Notes-Part-1-Class-11-Science-Biology-Chapter-8-Plant Tissues and Anatomy-Maharashtra Board

Plant Tissues and Anatomy

Maharashtra Board-Class-11-Science-Biology-Chapter-8


Topics to be Learn : Part-1

  • Tissue
  • Meristematic Tissue
  • Permanent Tissue
  • Tissue Systems

Topics to be Learn : Part-2

  • Secondary Growth in Plants
  • Wood
  • Cork Cambium and Secondary Growth
  • Anatomy of Root, Stem and Leaf

Introduction :

  • Cell is the component that brings about important processes in the living organisms.
  • Organism → Organ system → Organs →Tissue system → Tissue → Cells

Tissue :

A group of cells having essentially a common function and origin is called as tissue

Simple tissue:

  • They are made up of only one type of cells.
  • They are found in all the plant parts.
  • Simple tissues in plants are Parenchyma, Collenchyma, Sclerenchyma
  • They perform many functions.

Complex tissue:

  • They are made up of many types of cells.
  • They are found only in the vascular regions of the plant.
  • They mainly perform the function of conduction of food and water
  • Complex tissues in plants are Xylem and Phloem.

Plant tissues are grouped as meristematic tissue and permanent tissue on the basis of its ability to divide.

Meristematic tissue :

Characteristics of meristematic tissue :

Characteristics of meristematic tissue :

  • It is a group of young, immature cells.
  • These are living cells with ability to divide in the regions where they are present.
  • These are polyhedral or isodiametric in shape without intercellular spaces.
  • Cell wall is thin, elastic and mainly composed of cellulose.
  • Protoplasm is dense with distinct nucleus at the centre and vacuoles if present, are very small.
  • Cells show high rate of metabolism.

  • Meristematic cells show the presence of large number of mitochondria. Due to which the rate of respiration is very high owing to rapid metabolism,
  • Meristematic cells usually divide in a particular plane of division.


Classification of meristematic tissue on the basis of origin :

Classification of meristematic tissue on the basis of origin:

(i) Promeristem / Primordial meristem:

  • It is also called as embryonic meristem.
  • It usually occupies very minute area at the tip of root and shoot.

(ii) Primary meristem:

  • It originates from the primordial meristem and occurs in the plant body from the beginning, at the root and shoot apices.
  • Cells are always in active state of division and give rise to permanent tissues.

(iii) Secondary meristem:

  • These tissues develop from living ‘permanent tissues during later stages of plant growth; hence are called as secondary meristems.
  • This tissue occurs in the mature regions of root and shoot of many plants.
  • Secondary meristem is always lateral (to the central axis) in position e.g. Fascicular cambiurn, inter fascicular cambium, cork cambium.


Classification of meristematic tissue based on its position :

Classification of meristematic tissue based on its position:

(i) Apical meristem:

  • It is produced from promeristem and forms growing point of apices of root, shoot and their lateral branches.
  • It brings about increase in length of plant body and is called as apical initials.
  • Shoot apical meristem is terminal in position whereas in root it is subterminal i.e. located below the root cap.

(ii) Intercalary meristem:

  • a.' Intercalary meristematic tissue is present in the top or base area of node.
  • b. Their activity is mainly seen in monocots.
  • c. These are short lived.

(iii) Lateral meristem:

  • It is present along the sides of central axis of organs.
  • It takes part in increasing girth of stern or root. e.g. Intrafascicular cambium.
  • It is found in vascular bundles of gymnosperms and dicot angiosperms


Types of meristematic tissue based on its function :

  • Protoderm : It is found in young growing region of a plant forming a protective covering like epidermis around the various organs,
  • Procambium : It is involved in developing primary vascular tissue.
  • Ground meristem : It forms structures like cortex, endodermis, pericycle, medullary rays, pith.

Functions of Meristem:

  • Meristems are responsible for growth by addition of new cells in various regions of the plants.
  • Formation of new leaves, branches and flowers.
  • Intercalary meristem helps in elongating the internodes, petiole and expanding leaf lamina.
  • Root apices continuously add new structures to the roots, i.e. root hairs.
  • Vascular cambium adds new vascular tissues as older ones become non-functional, hence helps in secondary growth.
  • Cork cambium forms protective covering around stems and roots.

Permanent tissue :

  • This is group of cells which have lost the capacity of division and acquired permanent size, shape and functions.
  • These are formed due to different morphological, physiological and functional changes

Depending upon types of cells, there are two types as simple and complex permanent tissues.

Simple permanent tissues : Complex Permanent Tissue :
1-These are made up of only one type of cells carrying similar functions.

