Notes-Part-1-Class-11-Science-Biology-Chapter-9-Morphology of Flowering Plants-Maharashtra Board

Morphology of Flowering Plants

Maharashtra Board-Class-11-Science-Biology-Chapter-9


Topics to be Learn : Part-1

  • Angiosperms
  • Morphology
  • Root
  • Stem

Topics to be Learn : Part-2

  • Leaf
  • Inflorescence
  • Flower
  • Fruit
  • Study of Some Important Families

Angiosperms :

Angiosperms are one of flowering plants from phanerogams.

Angiosperms can be classified into following types on the basis of habitat.

  • Hydrophytes - Growing in aquatic habitat e.g. Hydrilla
  • Xerophytes - Growing in regions with scanty or no rainfall like desert e.g. Opuntia
  • Psammophytes - Growing in sandy soil e.g. Elymus ‘
  • Lithophytes - Growing on rock e.g. Paphiopedilum orchids rock felt fern
  • Halophytes - Growing in saline soil e.g. Mangrove plants like Rhizophora

Morphology :

Morphologically plant shows

  • Vegetative structures : root, stem, leaf
  • Reproductive structures : flowers, fruits and seeds.

(A) Root :

  • Root is descending axis of plant body
  • Root is positively geotropic and hydrotropic but negatively phototropic and aerotropic.
  • Root grows beneath the soil surface towards gravity.
  • Roots are generally non-green, cylindrical and without nodes and internodes.

Typical Root Structure :

Regions of root :

A typical root has different regions :-

Root cap: A parenchymatous multicellular structure in the form of cap, present over young growing root apex is known as root cap.

  • Cell of root cap secrete mucilage for lubricating passage of root through the soil.
  • Cells of root cap show presence of starch granules which help in graviperception and geotropic movement of root.
  • Usually single root cap is present in plants. But in plants like Pandanus or screw pine multiple root caps are present.
  • In hydrophytes, root caps are replaced by root pocket e.g. Pistia, Eichhornia etc.
  • Due to presence of root cap the growing apex of root is subterminal in position

Meristematic region or region of cell division: The apex of the root is a growing point about 1 mm in length protected by root cap. This region is called as region of cell division or meristematic region.

  • The structure is developed by compactly arranged thin walled actively dividing meristematic cells.
  • These cells bring about longitudinal growth of root.

Region of elongation :

  • This region of cells is present just above zone of cell division.
  • The cells are newly formed and show rapid elongation to bring about increase in length of the root.
  • The cells help in absorption of mineral salts.

Region of root hair or region of absorption:

  • A region of root hair / absorption / piliferous zone is made up of numerous hair like outgrowths.
  • The epiblema or piliferous layer produces tubular elongated unicellular structures known as root hair
  • They are in close contact with soil particles and increase surface area for absorption of water.
  • Root hair are short lived or ephimeral and are replaced after every 10 to 15 days.

Region of maturation/region of differentiation:

  • It is the uppermost major part of the root.
  • The cells of this region are quite impermeable to water due to thick wall. The cells show differentiation and form different types of tissues.
  • This region helps in fixation of plant and conduction of absorbed substances.
  • Development of lateral roots also takes place from this region.


Function of Root :

  • Primary functions of root are,
  • Fixation or anchorage of plant body in the soil,
  • Absorption of water and minerals from soil
  • Conduction of absorbed materials up to the stem base etc.

Types of Root :

On the basis of origin, roots can be classified as Tap roots or true roots and Adventitious roots.

(i) Tap root :

  • It arises from radicle of an embryo during seed germination
  • It is differentiated into primary, secondary and teritary roots
  • The main root is called as primary root. Its branches of first order are called as secondary roots Branches of second order are called as tertiary roots e.g. Pea, Bean, Sunflower etc.
  • The main root is very thick as compared to others.
  • Tap root system is commonly seen in dicotyledonous plants.

(ii) Adventitious root :

  • Adventitious root system is found in plants like maize, wheat and sugarcane.
  • Adventitious root develops from any part other than radicle.
  • Such roots may develop from the base of the stem, nodes or from leaves.-
  • In monocots, radicle is short lived.
  • A thick cluster of equal sized roots arise from the base of a stem. It is also known as fibrous root system as they look like fibre. The growth of roots is superficial.
  • Adventitious roots in some plants are used for vegetative propagation. E.g. Euphorbia, Carapichea ipecacuanha (Ipecac) etc.

