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CORE COURSE BOTANY-PAPER II- Plant Ecology and Taxonomy (B. Sc. II Semester CBCS 2016)
Unit 4: Identification and Nomenclature
Flora:
The term “Flora” refers either to the plants growing in an area surrounded by a geographical
boundary or to the group of plants of a particular area or region. There are two important
terms related to floras are:
1)
Floristics: Refers to an investigation of flora extensively. So flora is a taxonomic
treatment of the plants of a defined geographical area i.e, an account of a particular region.
2)
Manual: Book that provides an inventory of flora and the means of identifying the
plants using descriptive keys.
A good flora should have following contents:
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Title.
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Geography (Site of information).
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Environmental information.
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Taxonomic treatment.
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Nomenclature with citations and synonyms
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Vernacular names, if any.
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Concise and clear description.
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Cultivator names.
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Phenology
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Distributional data with maps
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Ecological data
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Conservation/status.
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Exotic or native origin.
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Summary statistics.
Uses of flora:
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College and university teachers.
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Agricultural developments.
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Architects and landscape designs.
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Civil and mining engineering.
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Biodiversity assessments and managements.
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Conversation programmes.
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Land management.
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Forest management.
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Phylogeny of plants.
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Developments of botanical gardens.
Identification keys:
Identification is a basic activity and one of the primary objectives of systematics .It is easy to
identify a specimen by the uses of keys than to shuffle through a large number of previously
named specimens in a herbarium until a match is found .The use of modern keys for
identification is usually credited to Lamarck (1778).
Key is device or tool useful to identify an unknown plant.
Types of keys:
1.Single access keys.
2. Multi access keys.
1. Single Access keys (Dichotomous keys) or Sequential keys:
Single access key is characterized by fixed sequence of identification steps. If each step has
only two alternatives, the key is said to be dichomatous. If multiple alternatives are offered it
is known as polytomous. The conventional and most acceptable type of keys used today is
dichotomous. A dichotomous key provides two contrasting choices at each step. Each pair of
choices is called couplet and each statement of a couplet is known as lead. The key is
designed in such a way that at each step one lead of the couplet will be accepted and the other
rejected. The first contrasting characters in each couplet are usually the best contrasting
characters and they are known as primary key characters. The characters that follow the lead
are referred to as secondary key characters. Each time a choice is made one or more taxa are
eliminated. e.g., a key might separate taxa using the following choice in a couplet: aquatic
plants verses terrestrial plants, if aquatic, terrestrial plants are eliminated. At each step a
choice is made, the number of possibilities is reduced and eventually reduced to one
possibility.
There are different practices regarding the designation of couplet leads. The couplets of the
key are numbered; sometimes combination of numbering and lettering are also used.
In the numbered key each couplet is numbered i.e, 1,1;2,2 etc or sometimes the first lead of a
couplet is distinguished from the second by adding letters a and b respectively to the number,
i.e.,1a, 1b; 2a, 2b, etc.
The first step essential in the identification of a plant involves the use of keys in the
determination of the family to which it belongs. Once the family name is determined; next by
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the use of the key to genera, its generic name is determined; and then by means of the key to
species, specific identity of the plant is known.
Dichotomous keys are of two types.
A. Indented or yoked key
B. Bracket or parallel key
A. Indented or yoked key:
It is most widely used in floras and manuals. In this type of key the collateral leads of a
couplet are arranged in yokes. Each of successive couplets is indented a fixed distance from
the margin of the page. An example of indented key is given bellow in the form of
identification of five common genera of Ranunculaceae i.e Ranunculus, Clematis, Anemone,
Aquilegia and Delphinum.
