Tissue and Tissue System Chapter Unit IV: Plant Anatomy

219 Pages·2017·12.95 MB·English

Unit IV: Plant Anatomy
(Structural organisation)
Chapter
9
Tissue and Tissue System

Learning Objectives
The learner will be able to,
Nehemiah Grew
• Study major types of plant cells and Father of Plant
their function. Anatomy
• Differentiate the various types of
1641–1712
cells.
• Study the relationship between the Katherine Esau (1898–1997)
distribution of tissues in the various A legendary Role model for women in
parts of plants. science. She was a scintillating Botany
teacher and pioneering researcher for
• Describes the ground tissue system
six decades. Her classic book
[cortex and pith] and vascular Anatomy
is the best literature in
systems of Seed Plants
Plant Anatomy. In
• Interpret cross sections and
recognition of her
longitudinal sections of dicot and
distinguished service
monocot root, stem and leaf.
to science, she was
• Compare the internal organization awarded
National
of dicot root and monocot root.
Medal of Science
(1989) by USA.
This chapter introduces the internal
structure of higher Plants. The study of
Chapter Outline
internal structure and organisation of
9.1 Meristematic tissue plant is called plant Anatomy (Gk: Ana =
9.2 Permanent tissues as under; temnein = to cut). Plants have
cells as the basic unit. The cells are
The tissue system
9.3
organised into tissues. The tissues in turn
Epidermal tissue system
9.4
are organised into organs. The different
Fundamental tissue system
9.5
organs in a plant have different internal
Vascular tissue system
9.6 structures. It is studied by means of
9.7 Comparision of primary structure dissection and microscopic examination.
1
of tissue is called Histology. A plant is
Milestones in Anatomy
made up of different types of tissues.
• 1837 Hartig: Coined the term
Sieve
There are two principal groups:
tubes
• 1839 Schleiden: Coined the term 1. Meristematic tissues
2. Permanent tissues
Collenchyma
• 1857 Hofmeister: Proposed
Apical cell
9.1 Meristematic Tissue
theory
• 1858 Nageli. C: Coined the term 9.1.1 Characteristics and classification
Xylem
supporter
and Phloem, Meristem and The characters of meristematic tissues:
of Apical cell theory (Gr. Meristos-Divisible)
• 1865 Mettenius: Coined the term The term meristem is coined by
Sclerenchyma C. Nageli 1858.
• 1868 Hanstein: Proposed Histogen • The meristematic cells are isodiametric
theory and they may be, oval, spherical or
• 1885 Tschirch: Coined the term polygonal in shape.
Named Four types of
Sclereids • They have generally dense cytoplasm
(Brachy, Macro, Osteo &
Sclereids with prominent nucleus.
Astro) in 1889
• Generally the vacuoles in them are
• 1914 Haberlandt: Coined the term
either small or absent.
xylem as and Phloem
Hadrome
as • Their cell wall is thin, elastic and
Leptome and Classification of
essentially made up of cellulose.
meristem.
• 1924 Schmidt A: Proposed Tunica – • These are most actively dividing cells.
Corpus theory
• Meristematic cells are self-perpetuating.
• 1926 Schűepp:
Mass, rib, & plate
meristem Classification of Meristem
• 1946 Bloch: Discovered the Meristem has been classified into several
types on the basis of position, origin,
Trichosclereids
• 1952 Popham: Explained the function and division.
organization of
Shoot apex of
Apical meristem
Angiosperms
• 1955 Duchaigne: Discovered the
Annular collenchyma
Intercalary meristem
• 1961 Clowes: Proposed
Quiescent
centre concept
• 1963 Sanio: Coined the term
Tracheids
Lateral meristem
The Tissues
A Tissue is a group of cells that are alike in Figure 9.1: Different types of meristems
origin, structure and function. The study on the basis of position in plant body
2
Classification of Meristem
Position Origin Function Plane of division
Apical meristem Protoderm
Mass meristem
Present in apices of root Primary It gives rise to
It divides in all
and shoot. It is responsible Meristem epidermal tissue
planes. Example:
for increase in the length It is derived system and
endosperm,young
of the plant, it is called as from develops into
embryo and
primary growth. embryonic epidermis,stomata
sporangium
stages and and hairs.
differentiated
into primary
Intercalary meristem
permanent
Rib meristem or
Occurs between the tissues.
