Tissue: Meristematic & Simple Permanent
Tissue : Meristematic & Simple Permanent
Q1 What is tissue?
A tissue can be defined as a group of cells having common origin, structure and function.
Q2 Types of tissue?
Tissues are of two types – (i) Meristematic tissue and (ii) Permanent tissue.
Q3 Meristematic tissue?
Meristematic tissues are a group of young living cells that remain in a state of continuous division to form new and newer cells.
Animals don't have Meristematic tissue.
Q4 Properties of Meristematic tissue?
(i) The cells of meristem are isodiametric in shape.
(ii) They are tightly packed with negligible intercellular spaces.
(iii) All cells of meristem are living.
(iv) The cell wall is thin and composed of cellulose only.
(v) Cells have large nuclei.
(vi) Generally vacuoles are absent, if present are very small and scattered.
(vii) Plastid and mitochondria underdeveloped.
(viii) They are located in the growing regions only.
Q5 Classify meristems on the basis of position.
According to position Meristematic tissues are of three types:
(i) Apical Meristem :- When meristematic tissues occupy apical position like shoot apex, root apex or leaf apex, they are termed as Apical Meristem.
Function : By the activity of the apical meristems the plant body grows in length.
(ii) Intercalary Meristem :- The meristems located at the base of internode and have permanent tissue below and above are called Intercalary Meristem . It remains widely separated from apical meristems .
Function: The derivatives of Intercalary Meristem differentiate into permanent tissues , as a result stem internode elongates.
(iii) Lateral Meristem :- The meristems located parallel to the long axis of root and shoot of Dicotyledons and Gymnosperms are called Lateral Meristems .
Function:- These tissues increase the girth of the plant body.
Q6 Permanent tissues ?
The fully differentiated mature cells which cannot divide further are called Permanent tissues.
Q7 Types of Permanent tissues?
Two types:
(I) Simple Permanent tissues and
(II) Complex Permanent tissues
Q8 Simple Permanent tissues?
The tissues, which are composed of one type of fully differentiated non-dividing cells, are called Simple Permanent tissues.
Q9 Types of Simple Permanent tissues?
Three types:
Parenchyma
Collenchyma and
Sclerenchyma
Q10 Parenchyma?
The plant tissues composed of only one type of non- dividing living cells with live nucleate protoplast and thin cellulosic cell wall are called parenchyma.
Properties/ Characteristics:
(i)All cells are living.
(ii) Cells are generally oval, polygonal and spherical in shape .
(iii) Intercellular spaces present.
(iv)The cell wall is thick or thin, made up of cellulose only.
(i) Normal type:
In this type, cells are isodiametric and present in the epidermis, cortex, endodermis , pith and ground tissue.
(ii) Chlorenchyma:
These are chloroplasts containing parenchyma present in green parts of a plant. There are two types of such tissues in leaves :-
Palisade parenchyma: Elongated green cells without intercellular spaces.
Spongy parenchyma: Round or oval green cells with intercellular spaces.
Fig: Leaf T.S. showing Chlorenchyma
(iii) Aerenchyma:
Parenchyma with large air cavities to provide buoyancy and to help in gas exchange. Generally present in aquatic plants.
Fig: T.S. of Nymphea petiole showing Aerenchyma.
Functions:
(i) Stores foods and water.
(ii) Parenchyma of epidermis protects inner tissues.
(iii) Chlorenchyma performed photosynthesis.
(iv) Aerenchyma helps buoyancy.
Q10 Collenchyma?
Collenchyma are thick walled and compactly packed( without any intercellular space due to deposition of pectin at corners) living simple permanent tissues with relatively more thick corners.
Properties:
(i) Cellwall is made up of cellulose and pectin.
(ii) Cells are living, elongated and have irregularly thick cell walls at corners.
(iii) Intercellular spaces are filled by the deposit of thickening materials.
Distribution:
(i) Below the epidermis (as hypodermis) in stems of non- woods dicotyledons, leaves and petioles.
(ii) Present in leaf stalks ( below the epidermis).
(iii) Absent in roots , monocotyledonous stems and leaves.
Functions:
(i) Provide plasticity/ flexibility and mechanical strength like bending of tendrils and stems of a climber plant.
(ii) If green, perform photosynthesis.
Fig: A T.S. of stem showing different types of plant tissues.
Q11 Sclerenchyma?
Sclerenchyma is the simple permanent tissue of lignified dead cells with pointed ends and without intercellular spaces. Sclerenchyma are also called fibres.
