Principles of Propagation by Cutting

• Cutting propagation is the most important means for clonal regeneration
• Propagation by stem and leaf-bud cuttings requires only that a new adventitious root system be formed
• Root cuttings and leaf cuttings must initiate both a new shoot system from an adventitious bud and new adventitious roots
• Inverse relationship between physiological and chronological age
• chronological age: the successive growth sequences, designated by the number of years that the plant has grown from either seed or vegetative propagule
• ontogenetic aging: the phases of development that the seedling plant undergoes from embryonic to juvenile to intermediate to mature
• homoblastic: very little obvious change in the plant's appearance as it grows from a seedling to its mature condition
• heteroblastic: distinct variation in specific traits that occur with age
• Ontogenetic aging is important in vegetative propagation because buds perpetuate their ontogenetic age in the progeny plant
• Physiologically mature material is more desirable for propagation
• Propagules taken from the top or at the periphery of the plant tend to produce progeny that are biologically mature
• Juvenile plant parts must be used for "difficult-to-root" woody plant species
• Most juvenile parts of plant are near the base
• Major factors for successful cutting propagation:

  • selection and management of stock plants
  • treatment of cuttings
  • environmental manipulation of cuttings
• stock plants: plants that are maintained for the purpose of harvesting cuttings or grafting wood for vegetative propagation
• Stock plants may be grown:

  • in the field (nursery, orchard, etc)
  • in containers (nursery, greenhouse)
  • in-vitro
• Stock plants should be:

  • true-to-name
  • true-to-type
  • pathogen free
  • maintained in the proper physiological state to ensure good propagules
• Management of stock plants to maximize cutting propagation:

  • Selection of source material that is easy to root
  • Maintenance of stock plants in the juvenile/transition phase to maximize rooting
  • Rejuvenation of stock plant material to reestablish high rooting potential
• Stock plants should be free of viruses, bacteria, fungi, and other pathogenic organisms
• Juvenile phase has a higher rooting ability
• serial propagation: annual harvesting and rooting of cuttings from previously rooted, containerized plants to help maintain a high rooting potential from generation to new cutting generation
• Hedging, pruning, and stooling maintain high rooting potential
• Softwood cuttings can be forced from woody stem segments to propagate hardwood species
• inducing rejuvenation: forcing juvenile growth from sphaeroblasts, wartlike protuberances containing meristematic and conductive tissues sometimes found on trunks or branches
• Periodic, controlled water stress may increase rooting in some species
• Unrooted cuttings are highly susceptible to water stress
• Water stress generally decreases rooting success
• Take cuttings early in the morning when the plant material is in a turgid condition
• Level of auxin is determined by photoperiod and temperature
• Higher temperature may result in increased vegetative growth and rooting potential
• Excessive temperature increases respiration and may decrease rooting potential
• Light quality (wavelength) can affect stock plant potential
• Red shade cloth increases root initiation and development of cuttings
• Photosynthesis maximizes production of assimilates
• photomorphogenic effect: photoperiod favors vegetative growth and suppresses reproductive growth
• Too much irradiance results in photo-destruction of auxin
• Reducing irradiance can sometimes enhance the rooting of difficult-to-root species
• etiolation: the total exclusion of light
• banding: localized light exclusion pretreatment that excludes light from that portion of a stem that will be used as the cutting base
• shading: any stock-plant growth under reduced light conditions