Anatomy of Flowering Plants
Part – 1
Tissues
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Prepared by
Rajalakshmi.K
GGHSS Kallai
Tissues
A tissue is a group of cells having
a common origin and usually
performing a common function.
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Tissues are classified as follows
Meristematic tissues Permanent tissues
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Apical Intercalary Lateral Simple tissue Complex tissue
✓ Root apical ✓ Fascicular ✓ Parenchyma ✓ Xylem
✓ Shoot apical cambium ✓ Collenchyma ✓ Phloem
✓ Interfascicular ✓ Sclerenchyma
cambium
✓ Cork-cambium
Meristematic Tissues
✓ Apical meristems - The meristems which occur at the tips of
✓ roots and shoots
✓ Root apical meristem occupies the tip of a root
✓ Shoot apical meristem occupies the tip of a shoot
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Intercalary meristem -
❖ The meristem which occurs between mature tissues
❖ They occur in grasses and regenerate parts removed
by the grazing herbivores.
Lateral meritsem CBTA
❖ They are responsible for producing the secondary tissues.
❖ Eg: Fascicular vascular cambium
Interfascicular cambium
Cork-cambium
❖ Following divisions of cells by meristems,
the newly formed cells become structurally and
functionally specialised and lose the ability to divide.
❖ Such cells are termed permanent cells which forms
Permanent tissues.
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Permanent tissues are of two types
● Simple tissues -
A simple tissue is made of only one type of cell.
● Complex tissues -
A complex tissue is made of different type of cells.
The various simple tissues in plants are
Parenchyma, Collenchyma and Sclerenchyma
Parenchyma
✓ Thin walled living cells
✓ They may be spherical, oval, round, polygonal or elongated
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✓ They may be closely packed or have small intercellular spaces.
✓ The parenchyma performs various functions like
Photosynthesis, Storage, Secretion.
Parenchyma
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Collenchyma
✓ Cells which are much thickened at the corners
✓ .Intercellular spaces are absent.
✓ They provide mechanical support to the growing parts of
the plant such as young CBTA
stem and petiole of a leaf.
Collenchyma
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Sclerenchyma
✓ They are dead cells without protoplasts.
✓ It provides mechanical support to organs.
✓ Sclerenchyma may be either fibres or sclereids.
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✓ The fibres are thick-walled, elongated and pointed cells
Lumen
Thick wall
Fibre
✓ The sclereids are spherical, oval or cylindrical
✓ They are dead cells with very narrow cavities (lumen).
✓ These are commonly found in the fruit walls of nuts,
pulp of fruits like guava,
CBTAsapota etc.
Lumen
Thick wall
Sclereid
Sclerenchyma
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Anatomy of Flowering Plants
Part –
CBTA 2
Complex Tissues - Xylem & Phloem
Prepared by
Rajalakshmi.K
GGHSS Kallai
Complex Tissues
✓ The complex tissues are made of more than
one type of cells and these work together as a unit.
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✓ Xylem and phloem constitute the complex tissues
Xylem
Function
✓ conduction of water and minerals from roots to the
stem and leaves.
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✓ provides mechanical strength to the plant parts.
It is composed of four different kinds of cells
❖ Tracheids
❖ Vessels
❖ Xylem fibres
❖ Xylem parenchyma.
Tracheids
✓ Tube like cells with thick and lignified walls
and tapering ends.
✓ These are dead cells without protoplasm.
Vessel CBTA
✓ Long cylindrical tube-like cells
✓ They have lignified walls and a large central cavity
without protoplasm.
✓ The presence of vessels is a feature of Angiosperms.
✓ Gymnosperms lack vessels in their xylem.
Xylem fibres
✓ They have highly thickened walls Xylem fibre
with narrow central lumens.
Xylem parenchyma
✓ They are livingCBTA
and thin-walled cells
✓ They store food materials in the form of
starch fat, tannins.
✓ The radial conduction of water takes place by the
Ray parenchymatous cells.