Properties:
Cell wall materials: cellulose and lignins.
Intercellular spaces absent.
Simple pits present.
Distribution: Occurs in stems as hypodermis, pericycle, above or around the vascular bundles, in the veins of leaves, in xylem and phloem, hard covering of seed and nuts too.
Functions:
(i) Since it is lignified,it provides mechanical strength to plant parts to bear compression, pull, bending ,etc.
Q12 Differences:
Parenchyma | Collenchyma | Sclerenchyma |
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Sclerides are highly thickened and lignified short sclerenchyma present in seed- coat ( Pisum) flesh of hard fruits(Pyrus) and shell , leaves of Camellia , etc.
Q.14 What do you mean by epidermis?
The outermost layer of a plant is generally made up of a single layer of parenchyma and called epidermis.
Q.15 Properties of epidermis?
(i) Generally epidermis is unilayered.
(ii) Most epidermal cells are flat.
(iii) The outer and lateral walls of epidermal cells are thicker than the inner wall.
(iv) Epidermis of dorsal surface of dorsiventral leaf , desert plant ,etc. has waxy coating of cutin to prevent water loss.
(v) In leaf epidermis is punctured by stomata.
Q.16. What is a stoma?
A stoma is a tiny pore present in leaf epidermis. It is enclosed by two Kidney- shaped guard cells.
Q.17. Functions of Stomata?
(i)Stomata are those pores through which exchange of CO2 and O2 take place.
(ii) Transpiration in plants takes place through stomata.
Q18. What is cork?
A cork is a multilayered dead and compactly arranged suberin containing permanent tissue obtained from the activity of a secondary meristem present in the cortex of plants having secondary growth.
Q19 Functions of cork?
Cork prevents entry and exit of water and gases through injured critical cells of dicot plants showing secondary growth.
Q 20 Why is cork impervious to gases and water?
It is due to the presence of suberin.
Q 21 Differentiate stem hair and root hair.
Stem hair:
(i) Stem hair is multicellular .
(ii) It is not a part of an epidermal cell.
Root hair:
(i) Unicellular.
(ii) It is the part of epidermis as the outer wall of an epidermal cell extends as a tube to form a root hair.
MCQ
1.Cambium is
(a) Apical meristem
(b)Intercalary meristem
(c )Lateral meristem
(d) None of the above
2.Apical meristems are located at the
(a) Apex of stem only
(b) Apex of root only
(c ) Both of shoot and root apex
(d) All of the above
3.Cell walls of plant meristems are composed of
(a)Cellulose only
(b) Cellulose and pectin
(c) Cellulose and lignins
(d)Pectin and lignins
4.Chlorenchyma is a kind of
(a)Thin walled living cell
(b)Simple permanent tissue
(c)Chloroplast containing cell
(d)All of the above
5 Bending of tendrils in cucumber is provided by
(a)Parenchyma
(b)Collenchyma
(c )Sclerenchyma
(d)Aerenchyma
6. The plant tissue having dead cells is
(a)Parenchyma
(b)Collenchyma
(c )Sclerenchyma
(d)Chlorenchyma
7.Generally epidermis is
(a)Unilayered
(b)Bilayered
(c) Multilayered
(d)None of the above
8. Cork cells are
(a)Dead and without intercellular space
(b) Dead with intercellular space
(c )Living without intercellular spaces
(d) Living with intercellular spaces
9. A stomata is guarded by
( a)1 cell
(b)2 cells
(c )3 cells
(d)4 cells
10. Lignins is found in
(a)Plant meristems
(b)Parenchyma
(c )Collenchyma
(d)Sclerenchyma
Answers
1 C 2 C 3 A. 4 D. 5 B. 6 C. 7 A. 8 A 9 B 10 D
Cell Wall
Definition: Cell wall is the outermost, rigid, protective and supportive layer found in all the plant cells, bacteria, cyanobacteria and some protists.
Discovery: It was first discovered by Robert Hooke in 1665 AD.
Structure:
Middle lamella:- It is a thin amorphous binding layer between the cell wall of adjacent plant cells. It is absent on the free surface of plant cells . It is the first structure that is formed from a cell plate between the newly formed daughter cells at the time of cytokinesis.
