary where ovules are borne.

7. The fruit : After fertilisation, the mature ovary develop into fruit. The parthenocarpic fruits are formed from ovary without fertilisation (seedless fruit-Banana)

Monocotyledonous seed : Endosperm bulky and stores food, covered by proteinaceous Aleurone layer. Seed has single large cotyledon-scutellum.


Plumule is enclosed in Coleoptile and Radicle is enclosed in Coleorrhiza.


Dicotyledonous Seed -

Hilum Is a scar on the seed coat through which seeds attached to the fruit.

Microphlye Small pore, above hilum.

Cotyledons Two; Fleshy full of preserve food materials.

Embryonal axis Radicle and plumule.

Endospermous seed Endosperm present in mature seed e.g. Castor

Non-endospermous seed Endosperm not present in mature seeds, e.g., Bean.