Permanent Tissues: Simple & Complex | Science for ACT PDF Download

Permanent Tissues

• Permanent tissues are composed of cells which have lost the power of division temporarily or permanently.
• They are formed by division and differentiation of meristematic tissues.
• Their cells may be living or dead. 

Permanent tissues are of three types :-

A. Simple tissue (Homogenous tissue)

B. Complex tissues (Heterogenous tissue)

C. Special tissue

[A] Simple Permanent Tissues 

These tissues are made up of similar type of cells or only one type of cells that perform a common function.

Simple tissues are of three types: 

I. Parenchyma 

It is very primitive type of tissue. It is first evolved tissue. Remaining all different types of tissues are derived from this tissue.  so it is also called as fundamental tissue l Parenchyma name coined by Grew.

Characteristic Features:

• It is a living tissue.
•  It is first differentiated tissue derived from meristem.
•  It is a universal tissue.
•  Flesh of a fruit is mainly composed of parenchyma.
•  Body of bryophyte plants is mainly composed of parenchyma.
•  Parenchyma is most common tissue which is morphologically and physiologically unspecialized.
• The cells of parenchyma are thin walled. Cell wall is made up of pectocellulose (mainly cellulose). So parenchyma is a soft tissue.
•  Each cell containing large central vacuole. So the main function of a parenchyma cell is storage of food.
•  Usually Inter cellular spaces are present between cells of this tissue, it is a loose tissue. Intercellular spaces are usually schizogenous in origin.
•  The cells are usually isodiametric.

Shape: 

Modifications of Parenchyma

1. Prosenchyma :- The cells of this parenchyma are long with pointed ends. This parenchyma forms the pericyle of roots. Function : Provide support to plant organ.

2. Aerenchyma :- This parenchyma is made up of rounded cells. These cells surrounds the large air chambers.
Air chambers are lysigenous in origin. Aerenchyma is found in cortex region. It provide buoyancy to hydrophyte plants.

3. Stellate Parenchyma :-The cells of this tissue are stellate and branched. Air spaces are also present but they are less developed.  Main function of this parenchyma is to provide mechanical support and provide mechanical strength to leaf bases of banana.

4. Chlorenchyma :- Such type of parenchyma in which abundant quantity of chloroplasts are found. Two types of chlorenchyma are present in dorsiventral leaves :-

(a) Palisade Tissues :- Inter cellular spaces are absent. Their cells are tightly fitted together. They are present towards adaxial/ ventral/upper side of leaf. Number of chloroplasts are more in palisade tissue as compare to spongy tissue. So upper surface of a leaf appears more green as compared to lower surface.

(b) Spongy Tissues :- Large intercellular spaces are present. So they facilitates transpiration and gaseous exchange.They are present towards abaxial/dorsal/lower side of leaf.

5. Mucilage Parenchyma :- In the Mucilage parenchyma large vacuoles and Mucilage will be found. e.g. Succulent xerophytic plants. e.g. Aloe. Function -storage of water.

Functions of Parenchyma

1. The main function of this tissue is storage of food.

2. Some cells of parenchyma store waste materials. They are called "idioblast cells". Idioblast cells store  oils, tannin and crystal of calcium oxalate .

II. Collenchyma

Term coined by Schleiden.

Characteristic Features:

•  Collenchyma is a living mechanical tissue. Lignin is absent.
•  It is made up of elongated (In transverse section cells are oval, spherical or polygonal in shape) cells.
•  localized deposition of pectocellulose (mainly pectin) & hemi cellulose is the characteristics feature of collenchyma.
•  Usually intercellular spaces are absent.
•  Vacuolated cytoplasm is found in the cells of collenchyma . Chloroplast may be found in the cells of collenchyma.

Occurence

• Collenchyma is not a universal tissue. It is found in the stems of herbaceous dicotyledons below epidermis either as a homogenous layer or in patches.
• Collenchyma is absent in woody plant parts (After secondary growth in plant parts), roots and monocotyledons.
• Collenchyma forms the hypodermis of dicotyledon stems. Cells of collenchyma are flexible due to hydrophilic nature of pecto-cellulose so flexibility occurs in dicotyledonae stems.
• Lamina margins of leaves also bears collenchyma. This protects the cracking of lamina margin due to the action of wind.

