1 / 46

PLANT PROPAGATION

PLANT PROPAGATION. Choice of Methods. Sexual Propagation by seed Asexual (vegetative) Cuttings Grafting Layering Division. Propagation Method Distinctions. Sexual “True” to seed implies . . . No characteristics changed Cultivar termed a Line Line is homozygous

Télécharger la présentation

PLANT PROPAGATION

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. PLANT PROPAGATION

  2. Choice of Methods • Sexual • Propagation by seed • Asexual (vegetative) • Cuttings • Grafting • Layering • Division

  3. Propagation Method Distinctions • Sexual • “True” to seed implies . . . • No characteristics changed • Cultivar termed a Line • Line is homozygous • Self-pollinated gives progeny like parent • Cereals and vegetables are examples

  4. Other Seed-propagated Cultivars • Inbred lines • Pure lines, self-pollinated and selected • Used to produce hybrid cultivars • Hybrids • Example: hybrid corn

  5. Propagation Method Distinctions • Asexual (vegetative) • Necessary when plant is heterozygous • Heterozygous implies: • Many dissimilar genes • Meiosis segregates/recombines genes • Seed propagation can’t maintain characteristics of parent

  6. Propagation Method Distinctions • Asexual (cont) • Used with heterozygous plants • Piece of vegetative tissue • Suitable environment • “missing parts” develop • Whole plant genetically identical to original • Flower not involved in asexual propagation

  7. Asexual Propagation Facts • No genetic change (barring mutations) • Heterozygous cultivars carried generations • Cultivars are clones • Numerous methods (see text, Table 5-1)

  8. SEXUAL PROPAGATION • Seed produced in flower • Meiosis involved • Reduction division yields haploid gametes • Gametes combine in fertilization • Zygote develops into embryo

  9. SEED PRODUCTION • Cultivar preservation • Control of seed source essential • If homozygous, self-pollinated . . . • purity assured • If homozygous but cross pollinating . . . • Must separate plants • Prevent pollen contamination

  10. SEED CERTIFICATION PROGRAM • Government standards • Isolation • Culling • Inspection • Final seed testing • Harvesting equipment cleaning

  11. CERTIFICATION PROGRAMS (cont) • Four classes of seeds (agronomic crops): • Breeder seed • White tag; plant breeders • Foundation seed • White tag; public/private foundation stock • Registered seed • Purple tag; progeny of breeder/foundation • Certified seed • Blue tag; sold to farmers; known genetics and purity

  12. Vegetable and Flower seeds • Regulated by seed companies • Seed purity continually tested • Special test gardens

  13. SEED FORMATION • Seed essential parts: • Embryo • Develops into new plant • Food storage material • Nourishes embryo; endosperm/cotyledon(s) • Seed coverings • Seed coats/other parts ovary wall

  14. SEED FORMATION (cont) • Development • Ovary to Fruit • Ovule to Seed • Integuments to Seed coats • Nucellus to Perisperm • 2 polar nuclei/1 sperm to Endosperm (3n) • Egg nucleus/1 sperm to Zygote to Embryo (2n)

  15. SEED STORAGE AND VIABILITY • Some seeds short-lived • Willow, maple, elm • Others may live many years • Hard-seeded legumes • Many seeds range between extremes • Often dependent on storage conditions

  16. SEED VIABILITY TESTS • Cut test • Float • X-ray • Only tell you there is an embryo! • Still don’t tell you the viability!

