I. THREE METHODS OF PLANT PROPAGATION

a. Sexual Propagation - propagation by seeds
      Plants are propagated by seeds formed through pollination and fertilization
b. Asexual Propagation - propagation by vegetative plant parts
     Plants are propagated by division, cuttings, grafting, layering, and underground organs such as bulbs, rhizomes, and corms
c. Micropropagation - A form of asexual propagtion
Small pieces of plant tissue are grown into new plants using a combination of growth hormones and augar in a sterilized container

          a. Seed Production
              1.  Location...........Western States (California, Idaho, Washingtion)
                                            Low humidity (less fungal infections, bacterial diseases)
                                            Mild  temp (for flowering and seed set)
                                            Isolated areas (to guarantee maintenance of pure-line seeds:

    2.  Hybrid seed production
           -hybrids are a cross between two different varieties
                 In the US -Use of male sterility genes to ensure there is no pollination from the same variety
                 In developing countries-Hand pollination
    3.  Labor intensive
          -much labor is needed for harvesting, cleaning, and handling of the seeds

b. Seed Strorage
    1.  Optimum condition
         - Low temperature (0-35° F)
         - Low humidity (4-6 % Relitive Humidity)
    2.  Practical conditions
        - 32-50° F (0-10° C) and 50-60% RH
   3.  Longevity varies by species
       - Anual flowers   1-2 years
      -  Lotus               > 1000 years
   4. Cryogenic storage (-196° C)......... Permanent

c. Seed Germination
    1. Viability ( percent germination)
         -Determined by percent germination
         -Tetrazolium test to check tissue viability (T2T or TTC -two forms of tetrazolium)
        -Seed priming is done for vigorous, uniform germination
           (seed priming- uses water imbibition to prepare seeds for germination without allowing for radicle emergence
                                - the seed are then dried again until planting)
    2.  Breaking Seed Dormancy
         - Scarification- methods used to overcome physical dormancy ( physical dormancy- seed coat is impermeable to water and gases)
            a. mechanical abrasive method*
            b. hot water (170-212° F)
            c. Sulfuric acid (concentrated) 1-5 hours
         - Stratification method used to remove physiological dormancy (physiological dormancy- dormancy due to inhibitors within the seed)
            a. Cold Stratification
                -seed is stored at 32° F for 6-8 weeks with both moisture and aeration
                -most popular method for woody plant seeds
            b. Warm Stratification
                -seed is stored at warm temperature (>45° F) with moisture
                -required for some species (Viburnum, redbud)
    3.  Embryo Culture (Embyo Rescue)
         Immature zygotic embyos are taken out of ovary and cultured in vitro-----> viable seeds cam be obtained
         -used in abortive interspecific crosses (potatoes)- Tuckey's medium
         -embryos lacking endosperm (orchids)- Knudson's medium

 
d. Planting -
    1. Direct Seeding
        -use of pelletized seeds
        -fluid drilling
    2. Transplanting
        -Mechanical transplanting
           * lettuce, cabbage, cellery in California

e. Germination

       1. Apomictic seed - seed formed with out pollination
       2. Use of specialized vegetative structures- cuttings
       3. Advetitious roots and shoots -shoots and roots formed where they normally would not form
       4. Grafting - graft top of desired plant on a hardier rootstock.

      a. Use of Apomictic Seeds
       Apomixis- development of seeds without fertilization  - seeds are formed by megaspore mother cells and so are genetically the same as maternal parent
            Examples:  Mango, Kentucky Bluegrass, Citrus

      b. Use of Specialized Vegetative Structures
           1. Runners- stolons fo strawberry, strawberry Geranium
           2. Bulbs- Onion, tulip, Easter lily, Hyacinth
           3. Corms- Gladiolus, crocus  cormel- small corms
           4. Rhizomes- Iris, turfgrass, lily-of-the-valley, orchid
           5. Off-shoots- pineapple (slip), Dendrobium, Cymbidium, daylily
           6. Stem tubers- potato (eyes)

           7. Tuberous roots- sweet potato, dahlia, tuberous begonia
           8. Root suckers- Raspberry

      c. Induction of Adventitious Shoots and Roots
           1. Layering-  Regenerated vegetative parts attached to the plant
                 Kinds- tip, simple, trench, serpentine, mound, air

2. Cutting propagation- Detached stems and roots are rooted or shoot-generated
    -Stem cuttings-

                                                                                                                                                                                                                                                                                                                                                          Hardwood (Rose, apple)   Softwood (Peach)  Semi-hardwood (most plants)

    -Root cuttings- Rose, sumac, lilac
                         - root cuttings will have a problem with phenotype conversion in chimeric plants

.
3. Origins of Adventitious Shoots and Buds
     Adventitious buds (roots)-  arising from any plant part other than root or shoot primordia (Apex, axillary bds, on nodes)
     - generally occurs form secondary meristematic tissues (on internodal area, leaf edges)

 

4. Rooting stimulation
   - use of rooting hormones (IBA, NAA--- Auxins)
       IBA= Indolebutyric acid
   - presence of light
   - Temperature Gradient (cooler air, warmer soil)

IV. GRAFTING
      - The joining of plant parts by means of tissue regeneration
      - Stock (provides root) and scion (becomes stems and shoots)
      - Compatibility between stock and scion essential
          (Graft incomatibility may be shown after 10-15 years)
      - Alighnment of cambium layers important

      a. Kinds
          1. Cleft graft
          2. Whip-and-tounge graft
          3. Side graft
          4. Budding (T-bud, chip bud, patch bud, flute bud)
          5. Inarching
          6. Bridge graft
          7. Topworking

V. MICROPROPAGATION (Tissue culture)

      a. Asexual Embryogenesis (Somatic)
          In vitro induction of somatic embyos which can be grown into plants

      b. Rapid Shoot Multiplication
          Apical or axillary shoot meristems are cultured shoot proliferation is fast:
            (One explant can produce over one million plants in one year)
            - about 120 species are commercially micropropagated

      c. Organogenesis
          Shoot and root formation from callus tissue