Biology

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Classification of Plants

Imagine walking into a library and looking for a Harry Potter story book. As you walk into the library you notice that it is under renovation and all the books are scattered. Will it not be hard to find the exact book you are looking for? It might take hours. So you decide to come the next day when all the books are arranged according to the genres. One rack for adventure, another for Detective, Fantasy, Horror, Encyclopaedia and so on.

You automatically know Harry Potter is in the fantasy section and it takes less than ten minutes for you to find it. That is because the books have been classified and arranged according to a system. Similarly there is a vast assemblage of group of plants in the world. Is it possible to study and understand all of these? No Since it is difficult to study all these plants together, it is necessary to device some means to make this possible.

Classification is essential to biology because there is a vast diversity of organisms to sort out and compare. Unless they are organized into manageable categories it will be difficult for identification. Biological classifications are the inventions of biologists based upon the best evidence available. The scientific basis for cataloguing and retrieving information about the tremendous diversity of flora is known as classification.

Classification paves way for the arrangement of organisms into groups on the basis of their similarities, dissimilarities and relationships. The purpose of classification is to provide a systematic arrangement expressing the relationship between the organisms. Taxonomists have assigned a method of classifying organisms which are called ranks.

These taxonomical ranks are hierarchical. The scheme of classification has to be flexible, allowing newly discovered living organisms to be added where they fit best. While there are many ways to structure plant classification, one way is to group them into vascular and non-vascular plants, seed bearing and spore bearing, and angiosperms and gymnosperms. Plants can also be classified as grasses, herbaceous plants,
woody shrubs, and trees.

Classification is based on the following criteria: Plant body: Presence or absence of a well-differentiated plant body. E.g. Root, Stem and Leaves. Vascular system: Presence or absence of a vascular system for the transportation of water and other substances.

Within the plant kingdom, plants are divided into two main groups. These are flowering plants (angiosperms) and conifers, Ginkgos, and cycads (gymnosperms). The other group contains the seedless plants that reproduce by spores. It includes mosses, liverworts, horsetails, and ferns.

The major plant groups include bryophytes (mosses), pteridophytes (ferns), gymnosperms (conifers), and angiosperms (flowering, seed-bearing plants). Mosses are short plants and their leaves are usually only one cell thick. Ferns have many leaves branching out from their fronds.

Natural system of classification is that in which all natural characters of plants both vegetative and reproductive are taken in to consideration as the basic of classification principally the plants are grouped according to their related characters.

What are different types of flowers? They can be classified in many different ways: Based on presence or absence of seeds, Based on whether the plants produce flowers or not, Based on the presence of stems, leaves, and roots.

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Herbarium – Preparation and Uses

Herbaria are store houses of preserved plant collections. Plants are preserved in the form of pressed and dried specimens mounted on a sheet of paper. Herbaria act as a centre for research and function as sources of material for systematic work.

Preparation of Herbarium Specimen

Herbarium Specimen is defined as a pressed and dried plant sample that is permanently glued or strapped to a sheet of paper along with a documentation label. Preparation of herbarium specimen includes the following steps.

1. Plant Collection: Field collection, Liquid preserved collection, Living collection, Collection for molecular studies.
2. Documentation of field site data
3. Preparation of plant specimen
4. Mounting herbarium specimen
5. Herbarium labels
6. Protection of herbarium sheets against mold and insects

Uses of Herbarium

1. Herbarium provides resource material for systematic research and studies.
2. It is a place for orderly arrangement of voucher specimens.
3. Voucher specimen serves as a reference for comparing doubtful newly collected fresh specimens.
4. Voucher specimens play a role in studies like floristic diversity, environmental assessment, ecological mechanisms and survey of unexplored areas.
5. Herbarium provides opportunity for documenting biodiversity and studies related to the field of ecology and conservation biology.

Kew Herbarium

Kew Garden is situated in South West London that houses the “largest and most diverse botanical and mycological collections in the world” founded in the year 1840. Living collection includes more than 30,000 different kinds of plants.

While herbarium which is one of the largest in the world has over seven million preserved plant specimens. The library contains more than 7,50,000 volumes and the illustrations and also a collection of more than 1,75,000 prints, books, photographs, letters, manuscripts, periodicals, maps and botanical illustrations.