  17. GERMINATION TEST • % seedlings developing from seeds planted • Use on seeds with no dormancy problems • e.g. flower, vegetable, grain • Several methods • Moist paper towel (simple) • Plant in seed flats (greenhouse) • Germination chambers (seed-testing labs)

  18. CHEMICAL TEST • Tetrazolium Test • Living tissue test • Chemical reacts with enzymes in tissue • Color change • Interpretation variable

  19. EXCISED EMBRYO TEST • Used on wood plant species with dormancy • Don’t respond in direct germination tests • Embryo cut from seed • Seed laboratory technique • Moist paper tested in covered dish • Viable embryos show activity (greening) • Non-viable embryos remain white and die

  20. SEED DORMANCY • Dormancy may allow a seed to resist germination even though conditions would be favorable to germinate • Survival mechanism • May require specific techniques to overcome

  21. TYPES OF SEED DORMANCY • Seed coat dormancy • Impermeable to water and gases (oxygen) • Associated with hard seed coats • Legumes, pine, birch, ash • Natural weathering softens seed coat • Artificial methods: • Scarification • Heat treatment • Acid scarification

  22. TYPES OF SEED DORMANCY • Embryo dormancy • Common in woody perennials • Physiological conditions • Germination blocks in embryo • Break by stratification: • Chilling temperatures • Moisture • Oxygen • Time

  23. ADDITIONAL DORMANCIES • Double dormancy; e.g. Redbud • Rudimentary embryos; e.g. Magnolia • Chemical inhibitors: • Coumarin • Caffeic acid • e.g. tomatoes, lemons, strawberries • Secondary dormancy; e.g. some woodies

  24. GERMINATION REQUIREMENTS • Adequate moisture (varies with species) • Proper temperature (varies with species) • Good aeration • Light (some cases) • Free from pathogens • Free from toxic salts

  25. VEGETATIVE PROPAGATION • Asexual – Not involving flowers or fusion of egg and sperm • Accomplished through mitosis: • Nucleus contains genetics for entire plant • Cells genetically identical • Cells can still differentiate • Capable of becoming any kind of cell • Due to:

  26. VEGETATIVE PROPAGATION • Totipotency – ability of mature cell to return to embryonic state and produce whole new individual • Plant cells easy • Many plants use totipotency to self-propagate • Importance – yields genetically identical plant • Not possible with seed (sexual) reproduction • Meiosis combines genes at random

  27. VEGETATIVE PROPAGATION • Mitosis produces: • Adventitious roots • Adventitious shoots • Callus

  28. VEGETATIVE PROPAGATION • Used primarily for woody perennials • Highly heterozygous • Don’t breed true from seed • Desirable characteristics lost • Produces clones • Fruit, nut, ornamental cultivars • Many are ancient e.g. ‘Thompson Seedless’ grape

  29. Cultivated Clones • Two processes: • Vegetative propagation of superior seedlings • Typical method • e.g. ‘Golden Delicious’ apple • Mutations • Budsports; e.g. ‘Ruby’ from ‘Thompson Pink’ • Chimeras; e.g. variegated pink lemon (fig. 5-6) • Range from slight to serious • Depends on where in mitosis and where in plant

  30. Apomixis • Interesting phenomenon • Asexual production of seedling from seed formation in the usual sexual structures of the flower but without the mingling and segregation of chromosomes • no union of male and female gametes • Seedling characteristics same as maternal parent

  31. Propagation by Cuttings • Classified according to part of plant obtained • Stem cuttings • Hardwood • Semi-hardwood • Softwood • herbaceous • Leaf cuttings • Leaf-bud cuttings • Root cuttings

  32. Grafting • Joining of two separate plant structures • Used on difficult to root plants • Make use of particular rootstock characteristics

  33. Budding

  34. Grafting and Budding Notes • Cambial layers of stock and scion must meet • Parts must be held securely • Keep air out! • Union heals by callus production from parenchyma cells • Adequate temperature for cell division • There are limitations!

  35. Layering

  36. Additional Layering Techniques • Simple layering (like tip layering) • Mound layering • Air layering

  37. Other Plant Structures • Runners (stolons); e.g. strawberries • Suckers (adventitious shoots); e.g. blackberry • Crowns (used in division) • Specialized stems and roots • Bulbs - Tuberous roots • Corms - Rhizomes • Tubers

  38. Tissue Culture • Micropropagation • Utilizes small ‘explants’ • Callus formation • Cell differentiation • First used on ferns, orchids and carnations

More Related