Colorado Agriscience Curriculum Section: Plant Reproduction Unit 4: Plant Reproduction Lesson Number 4: Asexual Propagation I Colorado Agricultural Education Standards: AS 11/12.4 The student will demonstrate an understanding of physiological processes in agriculturally important plants HRT 11/12.2 The learner will understand and describe the anatomy of horticulture plants. Colorado Science Standards: SCI 1.1 Asking questions and stating hypotheses, using prior scientific knowledge to help guide their development SCI 3.1 Students know and understand the characteristics of living things, the diversity of life, and how living things interact with each other and with the environment. SCI 3.3.5 Using examples to explain the relationship of structure and function in organisms. SCI 3.3.6 Describing the pattern and process of reproduction and development in several organisms. Student Learning Objectives (Enablers) As a result of this lesson, the student will … Objective 1: Understand the types of stem cuttings and how to perform them. Objective 2: Understand the types of leaf cuttings and how to perform them. Objective 3: Understand root cuttings and how to perform them. Time: Instruction time for this lesson: 55 minutes. Tools, Equipment, and Supplies Power Point or Colored Overheads Introduction to Plant and Soils Science and Technology Text (page 60) Agriscience: Fundamentals and Application Text Key Terms Cuttings Fungicide Rooting Hormone Stem Tip Cuttings Stem Section Cuttings Cane Cuttings Heel Cuttings Single-eye Cuttings Double-eye Cuttings Leaf Cutting Leaf Petiole Cutting Leaf Section Cuttings Split-vein Cuttings Root Cuttings Interest Approach Much of the seed stock that is used to produce potatoes is replaced with better cultivars or varieties over a period of a few years. Farmers who produce “seed potatoes” are constantly seeking plants that are resistant to diseases and pests. Individual potato plants that are identified in the field as being superior to other potato plants are often selected as parent stock. From the plant materials obtained from these plants, many new potato plants are cloned. These valuable young plants are initially raised in a greenhouse environment, and the supply of “seed potatoes” is expanded in the field until and adequate supply is available for commercial plantings. The “seed potatoes” are then cut into pieces for planting. A field of potatoes is a perfect example of massive cloning efforts that have been advanced to a commercial scale of operation. We will take the next couple of days to explore the fascinating field of asexual propagation in plants and how these practices are utilized in the agricultural industry. Summary of Content and Teaching Strategies Objective 1. Understand the types of stem cuttings and how to perform them. Slides 1 – 11 Slide 2: As stated previously, asexual propagation is using the vegetative parts of the plant to increase the number of plants. Its primary advantages are economy, time, ad plants that are identical to the parents. The primary methods of asexual propagation are cuttings, layering, division, grafting, and tissue culture. Slides 3: Herbaceous and woody plants are often propagated by cuttings. Types of cuttings are named for the parts of the plant from which they come. There are stem tip cuttings, stem cuttings, cane cuttings, leaf cuttings, leaf petiole cuttings, and root cuttings. The procedure for taking cuttings is relatively simple. The equipment needed is a sharp knife or a single-edge razor blade. Sharp equipment will make the job easier and will reduce injury to the parent plant. To prevent the possibility of disease spreading, it is best to dip the cutting tool in bleach water made with one part bleach to nine parts water. The tool can also be dipped in rubbing alcohol. Slide 4: Show slide four and have the students to a quick drawing to illustrate the anatomy of the plant. This is needed to give them the proper terminology for the remainder of the lesson. When performing cuttings the lowers and flower buds should be removed from all cuttings. This allows the cutting to use its energy and food storage for root formation instead of flower and fruit development. A rooting hormone containing a fungicide is used to stimulate root development. A fungicide is a pesticide that helps to prevent disease. Rooting hormone is a chemical that will react with the newly formed cells and encourage the plant to develop roots faster. The proper way to use a rooting hormone is to put a small amount in a separate container and work from that container. This procedure will ensure that the rooting hormone does not become contaminated with disease organisms. Do not put the unused hormone back in the original container. Cuttings are normally placed in a medium consisting of coarse sand, perlite, soil, a mixture of peat and perlite, or vermiculite. It is best to use the correct medium for a specific plant to obtain the most efficient production in the shortest possible time. The rooting medium should always be sterile and well drained, with moisture retention ability to prevent the medium from drying out. The medium should be moistened before inserting the cuttings. It should then be kept continuously and evenly moist while the cuttings are forming roots and new shoots. Stem and leaf cuttings do best in bright, but indirect, light. However, root cuttings are often kept in the dark until new shoots are formed and start to grow. For most plants, the most popular method of making cuttings is by stem cuttings. On herbaceous plants, stem cuttings may be made almost any time of year. However, stem cuttings of many woody plants are normally taken in the fall or the dormant season or both. Slide 5: Stem tip cuttings normally include the terminal bud. They are taken from the end of the stem or branch. A piece of stem between two and four inches long is selected, and the cut is made just below the node. The lower leaves that would be in contact with the medium are removed. The stem is dipped in the rooting hormone and is gently tapped to remove excess rooting hormone. The cutting is then inserted into the rooting medium. The cutting should be inserted deep enough so the plant material will support itself. It is important that at least one node be below