Primary xylem is of two types –
✓ Protoxylem
✓ Metaxylem
✓ The first formed primary xylem elements are called as
Protoxylem.
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✓ The later formed primary xylem is called as Metaxylem.
Metaxylem
Protoxylem
✓ In stems, the protoxylem lies towards the centre (pith)
and the metaxylem lies towards the periphery
✓ Such arrangement of primary xylem is called Endarch.
✓ In roots, the protoxylem lies towards periphery and
metaxylem lies towards the centre.
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✓ Such arrangement of primary xylem is called Exarch.
Protoxylem
Metaxylem
Endarch Exarch
Phloem
Phloem transports food materials, from leaves to other
parts of the plant.
Phloem in angiosperms is composed of
✓ Sieve tube elements
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✓ Companion cells
✓ Phloem parenchyma
✓ Phloem fibres.
Sieve tube elements
✓ Long, tube-like structures, arranged
longitudinally and are associated with the
companion cells.
✓ Their end walls are perforated
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manner to form the sieve plates.
✓ A mature sieve element has cytoplasm and
a large vacuole but lacks a nucleus.
✓ The functions of sieve tubes are controlled
by the nucleus of companion cells.
Companion cells
✓ Specialised parenchymatous cells, which are
associated with sieve tube cells
✓ The companion cells help in maintaining the pressure
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gradient in the sieve tubes.
Phloem parenchyma
✓ Elongated, tapering cylindrical cells which have dense
cytoplasm and nucleus.
✓ The phloem parenchyma stores food material and
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other substances like resins, latex and mucilage
Phloem fibres (bast fibres)
✓ Made up of sclerenchymatous cells.
✓ These are much elongated, unbranched and have pointed,
needle like apices.
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✓ Phloem fibres of jute, flax and hemp are used commercially.
Anatomy of Flowering plants
Part
CBTA 3
Epidermal Tissue System
Prepared by
Rajalakshmi.K
GGHSS Kallai
The tissue system
On the basis of their structure and location,
there are three types of tissue systems.
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✓ the epidermal tissue system
✓ the ground or fundamental tissue system
✓ the vascular or conducting tissue system.
Epidermal Tissue System
The epidermal tissue system forms the outer-most
covering of the plant body
It comprises of
✓ Epidermal cells CBTA
✓ Stomata
✓ Epidermal appendages – the trichomes and hairs.
Epidermis
✓ The epidermis is the outermost layer of the primary
plant body which is usually single layered.
✓ It is often covered with a waxy thick layer called
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as cuticle which prevents loss of water.
✓ Cuticle is absent in roots
Stomata
✓ Stomata are structures present in the epidermis.
✓ Stomata regulate the process of transpiration
and gaseous exchange.
✓ In Dicots the stomatal pore is guarded by two
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bean shaped cells known as Guard cells
✓ In Monocots like grasses, the guard cells
are dumb-bell shaped.
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✓ The guard cells possess chloroplasts and regulate the
opening and closing of stomata.
✓ The epidermal cells, which lie close to guard cells are
known as Subsidiary cells.
✓ The Stomatal pore, Guard cells and the surrounding
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Subsidiary cells are together called Stomatal apparatus
Stomata of Dicots Stomata of Monocots
Epidermal appendages
✓ The root hairs are unicellular elongations of the epidermal cells
of roots which absorb water and minerals from the soil.
✓ On the stem the epidermal hairs are called trichomes.
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✓ The trichomes help in preventing water loss due to transpiration.
Anatomy of Flowering Plants
Part – 3
Anatomy of Stem ,Root & Leaf
CBTA
Prepared by
Rajalakshmi. K
GGHSS Kallai
The Ground Tissue System
All tissues except epidermis and vascular bundles
constitute the Ground tissue.
The different regions of ground tissue of stem & roots are
Cortex, Pericycle, Pith and Medullary rays
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Epidermis Cortex
Pericycle Ground
tissue
Vascular
tissues Pith
Medullary rays
The Vascular Tissue System
✓ The vascular system consists of complex tissues,
the phloem and the xylem.
