PLANT TAXONOMY
Definition and Background
Taxonomy or systematic is the study or description on
variations among organisms in order to come out with a
classification system.
Organisms that are arranged into groups enable a large
population to be categorized and understood.
Taxonomy began about 300 years before christ by Theophratus
(370-285 BC)
Carolus Linneaus (1707-1778) is regarded as the founder of
taxonomy (father of taxonomy) till today.
Importance of Plant Taxonomy
1. To arrange elements or taxa of plants into a more
systematic manner so that they can be better
understood and could be used easily and more
effectively.
2. To arrange data or information and knowledge about
plants.
3. To indicate the source and genetic relationship
(phylogenetic), ancestry and origin of plants.
4. To indicate the distribution and habitat of plants on
earth and their benefits.
Taxonomic Components
1. Classification
Plants are arranged into groups of similar characteristics.
The groups are considered as categories or taxa and form
the taxonomic system.
2. Identification
To identify and derive the name of an organism by referring
to an existing classification.
3. Nomenclature
To provide a scientific name to an organism.
4. Description
To describe the characteristics of a taxon e.g. a family.
Taxonomic System
Plant kingdom
Animal kingdom
Division
Phylum
Class
Order
Family
Genus
Species
Kingdom :
 The highest level in a classification e.g. animal
and plant kingdom
Division :
 The number of groups in this taxon is not fixed,
it depends on the classification system.
 Based on similar characteristics observed on a
few elements or organs e.g. : dominance of a
sporophyte to a gametophyte, presence of an
ovule, seed formation and several other
morphological and anatomical characteristics.
 Those are hereditary characteristics and will
continue to exist from generation to generation.
Class :
 The number of groups in this taxon is also not fixed,
depending on the classification system.
 Separation is based on important basic differences
that exist between the groups.
Order :
 Separation is based on a more convincing genetic
relationship which earlier had been detected at the
class and division level.
Familiy
 Based on more characteristics compared to order,
class and division e.g. the morphological
characteristics of reproductive organs (inflorescence,
ovary position, placentation, number of pistils and
carpels, types of ovule and androecium)
Genus
 Genus involves more similar characteristics including
a closer family relationship but they do not cross. If a
hybrid cross does occur the offsprings are normally
infertile or will not survive.
 Phylogenetically, new genus arises and separates
from the same parental origin.
Kingdom
Whittaker (1969) :
Monera (bacteria, prokaryotic cell)
Protista (algae, protozoa, eukaryotic)
Fungi
(absorb food in liquid form)
Plantae (photosynthesis) **
Animalia (ingest food)
PLANT KINGDOM
DIVISION:
Bryophyta (Mosses: non-vascular)
Pterophyta (Ferns: vascular, spores on leaves)
Pinophyta (Conifers, Pinus : seeds in cones)
Ginkgophyta (Ginkgo : fan-shaped leaves)
Cycadophyta (Cycads : palm-liked leaves)
Gnetophyta (Gnetum: vessel-filled wood)
Magnoliophyta (Flowering plants) :
Class: Magnoliopsida (Dicot)
Class: Liliopsida (Monocot)
DIVISION (PLANT KINGDOM)
SPERMATOPHYTA (seeded plants)
PTERIDOPHYTA (ferns)
BRYOPHYTA (mosses)
THALLOPHYTA (plants with thallus)
SPERMATOPHYTA (SEEDED PLANTS)
ANGIOSPERMAE
DICOTYLEDONEAE
EUPHORBIACEAE
SOLANACEAE
LEGUMINOSAE
CRUCIFERAE
RUTACEAE
MALVACEAE
CUCURBITACEAE
GYMNOSPERMAE
MONOCOTYLEDONEAE
PALMAE
GRAMINEAE
MUSACEAE
ZINGIBERACEAE
ORCHIDACEAE
CYPERACEAE
CLASSIFICATION OF BANANA
KINGDOM: Plantae
DIVISION : Magnoliophyta/Spermatophyta
CLASS : Liliopsida/Monocotyledoneae
ORDER : Zingiberales
FAMILY : Musaceae
GENUS : Musa
SPECIES : Musa acuminata
ENDING OF EACH TAXON FOR THE
IDENTIFICATION OF THE CLASSIFICATION
LEVEL
*(excluding KINGDOM, GENUS and SPECIES)
DIVISION :
-phyta
CLASS :
-opsida / -eae
ORDER :
-ales / -ae
FAMILY :
-aceae / -ae
Sub family :
-oideae
SUB AND SUPER CATEGORIES
Besides the 7 main categories, there are infra taxa to describe
varitions within a taxon:
KINGDOM, Subkingdom, DIVISION, Subdivision, CLASS, Subclass,
(Superorder), ORDER, Suborder, FAMILY, Subfamily, Tribe, Subtribe,
GENUS, Subgenus, Section, Subsection, Series, Subseries,
SPECIES, Subspecies, Variety, Subvariety, Form, Subform
Example: There are infraspecific categories Subspecies,
Variety, Subvariety, Form and Subform to describe
variations within Species
Subspecies and Variety : based on morphological
variations that can be identified within a species as a
result of adaption to different ecology.