1. Fruit a group of achenes; un spurred flowers.
2. Petals absent.
3. Sepals usually 4; involucres absent. …………………….Clematis
3. Sepals usually 5; involucre present………………………Anemone
2. Petals present
…………………………….………………Ranunculus
1. Fruit a group of follicles; spurred flowers
4. Spurs 5, flowers regular …………………………….Aquilgia
4. Spur 1, flowers irregular……….……………………Delphinium
B. Bracket or parallel key:
Bracket keys are those keys in which two couplets are always next to each other in
consecutive lines on the page .At the end of each line in the key, there is either a number or a
name referring to a couplet .An example of the bracket key is given below, in which all the
same five genera of Ranunculaceae (i.e, Ranunculus, Clematis, Anemone, Aquilegia and
Delphinium) are identified:
(1)
Fruit a group of achenes; unspurred flowers……………………….(2)
(1)
Fruit a group of follicles ;spurred flowers………………………….(4)
(2)Petals absent………………………………-……(3)
(2) Petals present………………………………Ranunculus
(3) Sepals usually 4; involucres absent………………………….Clematis
(3) Sepals usually 5; involucres present………………………….Anemone
(4) Spurs 5; flowers regular…………………….Aquilegia
(4) Spur 1; flowers irregular…………………Delphinium
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CORE COURSE BOTANY-PAPER II- Plant Ecology and Taxonomy (B. Sc. II Semester CBCS 2016)
Multi-access keys or Polyclaves:
In a polyclave method of identification the user of the system is free to choose any character,
in any order or sequence, and thus avoid the rigid format of traditional dichotomous keys.
Thus it allows the free choice of identification steps and are easily adoptable to different taxa
(e.g., very small or very large) as well as different circumstances of identification (e.g., in the
field or laboratory).
One form of the polyclave is a diagnostic key in which cards are utilized. The cards are placed
on top of one another to eliminate taxa which disagree with the plant to be identified. The
second form of the polyclave is a computer stored multi entry key, and the third form is a
printed table which gives the status of different taxa and characters useful for separating the
taxa.
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Figure: A body- punched card for herbaceous habit for the representative genera of
Ranunculaceae: 1. Ranunculus, 2. Adonis, 3. Anemone, 4. Clematis, 5. Caltha, 6. Delphenium,
7. Aquilegia.
Recent years have seen the emergence of a new efficient method of information exchange
through internet. A number of electronic lists are maintained by list servers. Texacom is one
such list very active on taxonomic matters all over the world. In last few years a number of
interactive online identification programs have been developed which are based on Delta
intkey provides online identification facility for the vascular flora of Western Australia and is
available in Flora Base, http://florabase.calm.wa.gov.au.
Plant taxanomic evidence from Cytology:
According to Solbrig (1968) and Stebbins (1971) the chromosomes have been used in
resolving many taxonomic problems utilization of characters and phenomenon of cytology for
explanation of taxonomic problems is also known as cytotaxonomy, which includes:
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Chromosome number
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Chromosome size
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Chromosome morphology
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Chromosome behavior during meiosis
Chromosome Number
In angiosperms, the haploid chromosome number varies between n=2 (Haploappus gracilis of
compositea ) and n=132 (Poa littorosa of Gramineae). The highest chromosome number
recorded for vascular plants is found in Pteridophyte, Ophioglossum reticulatum (2n=1260).
Chromosome Size
The chromosome size has been very useful in understanding relationships in several taxa. In
most plants, the length of chromosome varies from 0.5 to 30 µ. Among monocots, the
members Zingiberaceae possess small chromosomes, of Iridaceae small to medium sized, of
Amaryllidaceae large sized, with those of Liliacae possess chromosomes of varying sizes.
Except Elocharis and Fimbristylis, all the members of Cyperaceae possess extremely small
chromosomes. According to Stebbins (1938) the chromosome size is characteristic of only
certain groups and families and not to the Phylogeny of Angiosperms.
Chromosome morphology
Usually the chromosomes are characterized as median, submedian, subterminal or terminal
with reference to their length and the position of the centromere. The centomere location
marks the position of the primary constriction. Additional constrictions are called secondary
constrictions. Occasionally secondary constrictions may be present near the terminal end of
chromosome separating its small segment called satellite. The chromosomes may be
symmetrical or asymmetrical. Symmetrical ones possess two equal arms and a median
centromere. Asymmetrical ones possess unequal arms and subterminal centromeres.
Chromosome behavior during meiosis
Significant taxonomic information may be obtained by the study of the behavior of the
chromosomes during 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 of systematic value.
Examples:
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1. Members of Cyperaceae and Juncaceae possess chromosomes with diffuse and non
localized centromers, and also show inverted meiosis which shows association between these
two families.
