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- Taxonomy, Botany and Nomenclature and its Relevance in Aromatherapy Training
- Adverse Media Hype on Tea Tree Essential Oil
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- Removing Toxins The Natural Way
- Chavutti Thirumal An Intoduction To A Unique Massage Therapy
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- The Magic Pill Within
Taxonomy, Botany and Nomenclature and its Relevance in Aromatherapy Training
04/05/2008 - By Carole Preen The aromatherapy profession developed the over-arching Core Curriculum for the new voluntary self-regulatory body, the Aromatherapy Council, in March 2005.
This included the study of taxonomy, botany and nomenclature, which was incorporated into the revised National Occupational Standards (NOS) for aromatherapy in 2006. Many schools have been including this subject within training for many years already, but the majority have not, and it was felt that basic knowledge about this subject would give aromatherapists a much deeper understanding of the plants used to obtain essential oils, the importance of learning the plant families and Latin names and, ultimately, knowing how essential oils are formed in the plant and their raison d'être.
Taxonomy is concerned with classification, nomenclature and identification of natural objects, whether these are plants, insects, reptiles, birds, etc.
Significance
Taxonomy is one of the oldest botanical sciences. It continually develops along with the exploration of the earth, allowing us to understand life.
A conservative estimate of the number of described species of plants in the world is more than 450,000. Out of these, 286,000 belong to the flowering plants.
Taxonomy made it possible to classify a plant as a number of a particular genus. Every genus then belongs to a family, the family to an order, the order to a class, and so on.
Nomenclature: Naming of plants
Binomial system of nomenclature and its basis
The system of naming every plant in two parts in Latin words is called the 'Binomial System of Nomenclature'. The first part is the generic name, which represents the genus, and the second part is the name of the species. Therefore, we have Rosa (genus - initial capitalisation) damascena (species - all lower case). When Latin names are printed, they must always be in italics.
You can obtain correct Latin names, which need to include the author's name, from the AC Core Curriculum and NOS
(see www.aromatherapycouncil.co.uk). The table lists each plant by family name and includes the parts of the plant used to obtain essential oils. Brief history of plant nomenclature This system of binomial nomenclature was first adopted by Carolus Linnaeus (1707-78), a great Swedish naturalist and physician. It was published in his first edition of Species Plantarum in 1753. This was organised at the First International Botanical Congress (IBC) in Paris, 1867, for use by botanists everywhere. By 1935 the code of International Rules of Botanical Nomenclature was finally settled. The same system has also been adopted by Lawrence (1951) and by the 12th IBC held at Leningrad in 1975, with slight changes. This version of the system was published in the International Code of Botanical Nomenclature (ICBN) in 1978.Levels of hierarchy As mentioned, plants are grouped by genus, family and so on. These levels are hierarchical.
Let's look at Magnolia as an example:
Kingdom - Plantae
Division - Magnoliophyta
Order - Magnoliales (orders end with 'iales')
Family - Magnoliaceae (plant families end with 'aceae')
Genus - Magnolia
Species - officinalis
Now let's use Lavender:
Kingdom - Plantae
Division - Magnoliophyta
Order - Lamiales
Family - Lamiaceae
Genus - Lavandula
Species - angustifolia
The flowering plants (also called angiosperms) are a major group of 'land plants', with over 250,000 having been identified, and many more that have not yet been named! Approximately 2,500 of these are aromatic and roughly 10% are used commercially. From this percentage around 250 produce essential oils that we currently know of. Traditionally, the flowering plants are divided into two groups: 'dicotyledon' and 'monocotyledon', or 'dicot' and 'monocot'. These names derive from the fact that the dicots often (but not always) have two cotyledons (embryonic leaves) within each seed, while the monocots typically have only one. The cotyledon is like our chromosomes, as the seed contains the genetic code of the plant.
Genera can hybridise, but the resulting species is sterile. This happens all the time with plants as they are visited by insects and butterflies that are not choosy which plant they visit next and are not aware of the individual species! Examples are Lavandula x intermedia and Mentha x piperita. The 'x' denotes that it is a hybrid; so to grow these on they must be taken from a cutting, as any seed would be sterile.
The most diverse families of flowering plants, in order of number of species, are:
Orchidaceae (Orchid family): 25,000 or more species
Asteraceae, formerly known as Compositae (Daisy family): 20,000 species
Fabaceae, formerly known as Leguminosae (Pea family): 17,000
Poaceae, formerly known as Gramineae (Grass family): 9,000
Rubiaceae (Madder family): 7,000
Euphorbiaceae (Spurge family): 5,000
Malvaceae (Mallow family): 4,300
Cyperaceae (Sedge family): 4,000
Araceae (including aroids subfamily): 3,700
In the list above (showing only the nine largest families), the Orchidaceae, Poaceae, Cyperaceae and Araceae are monocot families; the others are dicot families. In reality, then, there are possibly a lot more essential oils out there; and with advancement in distillation methods, the possibilities are quite exciting.