Form is the category used for only slight variations.
** Cultivar the result of crossing over several generations
and does not occur naturally.
** Clone refers to a uniform population of plants, identical
to the mother plant, produced either asexually or
naturally.
THE CONCEPT OF SPECIES
1. Morphological species concept
 species is the smallest group of organisms
which can be consistently differentiated using
morphological characteristics.
 the concept is widely used among taxonomists
as it is the most practical.
2. Biological species concept
 using reproductive biology to define species.
 population group which is able to breed but
prevented from gene exchange with population
of other species.
 cannot be used for self-pollinated species or
asexually produced species (which do not
undergo crossing)
CLASSIFICATION SYSTEMS
1. Artificial system
Based on growth habits and uses. A primitive system
300 BC- AD 1500. Theophratus and Dioscorides, Greece.
2. Mechanical system
based on one or a few chosen characteristics. 1580-1760.
Caesalpino, Italy; Bauhin, Swiss; Linnaeus, Sweden.
3. Natural system
Based on many characteristics. 1760-1880. Adanson, France;
de Candolle, Swiss; Bentham and Hooker, Britain.
4. Phylogenetic system
Based on many characteristics, with evolutionary interpretations.
1880-present. Engler, Germany; Bessey, America; Hutchinson,
Britain; Thorne, America.
NOMENCLATURE
- Nomenclature is important in order to provide the
correct name for a plant.
The naming activity is under the control of the `International
Codes of Botanical Nomenclature’ (ICBN) published by the
`International Association of Plant Taxonomy’ (IAPT).
- The codes are revised at every `International Botanical
Congress’
 Scientific name is based on the binomial system
popularised by Carolus Linnaeus (1753). Consists of
genus and species names
 The third element is the name of the person who
formally gave the name
Oryza sativa L. Oryza sativa Linn. (Binomial)
Oryza sativa subsp. indica
Oryza sativa subsp. japonica (Trinomial)
Bupleurum falcatum ssp. eufalcatum var. hoffmeisteri
(Quadrinomial)
 Populus alba var. canescens Aiton
Brassica oleraceae var. capatita
Prunus cornuta forma villosa
(Trinomial)
 Name of genera and that of higher taxon,
(Monomial / Uninomial)
Rosa L.
Rosaceae Juss.
 Cultivar taxonomic category
Oryza sativa cv. Mat Candu
Oryza cv. Mat Candu
Padi kv. Mat Candu
- For species that have been named earlier it is adequate to name
the species from then on using only the first letter of the generic
name
Solanum melongena, S. melongena
- For specific name consisting of two words, a hyphen is needed
between the two words:
Hibiscus rosa-sinensis
- If the specific name is not known:
Lathyrus sp. or Lathyrus spp. (if many species)
- Scientific name in capital letters and italised is also accepted
CARICA PAPAYA, HEVEA BRASILIENSIS
- When two or more authors suggest a scientific name, their names are
linked by `et’
Delphinium viscosum Hook.f et Thomson
- The original name for a species is Panicum dactylon Linn. When C.H.
Persoon changed the genus name to Cynodon, the original specific
name remains while the original author’s name is placed in bracket:
Cynodon dactylon (Linn.) Pers.
- When the first author suggests a name but was officially published by
a second author, both names are linked by `ex’
Cerasus cornuta Wall ex Royle
HYBRID NAMES
- Interspecific and intergeneric hybrids:
Agrostis x Polypogon
Agrostis stolonifera x Polypogon monspeliensis
Salix auritia x S. caprea
- Binary names are given to interspecific hybrids:
Salix x capreola (S. aurita x S. caprea)
Rosa x odorata (R. chinensis x R. gigantea)
- A graft between two species uses `+’ :
Rosa webbiana + R. floribunda
TAXONOMIC CHARACTERISTICS
1. Morphology
Plant growth habit, leaf arrangement and shape, flower
and fruit characteristics.
2. Anatomy
Secondary xylem characteristics, epidermis including
trichomes and stomata.
3. Palinology
Pollen characteristics including size, shape, aperture
and exine sculpture.
TAXONOMIC CHARACTERISTICS
4. Cytology
The chromosome number, structure and habit
5. Chemical and molecular
Alkaloid, phenolic and amino acids contents.
Protein, enzyme and DNA