2-This tissue is either living or dead.

3-Parenchyma, Collenchyma and Sclerenchyma are the simple permanent tissues in plants.

1-This tissue is heterogenous comprising of more than one type of cells and all function as a single unit.

2-This tissue is involved in conducting the sap and food from source to sink area.

3-Xylem and phloem are the complex permanent tissues in plants.


Parenchyma :


  • It is a type of simple permanent tissue.
  • Cells in this tissue are thin walled, isodiametric, round, oval to polygonal or elongated in shape.
  • Cell wall is composed of cellulose.
  • Cells are living with prominent nucleus and cytoplasm with large vacuole.
  • Parenchyma has distinct intercellular spaces. Sometimes, cells may show compact arrangement.
  • The cytoplasm of adjacent cells is interconnected through plasmodesmata and thus forms a continuous tissue.
  • This is less specialized permanent tissue.


  • These cells are distributed in all the parts of a plant body viz. epidermis, cortex, pericycle, pith, mesophyll cells, endosperm, xylem and phloem.


  • These cells store food, water help in in gaseous exchange, increase buoyancy, perform photosynthesis and different functions in plant body.
  • Dedifferentiation in parenchyma cells develops vascular cambium and cork cambium at the time of secondary growth.


Know This :

Types of parenchyma :

Parenchyma is modified to perform special functions:

  • Prosenchyma: Sometimes the parenchymatous cells become thick walled due to deposition of cellulose. They are fibre — like , elongated and pointed at both ends called prosenchyma, which provides strength and rigidity.
  • Aerenchyma: Parenchyma cells which have large intercellular spaces filled with air are called aerenchymaa. It gives aeration and buoyancy to aquatic plants. e.g. Eichhornia, Hydrilla, etc.
  • Chlorenchyma: Chlorenchyma is a parenchyma tissue, which contains large number of chloroplasts. It helps in the process of photosynthesis.
  • Xylem and Phloem parenchyma: This parenchyma present in the xylem and phloem acts as a packing tissue. It helps in storage and conduction of water and food materials.


Collenchyma are often found under the epidermis or the outer layer of cells in young stems and in leaf veins.

Characteristics of Collenchyma :

Characteristics of Collenchyma:

  • It is a simple permanent tissue made up of living cells.
  • The cell wall is cellulosic but shows uneven deposition of cellulose and pectin especially at corners.
  • The walls may show presence of pits.
  • Cells are similar like parenchyma, containing cytoplasm, nucleus and vacuoles but small in size and without intercellular spaces. Thus, the cells appear to be compactly packed.
  • The cells are either circular, oval or angular in transverse section.



  • Collenchyma is a living mechanical tissue and serves different functions in plants.
  • It gives mechanical strength to young stem and parts like petiole of leaf.
  • It allows bending and pulling action in plant parts and also prevents tearing of leaf.
  • It also allows growth and elongation of organs.
  • Collenchyma is usually absent in monocots and roots of dicot plant.

Sclerenchyma Tissue:

Characteristics of Sclerenchyma :

Characteristics of Sclerenchyma :

  • It is simple permanent tissue made up of compactly arranged thick walled dead cells.

  • The cells are living at the time of production but at maturity they become dead.
  • Cells are devoid of cytoplasm.
  • Their walls are thickened due to uniform deposition of lignin.
  • Cells remain interconnected through several pits.


Types of Sclerenchyma:

Sclerenchyma cells are categorized into two types on the basis of their size and shape as fibres and sclereids.

(a) Fibres:

  • Fibres are thread-like, elongated and narrow structures with tapering and interlocking end walls.
  • Fibres are mostly in bundles. Pits are narrow, unbranched and oblique.
  • They provide mechanical strength.

(b) Sclereids:

  • Sclereids are usually broad, with blunt end walls.
  • These occur singly or in loose groups and their pits are deep branched and straight.
  • These are developed due to secondary thickening of parenchyma cells and provides stiffness only.
Know This :

The sclereids are commonly found in the fruit walls of nuts; pulp of fruits like guava, pear and sapota; seed coats of legumes and leaves of tea.

 Functions of Sclerenchyma :

  • This tissue functions as the main mechanical tissue.
  • It permits bending, shearing and pulling.
  • It gives rigidity to leaves and prevents it from falling.
  • It also gives rigidity to epicarps and seeds.

 Complex permanent tissues :

  • These tissue are heterogenous comprising of more than one type of cells and all function as a single unit.
  • This tissue is involved in conducting the sap and food from source to sink area. Xylem and phloem are the complex tissues present in plants.

