Biology of Plant Propagation

• Two types of propagation: sexual and asexual
• Sexual:

  • seed
  • fertilization
  • meiosis
  • genetic recombination
  • individual
  • inexpensive
• Seed is the most commonly used form of propagation because they are cheap and readily available
• Asexual:

  • vegetative
  • no fertilization
  • mitosis
  • no recombination
  • clone
  • expensive
• annual: germination, flowering, seed production, and dissemination in one growing season
• Annuals are monocarpic
• monocarpic: produce flowers once in life cycle
• biennial: germination, flowering, seed production and dissemination in two growing seasons
• vernalization: cold period that induces flower production
• perennial: lives for more than two growing seasons and after reaching the adult phase, repeats vegetative-reproductive cycle annually
• herbaceous perennials: produce shoots that grow during one season and die back during the winter or drought period
• woody perennials: develop permanent aboveground woody stems that continue to increase annually from apical and lateral buds with characteristic growth and dormancy periods
• seedling: growth and development of a plant when propagated from a seed
• clonal: plants produced by vegetative propagation
• apomixis: reproduction in which vegetative cells in the flower develop into zygotes to createseeds by a clonal reproduction process
• juvenile: period of vegetative growth only, cannot respond to flower-inducing stimuli
• mature: period of vegetative and reproductive growth, can respond to flower-inducing stimuli
• Life cycle of a seedling:

  • Phase I Embryonic
  • Phase II Juvenile
  • Phase III Transition
  • Phase IV Adult
• Phase I: Embryonic phase:

  Begins with the formation of a zygote. Cells grow into embryo, which receives nourishment from the mother plant through physiological stages ofdevelopment and then embryo develops its characteristic structure
• zygote: fertilized egg
• embryo: zygote after many cell divisions plus differentiation yielding embryonic root, shoot and cotyledons
• embryogenesis: development from zygote to embryo
• Phase II: Juvenile phase:

  seed germination initiates -> embryonic stage to the seedling stage. Vegetative growth is polar. Cell division is concentrated in: root tips, shoot tips and axillary growing points. Increase in volume. New nodes appear.
• Phase III: Transition phase:

  vegetative period at the end of Juvenile phase and before reproductive stage. Subtle changes in growth and morphology. Decline in plant growth.
• Phase IV: Adult phase:

  shoot meristems produce flower buds, and theplant produces flower fruit and seeds
• apomixis: embryo develops directly from specific vegetative cells of the reproductive structure and bypass meiosis; embryo is basically a clone produced asexually
• Kinds of propagules: bud, scion, cutting, layer, bulb, corm, tuber, and explant
• Each propagule may represent a different phase of the life cycle
• plant breeding: to recreate patterns of genetic variation in its many forms from which to select new kinds of plants useful to humans
• plant propagation: to multiply these selected cultivars and to do it in such a manner as to maintain the genetic characteristics of the original population
• phenotype: observable properties of plant
• genotype: gene(s) describing specific characteristics
• Sexual propagation involves seed and meiosis
• Asexual propagation involves other plant parts and mitosis
• Interphase: phase between mitosis events
• Interphase:

  • G1: increase in cell size
  • S: DNA replication and protein synthesis
  • G2: preparation for mitosis
• mitosis:

  • prophase
  • metaphase
  • anaphase
  • telophase
• prophase: chromosomes condense and appear as short, thickened structures, nuclear envelop and nucleolus disappear
• metaphase: spindle fibers form and chromosomes line up in the center
• anaphase: spindle fiber contracts and chromosomes separate, daughter chromosomes move to opposite ends