Modification of root :

  • Metamorphosed roots : When roots have to perform some special type of function in addition to or instead of their normal function they develop some structural changes. Such roots are called as metamorphosed roots.

Modification of tap root :

(i) Modifications of tap root for food storage :

(i) Modifications of tap root for food storage :

  • When tap root stores food it becomes swollen fleshy and also develops definite shape.
  • Main or primary root is the main storage organ but sometimes hypocotyl part of embryo axis also joins the main root. Secondary roots remain thin.

On the basis of shape swollen tap roots are classified as Fusiform, Conical and Napiform.

  • Fusiform root: The fusiform root is swollen in the middle and tapering towards both ends forming spindle shaped structure e.g. Radish (Raphanus sativus)
  • Conical root: The conical root is broad at its morphological base and narrows down towards its apex. e.g. Carrot (Daucus carora)
  • Napiform root: In napiform root, base of root is highly swollen, almost spherical in shape and abruptly narrows down towards its apex. e. g. Beet (Beta vulgaris)


(ii) Modifications of tap root for respiration :

(ii) Modifications of tap root for respiration :

Halophytes plants grow in saline swamps, marshy places and salt lakes. The main root system of these plants do not get sufficient air for respiration as soil is water logged. Due to this, mineral absorption of plant also gets affected. To overcome this problem underground roots develop special roots.

  • Halophytes plants produce special kind of roots called as pneumatophores or breathing roots.
  • These special roots are negatively geotropic; growing vertically upward.
  • These roots are conical projections present around main trunk of plant.
  • The roots show presence of lenticels i.e. minute pores for gaseous exchange
  • e.g. Rhizophora, Avicennia, Sonneratia, Heritiera (ver. sundri) etc.


Modifications of Adventitious Roots :

(i) Modifications of adventitious root for food storage :

(i) Modifications of adventitious root for food storage :

Fibrous roots also show food storage like tap root but the main difference is that fibrous root usually do not develop definite shape.

These roots are further classified as Simple tuberous, Fasciculated tuberous, Beaded and Nodulose roots.

Simple tuberous root :

  • Simple tuberous roots become swollen and do not show definite shape.
  • They are produced singly.
  • The roots arise from nodes over the stem and penetrate into the soil.
  • e.g. sweet potato or shakarkand (lpomoea bataras).

Fasciculated tuberous roots :

  • A cluster of roots arising from one point which becomes thick and fleshy due to storage of food is known as fasciculated tuberous root.
  • These clusters are seen at the base of the stem.
  • e.g. Dahlia, Asparagus, etc.

Moniliform roots :

  • Some adventitious roots get swollen at regular intervals.
  • These gives them the appearance of beads of a necklace. Such roots are called as Moniliform roots.
  • e.g. Spinacia oleracea (Indian Spinach).

Nodulose roots :

  • The cluster of long slender roots become enlarged at the tips forming nodules is known as nodulose roots.
  • e. g. Arrow root (Maranta), Amhaldi or mango ginger (Curcuma amada).


(ii) Modifications of adventitious root for mechanical support :

Prop roots:

  • These roots arise from horizontal branches of tree like Banyan tree (Ficus benghalensis) and grow vertically downwards till they penetrate the soil.
  • These prop roots show secondary growth, become thick, act like pillars to provide mechanical support to the heavy branches.

Stilt roots:

  • These roots normally arise from a few lower nodes of a weak stem in some monocots, shrubs and small trees
  • They show obliquely downward growth penetrating soil and provide mechanical support to the plant.
  • In the members of family Poaceae, the plants like Maize, Jowar, Sugarcane etc. produce stilt root in whorl around the node.
  • These roots provide additional support to the plant body.
  • In Screw pine or Pandanus (Kewada), stilt roots arise only from the lower surface of obliquely growing stem for additional support. These roots show multiple root caps.

Climbing roots:

  • Different climbers with weak stem produce roots at their nodes by means of which they attach themselves to support and thereby raise themselves above the ground.
  • e.g. Betel leaf or Pan, black pepper or Piper nigrum (Kali Mirch), Pothos or money plant.

Clinging roots:

  • These tiny roots develop along intemodes, show disc at tips, which exude sticky substance.
  • This substance enables plant to get attached with walls of buildings.
  • They do not damage substratum.
  • e.g. English Ivy (Hedera helix). -

Plank roots/Buttress:

  • These roots often develop at the base of large trees and form plank like extensions around stem.
  • These roots provide additional support.
  • e.g. Silk cotton, Peepal, etc.

