Effect of polarity on rooting

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Title: Effect of polarity on rooting


1
Effect of polarity on rooting
  • stem cuttings form shoots at the distal end,
    roots at the proximal end
  • auxin always moves from shoot tip to base (no
    matter the stem orientation)

2
Effects of buds and leaves on rooting
  • active buds promote rooting, dormant buds have
    no effect
  • leaves exert a strong stimulatory influence (both
    carbohydrates and auxin are translocated from
    leaves)

3
Effect of wood type on rooting of woody cuttings
  • Seedling (genotype) differences (Norway spruce,
    white pine, red maple)
  • lateral shoots usu. better than terminals
  • beware plagiotropic growth of laterals
  • basal and medial shoot portions are usu. better
    than terminals
  • flowering wood is slower than vegetative
  • heel cuttings are better for some spp. (quince,
    narrow-leaved evergreen spp)

4
Seasonal timing (when cuttings are taken) can
affect rooting of woody cuttings
  • hardwood cuttings with resting buds are best
  • softwood cuttings are usu. best from the first
    flush
  • narrow-leaved evergreens are best taken from late
    fall to late winter
  • broad-leaved evergreens (e.g., olive cuttings
    root best when taken during late spring, poorest
    when taken in midwinter)

5
Cold storage of rooted and unrooted leafy cuttings
  • Several days to several weeks (for convenience)
  • Temperature near 40o F (4o C) for temperate spp.
  • High RH
  • Pathogen control

6
Handling field-propagated woody cuttings (after
rooting and lining out)
  • bare-root nursery stock - deciduous shrubs, trees
  • balled-and-burlapped (B B) stock - broad- or
    narrow-leaved evergreen spp.
  • container production - is rapidly replacing field
    production
  • easier handling
  • improved marketability
  • better cultural control
  • faster product turnover
  • newer alternatives - pot-in-pot, grow bags, etc.

7
Pathogen/pest management in propagation
  • Pests (insects, mites, nematodes, weeds)
  • Pathogens (fungi, bacteria, viruses)
  • Goals
  • to keep stock plants and propagules as clean and
    pest-free as possible
  • identification, indexing of systemic pathogens

8
Pathogen identification methods
  • visual inspection - specific symptoms
  • culture indexing - systemic bacteria, fungi
  • virus indexing (e.g., indicator cultivars)
  • serological tests (e.g., ELISA tests)
  • biochemical/molecular methods (e.g., specific
    viral RNA patterns on a gel)

9
Methods of pest/pathogen management in propagation
  • preventive measures (e.g., clean stock, use of
    cultivar resistance, scouting)
  • integrated pest management (IPM)
  • chemical control (e.g., quantity control,
    rotation)
  • biological control (the fungus Gliocladim virens
    instead of fungicidal control of Rhizoctonia and
    Pythium damp-off)
  • cultural control (e.g., sanitation, healthy stock
    plants, heat pasteurization of propagation medium)

10
Aphid control - a case study of IPM used in a
propagation house
  • microscreens on vents/doorways of propagation
    houses
  • scouting (e.g., yellow sticky cards)
  • use of a natural predator (the midge Aphidoletes
    aphidimyza)
  • natural pyrethrin insecticides (for populations
    too large for cultural, biological control)
  • use of insect growth retardants (Enstar II
    specific to immature aphids)
  • careful use (and rotation) of more toxic
    insecticides

11
Best management practices (as applied to nursery
and greenhouse plant propagation)
  • a set of practices voluntarily adopted by
    nurseries and greenhouses to control irrigation
    and fertilization
  • includes
  • collecting run-off water when injecting
    fertilizer
  • applying fertilizer only to obtain a growth
    response
  • monitoring the quantity of irrigation (to prevent
    overwatering)
  • recycling run-off water where feasible
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