Preparation of Herbarium Specimen

International Herbarium

National Herbarium

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Botanical Gardens and its Significance

In true sense all gardens are not botanical gardens. Botanical gardens are centres for collection of plants in their various stages of living. Gardens existed for growing ornamental plants for aesthetic value, religious and status reasons. The famous “hanging gardens” of Babylon in Mesopotamia is an example. For the purpose of science and education the first garden was maintained by Theophrastus in his public lecture hall at Athens.

First modern botanical garden was established by Luca Ghini (1490-1556) a professor of Botany at Pisa, Italy in 1544. Botanical garden contains special plant collections such as cacti, succulent, green house, shade house, tropical, alpine and exotic plants. Worldwide there are about 1800 botanical gardens and arboreta.

Role of Botanical Garden:
Botanical Gardens play the following important roles.

1. Gardens with aesthetic value which attract a large number of visitors. For example, the Great Banyan Tree (Ficus benghalensis) in the Indian Botanical Garden at Kolkata.
2. Gardens have a wide range of species and supply taxonomic material for botanical research.
3. Garden is used for self-instruction or demonstration purposes.
4. It can integrate information of diverse fields like Anatomy, Embryology, Phytochemistry, Cytology, Physiology and Ecology.
5. Act as a conservation centre for diversity, rare and endangered species.
6. It offers annual list of available species and a free exchange of seeds.
7. Botanical garden gives information about method of propagation, sale of plant material to the general public.

Royal Botanic garden, Kew- England

Royal Botanic garden Kew – England is a non – departmental public body in the United Kingdom. It is the largest botanical garden in the world, established in 1760, but officially opened in the year 1841. Plant collections include Aquatic garden, Arboretum with 14,000 trees, Bonsai collection, Cacti collection and Carnivorous plant collection.

Botanical garden, also called botanic garden, originally, a collection of living plants designed chiefly to illustrate relationships within plant groups. A display garden that concentrates on woody plants (shrubs and trees) is often referred to as an arboretum.

How do I get official Botanical Garden status? The garden is open to the public on at least a part-time basis. The garden functions as an aesthetic display, educational display and/or site research. The garden maintains plant records.

Royal Botanic Gardens in Kew, England – known as the largest botanical garden in the world, this 300-acre garden near London is home to the world’s biggest collection of living plants.

Botanical gardens devote their resources to the study and conservation of plants, as well as making the world’s plant species diversity known to the public. These gardens also play a central role in meeting human needs and providing well-being.

These are specialised gargens which have collections of living plants for reference plant species in botanical gardens are grown for identification purposes and each plant is labelled by indicating its botanical name and family. e.g: 1. Kew (England).

Advantages. Botanical gardens devote their resources to the study and conservation of plants, as well as making the world’s plant species diversity known to the public. These gardens also play a central role in meeting human needs and providing well-being.

Botanical gardens make money based on their purpose. For example, a botanical garden may have a contract with a university or company to produce research on new plant species. If the space is being used largely for the public, patrons will pay an admission fee to tour the garden.

For the adjective meaning of or relating to botany or the cultivation of plants, botanic and botanical are both acceptable, and there is no difference between them. Botanical is more common, however, especially in modern.

Botanical is more common, however, especially in modern English. Firstly, botanical gardens can provide the new plants of economic importance to society, including ornamentals, medicinal, trees for reforestation, plants for industry, fruits, and cash crops. Next, some plants are collected for the study of adaptability, growth, and also the economic and genetic characteristics.

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Taxonomic Aids

Taxonomic aids are the tools for the taxonomic study. Some techniques, procedures and stored information that are useful in identification and classification of organisms are called taxonomical aids. They are required in almost all branches of biological studies for their proper identification and for finding their relationship with others. Some of the taxonomical aids are keys, flora, revisions, monograph, catalogues, herbarium, botanical gardens etc.

Keys

Taxonomic keys are the tools for the identification of unfamiliar plants. These keys are based on characters which are stable and reliable. The most common type of key is a dichotomous key. It consists of a sequence of two contrasting statements. A pair of contrasting statements is known as couplet. Each statement is known as lead. The plant is correctly identified with keys by narrowing down the characters found in plant.

Example:

1.
(a) Flowers cream-coloured; fruiting calyx enclosing the berry …… Physalis
(b) Flowers white or violet; fruiting calyx not enclosing the berry ……… 2

2.
(a) Corolla rotate; fruit a berry ….. Solanum
(b) Corolla funnel-form or salver-form; fruit a capsule: …. 3

3.
(a) Radical leaves present; flowers in racemes; fruits without prickles ….. Nicotiana
(b) Radical leaves absent; flowers solitary; fruits with prickles ….. Datura

Another type of key for identification is the Polyclave or Multi-entry key. It consists of a list of numerous character states. The user selects all states that match the specimen. Polyclave keys are implemented by a computer algorithm.

