ANATOMY OF DICOTYLEDONOUS AND MONOCOTYLEDONOUS PLANTS

Anatomy of Dicotyledonous plant and Monocotyledonous plant:-

·         For batter understanding, we study a transverse section of roots, stems and leaves at mature stage of plants.

For Roots:-

Dicotyledons

·         Epidermis- The outermost protective layer with root hairs.

·         Then Cortex- It consist of parenchymatous cells having thin wall. It is many layered with intracellular spaces.

·         Then Endoderm- It consists of barrel shaped endodermal cells of impermeable cell wall having waxy material called suberin. It is inner most layer of cortex which is single layered.

·         Then Pericycle- It consists of parenchymatous cells of thick cell wall. These cells are responsible for secondary growth.

·         Then Xylem and Phloem- It is present as 2-4 patches. In between xylem and phloem a parenchymatous cells are present called conjuctive tissue.

Monocotyledons

·         Its tissue arrangement is almost same as Epidermis, Cortex and pericycle except following as

·         Endodermis is thicker than dicot

·         Xylem and Phloem- It is more than 6 bundled.

·         Pith is large and well developed

·         It doesn’t take part in secondary growth.

For stem:-

Dicotyledons

·         Epidermis- It is outermost protective layer. It externally covered with cuticle having stomata.

·         Then Cortex- It divisible into three layers as-

1.       Hypodermis- It consists of collenchyma cells and provide mechanical strength to stem.

2.       Cortical layer- It consists of rounded parenchymatous cells having thin cell wall.

·         Then  Endodermis- It consists of endodermal cells having a lot of starch

·         Then Pericycle- It consist of sclerenchymatous cells as a semi-lunar patches.

·         Then Vascular Bundle- It consists of xylem and phloem. It is arranged in a ring which is characteristic feature of dicot stem.

·         Then Pith- It consist of parenchymatous cells with large intracellular spaces. It is the central position of the dicot stem.

Monocotyledons

·         It is different from dicot stem only its Epidermis is same as dicot.

·         Then Cortex only hypodermis- It is consists of sclerenchymatous cells

·         Then Ground Tissue- It consists of parenchymatous tissue and present in large quantity in circular area.

·         Then Vascular Bundles- It is present in the ground tissues and consists of xylem and phloem. It is rounded and larger at central portion than peripheral region.

For Leaf:-

Dicotyledons (Dorsiventral Leaf)

·         Lamina consists of three parts – Epidermis, Mesophyll, Vascular system.

·         Epidermis- It is outermost protective layer. It present at upper surface called adaxial epidermis and at lower surface called abaxial epidermis. Abaxial epidermis bears more stomata than adaxial epidermis.

·         Mesophyll- It is present between adaxial and abaxial epidermis. It consists of parenchymatous cells having chloroplast so take part in photosynthesis. There are many large spaces or air cavities are present between cells. Its cell is divisible into two types-

1.       Palisade Parenchyma- It is elongated cells, which arrange ventrally and parallel to each other.

2.       Spongy Parenchyma- It is oval or rounded cells, arranged loosely and below palisade parenchyma cell.

·         Vascular System- Is consists of vascular bundles seen in the veins and midrib. The vascular bundle surrounded by a layer of thick walled called Bundle Sheath cells and its size is depend on size of veins.

Monocotyledons (Isobilateral Leaf)

·         It is almost similar to dicot leaf, only a little differences is occurred as

·         In gases, some adaxial epidermis along with veins modified into large, empty, colourless cells called bulliform cell.

·         Mesophyll doesn’t differentiated.

TISSUE SYSTEM OF FLOWERING PLANT(ANATOMY)

The Tissue System:-

·         The tissue collectively form tissue system. Depending upon the location it has different structure and due to these it has different functions. It is of three types:-

1.      Epidermal tissue system

2.      Ground or Fundamental tissue system

3.      Vascular or Conducting tissue system

Epidermal tissue System:-

·         It is the outermost covering of plant. It is consist of epidermal cells, stomata and epidermal appendages-The trichomes and hairs.

Ø  Epidermal cells:- It is parenchymatous cell of cytoplasmic cell wall which  forms continuous, elongated outermost layer of epidermal tissue system. Exteriorly epidermis has a waxy thick layer of cuticle which functions to prevent water loosing. Cuticles are absent in root of plant.

Ø  Stomata:- It is present in epidermis of leaves which functions to regulate the process of transpiration and gaseous exchanges. It is consist of two bean shaped guard cells. Guard cell contains chloroplast and its outer wall is thin while inner wall is thickened. In  Gases the guard cell converted into dumbbell shaped. The main function of guard cell is to regulate the opening and closing of stomata.

Ø  Epidermal Appendages:-  It is hair like projection and are of following type –

1.      Root hair:- it is unicellular elongation of epidermal cells. It helps to absorb the water and minerals from soil.

2.      Trichomes:- It is multicellular branched or unbranched epidermal hair cell. It may be soft or stiff and may perform secretary in nature. It is found in stem and perform transportation function.

The Ground Tissue System:-

·         It consists of simple tissues such as Parenchyma, Collenchyma and Sclerenchyma.

·         Parenchymatous present in cortex, pericycle, pith, medullary rays, in periphery of stem.

·         In leaves, the ground tissue consists of thin walled mesophyll cell containing chloroplast.  

The Vascular Tissue system:-  

·         It consists of complex tissues as xylem and phloem. Here xylem and phloem form vascular bundle. Vascular bundle may be are of two types.

1.      Open Vascular bundle:- The cambium is present between xylem and phloem in the dicotyledonous plant(Stem & leaves). Due to presence of cambium the bundle having ability to form secondary xylem and phloem tissues so this is called open type vascular bundles.