2. In Ranunculaceae, reshuffling of the genera has been done in the light of cytological data.
All the genera with n=7, 8 and 9 as well as genera with long chromosomes and short
chromosomes are accommodated in tribes Anemoneae and Helleboreae.
3. Naik (1977), differentiated three species of Chlorophytum of Liliaceae on the basis of
cytological data. According to him C. bharuchae has 2n=16 chromosomes while C. glaucum
and C. glaucoids have 2n=42. Both the latter species having 2n=42, differ in their
karyomorphology.
4. Genera Physaria and Lesquerella of Brassicaceae were treated as single genus by several
taxonomists. Their different cytological details suggest them to be treated as two different
genera.
Plant Taxanomic evidence from Phytochemistry (Chemotaxonomy):
Chemical evidences are used in determining the relationship among taxa of different
categories. Some of the major classes of chemical evidences include Flavonoids, Alkaloids,
Amino acids, Fatty Acids, Aromatic compounds, Terpenoids, Polysaccharids, Carotenoids,
etc.
Cronquist (1981) cited following examples to indicate the use of chemistry in solving
taxonomic problems:
1. Caryophyllales produce betalains and not anthocyanins.
2. Polygonales produce anthocyanins and not betalains.
3. Juglandales are aromatic plants while Fagales are not aromatic.
4. Highly aromatic compounds are found in Lamiaceae.
5. Alkaloids are very common in Solanaceae.
6. Sapindaceae have plenty of tannins.
7. Isomers of oleic acid are found in Umbelliferae and Araliaceae.
Infact, a large variety of chemical compounds are found in plants and quite often the
biosynthetic pathways producing these compounds differ in various plant groups. The natural
chemical constituents are broadly categorized as:
1.
Micromolecules: Compounds with low molecular weight (less than 1000).
2.
Primary metabolites: Compounds involved in vital metabolic pathways - citric acid,
aconitic acid, protein aminoacids etc.
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3.
Secondary metabolites:- Compounds which are the byproducts of metabolism and
often perform non vital functions- non protein amino acids, phenolic compounds, alkaloids,
glucosinolates, terpenes etc.
Primary Metabolites: These are universal in plants and of little taxonomic importance.
Aconitic acid and citric acid, first discovered from Aconitum and Citrus respectively
participate in Krebs cycle of respiration and are found in all aerobic organisms.
In
Gilgiochloa indurate (Poaceae), alanine is the main amino acid in leaf extracts, proline in
seed extracts and asparagines in flower extracts. Rosaceae is similarly rich in Arginine.
Secondary Metabolites:1. Non Protein Amino acids: Their
distribution is not universal but specific to certain
groups and as such, holds promise for taxonomic significance. Lathyrine is, thus known only
from Lathyrus. Canavanine occurs only in Fabaceae and shows protection against insect
larvae.
Phenolics: These are widely distributed in the plant kingdom, common examples are
catechol, hydroquinone, phloroglucinol and pyrogallol. coumarins, a group of natural
phenolic compounds
have a characteristic smell. The crushed leaves of Anthoxanthom
odoratum can thus be identified by this characteristic odour.
Flavonoids: Flavonoids are the phenolic glycosides consisting of two benzene rings linked
together through a heterocyclic pyrane ring. Common examples of flavonoids are flavonols,
isoflavones, malvadins and anthocynadines. Anthocynanins and anthoxanthins are important
pigments in the cell sap of petals providing red, blue and yellow colours in large families of
angiosperms.
According to Mabry et. al., (1963) on the basis of structure and metabolic path ways,
suggested the placement of only betalain – containing families in Centrospermae, Cactaceae
and Didiereaceae.
Alkoloids: Alkaloids are organic nitrogen containing bases, usually with a heterocyclic ring.
Nicotine (Nicotiana), and ephedrine (Ephedra) are familiar examples their distribution is
often specific and thus taxonomically significant. Morphine is present in opium poppy plant
(Papaver somniferum). Lupin alkaloids are the chrarcteristic of the tribes Sophoreae,
Genisteae and Podalyrieae of subfamily Lotoideae of Leguminosae. Families Papaveraceae
and Fumarieceae are closely related. This affinity is supported by the occurrence of the
alkaloid protopine in both.