Plant Structure
Plants contain the same biological processes and biochemistry as microbes and animals. However, plants are unique in that they have the ability to use energy from sunlight, along with other chemical elements for growth. This process of photosynthesis provides the world's supply of food and energy, as we cannot live without plants. Reproduction in flowering plants takes place sexually, resulting in the production of a seed. Reproduction can also occur via asexual ropagation.
A plant has two organ systems:
1. the shoot system 2. the root system
The shoot system is above the ground and includes leaves, buds, stems, flowers (if the plant has them) and fruits (if the plant has them). The root system includes those parts of the plant below ground, such as the roots (e.g., vetiver), tubers, and rhizomes (e.g., ginger).
Plants have only three tissue types:
1. Dermal 2. Ground 3. Vascular
Dermal tissue extends over the outermost surface of herbaceous plants. Dermal tissue is made up of epidermal cells that are closely packed together and which secrete a waxy cuticle which helps prevent loss of water. The ground tissue is the main part of the plant body. Parenchyma, collenchyma, and sclerenchyma cells are common in the ground tissue. Vascular tissue conveys food, water, hormones and minerals within the plant. Vascular tissue includes xylem, phloem, parenchyma, and cambium cells. Flowering plants will produce flowers when they are sexually reproductive, generating a diploid zygote and triploid endosperm. Flowers are collections of reproductive and sterile tissue arranged in a tight whorled array. Sterile parts of flowers are the sepals and the petals. Reproductive parts of the flower are the stamen (male), and the carpel or pistil (female).
Photosynthesis
As you may recall from biology lessons, Photosynthesis is where energy from sunlight is converted into chemical energy and subsequently stored as sugar. This happens in plants and also in some algae. Plants need only sunlight, CO2 and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts, using the green pigment chlorophyll. Sessile volatile oil gland on a mature leaf showing raised cuticle, with the space between the secretory cells and cuticle filled with oil. (Light microsope magnification x 400) This picture was originally seen in Aromatherapy Quarterly, 48. Most plant surfaces are said to be pubescent - i.e. they have hairs or trichomes either all over or just on some parts of the surface. Scent-producing herbs are often covered by non-secretory hairs (trichomes) or secretory hairs (glandular trichomes). Trichomes are simple hairs that guide the path of pollinators. They affect leaf temperature and water loss.Glandular trichomes are specialised secretory tissues. Their function is thought to be 'for production of pest or pollinator interactive chemicals'. Each glandular trichome develops from a single epidermal cell which has a large nucleus and dense cytoplasm.
There are two types:
1. capitate - one or two heads
2. peltate - as many as ten head cells
It is within the peltate trichomes that the essence is stored in spaces 'formed by the separation of the head cell walls from their covering cuticle, resulting in an expansion in the surface of the cuticle'. Although trichomes commence at different stages as the leaf develops, the majority are formed as the leaf becomes 2 mm long. The whole process is completed by the time the leaf is fully developed. Each species of plant has to be studied individually to establish gland density and development i.e. Melissa officinalis is a low oil producer (low yield), less than 0.05% volume by weight and has a very low density of glands per mm². This is therefore reflected in the price of the essential oil, despite the fact that it is prolific in growth. Oil storage capacity (yield) varies between species and also between trichomes. Once oil reserves are formed, they will not be lost until the cuticle is broken. A good example is eucalyptus leaves, where you have to snap the leaves in order to break the cuticles and release the essence. However, chemical constituents of essential oils and yields will vary depending on the age of the leaf and its developmental stage, a major consideration for oil producers. Biochemical experiments suggest that volatile oils are synthesised in glands and have been shown to be located exclusively in the trichomes, and not found anywhere else in the plant. We can only surmise why these 'essential' oils are produced in the plant: perhaps it is to attract pollinating beneficial insects, or as a deterrent against predators. There is also a possibility that each type of plant cell produces a different type of oil. This would explain the differences in chemical composition of volatile oils between leaf, stem and flower.
References
http://en.wikipedia.org (List of images/Nature/Animals/Insects)
Online Biology Book glossary at http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookglossT.html#tissues
Aromatherapy Quarterly, 48. Spring 1996, pp. 25-9.
Carole Preen AC Office
Tel: 0870 7743477
www.aromatherapycouncil.co.uk
To join the register the annual fee is £60.00, which is equivalent to just 16 pence a day in order to give you the credibility and status you deserve as a professional aromatherapist.
AC AGM Minutes 12th July 2006 available at www.aromatherapy-regulation.org.uk BMA, Complementary and alternative medicine - submission to public petitions committee 13 January 2003 Cancer Research UK http://www.cancerhelpuk.org/trials/understanding/default.asp?page=18284 Charlton Dr. Ed, The Management of Postoperative Pain Update in