Definition and Background

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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.
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Importance of Plant Taxonomy

• 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.

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Taxonomic Components

• Classification
• Plants are arranged into groups of similar
  characteristics. The groups are considered as
  categories or taxa and form the taxonomic system.
  
• 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.

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• 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.

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• 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.

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• 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.

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SPERMATOPHYTA (SEEDED PLANTS)
GYMNOSPERMAE
ANGIOSPERMAE
DICOTYLEDONEAE
MONOCOTYLEDONEAE
EUPHORBIACEAE SOLANACEAE LEGUMINOSAE CRUCIFERAE R
UTACEAE MALVACEAE CUCURBITACEAE
PALMAE GRAMINEAE MUSACEAE ZINGIBERACEAE ORCHIDACEA
E CYPERACEAE
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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
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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.

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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.

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CLASSIFICATION SYSTEMS

• 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.

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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

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• 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)

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• 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

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• 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

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• 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 authors 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

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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

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TAXONOMIC CHARACTERISTICS

• 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.

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TAXONOMIC CHARACTERISTICS
4. Cytology The chromosome number,
structure and habit 5. Chemical and molecular
Alkaloid, phenolic and amino acids
contents. Protein, enzyme and DNA