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Plant Taxonomic Evidences from Molecular Data:
Molecular systematic is the most exciting developments in plant taxonomy in last so many
years. It is the use of DNA and RNA to infer relationship among organisms. Molecular data
reflect more likely true phylogeny than morphological data, because they reflect gene level
changes, which are less subject to convergence. In many cases molecular data have allowed
the placement of taxa whose relationship were known to be problematic. Plant cell contain
three different genomes of the chloroplast, the mitochordon, and the nucleus. Systematists
use data from all the three genomes. Molecular phylogenetics is done by using either genome
rearrangements or sequence of DNA.
Nuclear DNA: The data from DNA and RNA hold promise for utilization in taxonomic
studies, although there has been limited exploration of information from nucleic acids as
taxonomic evidence. The total amount of nuclear DNA is usually highly constant for species.
The early studies on utilisation of nucleic acids in taxonomy involved DNA/DNA
hybridisation using the whole DNA for study.
In a method developed by Bolton and
Mecarthy (1962) extracted DNA is so treated that it converts into a single stranded
polynucleotide chain. The DNA of another organism is similarly made single stranded. The
two are subsequently allowed to hybridize invitro. The degree of reassociation (annealing)
expresses the degree of similarity in sequences of nucleotides of the two organisms. Bolton
(1966) found that only half nucleotide sequence in the DNA of Vicia villosa are homologous
with those of Pisum, While only 1/5th are homologous between Phaseolus and Pisum. In the
technique of DNA/RNA hybridisation the RNA is hybridised with the complementary DNA
of related plants. Marbey (1976) used this technique in Centrospermae is quite close to
betalain-containing families, but not as close as the later are to each other.
There has been considerable advancement in recent years. It is now possible to break (cleave)
DNA at highly specific points using restriction endonucleases, each of which can cleave DNA
at a highly specific recognition site, thus producing highly characteristic restriction fragments
of DNA. These fragments can be separated by electrophoresis and hybridised with radioactive
single-stranded DNA or RNA probes. The method has been used with encouraging results in
Atriplex, Secale and several other genera. Belford and Thomson (1979) using side-copy
sequence hybridization in Atriplex concluded that division into two subgenera in this genus is
not correct.
The DNA based molecular markers are applied in various aspects of taxonomy to analyse:
(i) Genetic identity.
(ii) Genetic relatedness among populations, geographic populations and species.
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(iii) Pedigree.
(iv) Differentiation among isolated species.
(v) Phylogenetic structure at various micro and macro levels.
A number of molecular parameters are useful in carrying out phylogenetic and systematic
studies. Of the various molecular approaches the PCR based technology offers maximum
potential for genetic analysis, phylogenetics and systematics. Taxonomists have realized
power of MAAP markers is recording taxonomic ambiguities.
Mitochondrial DNA: Mitochondrial DNA is studied in many plants. Each mitochondrian
contains several copies of mt DNA and each cell contains many mitochondria. Generally mt
DNA is circular but is linear in Chlamydomonas reinhardtii. mt DNA is larger circular with
many non-coding sequences in vascular plants.
Chloroplast DNA: cp DNA can be easily isolated and analyzed. The DNA of chloroplast is
highly conserved type. The cp DNA circular molecule with 2 regions in opposite direction
encoding same genes are called inverted repeats. Between inverted repeats single copy
regions are present.
In all cp DNA same set of genome are found but arranged differently in different species. The
genes present in cp DNA include genes for r-RNA, t-RNA, ribosomal proteins and about 100
different polypeptides and subunits of enzyme coupling CO2. The important gene on cp DNA
is rbcL encoding large subunit of photosynthetic enzyme i.e., RUBISCO. This gene is not
found in parasites. It is a long gene consisting of 1428 bp.
Examples: Eight species of Atriplex of Chenopodiaceae were compared on the basis of their
DNA nucleotide sequences. DNA of wheat, rye and barley of Triticaceae, compareded with
that of oat of Aveneae showed marked differences. Moreover, wheat DNA is more similar to
the DNA of rye than that of barley.