Procambium File meristem
mature tissues. It is
It gives rise to It divides
responsible for elongation
primary vascular anticlinally in one
of internodes.
Secondary tissues. Example: plane. Example:
It is xylem and phloem . development of
meristem
derived during cortex and pith
Lateral meristem
later stage of
Occurs along the
development
longitudinal axis of stem
of the plant Plate meristem
and root. It is responsible Ground Meristem
body. It It divides
for secondary tissues and It gives rise to
produces cork anticlinally in two
thickening of stem and all tissues except
planes. Example:
cambium and
root. Example: vascular epidermis and
development of
cambium and cork interfascicular vascular strands.
epidermis
cambium. cambium.
Theories of Meristem Organization and Shoot Apical Meristem
Function
Apical Cell Theory
Many anatomists illustrated the root Apical cell theory is proposed by
and shoot apical meristems on the basis (1852) and supported by
Hofmeister
of number and arrangement and accordingly (1859). A single apical cell is the
Nageli
proposed the following theories – An structural and functional unit.
extract of which are discussed below.
Apical cell
Tunica
Leaf primodium Leaf primordia
Dermatogen
Periblem Histogen Corpus
Plerome
a. b. c.
Shoot apical meristem a) Apical cell theory, b) Histogen theory,
Figure 9.2:
c) Shoot Tunica corpus theory
3
This apical cell governs the growth at their apices and the apical meristem
and development of whole plant body. It is present below the root cap. The
is applicable in Algae, Bryophytes and in different theories proposed to explain
some Pteridophytes. root apical meristem organization is
given below.
Histogen Theory
Apical Cell Theory
Histogen theory is proposed by
Hanstein
Apical cell theory is proposed by
(1868) and supported by The Nageli.
Strassburgur.
The single apical cell or apical initial
shoot apex comprises three distinct zones.
composes the root meristem. The apical
1. It is a outermost layer.
Dermatogen:
initial is tetrahedral in shape and produces
It gives rise to epidermis.
root cap from one side. The remaining
2. It is a middle layer. It gives
Periblem:
three sides produce epidermis, cortex and
rise to cortex.
vascular tissues. It is found in vascular
3. Plerome: It is innermost layer. It gives cryptogams.
rise to stele
Histogen Theory
Tunica Corpus Theory Histogen theory is proposed by Hanstein
Tunica corpus theory is proposed by and supported by .
(1868) Strassburgur
(1924). The histogen theory as appilied to the
A. Schmidt
root apical meristem speaks of four
Two zones of tissues are found in apical
histogen in the meristem. They are
meristem.
respectively
1. : It is the peripheral zone of
The tunica
i. It is a outermost layer. It
shoot apex, that forms epidermis. Dermatogen:
gives rise to root epidermis.
2. : It is the inner zone of
The corpus
ii. It is a middle layer. It gives
shoot apex,that forms cortex and stele Periblem:
of shoot. rise to cortex.
iii. It is innermost layer. It gives
Root Apical Meristem Plerome:
rise to stele
Root apex is present opposite to the
shoot apex. The roots contain root cap iv. Calyptrogen: It gives rise to root cap.
Epidermis Stele Cortex Cortex Stele Cortex
Protoderm
T
Ground tissue
Quiescent
Vascular cambium Root centre
cap Inverted ‘T’
division
(Y division) Cap
Plerome b. Calyptrogen c.
Periblem
Root apical meristem
Dermatogen / Calyptrogen Figure 9.3:
a) Histogen Theory, b) Korper kappe theory,
Root cap
c) Quiescent Centre Concept
a.
