Scope and significance of plant anatomyy

Scope and Significance in
Plant Anatomy and Role of
Anatomy in Phylogeny
Aleena Stanley
1st Msc Botany
St.Teresa’s College Ernakulam
1

Plant Anatomy..
● The study of Internal Gross Structure of by the technique of sectioning
and cutting is called as Plant Anatomy.
● Originally it included plant morphology, the description of the physical
form and external structure of plants, but since mid-20th century plant
anatomy has considered a separate field referring only to internal plant
structure .
● It is now frequently Investigated at the cellular level, and often involves
sectioning of tissues and microscopy.
2

Scope And Significance of Plant Anatomy.
1. ROLE IN TAXONOMY
Anatomy provides evidence concerning the inter relationships of large groups such as
families or in helping establishing the real affinities of genera of uncertain taxonomic
status.Anatomy form the backbone of taxonomy.
Study of anatomical features of flowering details has a long history of its own. The discovery
of various modern techniques and vast improvement in tools, especially the invention of
microscope have certainly add a lot to the finer detail of plant tissue.
Anatomy sometimes proves very helpful for individual identification. The anatomical methods
are great value in identifying the herbarium specimens which do not bear flowers or fruits.
The Anatomical methods are also used in identification of commercial sample of medicinal
plants, timber, fibers etc..
3

Significance of Anatomical Features in Relation To Taxonomy
According to Metcalfe (1968) identified several herbarium specimens
using vegetative Anatomy. According to Radford (1986) some of basic
evidentiary characters of well established taxonomic values were:- type,
size,shape,type of vascular bundles, rays, ground tissue parenchyma,
epidermal and mesophyll tissue, stomatal nodes etc..
4

1. EPIDERMIS OR EPIDERMAL CELLS
● Shape, size, outline, wall thickness and inclusions of epidermal cells are some of the
characters of taxonomic importance in different families and genera.
● Characters such as partly or wholly crystalliferous epidermis on the cells with specific
chemical contents are of importance because of their restricted occurrence.
● Epidermal cells with horizontal and vertical partition are of specific or almost generic
value.
● Presence and distribution of silica bodies in cyperaceae.
● Sclerification on the wall of epidermal cells in some genera of compositae and presence
of narrow epidermal cells in stylidiaceae are some characters of useful economic
importance.
5

2. STOMATA
Stomata are minute pores which occur in the epidermis of the plant cell. Each stoma is
surrounded by two kidney shaped epidermal cells the guard cells.It occurs on any part
except at the root. There are four types of stomata in Dicotyledons.
1. RANUCULACEOUS TYPE( Anomocytic)
Stoma is surrounded by a limited number of cells that are indistinguishable in size,
shape or form from those of the remainder of the epidermis.
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2. CRUCIFEROUS TYPE (Anisocytic type)
Stoma surrounded by three cells of which one is distinctly smaller that other two .
3. CARYOPHYLLACEOUS TYPE (Diacytic type)
Stoma enclosed by a pair of subsidiary cells whose common wall is right angle to the guard
cells.
4. RUBIACEOUS TYPE (Paracytic type)
Stoma surrounded by either side by one or more subsidiary cells parallel to the long axis of
the pore and guard cells.
8

STOMATA - MONOCOTYLEDONS
● The graminaceous type of stoma is believed to be confined to the
monocotyledons where it is specially characteristics of Gramineae and
Cyperaceae. The “Gramineous” stoma posses guard cells of which the middle
portions are much narrower than the ends so that the cells appear, dumbbell
shaped in surface view. The subsidiary cells are found lying parallel to the
long axis of the pore.
9

3.STEM ANATOMY
Anatomy of vegetative structures has been importance in separating higher categories, such as
gymnosperms from angiosperms and monocots from dicots.
1. CORK
The position in which the cork originates in a young stem is diagnostic value within limits.In
an individual species, the first cork to be formed is often more superficial than that which
arises later.In some families the origin of cork is seems to be constant.
1. ENDODERMIS
In most Dicot stems the endodermis is inconspicuous. In some the endodermis consists of a
distinct layer of cells which are differentiated from the neighbouring cells in containing starch
.In another group endodermis consists of cells with well marked casparian thickening In few
species it is wholly suberized.
10

3.Sclerenchyma of Pericycle
● The presence and absence of nature of sclerenchyma has a diagnostic
value.
● The most common type seen in T.S of the stem are 1)Stone cells are
present, no fibers present 2)An interrupted ring of fibres 3)continuous ring
of fibres 4)Interrupted ring of mixed fibres and stone cells 5)Continuous
ring of mixed fibre and stone cells - COMPOSITAE
● Percycle sclerenchyma is not found in the members of
PITTOSPORACEAE.
● Ring of sclerenchyma is found in all the members of GERANIACEAE.
12

