Plant Taxonomy

Plant Taxonomy- is the grouping of plants based on their presumed relationship. Nomenclature is the application of names to plants. Common Names are easy to pronounce and remember, but they can be confusing because of different areas use different names. Scientific names are formal names accepted by scientists around the world. Scientific names of taxonomic groups are treated as Latin regardless of their derivation.

Scientific names have a Genus name, the specific epithe, and the authority of individual(s) responsible for the name. The genus and species name are either italicized or underlined. The scientific name for the white oak is Quercus alba L. Scientific names published at the earliest date take precedence over names of the same rank published later.

In order to have a definite starting point, botanists have agreed that for flowering plants the starting point shall be Species Panktarum, published by Carl Linnaeus in The International Code of Botanical Nomenclature lists exceptions and additions to this rule. The code is supposed to keep botanists all over the world using the same system names. There is a disagreement over some plant groupings today, and we have several proposed classification systems.

Some of these systems have 20 or more principal groups of plants. The major classification groups for Botany and Zoology are different. There is movement to adopt only one classification system, The Bio Code, for all types of living things. Most literature usually refers only to one family name, and the genus and species of individual plants. Botanists have adopted the Type Method to stabilize the determining characteristics of a species.

The author of a species must designate a certain specimen as the Type Specimen of that species. The Type Specimen is not necessarily the most representative of the group, it just best shows the element on which the name for the group was originally based. The Type Specimen fixes the strict concept of that species and the application of its name. Type Specimen is carefully preserved in a herbarium that is accessible to research scientists. To allow for destruction of the Type Specimen, the system Isotope, Lectotype, Neotype, and others were devised for designating acceptable substitutes.

Holotype (Type Specimen) is the original specimen designated by the author. Types are the most valuable of all the specimens. Museums and Universities are very proud of the number of Type Specimens they have in their hebarium. Isotype is any specimen, other than the holotype, that duplicates the holotype. The isotope must come from the same collection, with the same locality, date, and number as the holotype. Lectotype is a specimen selected by a competent person from the original material studied by the author.

Neotype is a specimen selected to serve as a substitute for the hologype when all material on which the name was based is missing. Gymnosperms form “naked seeds”, not enclosed in fruit. Division Cycadophyta- only about 100 species of cycads are alive today, most of which are found in the tropics. Division Ginkgophyta- is the only living ginkgo example is Ginkgo biloba. The Ginkgo is a hardy delicious tree that is planted as an ornamental.

Division Coniferophyta- conifers are woody plants with needle or scale-like leaves that form cones. They include pines, cedar, junipers, redwoods, firs, and spruce. Angiosperms for their seeds enclosed in a fruit. Division Anthophyta- flowering plants. There are almost 300,000 species of angiosperms, making them dominate group of plants in the world today.

There are two classes of Angiosperms, based on their number of cotyledons (seed leaves) Monocotyledoneae (the Monocots)- all members of the group have one ctyledon. Monocots have about 90,000 species, 10% of the species are woody, most are grasses and grains, such as wheat, oats, corn, and rice.

Dicotyledoneae (The Dicots)- all members of this group have two cotyledons Dicots have almost 200,000 species. Dicots are 50% woody, and are a very diverse group.

Monocots and Dicots are the two most important groups to study. In this class, you will be able to differentiate between Monocots and Dicots.

Plants are sometimes grouped using the common names below. While these are not taxonomy groups, understanding their use is very helpful!

Tree- woody plants with one main stem or trunk

Shrub- woody plants with several stems growing from the ground

Forb- Herbaceous(soft-non woody) plants with flowering leaves

Grass-Herbaceous flowering plants with narrow leaves and jointed stems.

Succulent- Plants with thick, fleshy tissue in leaves or stems for storing water

The following terms are applied to herbaceous plants with green, non-woody stems. Annual plants- live for one growing season. They will sprout, grow leaves and flowers, produce seeds, and die. Biennial plants- complete their lifecycle over two growing seasons. In the first season, they usually only produce leaves. In the second season, they form flowers, produce seeds, and die. Perennial plants- continue to grow and flower for more than two years, and many live for decades. Most perennials die back to the ground in winter, the sprout from their underground growth in the spring.

Example of Annuals

Example of Biennials

Example of Perennials