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