evidences of anatomy, cytology and chemistry to plant taxonomy

Evidences of Anatomy, Cytology
and Chemistry in Plant Taxonomy

CONTENT
• Taxonomy
• Anatomy in relation to taxonomy
• Vegetative anatomy ( epidermis, stomata, trichomes,
stem anatomy, nodal anatomy, petiole anatomy, leaf
anatomy, sclereids, wood anatomy )
• Floral anatomy
• Cytology in relation to taxonomy
• Chemistry in relation to taxonomy
• Conclusion
• References
2

Plant Taxonomy
• Plant Taxonomy is the branch of science which
deals with the identification, nomenclature and
classification of plants.
3
Identification
Nomenclature
Classification

Anatomy in relation to plant taxonomy
• Parts of plant body that
serve to maintain its
individual life
• e.g. leaf, root, stem
Vegetative
anatomy
• Essential parts of the flower
• Means for reproductionFloral
anatomy
4

Vegetative anatomy in relation to
taxonomy
• Epidermis
• Stomata
• Trichomes
• Stem anatomy
• Nodal anatomy
• Leaf anatomy
• Sclereids
• Specialized cell and cell content
• Wood anatomy
5

Epidermis
• Shape, wall thickness, wall sculpturing and
inclusions in the epidermal cells.
• Papillate epidermal cells in Graminae
• Presence and distribution of silica bodies in
Cyperaceae
• Sclerification of the wall of epidermal cells in
some genera of Compositae
• Presence of very narrow epidermal cells in
Stylidiaceae
6

Epidermis
• Sharma and Shiam (1984) described the
taxonomic importance of silica bodies in 22
Indian species of Cyperus.
7

Different types of epidermal cells in
plant
8

Stomata
• Morphology and development of different
stomatal types is important in assigning taxa
of uncertain affinities to proper position.
• Morphology and ontogeny, number and
arrangement of subsidiary cells and their
relationship with other epidermal cells are
characters of taxonomic significance
9

• Significance of stomata has been confirmed in the
taxonomy of
• Graminaeae
• Epacridaceae
• Combretaceae
• Rubiaceae
• Acanthceae
• Umbelliferae
• Papilionaceae
• Araliaceaea
• Myrtaceae
• Cyperaceae
10
Stomata

Trichomes
• Trichomes types and their distribution are
useful characters in distinguishing various
genera of Fabaceae and Icacinaceae.
• Position of Nyctanthes in Oleaceae has been
confirmed by Inamdar( 1967) on the basis of
the structure and ontogeny of trichomes
• Trichomes have been the main basis of the
formation of generic key for the Indian
members of Compositae.
12

Stem Anatomy
• Stace (1970) has shown that anatomy of the
stem can be used to distinguish the majority
of its British species.
• Dioscorea species are distinguished on the
basis of stem anatomy.
14

• Transformation of cortex into transfusion tissue in
Casuarina
• structure of stem endodermis in families such as
Ateraceae and Piperaceae
• Presence of bicollateral vascular bundles in two
alternate rings in Cucurbitaceae
• Occurance of cortical and medullary bundles in
some families such as Amaranthaceae,
chenopodiaceae and nyctaginaceae, are some of
the features of taxonomic importance.
15
Stem Anatomy

Internal structure of stem of monocot
and dicot plant
16

Nodal anatomy
• According to Dickison (1975) correlations of
nodal anatomy with some other features
might help significantly in tracing the
phylogeny of angiosperms
• Philipson (1968) attempted to use nodal
anatomy as an aid to taxonomy
• Sinnott(1914) considered the trilacunar node
as primitive and unilacunar and multilacunar
nodes as advanced.
17

• According to Paliwal and Anand (1978) majority
of dicotyledons possess trilacunar nodes.
• Unilacunar nodes are found in Laurales,
caryphyllales, Ericales, Ebenales, Primulales,
Myrtales and a few Tubiflorae and Asteridae
members.
• Multilacunar nodes are found in Magnoliales,
Piperales, Trochodendrales, Umbellales and
Asterales.
18
Nodal anatomy

