Plant Propagation Basics

Plant Propagation

• Plant propagation is a science, art, and business of producing high-quality plant propagules.
• Two main types: sexual and asexual (vegetative) propagation.

Sexual Propagation

• This is the most common method in nature and widely used for cultivated crops.
• Seeds develop from the fusion of male and female gametes within the flower's ovule.

Types of Sexual Propagation: Seed Propagation

• An easy and inexpensive way to multiply plants, especially annuals like grain crops, legumes, and vegetables
• The most useful and profitable method for crops like papaya and coconuts.

Seed Germination

• The resumption of embryo growth in a seed after absorbing water.
• A series of events leading to a seedling emerging from the embryo.
• Two ways:
  • Epigenous germination: the hypocotyl lengthens, pushing the cotyledons above the ground.
  • Hypogenous germination: the epicotyl emerges, while the cotyledons remain below the ground.

Seed Dormancy and Quiescence

• Seed dormancy: a physiological or physical state of a viable seed preventing germination even in favorable conditions.
• Seed quiescence: a seed's inability to germinate due to unfavorable conditions.

Types of Seed Dormancy

• Primary dormancy:

  • Exogenous or coat-imposed dormancy: Dormancy due to seed coat characteristics.
  • Endogenous dormancy: Dormancy caused by the environment during seed development and maturation.

• Secondary dormancy:

  • Imposed by environmental factors like temperature, light, darkness, water quantity/quality, and chemicals/gases.

Dormancy Technology

• Ecodormancy: Dormancy due to unsuitable environmental conditions.
• Paradormancy: Dormancy due to external physical factors or signals.
• Endodormancy: Dormancy regulated by physiological factors within the seed.

Hastening Seed Germination/Breaking Dormancy

• Scarification: Any treatment to remove or alter the seed coat, making it more permeable to water and air. Techniques include physical (soaking), mechanical (piercing/sandpapering), or chemical scarification (acids, solvents).

• Stratification: Placing seeds in moist media (sand, soil, or sawdust) at specific high or low temperatures to soften the seed coat.

• Vernalization: Treating seeds with cold temperatures before germination to induce or promote germination.

Embryo Culture

• Asexual method of seed propagation
• Embryos are removed from the seed, and placed in a sterilized culture medium for germination.

Disadvantages of Sexual Propagation

• Crops have a longer juvenile period.
• Traits of the mother tree (e.g., productivity, fruit quality) might not be consistent in offspring.
• Crops might grow into taller plants with larger canopies, impacting crop management.

Asexual or Vegetative Propagation

• No union of male and female gametes
• Uses vegetative parts (roots, stems, leaves).
• Sections of the plant can be separated, attached to another plant, or maintained on the same mother plant for propagation.

Types of Asexual Propagation

• Asexual methods of propagation can be broadly classified into propagation by apomictic seeds or vegetative propagation.

  • Types of Sexual Propagation: Embryo Culture

  • Types of Asexual Propagation:

    • Separation: Naturally detaching organs from the parent plant.
    • Division: Cutting the plant into sections with buds.
    • Cuttage: Using a cut piece of stem, root, or leaf to establish a new plant.
    • Layering: Stimulating the formation of adventitious roots on a stem while a part is still attached to the plant.
    • Propagation by apomictic embryos
      • Apomixis is the asexual development of seeds.
      • Apomixis means 'away from mingling'.

Specialized Organs Used in Propagation (Separation and Division)

• Bulbs

• Corms

• Crowns

• Offsets

• Pseudobulbs

• Rhizomes

• Runners

• Slips/Cuttings

• Stolons

• Bulbils

• Descriptions of propagation by specialized organs, such as bulbs, corms, and rhizomes.