4.Bicollateral Bundle
● The occurrence of bicollateral bundle in the
axis of Cucurbitaceae is of much taxonomic
value.
● In certain families e.g Solanaceae,
Asclepiadaceae the presence of internal
phloem make a good taxonomic value.
13

4.Nodal Anatomy
According to Dickison (1975) correlations of nodal anatomy
with some other features might help significantly in tracing
phylogeny in angiosperms. Nodal Anatomy is an aid to
taxonomy.
● Unilacunar Nodes(Single gap and single trace to a leaf)
are found in Lurales, Caryophyllales, Ericales, Ebenales,
Primulales.
● Multilacunar Nodes (several gaps and trace associated
with single leaf) found in Magnoliales, Piperales,
Umbellales, Asterales etc..
14

5.Leaf Anatomy
● It provides various characters of taxonomic
importance.Leaf Anatomical studies associated
with C4-Photosynthetic pathway have resulted in
a revised classification of several genera of grass
family.
● Leaf Anatomy characters include nature and
thickness of epidermis, mesophyll types, pattern
of sclerenchyma, venation patterns, crystals etc..
● Leaf Anatomy has been widely used in several
taxonomic groups such as Euphorbiaceae,
Gramineae, Cyperaceae and conifers of
Gymnosperms
15

6.Floral Anatomy
● The research in Floral Anatomy in the fifteen years (1963-77) has been active
at Meerut and Bombay.
● V.Singh (1966) in a series of papers has described the vascular anatomy of
members of the flower of Alismaceae,Butomaceae, Hydrocharitaceae.
● On the basis of Kala and Pai(1979) have supported the removal of genus
Trichopus from family Dioscoreaceae and creation of a new family
Trichopodiaceae.
● Saxena N.P(1964) has worked out the floral anatomy of 37 species like
Moringaceae, Papaveraceae etc.The placentation of these families is parietal,
but the placental strands occur on the secondary marginal bundles
possessing normal orientation.
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● On the basis of floral anatomical studies, Roy(1949) proposed the removal
Trapa from Onagraceae and placed in another separate family Tapaceaea.
● N.P Saxena (1977) described the floral anatomy of 7 species of sub family
Hydrangeaceae and Saxifragaceae.
The Contribution of Floral Anatomy in Resolving Taxonomic Positions of some
Families
● Floral Anatomy of Annonaceae, Calycanthaceae confirms that all these
originated from Ranunculaceae.
● Uniformity in vasculature of Solanaceae and Scrophulariaceae suggest that
both should be included in one single order, Scrophulariales.
● Separation of Paeonia from Ranunculaceae and placed in a separate family
was supported by anatomical studies.
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2. Significance of Wood Anatomy
● Secondary xylem is a complex tissue, known as Wood. The study of wood by
Preparing for microscopic observations is defined as Xylotomy.
● Secondary Xylem is derived from vascular cambium. It develops in Stems
and roots of gymnosperms and angiosperms-dicotyledonous plants.
● Woods are divided into two-POROUS AND NON-POROUS ( based on the
presence and absence of vessels )
● Non-porous wood predominate in gymnosperms (tracheids with a small
amount of Parenchyma)
● Porous wood or Angiosperm wood is referred as hardwood.
18

Vessels
● Features like distribution, pattern, diameter, thickening and presence of
tyloses have been found useful in many Anatomical studies.
● Vessels found Solitary are considered as primitive than those aggregated
in groups, such as pore multiples, pore clusters etc..
● Similarly , Non- porous wood is more primitive without
vessels(gymnosperms),than porous wood, and diffuse porous wood is
more primitive than ring porous.
19

● Key to Identification of some common woods
1. Wood non-porous or without vessels
● Resin canal absent - Fir (Abies pindrow) white wood, less odour
● Resin canal Present
● 1. Resin canals in long tangential band- Deodar (yellow wood, light with strong pungent
smell)
● 2.Resin canals scattered - Spruce and Chir (Pinus varieties)
1. Wood ring porous to semi ring porous
● Rays distinct into very broad and fine types, pores arranged in long radial forms - Indian Oak
● Rays one type, not prominent and pores not arranged in long radial forms - Teak
1. Wood Diffuse porous
● Gum ducts vertical - Sal (Shorea robusta)
● Vertical gum ducts absent- Sisso and Ebony
20

● RAY PARENCHYMA
Ray Parenchyma cells are of various shapes and the two most common forms are
where the longest axis of the cell is either vertical or radial.The former one, where the
longest axis is oriented vertically is called erect ray cells.Where the latter one longest
axis is oriented radially.
In RLS the parenchyma cells appear as fine as horizontal lines. And it occurs variously
1) Uniseriate:the ray cells are entirely one cell in width e.g Pinus 2)Biseriate: any
portion is more than two cells in width e.g Quercus
The uniseriate and multiseriate rays both may be either homocellular or
heterocellular.In dicots homocellular rays consists of single type of cells only .In
heterocellular composed of both type of cells.
21

