- - AGRICULTURE CORE CURRICULUM - - (CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE (CLF6100) Unit Title: BOTANICAL CLASSIFICATION ____________________________________________________________________________ (CLF6101) Topic: HISTORY AND TERMINOLOGY Time Year(s) OF TAXONOMY 1 hour 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (A-1) - Define the word, "taxonomy." (A-2) - List three bases on which plants can be classified and/or identified (i.e., morphology, physiology, and evolution). (A-4) - List and discuss three applications the science of taxonomy has for the field of agriculture (e.g., plant, insect, and microorganism identification). Special Materials and Equipment: References: Cooper, Elmer L. (1990). AGRISCIENCE: FUNDAMENTALS AND APPLICATIONS. Albany, NY: Delmar Publishers. Bailey, L. H. (1976). HORTUS THIRD. New York: Macmillan. Harrington, H. D., & Durrell, L. W. (1957). HOW TO IDENTIFY PLANTS. Athens, OH: Ohio University Press. Hartmann, H. T., Flocker, W. J., & Kofranek, A. M. (1981). PLANT SCIENCE: GROWTH, DEVELOPMENT, AND UTILIZATION OF CULTIVATED PLANTS. Englewood Cliffs, NJ: Prentice-Hall. Evaluation: Unit Exam ===================================================================== *** INSTRUCTORS PLEASE NOTE *** The detail of this topic presentation goes beyond the scope necessary to meet the requirements of the Core Cluster in this area. It will take longer to teach than indicated above if covered entirely. It is included for local enrichment as appropriate to the class. ===================================================================== TOPIC PRESENTATION: THE HISTORY AND TERMINOLOGY OF TAXONOMY A. Taxonomy 1. Definition: Taxonomy is the orderly classification of plants and animals according to their presumed natural relationships. NOTE: While in horticulture we are concerned mainly with the classification of plants alone, we are often interested in how animals such as insects, mollusks, microorganisms such as fungus and bacteria, and mammals are grouped and the characteristics they have in common. This is often important information with regard to pest identification and control. The general principles we learn about plant classification can be applied very closely to the taxonomy of other types of organisms. 2. Practically speaking, plant taxonomy involves four interrelated fields: a. Botany--The systematic pursuit of specific facts and knowlege about plants. b. The Taxonomic System--Based on the facts that are found, and using that knowlege to set up classifications and arrangements of plant groups (taxa) and concepts of the evolutionary sequence of characteristics; also provides descriptions of taxa. c. Nomenclature--A uniform method of naming plants based on international rules that botanists have agreed on in order to promote a reasonably stable system; provides for one name only for each kind of plant. d. Documentation--Includes the illustration, photography, and preservation of actual plant specimens in museums or herbariums. B. History of Botanical Classification 1. Classification of plants has been ongoing for over 4000 years. a. Theophrastus (370-285 B.C.), the "Father of Botany" classified plants as a function of texture or form. Also, Theophrastus distinguished between: 1) Herbs, shrubs, trees 2) Annuals, biennials, perennials 3) Groups of plants, depending on different flower parts b. Many botanists in the fourteenth to eighteenth centuries developed systems of plant classification. c. Carl von Linn_ (Carolus Linnaeus) developed classifications in the 1730s, based on the sexual parts of flowers. (Genera plantarum described close to 1000 genera of plants.) This system was dropped, but the accompanying nomenclature (the "binomial" system of naming plants) has become convention. 2. Plant classification efforts are still ongoing. New species, varieties, and cultivars are constantly being added, and the names of recognized plants are occasionally changed as more is learned about them. C. Modern Classification of Plants 1. Criteria for classification--Plants can be grouped according to many different criteria, either formally or informally. Following are some of the more common ways plants are grouped. The examples given relate to ornamental plants, but can also be applied to agricultural and botanical specimines. The last three categories provide the basis for the formal classification of plants by botanists. a. Climatic--Temperate zone plants such as stone fruits vs. tropical zone plants such as the Ficus houseplants b. Season--Winter annual weeds vs. summer annual weeds c. Temperature--Warm season crops such as zinnias and petunias vs. cool season crops such as primroses