INTRODUCTION TO PLANT TAXONOMY
What is Plant Taxonomy?
Plant taxonomy is the science that finds, describes, classifies, identifies, and names plants. It thus is one of the main branches of taxonomy.
Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two. In practice, "plant systematics" is involved with relationships between plants and their evolution, especially at the higher levels, whereas "plant taxonomy" deals with the actual handling of plant specimens.
Taxonomy is a science which includes identification, nomenclature and classification of objects ( biological origin). - G. H. M. Lawrence. When the taxonomy is concerned with plants it is called as systematic botany.
"Classification of Organisms basing on totality of their similarities and differences"
Plant Taxonomy is a synthesis of the following related field:
1. Systematic Botany
2. Taxonomic System
Identification: Determination of a taxon* as being identical with or similar to another and already known element.(* each unit of classification is termed as taxon: Plural is taxa).
Nomenclature: System of naming plants (i.e. Methods or ways of giving names to plants)
Classification: is the arrangement i.e. placing of a plant or a group of plants in a series of groups or categories according to a particular system and in accordance with the rules of nomenclature.
Latin name = Scientific name. Name of any plant is given in two parts, e.g. Pinus wallichiana. Here the first name is the generic (genus) name and the second name is the specific (species) name. This type of naming (nomenclature) is called as binomial system of nomenclature. (Latin names are always represented in italics or in addition underlined)
Species: is the basic unit of classification (or a group of individuals alike in essential particulars or sub divisions of a genus).
Genus: is formed of species which are similar to each other. Like wise similar genus give rise to family: families to order: orders to class and classes to division.
Units of classification (with examples)
Kingdom : Plant kingdom
Sub kingdom : Embryophyta (the embryo plant)
Division (=Phyllum) : Tracheophyta (the vascular plant)
Sub division : Pteropsida (the ferns and seed plants)
Class : Angiospermae (flowering plant)
Sub class : Dicotyledonae (2 cots in embryo)
Order : Rosales
Family : Rosaceae
Genus : Prunus
Species : ceresoides
STRUCTURE OF HIERARCHY
1. Species (Basic unit)
2. Genus (Pl. Genera)
3. Family (ends in 'aceae')
4. Order (ends in 'ales')
7. Plant Kingdom
SUBDIVISIONS FOR THE CONVENIENCE (Examples)
SUBDIVISIONS ENDING IN
A tribe 'eae'
Subgenus as Eurosa or Section
Subspecies as ssp
Why to study taxonomy?
1. Classify all kinds of plants under plant kingdom
2. To identify, name and arrange the plants in a recognized system of classification showing phylogeny and relationship among groups of plants.
3. Study of distribution of plants and their habitat- character.
4. Organized reconstruction of the plants kingdom including changes in nomenclature.
Types of classification
2. Natural and
Artificial system: This classification is based on one or few superficial characters only. Eg. plants are grouped into herbs, shrubs, under shrubs and trees based on habitat character.
Linnaeus system of classification is purely an artificial one based on sexual character.
Natural system: In this system several common and constant characters are taken into consideration. Benthem and Hookers system of classification is one of the most commonly used in this categories.
Phylogenetic system: Classified according to evolutionary sequence. It also reflects the genetic relationships. Engler and Prantle's system and Hutchingson's system of classifications are some examples in this category.
INTERNATIONAL CODE OF BOTANICAL NOMENCLATURE (ICBN), Recognised twelve main ranks:
01. Plant Kingdom
Always begin with a Capital Letter
Always a noun
(e.g. Pinus roxburghii)
Origin of Generic names:
1. Honour of Botany or Horticulture Patron; Examples
Candollea Augustin de Candolle
Einsteinia Albert Einstein
Gravia Asa Gray
Jeffersonia Thomas Jefferson
2. Generic names express some features of a plant: Examples
Callicarpa Beautiful fruit
Oxydendrum Sour tree
3. Fanciful or poetic: Example
Dodecatheon Twelve gods
4. Aboriginal origin: Examples
A. Usually descriptive adjective
How it is named? Various ways depending on the Authors: Examples
aquatica in water
arvensis in field
muralis on wall
palustries in swamps
sylvatica in woods
4. Size, shape and habit
edulis or esculenta edible
hortensis grown in garden
officinalis sold in market
sativus sown for crops
autumnalis of Autumn
hiberna of winter
toxicaria poisonous, etc.
6. Relative abundance
B. In honour of renowned botanist
C. Indicate affinity and resemblance
amaranthoides similar to Amaranthus
D. Refer to distinctive features of the plant
cordifolia heart-shaped leaved
Citation and Authority
Solanum tuberosum L. (Linnaeus)
Asystasia gangetica T. (Thomas Anderson)
When there are similar names
Robert Brown R.Br.
William Brown Wm.Br.
When father and son, both are Authors
William Hooker (Father) Hook.
Joseph Dalton Hooker (son) Hook.f. (F=filius=son)
When father, son and grandsons are authors
Augustin de Candolle (father)
Alphones A. DC.
Casimer C. DC.
Proposal made by one author and publication made by other than him.
Acer oblongum Wall. ex DC.
When there is change of Taxonomic ranks and position
Medicago polymorphic L. Variety orbicularis L
Medicago orbicularis (L) All (Rank changed by Allioni)
Malva rosea L.
Althea rosea (L) Cav. (Position/genus changed by Canavilles)