Taxonomic hierarchy:
The process in which organisms are first recognized and assembled into groups on the basis of
certain resemblance. These groups are in turn assembled in to larger and more inclusive
groups. The process is repeated until finally all the organisms have been assembled in to a
single largest most inclusive group. These groups (taxa) are arranged in order of their
successive inclusiveness, the least inclusive at the bottom, and the most inclusive at the top.
The groups thus formed and arranged are next assigned to various categories , having a fixed
sequence of arrangement (taxonomic hierarchy ), the most inclusive group assigned to the
highest category (generally a division) and the least inclusive group to the lowest category
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(usually a species). The names are assigned to the taxonomic groups in such a way that the
name gives an indication of the category to which it is assigned. Rosales, Myrtales, and
Malvales all belong to the order category and Rosaceae, Myrtaceae and Malvaceae to the
family category. Once all the groups have been assigned categories and named, the process of
classification is complete, or the taxonomic structure of the whole largest most inclusive
group has been achieved. Because of the hierarchical arrangement of categories to which the
groups are assigned, the classification achieved is known as hierarchical classification.
Taxonomic groups, Taxonomic categories and Taxonomic Ranks: Taxonomic groups,
Categories and Ranks are inseparable once a hierarchical classification has been achieved.
Rosa alba is a species, in which Rosa is a genus. The categories are like shelves of an almirah,
having no significance when empty, and importance and meaning only after something has
been placed in them. Thereafter, the shelves will be known by their contents: books, toys,
clothes, shoes etc. Categories in that sense are artificial and subjective and have no bases in
reality. They correspond to nothing in nature. However, they have a fixed position in the
hierarchy in relation to other categories. But once a group has been assigned to a particular
category the two are inseparable and the category gets a definite meaning because it now
includes something actually occurring in nature.
If categories are like shelves, ranks are like partitions, each separating the given category
from the category above. Taxonomic groups, on the other hand are objective and non
arbitrary to the extent that they represent discrete sets of organisms in nature. Groups are
biological entities or a collection of such entities. By assigning them to a category and
providing an appropriate ending to the name (Rosaceae with ending- aceae signifies a family
which among others also includes roses, belonging to the genus Rosa) we establish the
position of taxonomic groups in the hierarchical system of classification.
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Figure: Process of assembling taxonomic groups according to the hierarchical system,
depicted by box-in-box method. In the above example, there are 18 species grouped into 10
genera, 6 families, 4 orders, 2 classes and 1 division.
Some important characteristics, which enable a better understanding of the hierarchical
system of classification, are as:1. Different categories of the hierarchy are higher or lower according whether they are
occupied by more inclusive or less inclusive groups. Higher categories are occupied by more
inclusive groups than those occupying lower categories.
2. Plants are not classified into categories but into groups. It is important to note that a plant
may be a member of several taxonomic groups, each of which is assigned to a taxonomic
category, but is not itself a member of any taxonomic category. A plant collected from the
field may be identified as Poa annua. It is a member of Poa (assigned to genus category),
Poaceae (assigined to family category) and so on, but the plant cannot be said to be belonging
to the species category.
3. A taxon may belong to other taxa, but it can be a member of only one category. Urtica
dioca, thus, is a member of Urtica, Urticaceae, Urticales and so on, but it belongs to species
category.
4. Categories are not made of lower categories. The category family is not made up of the
genus category, since there is only one genus category.
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Utilization of categories:Taxonomic categories possess only relative value and an empty category has no foundation in
reality and obviously cannot be defined. An important step in the process of classification is
to assign taxa to an appropriate category. It thus becomes imperative to decide what should be
the properties of taxa to be included in a particular category. Only with a proper utilization of
the concept of categories can their application in hierarchical systems be meaningful.
Botanical Nomenclature:
The system of naming objects of biological origin is called as nomenclature. Man has been
interested in plants since prehistoric times and in all nations, names have been given to plants
in their own language. The local names would vary from place to place, even within a
country. It is thus clear that no plants can be identified on the basis of local name in different
regions of a country. Hence, there is a need to standardise the naming of a plant in such a way
that it may not be difficult to identify it in any part of the world. This necessitated the need for
assigning scientific names to plants.