Buoyant roots:

  • Roots developed at the nodes of aquatic herbs like (Jussiaea repens), become highly inflated and Spongy providing buoyancy and helping the plant to float.

(iv) Modifications of adventitious root for special function :

(iv) Modifications of adventitious root for special function :

Epiphytic roots :

  • Small epiphytic plants produce specialized root to hang in the air.
  • Epiphytic plants growing on the branches of huge trees in dense rain forests.
  • The roots are provided with a spongy membranous absorbent covering of the velamen tissue.
  • The cells of velamen absorb moisture from air. Velamen tissue is hygroscopic and have porous walls
  • The roots may be silvery white or green but without root cap
  • e.g. Vanda, Dendrobium etc.

Sucking roots or Haustoria :

  • These are the specialised microscopic sucking roots developed by parasitic plants to absorb nourishment from the host.
  • Viscum album is a partial parasite. It develops haustoria which penetrate into xylem of host plant for absorption of food.
  • In Cuscura reflexa or Dodder (Amawel) haustoria penetrates vascular strand and suck food from phloem, water and minerals from xylem.
  • Cuscura is leafless plant with yellow stem. It is a total parasite.


Stem :

The primary functions of the stem are to produce and support branches, leaves, flowers and fruits; conduction of water and minerals and transportation of food to plant parts.

Characteristics of stem :

Characteristics of stem:

  • Stem is the ascending part of the plant body which develops from plumule and reproductive units.
  • It is usually positively phototrophic, negatively geotropic and negatively hydrotropic.
  • It shows different types of buds (axillary, apical, accessory, etc.).
  • It is differentiated into nodes and internodes. -
  • At nodes it produces dissimilar organs such as leaves and flowers and similar organs such as branches
  • Young stem is green and capable of photosynthesis.


Modifications of stem :

Stem develops some modifications for additional or accessory functions. To perform such function stem shows different modifications :

Underground stem :

In some herbaceous plants the stem which develops below soil surface is called underground stem.

  • The underground stem remains dormant during unfavourable condition and on the advent of favourable condition produces aerial shoots.
  • Underground stems are modified to perform different functions like storage of food, perennation and vegetative propagation. However, they differ from root in having nodes and internodes.

Rhizome :

Rhizome :

  • Rhizome is a modification of underground stem for storage of food.
  • It is prostrate, dorsiventrally thickened and brownish in colour.
  • It grows either horizontally or obliquely beneath the soil
  • Rhizome shows nodes and internodes. It bears terminal and axillary buds at nodes.
  • Terminal bud under favourable conditions produces aerial shoot which degenerates at the end of favourable condition.
  • Growth of rhizome takes place with lateral buds, such growth is known as sympodial growth. e.g. Ginger (Zingiber officinale), Turmeric (Curcuma domesrica), Canna etc.
  • In plants where rhizomes grow obliquely, temiinal bud brings about growth of rhizomes. This is known as monopodial growth. e.g. Nymphea, Nelumbo (Lotus), Preris (Fem) etc.
  • Rhizomes perform functions like storage of food, vegetative propagation and perennation.


Stem Tuber :

  • Potato is a stem tuber.
  • It is an underground stem, modified for storage of food material.
  • Special underground branches of stem at their tips becomes swollen due to storage of food which is mostly starch.
  • Stem tuber shows distinct nodes, but not internodes hence it is classified as stem. '
  • At nodal part, it shows scale leaves with axillary buds, which are commonly called as ‘eyes’.
  • Under favourable conditions, ‘eyes’ can produce aerial shoots.
  • Potato tuber can be propagated vegetatively.

[Note: In stem tuber, internodes are present but they are not very distinct]

Bulb :

Bulb :

  • Bulb is an underground spherical or pyriform stem.
  • Stem is highly reduced and discoid.
  • The reduced stem produces adventitious roots at its base.

The bulb is of different types

  • Tunicated or layered bulb : It is made up of fleshy leaves arranged in concentric manner with outer dry scale leaf. e.g. Onion.
  • Scaly or compound tunicated bulb : These store food material. In garlic the bulb is scaly or compound tunicated. The fleshy scales (cloves) are arranged in overlapping pattern.


Corm :

Corm :

  • Corm is swollen underground spherical or subspherical vertically growing stem.
  • It is condensed structure with circular or ring like nodes.
  • It shows presence of axillary buds and scales.