Different types of nodes in plants
19

Petiole Anatomy
• Metcalfe and Chalk (1950) and HOWARD
(1963).
• According to Howard, families, genera and
even species may be identified by petiole
characters, such as its position on stem,
presence or absence of stipules, its
vascularization, nodal structure, number of
traces, etc.
20

• Petiole anatomy of 64 species of Baphia of
Leguminosae, some species of Phlomis and
Eremostachys of Labiate provide clear support
of use of petiole anatomy in the taxonomy of
these genera.
21
Petiole Anatomy

Leaf Anatomy
• Koyama (1967) and Govindrajalu studied the
leaf anatomy of several species of Cyperaceae
and formulated keys to identify various
species of Cyperus, Fuirena, etc.
• Leaf anatomy has been widely used in several
taxonomically different groups such as
Euphorbiaceae, Cyperaceae and Graminae of
Angiosperms and Coniferae of Gymnosperms,
23

• Patterns of distribution of sclerenchyma in
Carex and Festuca have been used in
distinguishing species.
• Sclerenchyma is also used in differentiating
two genera of Velloziaceae viz, Vellozia and
Barbacenia.
24
Leaf Anatomy

Sclereids
• Sclereids are the cells with very thick lignified
walls.
• They are extremely rare in monocots, except in
certain genera of Araceae, Agavaceae, Arecaceae
and a few other families.
• In dicots, they are more common in woody form
then in herbaceous ones.
• Rao and Das (1981) have shown their taxonomic
value in about 30 species of Limonium.
26

Specialized cells and cell content
• Microscopic characters of cell content such as
strach grains ( Solonum tuberosum )
• Proteins bodies ( some Cactaceae)
• Albuminoids (Laportea)
• Large silica bodies ( Musaceae, Arecaceae and
Zingiberaceae)
• Calcium oxalate crystals (Eichhornia, Allium)
• Cystoliths ( Moraceae and Urticaceae )
27

• Tanniniferous cells ( Xyridaceae) are important
diagnostic tools, and at time prove extremely
helpful in delineating species, genera and
families.
28
Specialized cells and cell content

Wood Anatomy
• Some important wood elements of taxonomic
importance are:
• Vessel elements
• Vascular rays
• Axial parenchyma
• Presence or absence of stroried wood
• Presence or absence of latex vessels, resins,
gums, crystals etc.
29

• Wood anatomy has prompted the allocation
of Amborella , Tetracentron and
Trochodendron to their respective
independent families.
• Placement of Myristicata close to Lauraceae,
delimitation of different subgenera of Quercus
of Fagaceae, and non-inclusion of
Calycanthaceae in Rosales or Myrtales are all
supported by the wood anatomy.
30
Wood Anatomy

Floral Anatomy
• Floral anatomy of Annonaceae, Calycanthaceae
and Menispermaceae confirms that all these
families originated from Ranunculaceae.
• Uniformity in floral vasculature of Solanaceae and
Scrophulariaceae suggests that both should be
included in one single order, Scrophulariales.
• Separation of Paeonia from Ranunculaceae and
its inclusion under a separate family Paeoniaceae
was supported by the floral anatomical studies.
32

• Formerly, Cyperaceae and Graminae were
treated together in one single order. But
Hutchinson(1973) treated them separately in
Cyperales and Graminales because of their
floral anatomy.
• Lilaea, earlier included under family
Scheuchzeriaceae, was later separated in an
independent family Lilaeaceae.
33
Floral Anatomy

Internal structure of flower
34

Cytology in relation to taxonomy or
Cytotaxonomy
• The term karyotype is used for the phenotypic
appearance of the somatic chromosomes.
• The diagrammatic representation of karyotype is
termed as idiogram.
• The characteristics of the chromosomes, which
have proved to be of taxonomic value include
• Chromosome number
• Chromosome size
• Chromosome morphology
• Chromosome behavior during meiosis.
35

Chromosome number
• Homoploids ( Pinus and Quercus, n=12
chromosomes )
• Polyploids (different species of Aster have n=9
or n=18 or n=27 )
• Euploidy
• Aneuploidy ( different species of Brassica bear
n=6,7,8,9, or 10 )
36