4
Korper Kappe Theory Parenchyma (Gk: Para-beside;
Korper kappe theory is proposed by enehein- to pour)
Schuepp. There are two zones in root Parenchyma is generally present in all organs
apex – Korper and Kappe of the plant. It forms the ground tissue in a
1. forms the body. plant. Parenchyma is a living tissue and made
Korper zone
up of thin walled cells. The cell wall is made
2. forms the cap. This
Kappe zone
up of cellulose. Parenchyma cells may be oval,
theory is equivalent to tunica corpus
polyhedral, cylindrical, irregular, elongated
theory of shoot apex.The two divisions
or armed. Parenchyma tissue normally has
are distinguished by the type of T
prominent intercellular spaces. Parenchyma
(also called Y divisions). Korper is
may store various types of materials like,
characterised by inverted T divisions
water, air, ergastic substances. It is usually
and kappe by straight T divisions.
colourless. The turgid parenchyma cells help
Quiescent Centre Concept in giving rigidity to the plant body. Partial
Quiescent centre concept was proposed conduction of water is also maintained
by Clowes (1961) to explain root apical through parenchymatous cells.
meristem activity. These centre is located
between root cap and differentiating Intercellular spaces
cells of the roots. The apparently inactive
region of cells in root promeristem is
called quiescent centre. It is the site of
hormone synthesis and also the ultimate
source of all meristematic cells of the
meristem.
9.2 Permanent Tissues
Parenchyma
Figure 9.4:
The Permanent tissues develop from apical
Occsionally Parenchyma cells which
meristem. They lose the power of cell
store resin, tannins, crystals of calcium
division either permanently or temporarily.
carbonate, calcium oxalate are called
They are classified into two types:
idioblasts. Parenchyma is of different types
1. Simple permanent tissues.
and some of them are discussed as follows.
2. Complex permanent tissues.
Types of Parenchyma
Simple Permanent Tissues
Starch
Simple tissues are composed of one type
ggrains
Intercellular
of cells only. The cells are structurally and
spaces
functionally similar. It is of three types.
1. Parenchyma
a. b.
2. Collenchyma
Types of Parenchyma
Figure 9.5:
3. Sclerenchyma
a) Aerenchyma, b) Storage parenchyma
5
1. Aerenchyma:
Parenchyma which contains air in its intercellular spaces. It helps
in aeration and buoyancy. Example: .
Nymphae and Hydrilla
5. Prosenchyma: 2. Storage Parenchyma:
Parenchyma cells became Parenchyma stores food
elongated, pointed and slightly materials. Example: Root and
Parenchyma
thick walled. It provides stem tubers.
mechanical support.
4. Chlorenchyma 3. How?.... Stellate
Parenchyma cells with
Parenchyma
chlorophyll. Function is Star shaped parenchyma.
photosynthesis. Example: Example: Petioles of
Banana
Mesophyll of leaves. .
and Canna
small chloroplast or none. Tannin maybe
Intercellular Intercellular
Space Spaces present in collenchyma.Based on pattern
Chloroplasts
of pectinisation of the cell wall, there are
Palisade
Parenchyma three types of collenchyma
Spongy
Parenchyma
Types of Collenchyma
a. b. c. 1. Angular collenchyma
It is the most common type of collenchyma
c) Stellate parenchyma,
Figure 9.5:
with irregular arrangement and
d) Chlorenchyma, e) Prosenchyma
thickening at the angles where cells meets.
Example:Hypodermis of Datura and
Collenchyma (Gk. Colla-glue;
Nicotiana
enchyma – an infusion)
Collenchyma is a simple, living mechanical
2. Lacunar collenchyma
tissue. Collenchyma generally occurs in
The collenchyma cells are irregularly
hypodermis of dicot stem. It is absent arranged. Cell wall is thickening on the
in the roots and also occurs in petioles walls bordering intercellular spaces.
and pedicels. The cells are elongated Example:Hypodermis of Ipomoea
and appear polygonal in cross section.
The cell wall is unevenly thickened.
3. Lamellar collenchyma
It contains more of hemicellulose and The collenchyma cells are arranged
pectin besides cellulose. It provides compactly in layers(rows). The Cell wall
is thickening is at tangential walls.These
mechanical support and elasticity to the
thickening appear as successsive tangential
growing parts of the plant. Collenchyma
layers. Example:Hypodermis of Helianthus
consists of narrow cells. It has only a few
6
Diagramatic structures
Nucleus
Thickened Intercellular
corners thickenings
Protoplasm
Vacuole Lamellar
Cell wall thickenings
a. b. c.