the surface of the medium because new roots will grow from it. Slide 6: Stem section cuttings are prepared by selecting a section of the stem located in the middle or behind the tip cutting. This type of cutting is often used after the tip cuttings are removed from the plant. The cuttings should be between two and four inches long, and the lower leaves should be removed. The cutting should be made just above a node on both ends. It is then handled as a tip cutting. Make sure that the cutting is positioned with the right end up. The axial buds are always on the tops of the leaves. Slide 7 - 8: Some plants, such as the dumbcane or bamboo have cane like stems. These stems are cut into sections that have one or two eyes, or nodes, to make cane cuttings. The ends are dusted with activated charcoal or a fungicide. It is best to allow the cane to dry in open air for one to two hours. The cutting is then placed in a horizontal position with half of the cane above the surface of the medium. The eyes, or nodes, should be facing upward. This type of cutting is usually potted when the roots and new shoots appear. Slide 9: Heel cuttings are used with woody-stem plants. A shield-shaped cut is made about halfway through the wood around the leaf and axial bud. Rooting hormone may be used in the same manner as in the other types of cuttings. The cutting is inserted horizontally into the medium. Slide 10: When the plant has alternate leaves, single-eye cuttings are used. The eye refers to the node. The stem is cut about a half inch above and below the same node. The cutting may be dipped in rooting hormone, and then placed either vertically or horizontally into the rooting medium. Slide 11: When plants have opposite leaves, double-eye cutting is the preferred type of cutting. It is often used when the stock material is limited. A single node is selected, and the stem is cut a half-inch above and below the node with a sharp tool. The cutting should be inserted vertically in the soil medium. Objective 2. Understand the types of leaf cuttings and how to perform them. Slides 12 – 17 Slide 12: For many of the indoor herbaceous plants, a leaf-type cutting will produce plants quickly and efficiently. This type of cutting will not normally work for woody plants, however. A cutting made from a leaf with a petiole cut to less than a half inch is referred to as a leaf cutting. To prepare a leaf cutting, detach the leaf from the plant with a clean cut and dip the leaf into the rooting hormone. Place the leaf cutting vertically inot the medium. New plants will form at the base of the leaf and may be removed when they have formed their own roots. Slide 13: For leaf petiole cuttings, a leaf with a petiole about half to one and half inches long is detached from the plant. The lower end of the petiole is dipped into the rooting hormone and then placed in the medium. Several plants will form at the base of the petiole. These plants may be removed when they have developed their own roots. The cuttings may be left in the medium to continue to form new plants. Slides 14 & 15: Fibrous-rooted begonias are frequently propagated using leaf section cuttings. The begonia leaves are cut into wedges, each containing at least one vein. The sections are then placed into the medium. New plants will form at the vein that is in contact with the medium. A section-type leaf cutting is made with the snake plant. The leaf is cut into sections two to three inches long. It is a good practice to make the bottom of the cutting on a slant and the top cutting straight. This is done so you can tell the top from the bottom. The sections are placed in the medium vertically. Roots will form reasonably soon, and new plants start to appear. These are to be cut off from the cutting as they develop roots. The original cuttings may be left in the medium for more plants to develop. Slides 16 & 17: Split-vein cuttings are often used with large leaf types, such as begonias and other large leaf plants. With split-vein cuttings, the leaf is removed from the stock plant, and the veins are slit on the lower surface of the leaf. The cutting is then placed on the rooting medium with the lower side down. It might be necessary to secure the leaf to make it lie flat on the surface. A good method is to use small pieces of wire, bending the wire like hairpins and pushing them through the leaf to hold it in place. The new plants will form at each slit in the leaf. Objective 3. Understand root cuttings and how to perform them. Slides 18 – 19: It is best to use plants that are two to three years old for making root cuttings. The cuttings should be made in the dormant season when the roots have a large supply of carbohydrates in reserve. In some species, the root cuttings will develop new shoots, which, in turn, will develop root systems. In others, the root system will be produced beore new shoots develop. If the plant has large roots, the root section should be four to six inches long. To distinguish the top from the bottom of the root, make the top cutting a straight cut and the bottom one a slanted cut. This type of cutting should be stored for two to three weeks in moist peat moss or sand at a temperature of about forty degrees Fahrenheit. When removed from storage area, the cutting is inserted into the medium in a vertical position. The slanted cut should be down, and the top straight cut just level with the top of the medium. If the plant typically has small roots, a section one to two inches long is used. The cutting is placed horizontally a half inch below the surface of the medium. Review/Summary Utilize a Hieroglyphic E-Moment for students to review and organize their notes. Application Extended classroom activity: Acquire different types of plants and develop a lab to demonstrate the different methods of asexual propagation covered in this lesson. FFA activity: Use Life Knowledge Lesson MS 35 to illustrate just as it is important to choose the correct propagation method for certain types of plants, it is important to choose the appropriate use of language and humor with certain groups of people. SAE activity: Use Life Knowledge Lesson AHS 51 for an upperclassman with a solid SAE program can, like a plant cutting, help other members get a new SAE started by brainstorming ideas.