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Sexual and Asexual Reproduction of Plants OVERVIEW INSTRUCTOR: UNIT: Performance of Technical Skills Related to Plant and Soil Science and Technology LESSON: Sexual and Asexual Reproduction of Plants IMS REFERENCE: IMS #8388 LESSON PLAN LESSON OBJECTIVES The student will be able to: discuss the sexual reproduction (pollination and fertilization) of flowering plants; explain asexual (vegetative) methods of propagating plants; and propagate plants sexually and asexually. TOOLS & EQUIPMENT Computer(s) with internet access KEY TERMS egg rootstock scion sperm zygote SUPPLEMENTAL MATERIALS & RESOURCES IMS #8388 Class Notes sheets for IMS #8388 Lesson Test for IMS #8388 horticultural and agronomic plant specimens bean seeds dissection tools live plant flowers containing both stamens and pistils vegetable and/or bedding plant seeds containers and growing medium for planting seeds plants for demonstrating and performing the plant propagation techniques of cuttings, layering, separation, division, grafting, budding, etc. TEACHING PROCEDURES Preparation Key Points Link: Methods Why do plants need to reproduce themselves? What would be Student Thought and Discussion the consequences if they didn’t? (Student discussion may include that plant reproduction is necessary for the survival and perpetuation of plant species. If plants did not reproduce, plant species would die out. Plants are an important source of food and oxygen for the existence of other living species. Without them, life would cease to exist.) Instructional Materials Service www.myimsservices.com 1 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants Motivation: Display of Plant Specimens Provide a variety of plant specimens for display. Throughout the lesson, have students identify each of the plant specimens and determine how each is capable of reproducing – whether by sexual and/or asexual means. Overview: Review of objectives In this lesson, the students will: discuss the sexual reproduction (pollination and fertilization) of flowering plants; explain asexual (vegetative) methods of propagating plants; and propagate plants sexually and asexually. Presentation Key Points Methods Although animals can only reproduce sexually, plants have the capability to propagate or multiply themselves by means of sexual and/or asexual reproduction. Teacher-led discussion What are the benefits of plants being able to reproduce by both sexual and asexual means? Student thought and discussion Sexual reproduction involves using seeds to produce new plants. Presentation A Asexual or vegetative reproduction includes using plant parts other than seeds to produce new plants. Agronomic and horticultural crops reproduced primarily by seeds include: field crops (corn, wheat, rice, sorghum) flowering greenhouse and bedding plants vegetable transplants Horticultural crops and plants produced quicker and more efficiently by vegetative means include: landscape & ornamental plants (flowering perennials, groundcovers, shrubs) turfgrasses Instructional Materials Service www.myimsservices.com 2 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants fruit crops Presentation B Sexual Reproduction Seeds are the means by which plants sexually reproduce. Although seeds contain the genetic characteristics of the parent plant, characteristics of plants grown from seeds may vary from the parent plant. Seed propagation: is an economical and widely used method of producing new plants. allows a grower to produce a large number of plants. Pollination and fertilization are part of the sexual process that occurs within the flowers or reproductive structures of a plant. These processes result in the formation and development of seeds. A seed consists of a: tiny plant, supply of stored food, and a protective covering. Complete Seed Dissection and Identification Activity at this time. Application #1 Pollination occurs when mature pollen grains (male sex cells) from the stamen come into contact with the moist, sticky surface of a flower stigma (female flower part). (Demonstrate the process of self-pollination and crosspollination using flowers of a live plant that contains both stamens and pistils.) Teacher demonstration Self-pollination occurs when pollen comes into contact with a stigma within the same flower or other flowers on the same plant. Cross-pollination occurs when pollen from the flower of one plant transfers to the stigmas of flowers on another plant. Pollen grains transfer to flower stigmas by means of: gravity insects Instructional Materials Service www.myimsservices.com 3 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants wind animals After a pollen grain anchors on the moist, sticky surface of a flower stigma, it germinates and produces a pollen tube. The pollen tube grows down through the style and into the ovary where it eventually reaches an ovule. During the fertilization process: one sperm cell from the pollen tube unites with the egg cell in the ovule to form a zygote. the second sperm cell from the pollen tube unites with two separate polar nuclei to form a primary endosperm nucleus. double fertilization results from the unions of the two male sex cells. The zygote formed through the union of the sperm and egg