Taxonomical aids are the collections of samples or preserved organisms which help in extensive research for the identification of various taxonomic hierarchy. Taxonomic studies of various species of plants, animals, and other organisms, which require correct classifications and identification.

Taxonomical aids are the samples or collection of samples of preserved organisms that help in the research of taxonomic hierarchy. The examples are herbarium, monograph, museum, zoological parks, flora, etc. Herbarium is a store that houses plant species or specimens and other related data for study. The most important taxonomical aids are herbaria, botanical gardens, keys, museums, and zoological parks.

Manual:
These provide information for identification of names of species occurring in an area.

Monograph:
These are handbooks which provide the available information of any one taxon. Common taxonomical aids include a herbarium, botanical gardens, zoological parks, museums, keys etc.

Separate taxonomical keys are required for each taxonomic categories like Family, Genus, Species for the identification purpose. The other type of key for taxonomic studies are Flora, Manuals, Monographs and Catalogues. These help in correct identification of organism.

The taxonomic aids are the aids which help in identification, classification and naming of a newly discovered organisms (plant or animal). It could be in the form of preserved document like herbaria or specimen kept at museums or scientific institutions.

Taxonomical aids are the representations or accumulation of samples of preserved bions that help in the study of the taxonomic hierarchy. The examples are herbarium, monograph, museum, zoological parks, flora, etc.

A manual serves as a taxonomic aid by guiding individuals to accurately identify and classify different plants and animals. A manual contains basic but necessary information for categorising plants and animals. The use of a manual is usually user-defined.

A taxonomic key is a device for quickly and easily identifying to which species an unknown plant belongs. The key consists of a series of choices, based on observed features of the plant specimen.it is often referred to as a dichotomous key.

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Taxonomic Hierarchy

Taxonomic hierarchy was introduced by Carolus Linnaeus. It is the arrangement of various taxonomic levels in descending order starting from kingdom up to species. Kingdom is the highest level or rank of the classification. Example: Plantae

“Taxonomic hierarchy is the process of arranging various organisms into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.” Each of this level of the hierarchy is called the taxonomic category or rank.

The current taxonomic system now has eight levels in its hierarchy, from lowest to highest, they are: species, genus, family, order, class, phylum, kingdom, domain. There are seven main taxonomic ranks: kingdom, phylum or division, class, order, family, genus, species.

Taxonomy is the branch of biology that classifies all living things. He also developed a classification system called the taxonomic hierarchy, which today has eight ranks from general to specific: domain, kingdom, phylum, class, order, family, genus, and species.

Plants, Animals, Protists, Fungi, Archaebacteria, Eubacteria. How are organism placed into their kingdoms? You are probably quite familiar with the members of this kingdom as it contains all the plants that you have come to know – flowering plants, mosses, and ferns.

Phylum, Species, and Class are taxonomic category. But, Glumaceae is not a category. It is a botanical name assigned to order including the family of grass, used by Bentham and Hooker.

This phylogeny overturned the eukaryote-prokaryote dichotomy by showing that the 16S rRNA tree neatly divided into three major branches, which became known as the three domains of (cellular) life: Bacteria, Archaea and Eukarya (Woese et al 1990).

Classification, or taxonomy, is a system of categorizing living things. There are seven divisions in the system:

1. Kingdom
2. Phylum or Division
3. Class
4. Order
5. Family
6. Genus
7. Species

An example of taxonomy is the way living beings are divided up into Kingdom, Phylum, Class, Order, Family, Genus, Species. An example of taxonomy is the Dewey Decimal system – the way libraries classify non-fiction books by division and subdivisions. The science, laws, or principles of classification.

The Animal Kingdom contains more than two million known species. The Animal Kingdom contains these seven Phyla: Porifera, Cnidaria, Platyhelminthes, Annelida, Mollusca, Arthropoda, and Chordata.

Tools and taxonomical aids may be different for the study of plants and animals. The important components of the taxonomical tools are field visits, survey, identification, classification, preservation and documentation.

Thus, molecular approaches have found a niche in taxonomy. Measurement of DNA hybridization between strains is the single most definitive tool for defining a species. Data on sequences of DNA and amino acids can be used to infer phylogeny.