- - AGRICULTURE CORE CURRICULUM - - (CLF6000) Advanced Core Cluster: ORNAMENTAL HORTICULTURE (CLF6100) Unit Title: BOTANICAL CLASSIFICATION ____________________________________________________________________________ (CLF6106) Topic: CHARACTERISTICS OF FRUITS Time Year(s) 1 hour 3 / 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson, the student will be able to: Learning Outcome #: (A-2) - List three bases on which plants can be classified and/or identified (i.e., morphology, physiology, and evolution). Special Materials and Equipment: Apples, knives, a variety of fruits as listed below under the second class activity References: 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. 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: CHARACTERISTICS OF FRUITS REVIEW: Fruit structure is one of the most important criteria for deciding how to identify and categorize plants. The reproductive structures of plants have historically been the primary basis for dividing plants into different orders and families. While in the field we don't use fruit as often as foliage as an identifying characteristic, it is important to know the terminology associated with fruits if our understanding of botanical classification is to be complete. A. Definitions 1. Fruit: The fruit is the matured ovary plus the associated parts (receptacle, etc.). Basically, the mature part of the plant which is associated with its sexual reproduction is thought of as the fruit. While we commonly think of bell peppers, tomatoes and zucchini as vegetables, they are, in fact, fruits. One rough way of thinking of it is "If it has seeds, it's a fruit." Two major types of fruit are: a. Seed-bearing (i.e., most fruits as we encounter them in nature) b. Without viable seed, or "parthenocarpic" (for example, navel orange). 2. Pericarp: The pericarp is the fruit wall, developed from the ovary wall. It consists of three different layers which can each take on a different form, depending on the type of fruit in question. Below, we use a peach as an example of one way the pericarp can develop: a. Exocarp: The outermost part of the fruit wall (i.e., the skin of a peach). b. Mesocarp: The middle portion of the fruit wall (i.e., the fleshy portion of a peach that we eat). c. Endocarp: The innermost part of the fruit wall (i.e., the stone portion of a peach). (Note: The seed within the stone is not part of the pericarp. The seed is a separate part of the fruit, defined below.) 3. Carpel: One individual part of a compound ovary. __________________________________________________________ ACTIVITY: 1. Have students cut apples in half (from side to side) to observe the distinctive star shape which results from the development of five separate carpels within the fruit. 2. The same thing can be done with zucchini, tomatoes, bell peppers, and other kinds of fruit to observe different numbers of carpels (often three). __________________________________________________________ 4. Seed: Seed is the mature ovule or egg, consisting of three main parts: a. Embryo: This is the immature "primordial" plant which will develop into the mature organism. b. Food storage: This takes the form of either endosperm (in the case of grains) or cotyledons (in the case of beans and other dicotyledonous plants). c. Seed coat: The protective covering surrounding the seed. B. Types of Fruits: In the descriptions given below, examples from the produce market are given in addition to horticultural specimens, for the sake of familiarity and clarity. Fruits which we consume for food are, as a group, much larger than fruits found in the landscape, and it is easier to observe and understand their structure. The listing below is not exhaustive--there are other types of fruits. However, these are the most common types of fruits, and will give a sound basis for identifying many ornamentals according to their fruit type. __________________________________________________________ ACTIVITY: 1. Divide students into groups of three. Pass out an assortment of fruits, both from the list below, and from examples cut from the landscape. (Many of the examples listed in the lesson below are commonly available in the landscape.) Each group should have at least three samples. 2. As the fruit types are discussed, students should determine together which types of fruit their group has. Each student should prepare to share at least one of their group's fruits after the discussion, tell what type of fruit it is, and state the factors that helped the group make its determination. 