Xylem :

Xylem :

  • Xylem is the water conducting tissue in higher plants. It is a dead complex tissue.
  • It also provides mechanical strength to the plant body.
  • Components of xylem are tracheids, vessels, xylem parenchyma and xylem fibres


  • These are elongated, tubular and dead cells (without protoplasm).
  • The ends are oblique and tapering.
  • The cell walls are unifonnly thickened and lignified. This provides mechanical strength.
  • Tracheids contribute 95% of wood in gymnosperms and 5% in angiosperms.
  • The different types of thickening patterns are seen on their walls such as annular (in the form of rings), spiral (in the form of spring/helix), scalariform (ladder like) and pitted (small circular area). Pitted is the most advanced type of thickening which may be simple or bordered.

Vessels :

  • Vessels are longer than tracheids with perforated or dissolved ends and formed by union of several vessels end to end.
  • These are involved in conduction of water and minerals.
  • Their lumen is wider than tracheids and the thickening is due to lignin and similar to tracheids.
  • In monocots, vessels are roxmded where as they are angular in dicot angiosperms.
  • The first formed xylem vessels (protoxylem) are small and have either annular or spiral thickenings while latter formed xylem vessels are larger (metaxylem) and have reticulate or pitted thickenings.
  • When protoxylem is arranged towards pith and metaxylem towards periphery it is called as endarch e. g. in stem and when the position is revert as in the roots is called as exarch.

Xylem parenchyma :

  • Xylem parenchyma cells are small associated with tracheids and vessels.
  • This is the only living tissue among this complex tissue.
  • The function is to store food (starch) and sometimes tannins.
  • Xylem parenchyma are involved in lateral or radial conduction of water or sap.

Xylem fibres:

  • Xylem fibres are sclerenchymatous cells and serve mainly mechanical support. These are called wood fibres.
  • These are also elongated, narrow and spindle shaped.
  • Cells are tapering at both the ends and their walls are lignified.



  • Phloem is a living tissue. It is also called as bast.
  • It is responsible for conduction of organic food material from source (generally leaf) to a sink (other plant parts).
  • On the basis of origin, it can be protophloem (first formed) and metaphloem (latterly formed).

Structure of phloem :

Structure of phloem:

  • It is composed of sieve elements (sieve cells and sieve tubes), companion cells, phloem parenchyma and phloem fibres.

Sieve elements:

  • Sieve tubes are long tubular conducting channel of phloem.
  • These are placed end to end with bulging at end walls.
  • The sieve tube has sieve plate formed by septa with small pores.
  • The sieve plates connect protoplast of adjacent sieve tube cells.
  • The sieve tube cell is a living cell with a thin layer of cytoplasm, but loses its nucleus at maturity.
  • The sieve tube cell is connected to companion cell through phloem parenchyma by plasmodesmatai.

  • Sieve cells are found in lower plants like pteridophytes and gymnosperms and sieve tubes are found in angiosperms.
  • The cells are narrow, elongated with tapering ends and sieve area located laterally.

Companion cells:

  • These are narrow elongated and living.
  • Companion cells are laterally associated with sieve tube elements.
  • Companion cells have dense cytoplasm and prominent nucleus.
  • Nucleus of companion cell regulates functions of sieve tube cells through simple pits.
  • From origin point of view, sieve tube cells and companion cell are derived from same cell. Death of the one result in death of the other type.

Phloem parenchyma:

  • Cells of phloem parenchyma are living, elongated found associated with sieve tube and companion cells.
  • Their chief function is to store food, latex, resins, mucilage etc.
  • The cells carry out lateral conduction of food material,
  • These cells are absent in most of the monocots.

Phloem fibres (Bast fibres):

  • Phloem fibres are the only dead tissue among this unit.
  • They are sclerenchymatous.
  • They are generally absent in primary phloem, but present in secondary phloem
  • These cells have with lignified walls and provide mechanical support.
  • They are used in making ropes and rough clothes.


Differentiate between xylem and phloem :

Differentiate between xylem and phloem :

Xylem Phloem
1-It is a dead complex tissue.

2-It is composed of xylem, tracheids, vessels, xylem fibres and xylem parenchyma,

3-It is also known as wood.

4-The cell walls are thick due to lignin.

5-Xylem conducts water and minerals from roots to the stem and leaves. It also provides mechanical strength to the plant parts.

1-It is a living complex tissue.

2-It is composed of sieve tubes, sieve cells, companion cells, phloem parenchyma and phloem fibres.

3-It is also known as bast.

4-The cell walls are thin.

5-It is the chief food conducting tissue of vascular plants responsible for translocation of food from leaves to other plant parts.


Tissue systems :

Plant tissues are derived from meristems and their structure and functions depend on the position.