Types of Collenchyma

On the basis of place of deposition, it is classify into three types by:-

1. Lamellar/Plate Collenchyma :- The cells of collenchyma arranged in lamellar forms. The cell have thickening on the tangential walls. Due to such type of deposition, cell looks like a lamellar or plates. Ex. Sunflower stem.

2. Angular Collenchyma :- This type of collenchyma abundantly found in plants. The cells of this tissue are angular. The deposition of pectocellulose at the angles of cell wall. e.g., Stem of Datura, Solanum and tomato

3. Lacunar Collenchyma/Tubular Collenchyma :- Large intercellular spaces are present in the cells of this tissue. Deposition of pectocellulose on the walls of intercellular spaces. e.g. Cucurbita stem and aerial roots of Monstera.

Functions of Collenchyma

• Mechanical as well as biological. It provides tensile strength for extensibility of various growing plant organs/provide tensile strength/provide tensile strength against bending & swaying.
• Due to the presence of chloroplast, photosynthesis process takes place in collenchyma.

III. Sclerenchyma 

Name coined by Mettenius. 

Characteristic Features:

• Sclerenchyma is the main mechanical tissue.
•  These cells are long, narrow, thick walled, lignified and dead.

Functions of Sclerenchyma

• It provide mechanical support/mechanical strength to plants.
• Various types of pits are formed due to the deposition of lignin on hard wall.

Types of Sclerenchyma

 On the basis of length of cells and amount of deposition of wall materials (Lignin), sclerenchyma cells are of two types:

(i) Sclereids
(ii) Sclerenchymatous Fibres

I. Sclereids

These cells are small, extremely thick walled and their ends are not pointed. Sclereids are isodiametric or irregular in shape. Sclereids cells have more pits and lumen is almost very small.

Their pit cavity is branched.

 Sclereids are classified on the basis of their shapes :-

(A) Stone Cells or Brachy- Sclereids or Grit Cells:-These cells are spherical or oval in shape. They are found in endocarp of drupe fruits, so endocarp becomes hard.

• They are present in endocarp of Coconut, Mango, Almond, Walnut etc.
• Brachy sclereids are also present in fleshy (edible) part of pear (Pyrus). Grittness in pear fruit is due to these sclereids.
• Brachy sclereids are also found in pulp of guava' and sapota.

 (B) Trichosclereids : These are also known as internal hairs. They are spines like, bifurcated cells. These are found in floating leaves of hydrophytes.

 (C) Astro Sclereids or Stellate Sclerenchyma : These cells are stellate (star) shaped. They are found in floating leaves.

 Note – Astro sclercids are also found in tea leaves.

(D) Macro-Sclereids or Rod Cells or Malpighi Cells :-They are small and rod like cells. They are present in seed coats. Ex. legume seeds.

In leguminous plants, hardest seed coat is found in french bean (Phaseolus vulgaris). 

(E) Osteo- Sclereids :-These are known asprop-cells. These are pillar like cells. Both end of pillar like cells spreads to form bone like structure.

Example :- These cells are found in leaves of Hakea and Osmanthus.

II. Sclerenchymatous Fibres

•  These cells are fibrous. They are longest cells in plant body. Their both ends are pointed (tapering). Due to thick cell wall, lumen is reduced.

•  Their cell wall contains simple and bordered pits.

 On the basis of structure fibres are classified into two groups: 

(a) Libriform Fibres :- They are highly thickened long fibres. They posses simple pits and narrow lumen.
Libriform fibres are found in phloem, xylem, pericycle and hypodermis (Maximum in phloem).

(b) Fibre Tracheids :-  They are also highly thickened. Bordered pits are present in these fibres and lumen is broad. They are only found in xylem.

 On the basis of position, fibres are divided into three types:

A. Surface Fibres

 They are present on the surface of plant. These fibres also called as filling fibres.

(i) Seed surface fibre 

Example 1 : Cotton fibres - Cotton fibres are out growth of seed coat/out growth of testa. Cotton fibres are composed of cellulose. They are non-lignified. So cotton fibres are not true fibres. Two types of fibres are found in cotton. Long fibres are called 'lint' and small fibres are known as'fuzz'. Lint fibres are used in cloth industry. Fuzz are filling fibre.

