Plant Propagation Study Notes

Plant Propagation

Propagation

  • Definition: Reproduction or increase in the number of plants.

  • Two Types:   - Sexual Reproduction   - Asexual Reproduction

Sexual Reproduction

  • Definition: Use of seeds to propagate plants.

  • Flowers contain the reproductive organs.

  • Embryo: an immature plant also known as a seed germ.

  • Goal: Creation of a genetically new individual.

Pollination

  • Pollination: The transfer of pollen from the anther to the stigma.   - Self-Pollination: Pollen from a flower of the same plant fertilizes that flower.   - Cross Pollination: Pollen from a flower of a different plant fertilizes the flower.

Fertilization

  • Definition: Union of the sperm and the egg.

  • Process involves:   - Long tube cell grows through the style to the ovary.   - Pollen develops two sperm cells:     1. One sperm fertilizes the egg to form the embryo.     2. The other sperm forms the endosperm, which provides an energy source.

  • This process is known as double fertilization.

Seeds

  • Importance of seeds in sexual reproduction:   - Most common method for reproducing plants.   - Rapidly increases the number of certain plants.   - Quick and economical method for propagation.

  • Germination Requirements:   - Temperature   - Light   - Moisture   - Medium

  • Definition of Germination: Special treatment of seeds to begin growing.   - Example of Scarification: Soaking or scratching seeds with hard seed coats.   - Cold Dormant Period: Some seeds require cold (e.g., 37°F for 8 weeks or longer); e.g., apples, peaches, pears, maples.   - Extreme Heat: Follow seed packet instructions for temperatures.

Plant Growth Factors

  • Climate Factors: Major importance in plant growth.   - Temperature   - Precipitation   - Humidity   - Length of daylight   - Growing Media

Temperature

  • Definition: Growing season is measured by the number of frost-free days from spring to fall.

  • Optimal Temperatures: 70°F - 80°F.

  • DIF: Difference between daytime and nighttime temperature.   - Positive DIF: Normal growth.   - Negative DIF: Slow growth.

  • Warm Season Crops: Require warm conditions; examples include bananas, papaya, orange, tomatoes, cotton.

  • Cold Season Crops: Require cooler conditions; examples include wheat, oats, and certain vegetables.

Climate Factors - Precipitation

  • Definition: The amount of water plants need varies by species.

  • Some plants require a lot of water, while others need much less.

  • Must be grown to suit specific precipitation levels.

  • Irrigation: Artificial application of water to meet plant needs.   - Irrigation methods include:     - Drip irrigation     - Pivot systems     - Sprinkler systems.

Climate Factors - Humidity

  • Definition: The amount of water vapor present in the atmosphere.

  • Optimal Humidity Levels:   - For final weeks of crops: 70-80%.   - For vegetative growth: 40-70%.   - For flowering: 40-50%.   - Less than 40% humidity is too dry.   - Excessive moisture can lead to mold, bud rot, and mildew—important to ensure ventilation to keep humidity low during harvest.

Climate Factors - Light

  • Light Requirements: Varies by plant species.   - Cool-season crops may die as days lengthen.   - Warm-season crops respond to shorter days, even with acceptable temperatures.

  • Photoperiod: Length of light period in a day.   - Day Neutral Plants: The length of light does not affect flowering; they will flower when ready.   - Short Day Plants: Begin flowering as light duration decreases.   - Long Day Plants: Begin flowering as light duration increases, typically in spring.   - Artificial Light: Can be employed to manipulate day length for growth purposes.

Tropism

  • Definition: The movement of plants in response to stimuli.   - Phototropism: Plants grow toward light (e.g., bending towards a window).   - Geotropism: Plants respond to gravity (e.g., roots grow down).   - Thigmotropism: Plants grow over and around solid objects (e.g., vines growing around a fence).

Germination Medium

  • Optimal germination medium should possess:   - Favorable pH levels.   - Adequate supply of nutrients.

  • Composition of Soil:   - 45% mineral matter   - 25% air   - 25% water   - 5% organic matter.

  • Vermiculite: Lightweight material with neutral pH (7), high water holding capacity.

