Transcript Propagation
Propagation Why we propagate plants. Why propagate? Why propagate? 1. Ensure future generations. 2. Keeps desired combination of traits alive. 3. Do not have to depend on seed germination. Some plants have seeds that are hard to germinate. Also, do not have to worry about pollination. Why propagate? Possible Problems 1. Will not have genetic variation. 2. Plants will not be able to change with the surroundings. Types of Propagation Two main types of propagation. They are: Asexual and sexual. Asexual – cloning – does not require fertilization 1. Vegetative – reproduce by mitosis (each daughter cell is an exact replica of it’s mother cell. (cont.) Types of Propagation Chromosome numbers and composition do not change during cell division). Ex: stolons and rhizomes. 2. Cuttings – taking parts of plants and planting them Stem cuttings Leaf cuttings Stem Cutting with terminal growing area. Stem Cutting Leaf cutting with petiole. Leaf cutting without petiole. Leaf Cuttings Leaf cutting that has rooted. Used leaf with petiole. Leaf Cutting Leaf cutting with the petiole attached. Placed in water and will result in roots being formed. Leaf cutting with petiole attached but placed in soil. This will be the result. Asexual Cuttings Stem cuttings Hardwood Semi-hardwood Soft wood Herbaceous Leaf cuttings Leaf-bud cuttings Root Cuttings Stem cutting showing an adventitious bud starting. Begonia plant. Stem cutting with an auxiliary bud attached. Stem Cuttings Leaf Bud Propagation For this type of propagation, you use a leaf and the axil of the leaf along with a portion of the stem. Place all of this into a medium and let grow. Type of plants you can use this on are: clematis, grape ivy, dracaena, camellia, jade plant and rhododendron. Asexual Cuttings Grafting – using woody stems Why do we graft? Things to remember when grafting. 3. Asexual Cuttings Grafting – when grafting, you use some part of the woody stem. There are many types of grafts. The following pictures show a procedure called whip grafting. 3. Step 1 Selection Step 2 - Tools Whip Grafting Step 3 - Cutting stem to make area for grafting. Step 4 - Showing how to make the cut. Step 5 – Adding the cut down through the middle. Step 6 – Making the cut on the grafting material. Step 7 – Making incision into the graft. Step 8 – Putting the two grafts together. Step 9 – Wrapping the graft. Step 10 – Finished product. Propagation Methods Budding – inserting bud into existing wood 5. Layering – taking a stem and promoting root growth. 4. Layering – Simple or mound Layering – taking a branch and placing it on the soil. Removing epidermis for layering. Packing moss around area to provide moisture. Wrap in saran wrap to keep moisture in. Air Layering Removing saran wrap to see new roots and bud. New bud with roots. Separation Method Separation – you take mature plants that were stolons or offspring from a parent plant and separate. 7. Runners Runners – stems that run along the top of the ground. They root at the node. 6. Stolons – Parent plant puts out runners and each node a new plant forms along with roots. Runners or Stolons Separation of runner from parent. Separation Method Division Division – taking tubers, roots, bulbs, or corms and dividing them. 8. Stem Tubers – potato – eyes become plants. Stem Tubers Division Division Corms – roots develop around the edge in a circle. The enlarged area is the stem and the leaf sprouts in the concave area on top. Each one of these leaves will become a corm next year. Crocus and glads are examples. Suckering – growth from the root or crown area. Would use division here because of the roots. Suckers Suckering – where plants are produced from roots. Raspberries, willows and dog woods are examples. Suckering Tissue Cultures Micro propagation – Tissue cultures Tissue cultures are taking a small part of a leaf or stem (usually cut into small pieces), placing them in a petri dish that contains agar (medium that has nutrients added to it). 9. Micro propagation Micro propagation – using a part of the plant such as a piece of the leaf (African violet) and placing it in a Petri dish that has agar in it. Roots form from this piece of leaf. Factors Influencing Rooting Factors influencing the rooting of cuttings. 1. Source of cutting material. Young, non flowering plants only a few years away from a germinated seed is best. 2. Time of year the cutting material is taken. Woody perennial (means grows for a number of years)- anytime Factors Influencing Rooting cuttings – late winter Softwood cuttings – spring after growth reaches 4-6”. Semi-hardwood cuttings – midsummer Herbaceous – anytime of the year (do not develop woody tissues). Hardwood Factors Influencing Rooting 3. Treatment of cuttings with Auxins (natural plant hormones) IAA (indoleacetic acid), IBA (indolebutric acid) or NAA (naphthalenoeacetic acid All stimulate root growth Factors Influencing Rooting Misting – needed in herbaceous cuttings. Need to keep hydrated so will not dry out. Mist the plant then cover with plastic cover. Keeps moisture in. Can also have an automated mist system. 5. Bottom heat – helps force rooting by stimulating the root to grow. 4. Sexual Propagation Seed formation is an example of sexual propagation Get genetic diversity from this form Where you have a male and a female and have cross pollination for fertilization between the two to form the seed. Meiosis – another form of sexual propagation Sexual Propagation In meiosis the number of chromosomes in the cells is reduced by half to form the male sperm cell and the female egg. The egg and sperm combine during fertilization in the ovule to form the zygote (fruit) that develops into the embryo (seed). California desert plant called Machaeranthera gracilis example Seed Germination Monocot Seed The seed imbibes (absorbs) water from the soil Emergence of radicle (primary root) and the plumule (primary shoot) These form the primary parts of the plant. Monocot Seed Dicot Seed Dicot Seed Seed imbibes water from soil and swells. Radicle emerges and grows downward. Hook of the bean (hypocotyl) emerges from soil, carrying the two cotyledons (leaves) with it. Dicot Seed Environmental Factors Influencing Seed Germination Adequate moisture in the soil. Proper temperature – cold versus warm Good aeration of soil. Light (in some cases) Freedom from pathogenic organisms. Damping off. Freedom from toxic amounts of salts.