● Axial Parenchyma
● The distribution of axial parenchyma is very characteristic in
dicotyledons wood. Parenchyma may independent of vessels
or they are distinctly associated with them.These two forms are
known as APOTRACHEAL AND PARATRACHEAL forms.
● APOTRACHEAL TYPE:- Parenchyma cells are not in contact
with the vessels.
● Diffuse Apotracheal type:- Parenchyma cells occur singly among
the fibres and tracheids.
● Terminal Apotracheal type:-The bands of parenchyma are
confined to the end of the growth rings.
● Banded Apotracheal type:- Parenchyma cells occurs in bands
22

● PARATRACHEAL TYPE :- Parenchyma cells which are in contact with the
vessels.
● Vasicentric Parenchyma: Forms complete sheaths or borders around the
vessels.It is also known as Aliform Confluent Parenchyma.
● Aliform Parenchyma: Tangential “wing like” arrangements appearing in
cross section as diamond shape areas.
● Confluent Parenchyma: Tangential Projections of parenchyma masses join
to form irregular bands.
23

3.Role of Anatomy in Forensic science and Pharmacognosy
● Anatomical Characters are potentially useful to identify small fragments or commercially
important herbal products as well as toxic plants that may be relevance in forensic
investigations.
● An Increased number of indigenous medicinal plants are used in both formal and informal
economy. Unfortunately very few among this has been studied anatomically.
● Plants often causes fatalities due to inappropriate use of herbal medicines or the use of
misidentified plants.
● Anatomical characters of these plants are useful as the evidence for forensic work which help
to identify the plant when medical diagnosis/ chemical forensic studies turn out to be
inconclusive.
● Anatomical characters of potential diagnosis value will be presented for a selection of herbal
medicines and highly toxic plants.
● Herbal Medicines - Nerium oleander, Catha edulis, Agathosma betulina , Aloe ferox
24

4.Role of Anatomy in Paleobotany
● Anatomical Features can aid in the identification of archaeological materials,
they can be employed in identification of fossils and place them among extant
plant families and genera.
● Anatomical features however allows us to determine if the plant part is a root
or stem or leaf simply by the presence and absence of exarch or endarch
protoxylem.
● Some fossils may be sectioned, others may be ground down to thin sections
suitable for microscopic examinations and still others are fossilized in the form
of charcoal.
25

5.Anatomy of Floral Parts
● A typical flower is composed of sepals, petals,
stamens and carpels.
SEPALS
● The anatomical features of sepal resemble leaf.Each sepal
consists of epidermis, ground parenchyma and branched
vascular system.
● The green sepals has chlorophyllous cells but usually there
is no differentiation into palisade and spongy parenchyma.
● Lactifiers and tannin cells are present in it. The hairs are
present on stomata and epidermis .
● Vascular traces found is similar in origin and number.
26

PETALS
● The anatomical features shows resemblance with
those of leaves. Each petal consists of epidermis,
ground parenchyma and more tiers of branched
vascular system.
● Crystal containing cell, lactifiers, tannin cells are
present. Sometimes, epidermal cells contain
volatile oils which emit the characteristic fragrance
to the flower.
● Stomata and epidermal trichomes may also be
present. Cells of ground tissue contain abundant
chromoplast rich in water soluble anthocyanin.
27

STAMENS
● Stamen consists of Filament, connective and
an anther. Commonly anther is dithecous or
two lobed.
● Anatomical features of Filament is relatively
simple. The epidermis is cutinised and bears
trichomes and stomata. It has a single
vascular bundle that runs throughout the
filament and end blindly in connective.
● The vascular bundle is amphicibral which
remains surrounded by parenchyma.
28

ANTHER
● The Anatomy of Anther is little complex. Its outermost wall is single layered epidermis
which is followed by single layered endothecium.
● Cells of endothecium are hygroscopic, fibrous bands arising from lower transverse wall
and almost touching upper transverse wall.
● Endothecium helps in dehiscence of pollen grains. Next to endothecium and towards
inner side are 4-3 layers cells of wall layers. The innermost layers is the Tapetum. It is
the nutritive layer.
● Tapetal cells undergo various types of divisions.
● Anther has a procambial strand in centre which later forms the vascular bundle.
● Atypical two lobed anther has 4 microsporangia, (two in each lobe). In each
microsporangium several pollen grain are formed.
● On maturation of pollen, the tapetum and wall layers usually disintegrate leaving pollen
sac surrounded by endothecium and epidermis.
● At the time dehiscence of anthers, pollen are released through stomium.
29