3. Shopping list for fruit identification activity: PEACH DRY BEANS (Soak some overnight if you want to observe the different parts of the seed!) BANANA GREEN PEPPER TOMATO ORANGE OR LEMON ZUCCHINI OR MELON APRICOT CHERRY NECTARINE, PEACH, ETC. ALMONDS (in the hull) APPLES (extra for the activity above) SNOW PEAS SUNFLOWER SEEDS CORN WHOLE WHEAT/BARLEY NUTS (for example, FILBERT, CHESTNUT, etc.) STRAWBERRIES RASPBERRIES/BLACKBERRIES FIGS __________________________________________________________ 1. Simple fruits: These are fruits derived from a single pistil. There are many kinds of simple fruits, described below. a. Fleshy fruits are those in which the entire pericarp and accessories develop into soft, succulent tissue. Different types are: 1) Berry: A pulpy fruit, with few to many seeds, for example, bananas, dates, grapes, tomatoes, peppers, papayas; passion fruit (Passiflora spp.), mirror shrub (Coprosma repens), and common myrtle (Myrtle communis). 2) Hesperidium: A leathery rind with inner pulp composed of juice sacks, for example, Citrus spp. 3) Pepo: A fruit from inferior ovary, with multiple carpels bearing many seeds, usually thick with a hard rind, for example, cucurbits: melon, zucchini, etc. b. Dry Fleshy Fruits: These are fruits in which some part of the pericarp becomes dry. Two types are: 1) Drupe: A very common type of fruit, from a single carpel and possessing a hard endocarp, for example, stone fruits (peaches, cherries, etc.), almonds, olives; prostrate myoporum (Myoporum parvifolium) and English laurel (Prunus laurocerasus). 2) Pome: A fruit in which the receptacle develops into the fleshy portion of the fruit, for example, apple, pear; Japanese flowering quince (Chaenomeles japonica), Parney cotoneaster (Cotoneaster lacteus), and firethorn (Pyracantha spp.). c. Dry fruits: In dry fruits the entire pericarp becomes dry, and often very hard. There are two principal types of dry fruits--those that split open, and those that don't. 1) Dehiscent Fruits: Fruits which split open at maturity to expose seeds. Three types of dehiscent fruits are: a) Capsule: Fruits which form on two or more carpels with each producing many seeds. This is a very common seed type, and there are several types of capsules. Identifying these different types of capsules goes beyond the scope of this lesson, but examples of these fruits are common in horticulture, e.g., Iceland poppy (Papaver nudicale), Douglas iris (Iris douglasiana), and the eucalypts (Eucalyptus spp.). b) Follicle: The fruit forms from one carpel which splits along one suture, for example, delphinium. c) Legume: Legumes form from one carpel which opens along two sutures. An entire plant family is named after this fruit type, the LEGUMINOSAE, also known as the FABACEAE; examples are, pod peas, snow peas, fava beans, and soybeans; the acacias (Acacia spp.), wisteria (Wisteria spp.), and the carob tree (Ceratonia siliqua). 2) Indehiscent Fruits: These do not split open. There are no sutures. The seed must break through the pericarp in order to germinate. The seed may do this on its own, or it may rely on other forces of nature, such as an animal or an abrasive environment, to accomplish this. Four types of indehiscent fruits are: a) Achene: These are one-seeded, thin-walled fruit attached to the ovary wall. They are generally small, and difficult to observe. Examples are strawberries (the "seed" part on the outside of the part we eat and normally think of as the fruit), sunflower "seeds," sycamores (Platanus spp.), and calendula (Calendula officinalis). b) Caryopsis: A one-seeded fruit with a thin pericarp. Essentially, these are the grains, for example, corn, rice, wheat, barley. c) Nut: Easily confused with the common usage, which usually refers to a seed only, such as the meat of a walnut or an almond. True nuts are one-seeded fruit with a thick, hard, stony pericarp, for example, chestnuts, filberts; oaks (Quercus spp.) have nuts to which we give the special name "acorn." d) Samara: a one- or two-seeded fruit with a wing-like structure, e.g., ash trees (FRAXINUS spp.), maples (ACER spp.), and elms (ULMUS spp.). 2. Compound Fruit: Compound fruit forms from several ovaries at one time. Two major types are: a. Aggregate Fruits: These develop from many ovaries on a single flower, e.g., blackberry, and raspberry. In the case of the latter, the aggregate is composed of many small drupes, the "true fruit" the raspberry is made of. b. Multiple Fruits--Develop from several to many separate flowers (ovaries) fused into a single structure. for example, mulberries, pineapple. The fig family (FICUS spp.), which is widely used in ornamental horticulture, bears multiple fruits called syconiums. Edible figs are very good examples for observing the structure of a syconium (The flowers all occur inside the receptacle!). 3. Accessory Fruit: These are fruits which develop from parts other than the ovary. The best example is the strawberry, in which the fleshy part of the fruit develops from the receptacle. (Note that we can correctly identify the strawberry fruit as an achene, an aggregate fruit, or as an accessory fruit, depending on what we consider!) Roses (ROSA spp.) have aggregate fruits called rosehips. Likewise, with the rosehip the "true" fruits are achenes, and the accessory is the swollen receptacles. In this case the achenes are on the inside of the receptacle instead of the outside. 1-7-91 MH/clh/dlc #%&C