Types of Collenchyma a) Angular collenchyma, b) Lacunar collenchyma,
Figure 9.6:
c) Lamellar collenchyma
1. Sclereids
Duchaigne (1955)
Annular Collenchyma:
2. Fibres
reported another type called Annular
collenchyma in petiole of Nerium. The
Sclereids (Stone Cells)
lumen is more or less circular in shape.
Sclereids are dead cells, usually these
are isodiametric but some are elongated
Sclerenchyma (Gk. Sclerous- hard:
too. The cell wall is very thick due
enchyma-an infusion)
to lignification. Lumen is very much
The sclerenchyma is dead cell and
reduced. The pits may simple or branched.
lacks protoplasm. The cells are long or
Sclereids are mechanical in function.
short, narrow thick walled and lignified
They give hard texture to the seed coats,
secondary walls. The cell walls of these cells
endosperms etc., Sclereids are classified
are uniformly and strongly thickened. The
into the following types.
sclerenchymatous cells are of two types:
Types of Sclereids
1. Branchysclereids or Stone cells: 2. Macrosclereids:
Isodiametric sclereids, with hard cell Elongated and rod shaped cells, found in
wall. It is found in bark, pith cortex, hard the outer seed coat of leguminous plants.
endosperm and fleshy portion of some Example: Crotalaria and Pisum sativum.
fruits. Example: - Pulp of Pyrus.
3. Osteosclereids (Bone cells):
Rod shaped with dilated ends. They occur in leaves and seed coats. Example: seed coat of Pisum
and Hakea
4. Astrosclereids: 5. Trichosclereids:
Star cells with lobes or arms diverging Hair like thin walled sclereids. Numerous
form a central body. They occur in petioles small angular crystals are embedded in the
and leaves. Example: Tea, Nymphae and wall of these sclereids, present in stems and
Trochodendron. leaves of hydrophytes. Example: Nymphaea
leaf and Aerial roots of Monstera.
7
Diagramatic Structures
Macro
Sclereid
Lumen
Lumen cell
Thick
cell wall
Lumen
Thick cell wall
Pith
a. b. c.
Thick Tricho
cell wall Sclereids
Lumen
d. e.
Types of Sclereids a) Brachysclereids, b) MacroSclereids, c) Osteosclereids,
Figure 9.7:
d) Astrosclereids, e) Trichosclereids
Pointed
pits. They provide
The sclereids end
Filiform Sclereids: m e c h a n i c a l
are present in the leaf lamina of
strength and
Olea europaea. They are very much
protect them
elongated fibre like and about 1m.m
from the strong
length.
wind. It is also
called supporting
tissues. Fibres
Sclerenchyma Found in Some Fruits
have a great
commercial value
in cottage and Lumen
textile industries.
Fibres are of five
a) Pear fruit,
Figure 9.8:
types
b) Strawberry, c) Guava T.S of fibre
Figure 9.9
Wood Fibres or Xylary Fibres
Fibres
These fibres are associated with the
Fibres are very much elongated
secondary xylem tissue. They are also
sclerenchyma cells with pointed tips.
called xylary fibres. These fibres are
Fibres are dead cells and have lignified
derived from the vascular cambium.
walls with narrow lumen. They have simple
These are of four types. a. Libriform fibres
8
b. Fibre  tracheids c. Septate fibres
Mesocarp Fibres
d. Gelatinous fibres.
Fibres obtained from the mesocarp of
drupes like Coconut.
Fibres are the longest
Leaf Fibres
plant cells. Longest
Fibres obtained from the leaf of
Musa,
Fibres occur in
Agave and Sensciveria.
(Ramie
Boehmeria
fibre) 55 cm long
Fibres in Our Daily Life
Economically fibres may be grouped as
a. These fibres have
Libriform fibres: follows
slightly lignified secondary walls with
1. Fibres utilized for the
Textile Fibres:
simple pits. These fibres are long and
manufacture of fabrics, netting and
narrow.
cordage etc.
b. These are shorter
Fibre tracheids:
a. : Example: Cotton.