cells proceeds through cell division and develops into a seed embryo. The primary endosperm nucleus develops to form a food source to be used by the embryonic plant during seed germination. For each seed a plant produces, a separate grain of pollen must reach and unite with an ovule. Begin Seed Germination Activity at this time. Application #2 Asexual Reproduction Presentation C Asexual or vegetative reproduction involves the production of new plants by means of using vegetative parts of an existing plant. The vegetative parts of many plants have the ability to produce new roots and/or shoots to form a new plant. Asexual reproduction is often advantageous over sexual reproduction because: new plants reach maturity in less time. disease-free plants can be produced in controlled environmental conditions. reproduction is possible for plants that do not develop reproductive parts or viable seeds. plant selection for desired characteristics is more Instructional Materials Service www.myimsservices.com 4 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants reliable. new plants are genetically identical to the parent plant. Vegetative plant parts used in asexual reproduction include: leaves stems (above-ground, below-ground) buds roots Methods of vegetative plant reproduction include: cuttings layering separation division grafting budding tissue culture Propagation by cuttings is the most widely used method of vegetative or asexual reproduction. A cutting is any plant part severed from the parent plant. Cuttings include: stem cuttings (portion of a stem that includes a node) root cuttings (2- to 3-inch section of thickened root) leaf cuttings (leaf blade and petiole, leaf blade only, or section of leaf blade) Layering involves forcing a vegetative plant part to form roots while still attached to the parent plant. Two types of layering are: air layering (forcing roots to form on a stem, outside the soil) ground layering (extending a plant part into the ground, covering it with soil, and allowing it to root) Separation involves removing new plants formed on specialized stems and separating them from the parent plant. Division is the technique of cutting specialized plant structures into sections and forcing each section to grow into a new plant. Instructional Materials Service www.myimsservices.com 5 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants Practice asexual propagation techniques at this time. Grafting consists of uniting a hardwood scion from one plant with the rootstock of another similar hardwood plant to form a vascular connection between the two plant parts. Budding, similar to grafting, consists of removing buds from one plant and placing them on stems of other closely related plants to form a vascular connection between the two plant parts. Teacher demonstration Tissue culture, or micro-propagation, involves placing a very small piece of plant tissue on a sterilized culture medium. Under sterile conditions, the plant tissue multiplies and grows into new plants. Advantages of tissue culture as a means of asexual reproduction are that it: allows large numbers of offspring to be produced quickly; allows growers to produce disease-free plants; is a cost-efficient method of reproducing plants; and allows plants to be produced that have the same characteristics as the parent plant. Disadvantages of tissue culture include: the costs of necessary tools and equipment; the preciseness of establishing and maintaining sterile conditions needed for plant development; and the requirement of additional time and labor as compared to other methods of asexual propagation. Begin Asexual Propagation Activity at this time. Application #3 Instructional Materials Service www.myimsservices.com 6 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants Evaluation #2 Application Key Points Seed Dissection and Identification Methods Dissect a bean seed and identify the embryonic plant, stored food supply for germination, and the protective seed covering. Student Activity Seed Germination Activity Student Activity Sow vegetable and/or bedding plant seeds in flats, individual containers, or in a class garden. As the seeds germinate and the plants begin to grow, refer to the benefits of sexual reproduction as a means of plant propagation. Asexual Propagation Activity Perform a variety of asexual propagation techniques using a Student Activity variety of plants. Record observations of root development and plant growth. Evaluation/Summary Key Points Complete Lesson Test for IMS #8388 Methods Worksheet REFERENCES/ ADDITIONAL MATIERIALS Poincelot, Raymond P. Horticulture: Principles and Practical Applications. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1980. Texas Cooperative Extension Service. Master Gardener Handbook. 3rd edition. College Station, TX. 1995. Web site references: http://plantfacts.ohio-state.edu/mg/manual/prop.htm Instructional Materials Service www.myimsservices.com 7 Texas Education Agency www.tea.state.tx.us Sexual and Asexual Reproduction of Plants http://aggie-horticulture.tamu.edu/propagation/propagation.html http://ag.arizona.edu/pubs/garden/mg/propagation/ COLLEGE & CAREER READINESS STANDARD Instructional Materials Service www.myimsservices.com 8 Texas Education Agency www.tea.state.tx.us