Example 2 :  Red silk cotton (Semal fibre) - Obtained from Salmalia malabaricum

Example 3 :  White silk cotton (Kapok) - Obtained from Ceiba pentendra (Both red and white silk cotton fibres are not true fibres and they are also an example of seed surface fibre.)

(ii) Coir of coconut is also a type of surface fibre. They are derived from the mesocarp. These are true fibres, becouse they are lignified.

B. Xylary or Wood Fibres 

These are hard fibres. They fibres are not flexible. They can not be knitted (weaved) easily so they are not useful. These are obtained from xylem.

Ex. Munj fibre (Saccharum munja)

C. Bast Fibres/Extra Xylary Fibres/Phloem Fibre

These are also known as commercial fibres. These fibres are flexible and can be knitted (weaved) easily. They have great economic value.

• These fibres are obtained from the phloem and pericycle of plants. 
• The bast fibres of Corchorus capsularis.(Jute),Crotalaria juncea (Sunn hemp) and Hibiscus sabdariffa (patua) are obtained from the secondary phloem of stem.
• The bast fibres of hemp (Cannabis sativa) and Linum usitatissimum(flax) are obtained from the pericycle.

Fibres which are obtained from pericycle are called perivascular fibres.

[B] Complex Permanent Tissue

•  The complex tissues are made of more than one type of cells and these work as a unit. Complex tissue are heterogenous.
• Complex tissues are absent in gametophytes.
•  During vascularization in plants differentiation of procambium followed by the formation of primary phloem and primary xylem simultaneously.

Complex tissues are of two types:
(a) Xylem
(b) Phloem

(a) Xylem

•  The term 'Xylem' is coined by Nageli.

• The function of xylem is to conduct water & minerals salts upwards from the roots to stem & leaves and to give mechanical strength to the plant body. 

• For conduction of water death of protoplasm is must. Dead tissues are more develop in water scares condition.

•  On the basis of origin, xylem is divided into primary xylem and secondary xylem.

1. Primary xylem originates from procambium during vascularization.
On the basis of development primary xylem divided into two parts
(1) Protoxylem
(2) Metaxylem  

•  Cells of protoxylem are small as compare to metaxylem

2. Secondary xylem originates from vascular cambium during secondary growth.

• The elements of xylem are

1. Tracheids 

•  Tracheids are primitive conducting elements of xylem.

•  A single tracheid is a highly elongated cell with hard, thick and lignified wall and a narrow lumen. The ends of tracheids are tapering or chisel like.

•  The tracheids found one above, the other are separated by cross wall which bear bordered pits.

•  Tracheids are dead and lignified cells. The deposition of lignin on cell wall is responsible to form a different type of thickenings.i.e., annular (primitive type), spiral, scalariform, reticulate and pitted.

Note : 

1. Usually bordered pits are present at the end wall of tracheids.

2. Maximum deposition of lignin is found in pitted type of thickening and pits are formed in this type of thickening.

3. Annular and Spiral type of thickening of lignin is found in protoxylem.

4. Reticulate and Pitted (mainly) type of thickening of lignin is found in metaxylem.

5. Scalariform type of thickening  is found in metaxylem tracheids of pteridophytes and  in metaxylem tracheids of Cycas.

6. End wall of tracheids are imperforated/pitted.

7. Tracheids are unicellular.

Note: Pits are unlignified areas on lignified wall

(2) Vessels

•  It is an advance conducting element of xylem. Vessels is a long cylindrical, tube like structure with lignified walls and, a wide central lumen.

•  The end wall is perforated (Transverse septum is absent between two vessel elements. If present then porous.) Thus vessels are more capable for conduction of water than tracheids. Due to presence of perforated end wall, vessels work as a pipe line during conduction of water.

•  The perforation may be simple (only one pore) or multiple (several pores). Vessels contain usually simple pits on their lateral walls. Types of thickening on the walls of vessels is the same as tracheids.

Note :

1. Vessels are found in most of the angiosperm but also present in some gymnosperms like Ephedra, Gnetum and Welwitschia.