On the basis of their structure and location, three types of tissue systems are present viz. Epidermal tissue system, ground tissue system and vascular tissue system.

Epidermis :


  • It is the outermost protective cell layer made up of compactly arranged cells without intercellular spaces.
  • Cells show presence of central large vacuole, thin cytoplasm and a nucleus.
  • The outer side of the epidermis is often covered with a waxy thick layer called the cuticle which prevents the loss of water.
  • Root epidermis (Epiblema) has root hairs. These are unicellular, elongated and involved in absorption of sap from the soil.
  • In stem, epidermal hairs are called trichomes. These are generally multicellular, branched or unbranched, stiff or soft or even secretory. These help in preventing water loss due to transpiration.

[In the given figures, Figure ‘A’ represents a section of upper epidermis of banana leaf through stomatal region showing extent of cuticle over guard cells.

Figure ‘B’ represents a section of banana leaf through pulvinar band showing pegs of cuticle over epidermal cells.]


Stomata :

Structure of stomata :

Structure of stomata :

  • Small gateways in the epidermal cells are called as stomata.
  • Stoma is controlled or guarded by specially modified cells called guard cells.
  • These guard cells may be kidney shaped (dicot) or dumbbell shaped (monocot), collectively called as stomata.
  • Guard cells have chloroplasts to carry out photosynthesis.
  • Change in turgor pressure of guard cells causes opening and closing of stomata, which enables exchange of gases and water vapour.
  • Stomata are further covered by subsidiary cells.
  • Stoma, guard cells and subsidiary cells form a unit called stomatal apparatus.


Guard cells :

  • Guard cells are modified epidermal cells.
  • The inner wall of guard cells surrounding the pore is thick and inelastic due to presence of secondary wall layer and the outer walls are thin, elastic and permeable.
  • Guard cells are living, uninucleate cells having central vacuole and peripheral granular cytoplasm.

Ground tissue:

  • All the plant tissues excluding epidermal and vascular tissue is ground tissue.
  • It is made up of simple permanent tissue e.g. parenchymai
  • It is present in cortex, pericyele, pith and medullary rays in the primary stem and root, Collenchyma and sclerenchyma in the hypodermis and chloroplasts containing mesophyll tissue in leaves is also ground tissue.

Vascular bundles :

Vascular bundles :

  • Vascular bundles occur in the form of distinct patches of the complex tissue viz. Xylem and Phloem.
  • On the basis of their arrangement in the plant body they are classified as radial, conjoint, collateral, bicollateral, concentric vascular bundle.
  • These bundles may be further of open type (secondary growth takes place) containing cambium in between them and closed type if cambium is not present (secondary growth absent).

Radial vascular bundles:

  • Vascular bundles of the root are radial.
  • When the complex tissues (xylem and phloem) are situated separately on separate radius as separate bundle, vascular bundle is called Radial vascular bundle. This is a common feature of roots.
  • The xylem and phloem bundles are arranged alternating with each other.

Conjoint vascular bundles:

When the complex tissue (xylem and phloem) is collectively present as neighbours of each other on the same radius, vascular bundle is called Conjoint vascular bundle.

They are of two types:

(i) Collateral vascular bundle:

  • In this type of vascular bundle, xylem lies inwards and the phloem lies outwards.
  • These bundles may be further of open type (secondary growth takes place) containing cambium in between xylem and phloem and closed type if cambium is not present (secondary growth absent).

(ii) Bicollateral vascular bundle:

  • When phloem is present in a vascular bundle on both the sides of xylem and intervening cambium tissue, it is called bicollateral vascular bundle. It is a feature of family Cucurbitaceaa.

Concentric vascular bundle:

  • When one vascular tissue is completely encircling the other, it is called as concentric vascular bundle
  • When phloem is encircled by xylem, it is called as leptocentric vascular bundle, whereas when xylem is encircled by phloem, it is called as hadrocentric vascular bundle.
  • When xylem is encircled by phloem on both faces, it is called as amphicribral vascular bundle. When phloem is encircled by xylem on both faces it is called as amphivasal vascular bundle.
  • Due to absence of cambium between xylem and phloem, concentric vascular bundles are always closed.


Q. Why vascular bundles of dicot stem are described as conjoint collateral and open?

Answer :

Vascular bundles of dicot stem are described as conjoint collateral and open because;

  • In dicot stem, the complex tissue is collectively present as neighbours of each other on the same radius in the form of xylem inside and phloem outside. Such type of vascular bundles are called as conjoint and collateral.
  • In dicot stem, a strip of cambium is present between xylem and phloem. Hence, it is called as open vascular bundle.


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