✓ The xylem and phloem together constitute
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vascular bundles.
✓ In Conjoint type of vascular bundles,
the xylem and phloem are jointly situated
along the same radius of vascular bundles.
1) Conjoint Open vascular bundle - cambium is present between
phloem and xylem , character of dicot stem
2) Conjoint Closed vascular bundle - cambium is absent between
phloem and xylem , character of monocot stem
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3) Radial -Xylem and phloem are arranged in an alternate manner
along the different radii as in roots
Open vascular bundle Closed vascular bundle Radial
Anatomy of Dicotyledonous Stem
✓ Epidermis is the outermost protective layer of the stem.
✓ Hypodermis is a few layers of collenchymatous cells just
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below the epidermis.
✓ Cortex lies below hypodermis which consists of
parenchymatous cells.
✓ Endodermis is the innermost layer of the cortex .
✓ Pericycle lies inner to endodermis as semi-lunar
patches of sclerenchyma.
✓ Medullary rays are parenchymatous cells seen in
between the vascular bundles
✓ Vascular bundles are limited
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arranged in a ring
✓ Each vascular bundle is conjoint, open, with
endarch protoxylem.
✓ Pith is parenchymatous in the central portion
of the stem
T.S Dicot Stem
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Anatomy of Monocotyledonous Stem
✓ Epidermis is the outermost single layer of cells
✓ Hypodermis is seen just below the epidermis and is
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sclerenchymatous
✓ Ground tissue is not differentiated into cortex and pith
✓ Vascular bundles a large in number scattered in the
ground tissue
✓ Each vascular bundle is surrounded by sclerenchymatous
bundle sheath
✓ Vascular bundles are conjoint and closed.
✓ Water-containing cavities are present within vascular bundles.
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T.S Monocot Stem
Anatomy of Dicotyledonous Root
➢ Epiblema is the outermost layer .
➢ Some cells of epiblema form root hairs.
➢ Cortex consists of several layers of thin-walled
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parenchyma cells
➢ Endodermis is the innermost layer of the cortex
The tangential as well as radial walls of the endodermal cells
have a deposition of water-impermeable, waxy material
suberin in the form of Casparian strips.
✓ Pericycle lies next to endodermis .
✓ Lateral roots arise from these cells.
✓ Conjuctive tissue are cells which lie between the
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xylem & phloem
✓ Vascular tissues xylem and phloem are arranged radially
✓ There are usually two to four xylem and phloem patches.
✓ The pith is small or inconspicuous.
T.S of Dicot Root
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Anatomy of Monocotyledonous Root
✓ The anatomy of the monocot root is similar to the dicot root
✓ It has epidermis, cortex, endodermis, pericycle,
similar to that of DicotCBTA
root
✓ Vascular tissues are arranged radially and usually
more than six – polyarch xylem bundles
✓ Pith is large and well developed.
T.S Monocot Root
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Anatomy of Dorsiventral (Dicotyledonous) Leaf
✓ The vertical section of a dorsiventral leaf shows three main parts,
namely, Epidermis, Mesophyll and Vascular system.
✓ Epidermis –the upper epidermis is Adaxial epidermis which bears
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more stomata & lower epidermis is Abaxial epidermis
which lack stomata.
✓ Mesophyll - The tissue between the upper and the lower epidermis
It possesses chloroplasts and carry out
photosynthesis. It is made up of parenchyma.
✓ Mesophyll has two types of cells –
✓ The Palisade parenchyma and the Spongy parenchyma.
✓ Palisade parenchyma is made up of elongated cell
✓ Spongy parenchyma is oval shaped loosely arranged cells
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with air cavities
✓ The vascular bundles are surrounded by a layer of
thick walled Bundle sheath cells.
✓ Vascular bundles are conjoint, closed bundles
T.S of Dicot Leaf
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Anatomy of Isobilateral (Monocotyledonous) Leaf
✓ Stomata are present on both the surfaces of the epidermis;
✓ Mesophyll is not differentiated into palisade and spongy parenchyma
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✓ In grasses, certain adaxial epidermal cells along the veins modify
themselves into large, empty, colourless cells called Bulliform cells.