The system of naming plants on the scientific basis is known as plant nomenclature.
Need for scientific names
Scientific names are preferred over vernacular names since the later pose a number of
problems:
1.
Vernacular names are not available for all the species known to man.
2.
Common names are restricted in usage and are applicable in one or a few languages
only. They are not universal in application.
3.
A single name is often used for two or more species (e.g., „touch me not‟ is the name
for both Impatiens balsamifera (Balsam) and Mimosa pudica (sensitive plant).
4.
Vernacular names usually do not provide information indicating family or generic
relationship.
The earliest botanical names were polynomials, composed of several words. For example, the
polynomial, given by Pulkonat as “Chrysophyllum foliis ovalis, superne glabris, parallel
striates, subtus tomentosiniditis” is now known as Sida acuta.
Binomial system of nomenclature:
Binomial system was first proposed by Gaspard Bauhin, 1623 in his book ‘Pinax Theatre
Botanica’. Carolous Linnaeus, 1753 used this nomenclature system for the first time on large
scale while publishing ‘Species Plantrum’. According to the binomial system of
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nomenclature, the name of a plant consists of two Latin or Latinised words, the first (generic
epithet) representing the genus and the second (specific epithet) the species. For example, the
botanical name of potato is Solanum tubersome.
Solanum
tubersome
(Generic name)
(Specific name)
The following rules are followed for Botanical Nomenclature as given below:
1.
The generic name starts with a capital letter, whereas the specific name with a small
letter.
2.
The scientific names should be either underlined in case of hand written or italicised if
printed.
3.
Name of the scientist (who proposed name) should be written in short after the
specific name e.g., Mangifera indica Linn.
4.
If any scientist has proposed wrong name then his name should be written in bracket
and the scientist who corrected the name should be written after the bracket. e.g., Tsuga
Canadensis (Linn.) Salisbury
5.
Scientific names should be derived from Latin or Greek languages because they are
dead languages.
6.
In Botanical Nomenclature tautonyms are not valid.
History of plant nomenclature
Prior to 1930 there was no significant code for plant nomenclature. Various countries
followed different codes such as Paris code, Kew rule, Rochester code, Vienna code. The first
organized effort was made by Alphonse de Candolle who circulated a copy of his manuscript
Lois de la nomenclature botanique and after deliberations of the First International Botanical
Congress at Paris (1867), the Paris code, also known as „de Candolle rules‟ was adopted. Not
satisfied with the Paris code, American botanists adopted a separate Rochester code (1892)
which introduced the concept of types, strict application of rules of priority even if the names
was a tautonym (Malus malus).
The Paris code was replaced by the Vienna code (1905) which established Species Plantarum
(1753) of Linnaeus as the starting point, tautonym was not accepted and Latin diagonosis was
made essential for new species.
Collection of rules regarding scientific nomenclature of plants is known as ICBN. The code is
divided into three parts: Principles, Rules and Recommendations.
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Principles of ICBN:
The Principles constitute the basis of botanical nomenclature which are as under:
1.
Botanical nomenclature is independent of zoological nomenclature.
2.
The application of names of taxonomic groups (taxa) is determined by means of
nomenclature type.
3.
Nomenclature of the taxonomic groups is based upon priority of publication.
4.
Each taxonomic group can bear only one correct name, the earliest that is in
accordance with the rules, except in specific cases.
5.
Scientific names of taxonomic groups are treated as Latin regardless of their
derivation.
6.
The rules of nomenclature are retroactive unless expressly limited.
RULES: The rules give detailed prescriptions on all the points connected with the naming of
plants. Some of the important rules are as under:
I.
Ranks of Taxa:- The term taxa (singular taxon) means „taxonomic group of any
rank‟. Here the rank of a species is taken as basis. The relative order of the ranks of taxa are;
species, genus, tribe, family, order, class, division and kingdom. A species is divided into subspecies, sub-species into varieties, variety into sub-varieties, sub-variety into forma and forma
into clone.
II.
Typification:
The names of different taxonomic groups are based on the type method, by which a certain
representative of the group is the source of the name for the group. This representative is
called the nomenclature type or simply the type, and methodology as typification. The code
recognises several kinds of types, depending on the way in which a type specimen is selected.