  • Perlite: Gray-white volcanic material that expands when heated; provides good drainage and aeration.

  • Peat Moss: Partially decomposed vegetation with high water-holding capacity but low nutrient capacity.

Indirect Seeding

  • Definition: When seed is sown in a location separate from where the plant will mature.

  • Flats (Seed Trays): Made of plastic in various sizes and shapes.   - Size selection based on the number of seeds to be sown.

  • Watering Process: Set flat in a tub of water to allow seeds to soak through capillary action. Avoid top watering to prevent washing out seeds.

Asexual Reproduction

  • Definition: Using vegetative parts of a parent plant to increase plant numbers without egg/sperm union.

  • Most frequently done by humans.

  • Examples: Strawberries, potatoes.

  • Goal: Ensure a duplicate of the parent plant, also known as a clone.

Propagation Methods

  • Methods Include:   - Seeds   - Grafting   - Layering   - Separation   - Division   - Cuttings   - Micropropagation

Types of Cutting

  • Definition of Cutting: A piece of a plant used to grow a new plant.

  • Types:   - Culling: Cuttings trimmed just below the node (e.g., Hydrangea).   - Softwood Cuttings: Taken from new shoot tips or basal shoots, usually in spring when developed but still soft.   - Hardwood Cuttings: Long lengths of fully mature young stems taken after leaf fall and before new growth starts in spring from deciduous woody plants or broadleaf evergreens.   - Semi-Ripe Cuttings: Taken from stems once new growth has slowed and shoots start to firm; generally conducted from midsummer to autumn.   - Whole Leaf Cuttings: Some plants can produce new plants from dormant buds at leaf bases when treated as cuttings.   - Part Leaf Cuttings: Some plants regenerate from leaf tissue; leaf sections can be taken at any time in the growing season.   - Leaf-Bud Cuttings: Semi-ripe cuttings with a short stem and one leaf taken from some plants to produce multiple cuttings from one stem.   - Root Cuttings: Healthy, strong root lengths (approximately pencil to medium thickness) harvested during dormancy can also propagate plants.

Vegetative Below-ground Propagation

Vegetative Methods

  • Methods Include:   - Separation   - Division   - Bulbs   - Corms   - Rhizomes   - Tubers

Bulbs

  • Definition: Composed of leaf scales, producing bulblets at the base.

  • Process: Bulblets must be separated from the bulb to form new plants.

  • Examples: Tulips, Amaryllis, Daffodils.

Corms

  • Definition: A solid, compact stem composed of leaf scales, with a short stem for food storage.

  • Process: Separate cormels off of the corm to create new plants.

  • Example: Gladiolus.

Rhizomes

  • Definition: Underground stems that grow horizontally, producing roots below and new plants above.

  • Process: Cut the rhizome apart to create new plants.

  • Example: Iris.

Tubers

  • Definition: Enlarged underground shoots or stems.

  • Process: Each eye can produce a separate plant as it sprouts.

  • Example: Potato.

Vegetative Above-ground Propagation

Vegetative Methods

  • Methods Include:   - Layering   - Cuttings   - Budding   - Grafting   - Tissue Culture/Micropropagation

Layering

  • Definition: Roots form at the nodes on the stem, and once roots are established, the stems can be cut to form new plants (e.g., strawberries).

Cuttings

  • Definition: A short section of the plant used to root new plants.

  • Types of Cuttings:   - Stem Cuttings
        - Hard
        - Soft
      - Leaf Cuttings
      - Leaf-Bud Cuttings
      - Root Cuttings

Budding

  • Definition: A bud is taken from one plant and grafted onto another plant to grow as a unified entity.

Grafting

  • Definition: A section of the stem from one plant is placed onto the stem of another to form a unified plant with characteristics of both.

  • Components:   - Scion: The part with the desired characteristics.   - Stock: The recipient plant that supports the graft.

Tissue Culture/Micropropagation

  • Definition: A plant grown from a single or group of excised cells or tissues.

  • Examples: Plant propagated from a piece of leaf or isolated cells.