2.      Closed Vascular bundle:- The cambium is absent in the monocotyledonous plant(Stem & leaves) i.e. they don’t have ability to form secondary xylem and phloem. So it is called closed vascular bundle.

·         The arrangement of xylem and phloem either of radial or conjugant type.

1.      Radial:- The xylem and phloem are arranged in alternate manner in different radii, called radial arrangement. This arrangement is present in roots of plants.

2.      Conjoint:- The xylem and phloem are arranged at the same radius in vascular bundle, called conjoint arrangement. This arrangement is present in stem and leaves. In this arrangement phloem located exteriorly than xylem.

TISSUES IN FLOWERING PLANT (ANATOMY)

    

Introduction:-

·         Study of internal structure of organisms is called anatomy.

The Tissue:-

·         Tissue is the group of cells having common origin and common function.

·         It is of two types:-

1.       Meristematic Tissu
2.    Permanent Tissue

Meristematic Tissue:-

·         The tissues whose cells having tendency to take part in cell division. This tissue is responsible for growth of plant.

·         It is are of three types:-

1.       Apical Meristem

2.       Intercalary Meristem

3.       Lateral Meristem

1.      Apical Meristem: - Occurs at the tips of roots & Shoots and are of Primary Meristem. It is responsible for increase in length length of plant.

                                                                                                                         

2.      Intercalary Meristem:- Occurs between the mature tissue and are of Primary Meristem. It is responsible for formation of branch of flower.

3.      Lateral Meristem:- Occurs in mature region of root and shoot and are of Secondary Meristem. It is responsible for Secondary growth. It activated after primary growth.

Auxiliary bud: - The buds which are present in the axils of leaves and are responsible for formation of branches or flowers in plants.

Fig- Type of meristem based on their position.

Permanent Tissue:-

·         The tissue whose cells lose their tendency to take part in cell division. It is formed in last division of primary and secondary meristem.

·         It is are of three types:-

1.      Simple tissue

2.      Complex tissue

1.      Simple Tissue:- It is made up of only one type of cells. It is also of three types

1.      Parenchyma

2.      Collenchyma

3.      Sclerenchyma

Ø  Parenchyma:- It is major component in the organ of plant. It is made up of isodiametric cells having thin cell wall of cellulose. It arranged with small intracellular spaces. It perform various functions as Photosynthesis, Storage and Secretion .

Ø  Collenchyma:- It is formed below the epidermis in dicotyledonous plant. It is made up of cells which are much thickened at corner due to deposition of cellulose, hemicellulose and pectin. Its arrangement is compacted i.e. don’t have any intracellular spaces. It also performs to give mechanical support to the plant. e.g. -Young Stem, Petiole of leaf etc.

Ø  Sclerenchyma:- It is made up of long, narrow dead-cells of thick and lignified cell wall having few numerous pits. It is of who types-

1)      Fibres:- It found in various part of plant body and made up of thick walled, elongated and pointed cells.

2)      Sclereids:- It is made up of oval, spherical and cylindrical thick cells with a lot of cavities (lumen). It is found in wall of nuts, pulp of fruits (guava, pear etc.) , seed coat of legumes and leaves of tea. It also provides mechanical support.

2.      Complex Tissue:-It consists of more than one type of cells which work together as a unit. It is of two types.

1.      Xylem

2.      Phloem

Ø  Xylem:- It functions in conduction of water and minerals from roots to stem and leaves. It also provides mechanical strength. It also consist of four type of elements

1)      Tracheids: - It is elongated or tube like cell of thick and lignified cell wall and tapering end. It helps in transporting water and minerals from roots to stems and leaves.

2)      Vessels:- It is cylindrical tube like cells of lignified cell wall and large central cavity called vessel members. It also help in transporting water and minerals from roots to stems and leaves.  

3)      Xylem fibres:- It is nonliving Sclerenchyma cell of highly thickened cell wall. It is present between tracheids and vessels. It gives mechanical support to xylem. 

4)      Xylem Parenchyma:- It is cells of thin cell wall made of cellulose. It performs a function to store food materials as starch and cellulose and also some other substances as tannin. It also perform radial conduction of water.

·         Primary xylem is of two types:-

                                                         I.            Protoxylem:- First formed primary xylem is called Protoxylem.

                                                       II.            Metaxylem:- Later formed primary xylem is called Metaxylem.

(Note-In stems occur endarch and Roots occur exarch)

Endarch-Protoxylem lies toward centre or pith and Metaxylem lies toward periphery.

Exarch- Metaxylem lies toward centre and Protoxylem lies toward periphery.

Fig-Type of Permanent tissue[Xylem a and Phloem]

Ø  Phloem:- It functions to transport the food materials generally from leaves to other parts of  plants. It also composed of followings:-

1)      Sieve tube elements:- It is long tube like structure which arrange longitudinally and associated with companion cells. A mature sieve tube aliment posses peripheral cytoplasm but lack in nucleus i.e. its function is controlled by nucleus of companion cell.

2)      Companion cells:- It is a specialized parenchymatous cell which loosely associated with sieve tube elements. Both are connected to each other through pit field. It functions to maintain pressure gradient in the sieve tube cell   

3)      Phloem Parenchyma:-It is consist of elongated, tapering and cylindrical cells of cellulosic cell wall having nucleus and dense cytoplasm. Each cell connected to each other with pits. It functions to store food material and other components as resins, latex and mucilage.

4)      4)      Phloem Parenchyma:- It consists of sclerenchymatous cells of thick cell wall. The fibre is much elongated, unbranched and needle like apices. At maturity it loses its protoplasm and become dead. It generally absent in primary phloem i.e. found in secondary phloem.