These included:
a.
Holotype: It is one specimen or the element used by the author of the name or
designated by him as the nomenclature type.
b.
Isotype: It is believed to be a duplicate of the holotype e.g., from several branches of
trees, one becomes holotype and others are treated as isotype.
c.
Lectotype: It is the specimen selected from the original material to serve as the
nomenclatural type if the holotype was not designated or missing.
d.
Syntype: It is any one of the two specimens cited by the author when no holotype was
designated or when two `or more than one specimens are designated as „type‟.
e.
Neotype: It is the specimen selected to serve as a nomenclature type of a taxon when
all the original material is missing.
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f.
Paratype: The specimen cited in the original description other than the holotype is
paratype.
g.
Cotype: it is the second specimen collected from the same plant from which the
holotype was collected.
h.
Topotype: it is a specimen collected from the same locality from where the holotype
was collected.
III.
Principle of Priority:
According to the Principle of Priority each taxon can bear only one correct name. The correct
name is the earliest legitimate name except if it is retained by conservation. If the same plant
is named differently by two or more author, its earliest correct name is considered as valid
proposed just after 1 May, 1753- the date of publication of Linnaeous Species Plantarum.
IV.
Name of Families: A family name is formed by adding the suffix-aceae to the stem of
legitimate name of an included genus, e.g., Rosaceae from (Rosa) and Cucurbitaceae from
(Cucurbita). Some family names which do not follow this rule were, therefore, changed.
However, the old names are also conserved due to their long use.
Compositae ------------- Asteraceae
Palmae
--------------
Cruciferae --------------- Brassicaceae
Leguminaceae ------------- Fabaceae
Gramineae -------------- Poacea
Labiatae
Guttiferae -------------- Clusiaceae
Umbelliferae -------------- Apiacea
-------------
Arecaceae
Lamiacea
Author Citation:
The name of a taxon is incomplete unless the name of the author or authors who first validly
published the name, is cited along with it. This helps in verifying the dates of publication and
in imparting precision in biological nomenclature.
There are several rules for author citation:
1.
The names of the authors are commonly abbreviated, e.g., Linn. or L. For Carolous
Linnaeus, Benth. for G. Benthem.
2.
If the name of the plant is jointly published by two authors, their names should be
linked by means of et al.
3.
When more than three authors are involved, citation is normally restricted to first
author and is followed by et al.
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CORE COURSE BOTANY-PAPER II- Plant Ecology and Taxonomy (B. Sc. II Semester CBCS 2016)
4.
These citations can indicate bibliographic references, which are especially helpful in
the recognition of homonyms.
5.
If a genus or taxon of lower rank is altered in rank or position, but retains its name or
epithet, the name of the author who first published the name (basionym) must be cited in
parenthesis followed by the name of the author who effected the change. This is called double
citation, e.g., Cynodon dactylon (Linn.) Pers., based on the basionym Panicum dactylon Linn.
Valid Publication:
The new name of a taxon is considered valid or effective for publication, only when it is
distributed in a printed form to the general public or atleast to ten well established botanical
institutions with libraries accessible to botanists generally. A valid publication should satisfy
the following requirements:
1.
Formulation: A name should be properly formulated and its nature indicated by a
proper abbreviation after the name of the author:
(i)
sp. nov. for species nova, a species new to science.
(ii)
comb. nov. for combination nova, a name change involving the epithet of the
basionym, name of the original author being kept within parenthesis.
2.
Latin diagnosis: Names of all new species published 01-01-1953 onwards should
have a Latin diagnosis. Full description of the species in any language can accompany the
Latin diagnosis.
3.
Typication: A holotype should be designated. Publication on or after 01-01-1958 of
the name of a taxon of the Rank of genus or below is valid only when the type of the name is
indicated.
Recomendations: The Recomendations are often practical application of rules. Their object
is to bring about greater uniformity and clearness, especially in future nomenclature.
Appendices: The code has three appendices:
Appendix I Deal with the names of hybrids.
Appendix II includes names of families which are conserved.
Appendix III lists the names of genera which are conserved against the principle of priority
because of their long use.
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