Plant Nomenclature

What is nomenclature?

This chapter will be describing nomenclature in relation to plants, an explanation of why it is necessary to classify and name plants, particularly the utilisation of such designations in horticulture. The importance Linnaeus’s bi-nominal system of nomenclature, and an evaluation of the major codes along with practises within taxonomy. Taxonomy is the study of principles and practises of classification. Strictly applying to the study and description of variation in the natural world and the subsequence compilation of classifications.

Plants are classified in a hierarchical system which attempts to illustrate the evolutionary relationships between various groupings. Broadly speaking there are five Kingdoms: ‘Animalia’ or animals, ‘Plantae’ or plants, ‘Fungi’, ‘Prokaryotic’ or bacteria (cells without a nucleus) and finally ‘Protista’ or eukaryotic (cell with a nucleus) bacteria including algae. As in many theories there are issues with the system, which currently results in a constant state of flux. This is more noticeable on the lower levels; however, even at the highest levels, groups are questioned and are cause for debate between taxonomists.

Various groupings in this list; Magnoliidae, Magnoliopsdia, Ranunculares and Ranunculaceae are called a taxon. In everyday mitigation, full classification is not necessary; instead the plant is referred to Genus and species. An example of this system (below) in its practical application:

A form is a type of plant within a species that has little differences, such as the shape of the leaves or colour of flora. Deliberate hybridisation results in a cultivar, and can be reproduced to make increased amounts of the same plant.

The number of different kinds of plants is exceedingly great; scientists are faced with an estimated total of 300,000, if included fungi, moulds, mushrooms and toadstools; it would increase to 450,000. Furthermore scientists’ still have much to learn about the world’s plants. Scientists’ estimate that 15-20% of plant species have not yet been described, and at present, approximately 2,000 new species of plants are discovered per annum. It has been an estimated that there are over 14 million living species on Earth, though only 1.8 million have been given botanical names. By using the Linnaean classification system, we are able to classify plants and animals and in turn learn more about our own biological evolution. This just demonstrates to us, that the plant kingdom is extremely large and diverse. In other words, it is the extensive size and great diversity of the Plantae kingdom which makes it necessary for plants to be classified, especially in industries like Horticulture which come in contact with plants on a day to day basis.

The purpose of a designation is to act as an efficient means of reference or an aid to communication. A plant name must be unambiguous if so this breaks down communication. An example of this would be, if a same plant is known to different people by different names, then they will fail to understand one another and confusion will result in when they try to communicate.

Greek and Roman scholars laid the foundations of the method of naming flora. The bi-nominal classification system used today was largely established in the 18th Century by Swedish Botanists Carl von Linne ‘Linnaeus’ (1707-1780). Linnaeus classified plants with two botanical words rather than descriptive text. The first word describes the Genus and the second species, for example, Dicksonia antarctica.Dicksonia’ being the genus and ‘antarctica’ being the species. Prior to 1753, plants were known by phrases, which were difficult to distinguish from simple descriptions. An example of this method is a plant called, Achillea ptarmica once carried the designation Achillea foliis lanceolatis acuminates argute serrates, which translates as Achillea with lanceolate leaves which taper to a sharp point and have sharp pointed, saw-toothed edges.

The genus comprises of related plants with features in common, such as Lilium which all derive from bulbs. Species are a group of plants that consistently and naturally reproduce themselves, mostly by seed or vegetative. Species regularly generate plant populations that share similar characteristics. The first letter of the genus is always capitalised and italics are used for the whole name for example: Cobaea scandens, observe no capital was used for the species, as it is not as important as the genus. Also the scientific names are only abbreviated when several species from the same genus are being used, for example: Passiflora caerulea, P. incarnate and P. quadrangularis. The purpose of a name is to act as an easy means of reference. It is, in other words, an aid to communication.

Using this structure allows horticulturists, botanists and other related industries to communicate clearly, so you can be assured you are getting what you are seeking. Bi-nominal nomenclature gives us the scientific name which is understood globally, otherwise known as a universal language. If you are visiting gardens overseas, you would see baffling collections of names on plant labels, but as long as the scientific name is also included, you can be assured of what you are seeing. It also enables the transfer of clear and easily understood information between people working with cultivated plants. Rather than being a framework, which is aimed to catalogue all living organisms, the bi-nominal system has more practical aims, for example to create a basis for Plant Breeders’ Rights Legislations and to uniform seed registration.

The International Code of Botanical Nomenclature (ICBN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants. Its intent is that each taxonomic group or taxa of plants has only one correct name, that is accepted globally. When a plant is discovered and believed to be new to science, it is given a botanical name and formally described with a botanical diagnosis according to a set of agreed international regulations. An innovation introduced to the latest edition of the ICBN regulations, is the standard specimen; a type of voucher specimen, stored in an appropriate herbarium for posterity, to help identify a new cultivars. The ICBN ensures that plants have the appropriate designation within the relegations of botanical naming. Without this system in place there would be nobody to monitor naming, so various plants would have an inappropriate designation thus destabilising the mitigation of taxonomic groups. This would result in ambiguity or even confusion through the scientific world (ICBN, 2010). The ICBN also seeks to develop the taxonomy of plants in the instance of Andrographis echioides it was segregated into a new genus Neesiella, by Sreemandhaven (1967) but the generic name Neesiella was already attributed to a genus Hepaticae by Schiffner (1893) and hence Sreemandhaven’s name is illegitimated. Later Sreemandhaven (1968) changed the genus to Indoneesiella.

The ICBN Code frequent developments in nomenclature have caused disputes among plant scientists as well as agriculturists and horticulturists. There are two main reasons for change, firstly, advancement in scientific knowledge and secondly, authors have not followed the provisions of the code. Ironically the code formulated to bring stability has in fact has become a source of instability due automatic transfers or changes within plant taxonomy.

The International Code of Nomenclature for Cultivated Plants (ICNCP) regulates the names of ‘cultigens’ or plants that have an origin due to human activity. These for the most part are plants with names in the category of cultivars and groups. Examples of plants that are regulated are as follows: Clematis alpina 'Ruby' a cultivar with a species, Magnolia 'Elizabeth' a hybrid between two species, Rhododendron boothii Mishmiense Group: a Group name, Crataegomespilus a graft of a Crataegus and Mespilus and Apple 'Jonathan' allowed use of an unambiguous name with a cultivar epithet.

The requirement for a comprehensive set of practical, understandable and internationally acceptable regulations on the naming of ‘cultivated’ plants has long been evident. The first major step in the formulation of the International Code set out below was made in 1862 by Alphonse de Candolle in a letter subsequently placed before The International Horticultural Congress of Brussels, 1864 from there a temporary code was setup and from there subsequent renewals were followed until 1952, where The ICNCP was formed. The ICNCP like the ICBN ensures that no misunderstanding and confusion occur in cultivar names, which are used throughout the commercial world.

To conclude, taxonomy is the classification of organisms into groups based on similarities of structure. It is necessary to classify plants in horticulture mainly due to the huge volume of diverse plants species and an estimated 2,000 new species discovered per year. It is highly important that Linnaeus’s bi-nomial system of nomenclature is in place, to describe in a common language of men, thus aiding global understanding and communication. The ICBN regulate plant names to ensure that taxonomy rules are followed, and The ICNCP regulates cultivated plants to aid the commercial and scientific industries.