Primary wall:- It is thinner ( 1-3 micro metre) ,elastic and living coat laid inner to the middle lamella and outer to the secondary wall ( if present). Thickness varies from 0.1-3.0 micro metre. It is the only wall in meristematic and parenchyma like mesophyll, cortex, pith, fruit, etc. It grows due to incorporation of materials into the inside of the wall,such growth is called intussusception.
Secondary wall:- It lies inner to the primary wall only in mature and non- dividing cells, like, tracheids, vessels, collenchyma and sclerenchyma cells. Generally the cells with secondary walls are devoid of protoplast at maturity.It’s thickness is 3-10 micro metre. It is formed of three layers called S1 , S2 and S3 . Sometimes, the number of layers may exceed three, and the innermost sometimes consists only of a helical band and such bands are called tertiary spirals or spiral thickenings( Eames and Mac Daniels,1947).
In tracheids and vessels, the deposition of the secondary cell wall is not uniform and absent in some places. This forms the pits in the wall. Pit pairs are opposite to each other and form the pit-canal. These pits are separated by a membrane made of middle lamella and primary wall.Pits are of two types: Simple pits ( pits of uniform size) and bordered pits ( pits with overhung secondary wall).
Fig:(i) Simple pit , (ii) Bordered pit
Bordered pits are generally found in the tracheids of Gymnosperms.
Chemical composition of plant cell wall:
Chemically , plant cell wall is formed of:
(1) | Cellulose ( In the form of fibrils) | 10-15% |
(2) | Hemicellulose | 5-15% |
(3) | Water | 30-60% |
(4) | Pectic substances | 2-8% |
(5) | Proteins | 1-2% |
(6) | Lipids | 0.5-3% |
(7) | Depositions | 0-25% |
Cell wall possess three parts:-
(1)Matrix: It is a highly crosslinked amorphous gel- like ground substance of the cell wall. It contains the following:-
(i) Water:- 30-60% of the plant cell wall is water.It forms the dispersion medium of the matrix .
(ii) Pectin:- It constitutes 2-8% of the cell wall. It forms the colloidal complex and filler substance of the matrix. This polysaccharide is made of galacturonic acid, galactose, arabinose,rhamnose,etc.It functions in cross - linking.
Pectins are present in larger amounts in the primary wall than the secondary wall.
(iii) Hemicellulose:- 5-15% of the plant cell wall is Hemicellulose . It binds microfibrils to the matrix.It is a heteropolysaccharide of xylans, arabans, mannans, galactans, arabinogalactans, etc.
The amount of Xylans in the primary cell wall and secondary cell wall are 5% and 20% respectively.
Glucomannan is chiefly present in the secondary wall.
Xyloglucan :- 20% of primary cell wall of dicots and 1-5% of primary cell wall of grasses are xyloglucan. It is absent from the secondary wall.
Callose: present in between plasma membrane and wall proper.
(iv) Lipids constitute 0.5-3% of the wall.
(v) Proteins form 1-2% of the wall. e.g. Extensin connects pectin with hemicellulose.
(2) Microfibrils: These are made of cellulose. They provide rigidity to the cell wall.In fungi microfibrils are made of chitin and fungus cellulose.
Cellulose composed 20-30% of the dry Wt of primary and 40-90% of secondary cell wall respectively.
(3) Wall deposits & others : Silica, Fe,Ca, Cutin, Suberin, Wax, Lignins, waxes, tanin, resin Gum ,etc. are the additions of inorganic and organic materials into and on the outside of the cell wall :-
(i) Silica is noted in the epidermal cells of Equisetum and grasses.
(ii) Calcium carbonate may deposit on the cell wall.
(iii) Leaves and fruit surface contain wax, above or below the cuticle or within the cutin.
(iv)Suberin is found in the cell wall of seed cost, cork and casperian strips.
(v) Cutin is present on the epidermal walls.
(vi) Lignins are found in sclerenchyma cells.
Basically, the first network of cell walls is Cellulose microfibrils, the second network is the Pectic polysaccharides and the third network is Structural proteins.
Minor Anatomy -Practical
Sample 2B...i
The T.S. of the supplied specimen shows the following layers of tissues:
Fig: T.S. of the specimen “B”...Nerium leaf
Epidermis : (i) Both upper and lower epidermis are multiseriate ( 3 layered) and composed of isodiametric colourless parenchyma without any inter cellular space.
(ii) Both the epidermis are cuticularised.
(iii) A number of” sunken stomata “ are present on the lower epidermis.
(iv) Numerous trichomes develop from border cells and these are projected within the stomatal pits.