✓ They make the leaves curl inwards to minimise water loss.
T.S of Monocot Leaf
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Anatomy of Flowering Plants
Part-6
Secondary growth & Wood
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Prepared by
Rajalakshmi.k
GGHSS.Kallai
SECONDARY GROWTH
✓ Apart from primary growth most dicot plants
exhibit an increase in girth.
✓ This increase CBTA
is called the Secondary growth.
✓ The tissues involved in secondary growth are
❖ Vascular cambium
❖ Cork cambium.
Secondary growth in Dicot stem
• In a young dicot stem Vascular Cambium is present
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as a single layer between the xylem and phloem.
• It cuts off new xylem cells towards the inner side &
new phloem cells towards outer side.
✓ The cells of cambium present between primary xylem and
primary phloem is called as the Intrafascicular cambium.
✓ The cells of medullary rays, near intrafascicular cambium
become meristematic and form the Interfascicular cambium.
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✓ Later the Intrafascicular cambium & the Interfascicular
cambium joins to form a continuous ring of cambium
called as Cambial ring.
Formation of cambial ring
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Intra fascicular cambium
Inter fascicular cambium
Cambial ring
Activity of the cambial ring
✓ The cambial ring becomes active and begins
to cut off new cells, both towards the inner
and the outer sides.
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✓ It cuts off more cells towards the pith which
mature into Secondary xylem and few cells
towards periphery which mature into
Secondary phloem.
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Spring wood and autumn wood
✓ In temperate regions, the climatic conditions are
not uniform through out the year.
✓ In the spring season, cambium is very active and produces
large number of xylaryCBTA
elements having vessels with wider
cavities called Spring wood or Early wood.
✓ In winter, the cambium is less active and forms fewer
xylary elements that have narrow vessels called
Autumn wood or Late wood.
✓ The spring wood is lighter in colour and has a lower density .
✓ The autumn wood is darker and has a higher density.
✓ The two kinds of woods that appear as alternate rings,
and forms an Annual ring.
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✓ Annual rings seen in a cut stem give an estimate about
the age of the tree.
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Heartwood and sapwood
✓ In old trees, the greater part of secondary xylem
is dark brown due to deposition of organic compounds
like tannins, resins, oils, gums, aromatic substances and
essential oils in the innermost
CBTAlayers of the stem.
✓ These substances make it hard, durable and resistant
to the attacks of microorganisms and insects.
✓ This region have dead elements with highly lignified walls
is called Heartwood.
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✓ The Heartwood it gives mechanical support to the stem.
✓ The peripheral region of the secondary xylem,
is lighter in colour and is known as the Sapwood.
✓ It is involved in the conduction of water and minerals
from root to leaf.
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Heartwood
Sapwood
Cork Cambium
✓ As the stem continues to increase in girth due to
the activity of vascular cambium, the outer cortical
and epidermis layers get broken and need to be replaced
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to provide new protective cell layers.
✓ Hence, another meristematic tissue called Cork cambium or
Phellogen develops, usually in the cortex region.
✓ Phellogen cuts off cells on both sides.
✓ The outer cells differentiate into Cork or Phellem
✓ The inner cells differentiate into Secondary cortex or
Phelloderm.
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✓ Phellogen, Phellem, and Phelloderm are collectively known
as Periderm or Bark
✓ At certain regions, the phellogen cuts off loosely arranged
parenchymatous cells on the outer side instead of cork cells.
✓ These parenchymatous cells soon rupture the epidermis,
forming a lens shaped openings called Lenticels.
✓ Lenticels permit the exchange of gases between the outer
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atmosphere and the internal tissue of the stem.
Secondary Growth in Roots
✓ It originates from the tissue located just below the
phloem bundles.
✓ A portion of pericycle tissue, above the protoxylem
forming a complete and CBTA
continuous wavy ring,
which later becomes circular .
✓ Further events are similar to those a dicotyledon stem.
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