Chromosome size
• 0.5 to 3 µ
• According to Stebbins (1938) the chromosome
size is characteristics of only certain groups
and families, and not related to phylogeny of
angiosperms.
37

• Relative length of the arms of the
chromosomes, position of the cento mere,
presence of satellites, etc. are some character
of taxonomic significance
• A secondary contraction may be present near
the terminal end of a chromosome, separating
its small segments called satellite.
• Chromosome may be symmetrical and
asymmetrical
38

Chromosome Behavior at Meiosis
• Degree of sterility and occurrence of
hybridization are determined by the behavior
of chromosomes during meiosis
• Abnormalities in meiosis, such as non-pairing,
crossing over, unequal interchanges or
translocations, bridge formation, lagging
chromosomes etc. have all proved to be
systematic value.
40

Systematic value of cytological studies
• Jackson (1971)
• Members of Cyperaceae and Juncaceae possess
chromosomes with diffuse or non-localized
centromere, and also show inverted meiosis. This
reflect a close association between these two families.
• Yucca had long been treated as a member of Liliaceae
because of superior ovary, and Agave of
Amaryllidaceae because of inferior ovary. Hutchinson
shifted both plants to Agavaceae because of the
presence of 25 small and 5 large chromosome in both
of them
41

• The basic chromosome number in Loranthaceae is n=9
while in Viscaceae there is a series of aneuploid
numbers ranging b/w 10 and 14. Wiens (1975)
separated them from each other on basis of cytological
evidence.
• In the subfamily Bambusoideae of Graminae n=12 and
in the subfamily Poideae n=7. this indicates that the
chromosome numbers have proved to be of taxonomic
utility also at the subfamily level.
• Stebbins (1958) provided information on the evolution
of grasses on the basis of cytogenetic.
42

• On the basis of cytological studies, Lewis (1951)
submerged the genus Godetia in Clarkia (
Onagraceae)
• Naik (1977) differentiated three species of
Chlorophytum of Liliaceae on the basis of
cytological data. According to him C.bharuchae
has 2n=16 while C.glaucum and C. glaucoides
have 2n=42. both the later species having differ
karyomorphology.
• Warburg(1938) studied taxonomy of Gerniales
on the basis of cytological studies.
43

• Manton(1932) confirmed the formation of subdivision
of Brassicaceae on the basis of cytological studies. All
the families have different base chromosome numbers.
• Genus Cistus ( Cistaceae), formerly included in
Helianthemum, has chromosome number 8 while
Helianthemum has base chromosome number 9. so
Cistus should be recognized as a separate genus
• A new classification of the genus Narcissus of
Amaryllidaceae has been proposed by Frenandes
(1951) on the basis of cytological studies.
44

• Sharma (1956) on the basis of his studies of
Araceae, Amaryllidaceae and Diosoreaeceae,
proposed that the changes in karyotypes of
somatic tissue play a distinct role in evolution. He
further proposed that large chromosomes, low
chromosome number and symmetrical karyotype
represent a primitive status, while small
chromosomes, high chromosome number and
extreme asymmetry of karyotype present the
advance status. These principles provided
interesting results in taxonomy of Alismataceae,
Liliaceae, Amaryllidaceae and Dioscoreaceae.
45

Chemistry in relation to taxonomy
• Application of chemistry to taxonomy is called
chemotaxonomy.
• Chemical evidences are used in determining
the relationship among taxa of different
categories.
• Some of the major classes of chemical
evidence include flavonoids, alkaloids, amino
acids, fatty acids, aromatic compounds,
terpenoids, polysaccharides, carotenoids etc.
46

• Cronquist ( 1981 ) cited following examples to indicate
the use of chemistry in solving taxonomic problems:
1. Caryphyllales produce betalains and not anthocyanins
2. Polygonales produce anthocyanins and not betalains.
3. Juglandales are aromatic plants while Fagales are non-
aromatic.
4. Highly aromatic compounds are found in Lamiaceae
5. Alkaloids are very common in Solanaceae
6. Sapindaceae have plenty of Tannins.
47
Chemistry in relation to taxonomy

evidences of anatomy, cytology and chemistry to plant taxonomy

More Related Content

evidences of anatomy, cytology and chemistry to plant taxonomy