  • In Colocasia and Amorphophallus corm is present, which is an underground stem modified for storage of food.
  • Adventitious buds are produced which help in vegetative propagation.
  • Adventitious roots are produced at lower part of the stem.


Sub aerial stems:

  • These are generally weak or straggling stems growing over the ground and need support for perpetuation.
  • Sometimes these stems are found to grow beneath the soil surface also. Thus, they show contact with both air and soil.
  • Sub aerial stems are meant for perennation and vegetative propagation.
  • Scale leaves and axillary buds are present over stem surface. Axillary buds develop into aerial shoots.

Types of sub aerial stems :

Types of sub aerial stems:

(i) Trailer:

  • The shoot spreads over the ground without striking adventitious roots.
  • The branches are either flat i.e. procumbent or partly vertical i.e. decumbent.
  • E.g. Euphorbia, Tridax etc.

(ii) Runner:

  • They are special narrow, prostrate or horizontal green branches which develop at the base of erect shoots known as crown.
  • Runners spread in all directions to produce new crowns with bunch of adventitious roots.
  • Presence of nodes with scale leaves and axillary buds is observed.
  • E.g. Cynodon (Lawn grass) Centella (Hydrocotyl / Brahmi), Oxalis etc.

(iii) Stolons :

  • The slender lateral branch arising from the base of main axis is known as stolon.
  • In some plants it is above ground (wild strawberry).
  • Primarily stolon shows upward growth in the form of ordinary branch, but when it bends and touches the ground terminal bud grows into new shoot and develops adventitious roots.
  • E.g. Wild Strawberry, Jasmine, Mentha, etc.

(iv) Sucker:

  • It is non-green, runner like branch of stem.
  • It grows horizontally below soil initially and then comes above the soil surface obliquely to produce a new plant.
  • Sucker can be tenned as underground runner.
  • E.g. Chrysanthemum, Banana etc.

(v) Offset:

  • These are one internode long runners in rosette plants at ground or water level.
  • Offset helps in vegetative propagation. -
  • E.g. Water hyacinth or Jal kumbhi (Eichhornia) and Pistia.


Aerial modification :

Stem or it's vegetative part modify to carry out specialized functions. Such modified stems are called as metamorphosed stems.

The different modifications as given below:


  • It is modification of apical or axillary bud.
  • Thom is hard pointed and mostly straight structure (except Bougainvillea where it is curved and useful for climbing).
  • It provides protection against browsing animals and also helps in reducing transpiration.
  • Apical bud develops into thorn in Carrisa whereas axillary bud develops into thorn in Duranta, Citrus, Bougainvillea, etc.


  • Modification of stem into leaf like photosynthetic organ is known as phylloclade.
  • Being stem it possesses nodes and internodes.
  • It is thick, fleshy and succulent, contains mucilage for retaining water e.g. Opuntia, Casuarina (‘Cylindrical shaped phylloclade) and Muehlenbeckia (ribbon like phylloclade).

Cladodes :


  • The branches of limited growth i.e. one intemode long and performing photosynthetic function are called as cladodes.
  • True leaves are reduced to spine or scales to reduce rate of transpiration. e.g. Asparagus.


Cladophylls :

  • These are leaf like structures bore in the axil of scale leaf.
  • It has floral bud and scale leaf in the middle i.e. upper half is leaf and lower half is stem.
  • It helps in photosynthesis e.g. Ruscus.


  • In plants like Agave, Dioscorea, etc. axillary bud becomes fleshy and rounded due to storage of food called as bulbil.
  • When it falls off it produces new plant and help in vegetative propagation.

Stem tendrils :

Stem tendrils:

  • Tendrils are thin, wiry, photosynthetic, leafless coiled structures.
  • They give additional support to developing plant.
  • Tendrils have adhesive glands for fixation.
  • Apical bud in Vitis quadrangularis gets modified into tendril. The further growth is carried out by axillary bud.
  • In Passiflora axillary bud gets modified in tendril.
  • Extra axillary bud is the one which grows outside the axil. This bud in cucurbita gets modified into tendril.
  • Normally floral buds are destined to produced flowers. But in plants like Antigonon they produce tendrils.


Q. Why the stem has to perform photosynthesis in xerophytes?

Answer :

  • Xerophytes are the plants which grow in regions with scanty or no rainfall like desert.
  • In Xerophytes, leaves get modified into spines or get reduced in size to check the loss of water due to transpiration
  • As the leaves are modified into spines, the stem becomes green in colour to do the function of photosynthesis.


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