GYNOECIUM
● It represent the female sex organs of the flower.
It is constituted by one or more units known as
carpels.
● Of these, ovary is the important structure within
which ovules are present attached on placenta.
● In general, ovary and style composed of
epidermis, parenchymatous ground tissue and
vascular bundle. Epidermis is cuticularised and
may possess stomata. Number of vascular
bundle are usually 3-5 in each carpel.
31

6.NODAL ANATOMY
● In Angiosperms and especially dicots, the primary
vascular cylinder is interrupted at each node by the
exit of one or more bundles that enter the leaves.
● The stelar bundle, which are the continuation of the
bundles in the leaf base, are called leaf trace.
● At each node, portions of the vascular system are
deflected into the leaf, which is attached at this
node.
● The parenchymatous regions in the vascular
system of the stem located adaxially from the
diverging leaf trace are called leaf gaps or
lacunae. 32

There are three common types of nodes in Dicots.
1. UNILACUNAR NODE
The node with a single gap and a single trace to a leaf is known as
unilacunar. Eg. Ocimum, Eucalyptus.
1. TRILACUNAR NODE
The node with three gaps and three traces to a leaf (one median and two
lateral) is known as trilacunar.Eg. Brassica, Annona.
1. MULTILACUNAR NODE
The node with several to many gaps and traces to a leaf is known as
Multilacunar. Eg: Rumex,Aralium.
33

PHYLOGENETIC CONSIDERATIONS:
1.Sinnotts View
Sinnot recognised 3 fundamental types of Nodal Anatomy in dicots unilacunar,
trilacunar and multilacunar. He put forward view concerning the phylogeny of
angiosperms on the basis of nodal organisation. He believed trilacunar is primitive
form.
2. Marsden and Baileys View
Marsden and Bailey (1955) discovered a Trilacunar and multilacunar types originated
by the addition of lateral traces arising from new gaps in vascular cylinder.
3. Takhtajan’s View
The most accepted concept is that the trilacunar condition is primitive in dicots and
unilacunar and multilacunar have been derived from it. Several monocots plants with
sheathing leaf bases and nodes with a large number of leaf traces separately inserted 35

6.Role of Anatomy in Phylogeny
● Phylogeny is the study of relationships among different groups of organisms
and their evolutionary development. Phylogeny attempts to trace the
evolutionary history of all life on the planet.
● It is based on the phylogenetic hypothesis that all living organisms share a
common ancestry. The relationships among organisms are depicted in what
is known as a phylogenetic tree.
● Relationships are determined by shared characteristics, as indicated through
the comparison of genetic and anatomical similarities.
● Anatomical features have played an increasingly important role in elucidation
of phylogenetic relationships.
36

● Anatomical characteristics are investigated with the help of a light
microscope whereas ultrastructure and micromorphology are brought out
using an electron microscope.
● Anatomical characters of vegetative and floral parts of flowering plants have
been successfully employed to solve taxonomic problems and for the
elucidation of phylogenetic relationships..
● It was Bureau, who for the first time used anatomical characters in plant
classification for the delimitation of taxa of various levels, within the family
Bignoniaceae.
37

Anatomical evidence can be useful in systematics in several ways:
(i) It can well be exploited taxonomically in the identification of fragmentary material, say a
piece of wood.
(ii) When morphological characters prove to be of no help in the preliminary identification of
herbarium material, anatomical study may prove helpful.
(iii) Anatomical data has proved to be very useful in discerning evolutionary trends and
interrelationships of taxa at and above the species level and at higher taxonomic categories.
They are most useful in determining relationship between different genera, families, orders
and other taxonomic categories.
(iv) The internal structures of the plants have added a lot in understanding the relationships
between the taxa. The organization of the vascular system in stem and leaf, petiole and
nodal anatomy, leaf vasculature and architecture and epidermal studies are considered
important characters in phylogeny and taxonomy.
38

Reference :-
Daniel, L. Molecular Biology And Evolution, Volume 17, Issue 12, December 2000, Pg 18885-1895
Fahn, A. (1977). Plant Anatomy. Oxford:Pergamon Press
Metcalfe, C. R. Comparative anatomy as a modern discipline. Adv. Bot. Res 1, 101-147, 1968
Murty, Y. S. and V. Puri, 1980, Floral anatomy in relation to taxonomy
Pandey, B. (1996). Plant Anatomy and Embryology. New Delhi: S Chand & Comp.
P.M. Tilney, B-E. Van Wyk Department of Botany and Plant Biotechnology, University of Johannesburg,
PO Box 524, Auckland Park 2006, South Africa.
Record, S. J Role of wood Anatomy in taxonomy. Trop Woods 37, 1-9
39

Scope and significance of plant anatomyy

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