Chapter 3. Naming and Organizing Plants

Taxonomy The process of giving names to newly discovered organisms The discoverer’s name follows the genus and species name Rules for naming plants follow the International Code for Botanical Nomenclature Plants named by Linneaus are followed by ‘L’

Agaricus xanthoderma Poisonous mushrooms look very similar to their edible relative, which can be member to the same genus and species. The importance of being able to identify mushroom by their scientific name with aide in the identification of those that are poisonous

Linneaus: Father of Biological Nomenclature Developed the system of identification by genus and species in 1758 Classification based on morphology and sex Introduced eroticism into botany Based on Greek and Latin words that are often descriptive of the physical characteristics of the organism

Genus and Species Each species of an organism has a unique name Closely related organisms are placed in the same genus Some organisms given names to honor a scientist or other person Some genus names are also common names (Pinus) Species names are descriptive adjectives that may be used with more than one genus name

Genera: Ginko Only surviving species in this genus, over 270 million years old

Genera: Pinus A) Pinus resinosa B) Pinus strobus C) Pinus banksiana

Linnaeus borealis

Narcissus Scientific name also used as a common name. Other examples are Hibiscus, Gladiolus, Vanilla

Species Names are Descriptive Adjectives Epithets used for species names

Salvia divinorum is a psychoactive herb which can induce dissociative effects. It is a herbaceous perennial in the Lamiaceae (mint) family. The specific name, Salvia divinorum, was given because of its traditional use in divination and healing[5]—it literally translates to "diviner's sage" or "seer's sage".[6][nb Source http://www.carolinanature.com/plants/salvia.html

Subspecies Subspecies – a group of organisms that inhabits a geographical area or type of habitat different from other members of the same species Ex. Zea mays subspecies parviglumis (teosinte) Corn in Mexico

Varieties and Cultivars Varieties – members of the same species that have small but consistent differences from each other Cultivar – a variety that does not occur in nature but occurs only in cultivation. Names selected to attract customers Ex. Phlox paniculata ‘David’

Hybrid Names Crossbreeding between 2 species Individuals that do not breed with parents become new species Species names combine the names of the 2 species that crossbread Ex. laeliocattleya = laelia + cattleya

Other Definitions Herbaceous- plants with nonwoody stems which die back at the end of the growing season Woody-plants that have woody stems Evergreen – plants that stay green year-round Deciduous-plants that lose their leaves in the winter Perennial – plants that come back each growing season Annual – plants that die after 1 growing season Biennial - plants that die after 2 growing seasons

Resources for Identifying Plants Herbariums – pressed and collected specimens Serve as reference libraries in which thousands of plants from all over the world are stored

National Herbarium The United States National Herbarium was founded in 1848, when the first collections were accessioned from the United States Exploring Expedition (50,000 specimens of 10,000 species). Current holdings total 4.5 million specimens, making this collection among the ten largest in the world representing about 8% of the plant collection resources of the United States.

Botanical Gardens Collections of living plants Resource for botanists, landscape architects, and gardeners, artists and photographers Serve to conserve rare species in danger of extinction

Dichotomous Key- a series of choices between Dichotomous Key- a series of choices between two possibilities to determine ID

Modern Classification of Plants Morphological features are deceiving and are not used to classify plants Some unrelated plants may appear to be related because of similar leaf shape Likewise, plants that are closely related may have very different leaf shapes

Ricinus (castor bean) and Begonia ricinifolia Unrelated plants can have similar leaves – but not be related – this is a problem when classifying based on Morphology

Very different looking, but all begonia species Very different looking, but all begonia species. Modern classification systems rely on a variety of characteristics including DNA sequences (molecular characteristics), structure and function of enzymes (biochemical characteristics), and structural characteristics to group organisms. Classification based on phylogeny

Linneaus used floral characteristics to classify plants Flowers of different begonia species are very similar in form reflecting close relationship. Linneas organized plants into 24 classes according to the number of male stamens in the flower

Hierarchy of Classification

Phylogenetic Systematics Classification of organisms according to evolutionary relationships

Cladistics A new method of classification using the number of characteristics that organism share in common and placing them in order on a phylogenetic tree (like a family Tree) Clade – a group of organisms defined by at least one shared characteristic, derived from a common ancestor Ex. All organisms producing seeds Preferred method of classification today Shape of a phylogenetic tree may change as new data becomes available Focuses on evolutionary relationships rather than morphological characteristics

Cladogram of Land Plants This tree illustrates the relationships in land plants. Illustrates which groups have specific characteristics, such as leaves and seeds Some shared characteristics such as seed production, present in some groups but not in all, indicate that all plants producing seeds had a common ancestor and diverged or branched away from non-seed producers at some time in the past.

Plant classifications may change as new discoveries are made DNA serves an important role in providing links between species Ex. Tomato (solanum licopersicon) and potato (solanum tuberosum) recently found to be so closely related that they belong in the same genus