Surface Fibres
than the libriform fibres with moderate
b. : Example: Flax, Jute and
secondary thickenings in the cell walls. Soft Fibres
Ramie
Pits are simple or bordered.
c. Example: Sisal,
c. Fibres that have thin Hard fibres:
Septate fibres:
Coconut, Pineapple, Abaca
septa separating the lumen into distinct etc.
chambers. Eg. Teak 2. Brush fibre: Fibres utilized for the
manufacture of brushes and brooms.
d. Fibres in which lignin
Gelatinous fibres:
is less in amount and cellulose is more in 3. Rough weaving fibres: Fibres utilized
this cell walls. in making baskets, chairs, mats etc.
4. Wood fibres
These fibres are characteristic of tension Paper making fibres:
utilized for paper making.
wood which is formed in the underside of
leaning stems and branches. 5. Filling fibres: Fibres used for stuffing
cushions, mattresses, pillows, furniture
Bastfibres or Extra Xylary Fibres etc. Example: and Silk cotton.
Bombax
These fibres are present in the phloem.
Natural Bast fibres are strong and Complex Tissues
cellulosic. Fibres obtaining from the
A complex tissue is a tissue
phloem or outer bark of jute, kenaf,
with several types of cells
flax and hemp plants. The so called
but all of them function
pericyclic fibres are actually phloem
together as a single unit. It
fibres.
is of two types – xylem and
phloem.
Surface Fibres
These fibres are produced from the surface
Xylem
of the plant organs. Cotton and silk cotton
The xylem is the principal water conducting
are the examples.They occur in the testa
tissue in a vascular plant. The term xylem
of seeds.
was introduced by (1858) and is
Nageli
9
derived from the Gk. – wood. The
Xylos Tracheids
xylem which is derived from Procambium is
Tracheids are dead, lignified and
called and the xylem which
primary xylem elongated cells with tapering ends. Its
is derived from vascular cambium is called
lumen is broader than that of fibres. In
. Early formed primary
secondary xylem cross section, the tracheids are polygonal.
xylem elements are called protoxylem,
There are different types of cell wall
whereas the later formed primary xylem
thickenings due to the deposition of
elements are called metaxylem.
secondary wall substances. They are
Protoxylem lies towards the periphery
annular (ring like), spiral (spring like),
and metaxylem that lies towards the centre
scalariform (ladder like) reticulate (net
is called It is common in
Exarch. roots. like) and pitted (uniformly thick except
Protoxylem lies towards the centre and at pits). Tracheids are imperforated cells
meta xylem towards the periphery this with bordered pits on their side walls.
condition is called Endarch. It is seen in Only through this conduction takes place
stems. in Gymnosperms. They are arranged one
Protoxylem is located in the centre above the other. Tracheids are chief water
surrounded by the metaxylem is called conducting elements in Gymnosperms
. In this type only one vascular and Pteridophytes. They also offer
Centrarch
strand is developed. Example:  mechanical support to the plants.
Selaginella
sp.
Protoxylem is located in the centre
surrounded by the metaxylem is
called .In this type several
Mesarch
vascular strands are developed.
Example: 
Ophioglossum sp.
Student Activity
Annular Spiral Reticulate Scalariform Pitted thickening
students prepare the slide
Cell lab: Types of secondary wall
Figure 9.10:
and identify the different types tissues.
thickenings in tracheids and vessels
Xylem Consists of Four Types of Cells
Vessels or Trachea
1. Tracheids
Vessels are elongated tube like structure.
2. Vessels or Trachea
They are dead cells formed from a row of
3. Xylem Parenchyma
vessel elements placed end to end. They
4. Xylem Fibres are perforated at the end walls. Their
lumen is wider than Tracheids. Due to
is called the dissolution of entire cell wall, a single
Xylem hadrome phloem
is called These terms are pore is formed at the perforation plate.
leptome.
coined by haberlandt (1914) It is called simple perforation plate,
Example: . If the perforation
Mangifera
10