2. Vessels are absent in some Angiospermic plants such as Dracaena, Yucca, Dagenaria,  Drimys.
There are some angiosperm families in which vessel less angiosperms are included. 

E.g.: Winteraceae, tetracentraceae and trochodendraceae.

3. Vessels are example of dead syncyte.

4. Vessels are multicellular.

3. Xylem Fibres

•  Xylem fibres provides strength to the tracheids and vessels. Mainly these fibres provide strength to the vessels.

•  They may be either septate or aseptate. They have obliterated central lumen.

• They are abundantly found in secondary xylem.

4. Xylem Parenchyma

•  It's cell wall is made up of cellulose.

Function : Radial conduction of water and  store food material in the form of starch or fats and tannin etc.

 Their walls possess pits.

Hadrom : – Tracheids and Vessels are collectively known as water conducting elements or "Hadrom". Hadrom term was proposed by Haberlandt.

(b) Phloem

• The term 'Phloem' is coined by Nageli.

•  The main function of the phloem is to conduct of food materials, usually from the leaf to other plant parts (eg. storage organ and growing regions) On the basis of origin, phloem is classified into two categories primary and secondary phloem.

• Primary phloem originates from procambium during vascularisation and secondary phloem originates from vascular cambium during secondary growth.

On the basis of development primary phloem categorised into protophloem and metaphloem.

•  The protophloem has narrow sieve tubes  whereas metaphloem has bigger sieve tubes.

•  Phloem remains active for less duration as compared to xylem.

Phloem consist of 4 types of cells:

1. Sieve Cell /Sieve Tube 

•  Sieve element was discovered by Hartig.

•  Sieve cells/sieve tube element are living and thin walled.

•  Mature sieve tube elements are enucleated living cells.

•  Central vacuole is present in each sieve cells/sieve tube element and around the central vacuole thin layer of cytoplasm is present.

•  In Angiosperm plants, sieve tube elements are joined their ends and  form sieve tube. Their end walls are perforated (Sieve Pores) in a sieve like manner to form the sieve plate. Translocation of food material takes place through these pores.

• Sieve elements contain special type of protein-P-protein (p-phloem). Most likely function of p-protein is sealing mechanism on wounding and it is also related with conduction of food.

Note :

1. Food conduction is bidirectional in sieve tube.

2. In sieve tube, oblique transverse perforated septa (sieve plates) are present at their end wall.

3. Sieve tube is an example of living syncyte.

2. Companion Cells 

These are thin walled living cells. The sieve tube elements and companion cells are connected by pit fields present in their longitudinal walls, which is common wall for both and, with the death of one, other cell also dies.

•  A companion cell is laterally associated with each sieve tube element in Angiospermic plants.(In carrot more than one)

•  Sieve tube element and companion cell originates together. Both of them originates from a single mother cell. So called as sister cells.

•  The companion cells and sieve tube elements maintain close cytoplasmic connections with each other through plasmodesmata.

•  Companion cell is a living cell with large nucleus. This nucleus also controls the activity of cytoplasm of sieve tube element.

•  Companion cells are only found in Angiosperms. (exception - Austrobaileya is angiosperm plant but companion cells are absent).

• Special type of cells are attached with the sieve cells in gymnosperm (mainly) and in pteridophytes in place of companion cells. These cells are called as albuminous cells/ strasburger cell.

Note :

(1) Albuminous cells in conifers are analogous to companion cells of angiosperms. They are modified phloem parenchyma cells.

(2) The companion cells play an important role in the maintenance of a pressure gradient in the sieve tubes.

(3) In phloem of pteridophytes and gymnosperms sieve cell are present which are comparable to the tracheids.

3. Phloem Fibres / Bast Fibres 

These are made up of sclerenchymatous cells.

•  These fibres are generally not found in primary phloem.

•  These fibres provide mechanical support to sieve elements (sieve cells and sieve tube).

4. Phloem Parenchyma 

•  It's cells are living and thin walled. It store various materials. eg. Resin, Latex, Mucilage etc.

•  The main function of phloem parenchyma is conduction of food in radial direction and storage of food. The conducting element of pholem is called Leptom.

•  Leptom term was proposed by Haberlandt.