and snapdragons d. Life Cycle--Annuals such as sweet alyssums and pansies vs. perennials such as gazanias or roses e. Growth Habit--Plants that grow tall such as trees and shrubs vs. plants that remain low to the ground such as ground covers and turf grasses f. Use--Plants used for street trees such as flowering plum and London plane vs. plants used for hedges such as privets and boxwoods g. Morphology--Plants with a particular form, structure, or development such as four-petal poppies vs. five-petal roses h. Physiology--Plants with particular functions and activities such as evergreen fir trees vs. deciduous larch trees i. Evolution--Plants with advanced characteristics such as flowering plants vs. those with more primitive systems such as ferns, which reproduce by spores 2. Organization and Nomenclature of the Major Taxa--These levels of orgnization help us divide groups of plants with major differences, but are less often used on an everyday basis by those in the horticultural trades. a. Kingdom--Historically, two kingdoms have been recognized, the plant and animal kingdoms. Today there are at least five, including: 1) Monera--such as bacteria and blue-green algae 2) Protista--mostly one-celled eucaryotes including diatoms, dinoflagellates, and certain algae 3) Animals--mostly mobile, relying on ready-made food (rather than photosynthesizing) and lacking rigid cell walls 4) Fungi--includes the slime and water molds, mildews, rusts, and organisms such as bread molds and mushrooms. Fungi are saprophytic, meaning they obtain their nourishment from the non-living parts of other organisms. Fungi don't photosynthesize. 5) Plants--Certain characteristics help us identify organisms as part of the plant kingdom. Plants: a) are stationary b) photosynthesize c) produce cellulose d) often exhibit indeterminate growth b. Division--Historically, there have been four divisions within the plant kingdom. These categories are still in use for the sake of simplicity. Strictly speaking there are as many as 28 divisions. The four generally recognized by non-specialists are: 1) Thallophyta--These exhibit little differentiation, and include the algae, bacteria, fungi. 2) Bryophyta--These possess no true roots or sophisticated vascular systems, and must live in or close to water in order to survive. Examples include the mosses and the liverworts. 3) Pteridophyta--These plants have advanced vascular tissue and true roots, but produce no seed, having comparitively primitive reproductive systems. Members include the horsetails and ferns. 4) Spermatophyta (also termed Magnoliophyta)--This group bears seeds. Virtually all plants of economic importance fall into this category. Spermatophytes are further broken down into smaller categories. c. Class--Within the Spermatophyta, there are two major classes of plants: 1) Gymnosperms--These bear "naked" seeds, on cone scales, usually. This group includes conifers such as pines, firs and cypress trees, the palm-like cycads and the maidenhair tree, Ginkgo Biloba. 2) Angiosperms--These plants have "covered" seeds borne in an ovary. This is the largest class, including all the plants with true flowers d. Subclass--Within the Angiosperms, for example, there are two important subclasses: 1) Monocotyledons (also known as Liliopsida or Monocots)-- These plants have one seed leaf, parallel veins, and fibrous roots. Examples are the grasses, palms, lilies, and tulips. 2) Dicotyledons (also known as Magnoliopsida, or Dicots)-- These plants have two cotyledons (seed leaves) and net veins. They often exhibit a tap root and broad leaves. This group includes most trees and shrubs used in horticulture. e. Order--Classes and subclasses are broken down into orders, which are too numerous to specify here. The suffix "-ales" indicates that the name of a plant group is an order. Examples are the Rosales and the Violales, both of which include many important ornamental plants. f. Family--This is the broadest level of classification commonly dealt with from a horticultural standpoint. Hundreds of plant families exist. The suffix "-ACEAE" indicates a family name (i.e., MALVACEAE, ROSACEAE). Notice that--properly written--family names appear in all capital letters. 2. The Minor Taxa--Plant groupings below the level of the plant family are considered the minor taxa and include the genus, the species, and a number of subspecific categories. These are the plant groupings and names that horticulturists use most commonly on a day-to-day basis, and they have specific rules governing their use. The minor taxa are of major practical importance, and are discussed in the next topic plan, (CLF6102) Practical Taxonomy. 1/6/91 MH/clh #%&C