Mesophyll : (i) Multiseriate upper and lower palisade parenchyma are present without any inter cellular space.
(ii) Spongy parenchyma are located in between the palisade parenchyma with air spaces.
(iii) A few calcium oxalate crystals are scattered within the mesophyll tissue.
Vascular bundles: (i) Vascular bundles are collateral and closed .
(ii) Xylems are on the upper sides and phloem on the lower sides of each bundle.
(iii) Each bundle is surrounded by bumble sheaths.
Adaptive anatomical features:
(i) Sunken stomata present on lower epidermis.
(ii) Stomatal pits have numerous trichomes to reduce loss of water.
( iii) Calcium oxalate crystals are present as excretory products.
(iv) Both epidermis are multiseriate and cuticularised.
Identification:
(i) Presence of stomata on lower epidermis.
(ii) Mesophyll tissue are of two types : palisade and spongy.
(iii) Vascular bundles collateral and closed.
Hence, the supplied specimen is a “ dorsiventral dicot leaf with xerophytic adaptive features.
Specimen no: 2 (B) ..ii
Date 12/08/2025
In T.S. the following tissue are observed under microscope:
Fig: T.S. of supplied specimen (Hydrila stem)
Epidermis: (i) Single layered and chlorenchymatous.
(ii) There is no cuticle on epidermis.
(iii) Epidermal cell walls are thin.
Cortex : (i) Cortex is wide.
(ii) Parenchyma tissue cell wall is thin.
(iii) Large air cavities are found in the cortex.
(iv) Endodermis distinct.
Vascular bundles: (i) Simple, concentric and closed.
(ii) The single central xylem is surrounded by phloem tissue.
(iii) Xylem is poorly developed.
(iv) Phloem composed sieve tube elements.
Pith : Absent.
Adaptive features and identifying features:
(i) Vascular bundle is single,simple and closed.
(ii) Development in xylem is very poor.
(iii) Mechanical tissue absent.
(iv) Stomata absent.
(v) No cuticle on the epidermis.
(vi) Many large sized air cavities are present at the cortex.
So, the supplied specimen is identified as a monocot stem with hydrophytic adaptation.
Specimen no 2B ….(iii)
Date : 12/08/2025
The T.S. of the supplied specimen shows the following tissue:
Fig: T.S.of the specimen (Nymphea ) petiole
Epidermis: (i) Single layered, parenchymatous , without any cuticle.
(ii) Multicellular hairs present on the epidermis.
Cortex: (i) Two layered thick walled hypodermis is present just inner to the epidermis.
(ii) Inner ground tissue is thin- walled parenchymatous with air- chambers.
(iii) Branched trichosclerides with calcium oxalate deposits are present in air- cavities.
Vascular bundles: (i) Poorly developed.
(ii) Sizes are different and scattered within the ground tissue.
(iii) Each vascular bundle is collateral, closed with ill developed xylem.
(iv) Smaller vascular bundles have 1 patch of phloem and larger ones have 2 patches of phloem.
Pith: absent.
Adaptive anatomical features/ identifying features:
(i) Epidermal cell wall thin, parenchymatous and without cuticle.
(ii) Air chambers are scattered on the ground tissue.
( iii) Trichosclerides present in the ground tissue.
Hence, the supplied specimen is identified as Nymphea petiole with hydrophytic adaptive features.
Specimen no : 2 B……iv
Anatomy:
Epidermis : Single layered without cuticle.
Cortex : (i) Aerenchymatous.
(ii) Air spaces are separated by single layered partitions.
(iii) One or two layers of parenchyma just below the epidermis and outer to the endodermis without any airspace.
(iv) Endodermis and pericycle are indistinct.
Mechanical tissue: (i) Absent.
(ii) A few xylem elements are present towards the centre.
(iii) Xylem is replaced by a cavity at the centre.
(iv) Phloem is well developed and formed of sieve tube and companion cells.
Adaptive features:
Morphological:
(i) Absence of root hair.
(ii) Leaves are thin, linear, small and narrow.
(iii) Stem is fistular and herbaceous.
(iv) Presence of mucilage cover on the plants.
Anatomical:
(i) Epidermis without cuticles.
(ii) Presence of extensive air spaces in the cortex for storage of air.
(iii) Poorly developed mechanical tissue.
(iv) Absence of water conducting tissue( xylem).
Hence, the specimen is identified as a plant with hydrophytic adaptive features.
Secondary Growth
Tissue : Meristematic & Simple Permanent
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