Note :

(1) Phloem parenchyma is absent in the stems of monocotyledon plants.  

(2) Phloem Parenchyma is absent in the stems of Ranunculaceae plants (dicot family).e.g. Thallictrum

Old NCERT Syllabus

Simple Permanent Tissues

Leaf Fibres 

• Fibres are longest plant cell. Longest fibres occur in Boehmeria nivea (Ramie fibre) length–55 cm. 
• In plant kingdom hardest and thickest (Largest) leaves are found in Victoria regia due to presence of astrosclereids. Diameter ( 1–1.5 m) 
• Longest leaves are found in Raphia vinifera. Length 10 – 15 m.
• Longest commercial fibres – Jute fibres
• Sclerenchyma is classified on the basis of variation in form, structure, origin and development.

Complex Permanent Tissue

SPECIAL TISSUE OR SECRETORY TISSUE

I. Lactiferous tissue : 

• These are made up of long, highly branched and thin walled cells. These cells are filled with milky juice, called as Latex.

•  Latex is the mixture of saccharides, starch granules, alkaloids, minerals and waste materials.

•  Starch granules present in latex are dumble shaped.

Function :

(1) Latex provide protection to the plant.

(2) It prevents the plants from infection of bacteria and fungus. In laticiferous tissue there are two types of cells.

1.  Latex vessels and 2. Latex cells

1. Latex vessels :

•  These are articulated.

•  These are syncytic cells and coenocytic (multinucleated).

Example :- Latex vessels are present in Hevea, Ficus, Papaver, papaya, Argemone and Sonchus.

•  Opium is obtained from the latex of Papaver somniferum. It contains an alkaloid named as morphine.

•  An enzyme papain is obtained from the latex of papaya (Carica  papaya).

•  Para rubber/Commercial rubber is obtained from Hevea bransiliensis and Indian rubber is obtained from Ficus elastica Mostly latex is white in colour but in some plants latex is coloured.

Ex. Papaver – Dark brown

Argemone            
Yellow colour
Sonchus

In some plants latex is colourless Ex. Banana (Family - musaceae).

2. Latex cells :

These are non articulated. These are long, branched and multinucleated cells (coenocytic cells).
Example - Latex cells are found in Calotropis, Euphorbia and Nerium (Apocyanaceae), Ficus religiosa Note : Latex vessels and latex cells are found in cortex.

II. Glandular tissue : 

• As the name indicates that this tissue is made up of glands. These glands contain secretory or excretory materials.

•  Glandular tissues have two types of glands :-

(1) Unicellular. Ex. - Urtica-dioica. These cells are present on the surface of the leaves. These are spiny glands.

(2) Multicellular : Multicellular glands are of two types.

1. External Glands :- These are located on the surface of the plants and arising as an outgrowth from the epidermis. These glands are of various types :-

   Glandular hairs :- They secrete gum - like sticky substances in tobacco and Plumbago.

    Nectar Glands :- These glands secrete sugar solution. These are found in floral parts mainly in thalamus.

These glands secrete nectar to attracting the insects.

Exception- In Passiflora, nectar glands are found in leaves.

2. Internal Glands :- These glands are embedded in the tissues. Internal glands are of following types.

 Digestive glands :- Digestive glands are found in insectivorous plants. These glands compensate the deficiency of N2 in insectivorous plants. These are found in Utricularia, Drosera, Dionaea etc. plants. they secrete proteolytic juice.

Mucous glands :- These glands secretes mucous. These are found in the leaves of betel.

Oil glands :- These secretes Volatile oil. It act as antiseptic. These glands are found in fruits & leaves of lemon & orange. Mostly, Oil glands are lysigenous but in sunflower these glands are schizogenous.

Note : Oil glands which secrete volatile oils called osmophores. Osmophores develop fragrance in flowers. Oils which are obtained from Eucalyptus leaves are used in medicines.

(d) Tannin, resin, gum secretory glands are also internal glands.These are schizogenous. Maximum resin glands are found in Pinus. Resin ducts are schizogenous. Gum glands are found in Acacia.

(e) Water glands/Hydathode.

These glands are related with guttation. Hydathodes are present in Tomato, Pistia and

Eichhornia etc.