Transcript Effect of polarity on rooting - An

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)
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)
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, narrowleaved evergreen spp)
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)
Cold storage of rooted and unrooted leafy cuttings
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Several days to several weeks (for convenience)
Temperature near 40o F (4o C) for temperate spp.
High RH
Pathogen control
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 narrowleaved evergreen spp.
• container production - is rapidly replacing field
production
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easier handling
improved marketability
better cultural control
faster product turnover
• newer alternatives - pot-in-pot, grow bags, etc.
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
Pathogen identification methods
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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)
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)
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
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
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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