II. Vegetative Propagation

Chap 12. Plant Propagation

I. Three Methods of Plant Propagation

a. Sexual Propagation (Seed Propagation)

b. Asexual Propagation (Vegetative Propagation)

c. Micropropagation (Tissue Culture)

II. Sexual Propagation

1. Seed production

Mostly in Western States

- California, Oregon, Washington, Idaho

- Low humidity (less fungal, bacterial diseases)

- Mild temperature (good for flowering, seed set)

- Even distribution of rainfall throughout year

- Isolated from major production areas

Hybrid Seed Production- Use of male sterility (US production)

- Hand pollination (Developing countries)

Labor Intensive Operation

- Pollination

- Harvesting, cleaning, and handling

A Commercial Flower Seed Company

Goldsmith Seed

Flower Seed Production in Western States

Flower Seed Farms

Field Drying of Seeds

Vegetable Cultivar Development and Trials

A B

A – Field testing of vegetable breeding lines in Santa Paula, California

B – Yield trial of tomato cultivars in California

Extraction and Cleaning of Tomato Seeds

A B

C

Fermented fruits are used to extract and clean seeds by gravity flow in water

(A, B), cleaned seeds are dried by rotating grain drying drums (D)

D

Seed Grading, Packaging, Storage

2. Seed Storage

• Optimum condition for seed storage

– Low temperature (0-32 oF)

– Low humidity (less than 10% RH)

• Practical storage conditions

– 32-50 oF, 50-65% RH

• Seed longevity varies by species

– Most annual flowers last 1-2 years

– Woody plants 5-20 years

– Lotus seed known to last over 1000 years

– Permanent storage at cryogenic temperature(-196 oC)

Lotus (Nerumbo nucifera)

Seeds stuck in mud for over 1000 years germinated well

3. Seed Germination

• Seed Germination Test

– Seed viability

– Determined by percent germination (100 seed

lots)

– Tetrazolium (TTC) test to find tissue viability

• Enhancement of % Germination

– Seed quality and storage conditions

– Seed priming to enhance germination vigor and

uniformity

Seed StorageNational Germplasm Storage Lab, Fort Collins, CO

Seed Priming

A process of prehydrating and redrying seeds to

enhance their subsequent germination performance

Used for flower and vegetable seeds for uniform

and vigorous germination

Us e of osmotic solution

Germination of Primed Seeds

Irregularities in seed germination,

poor quality seeds

Uniformity in the germination of

primed seeds

Breaking Seed Dormancy

• Scarification– Overcomes physical seed dormancy

(Seed coat is impermeable to water)

– Three methods• Mechanical abrasion

• Hot water (170-212 oF)

• Acid treatment (concentrated sulfuric acid)

(Seed coat is impermeable to water)

• Stratification– Overcomes physiological seed dormancy

• (Embryo dormancy, internal dormancy)

– Moistened, cold storage• Storage at 32 oF for 1-9 months)

– Some species may require warm stratification• Viburnum, Redbud

Two Different Types of Germination

• Epigeous Germination

– Cotyledons are exposed above ground

– Epicotyl and hypocotyls are also visible

– Cherry, soybean, radish

• Hypogeous Germination

– Cotyledons are buried in the ground

– Only epicotyl are visible

– Peach, pea, apricot

Germination of Angiosperm Seeds

Embryo Culture

Immature zygotic embryos are excised and cultured in

vitro to obtain viable seeds

Used in abortive inter-specific crosses (i.e., potato)

Used for embryos lacking endosperm (i.e., orchids)

Double

fertilization

In-ovulo

Embryo cultureSeed germination

Production of Vegetable Seeds, Maxwell, California

Onion Seed Production, Maxwell, CA

Production Herb Seeds, Maxwell, CA

4. Field Establishment

• Direct Seeding

– Use of pelletized seeds

– Mechanical planting

• Transplanting

– Mechanical transplanting

• Use of fluid drilling

• Plug-grown seedlings

– High value vegetable crops

• Lettuce, cabbage, celery (i.e., California, Arizona)

Field Production of Vegetables, California

Seedling Production in Greenhouse

Plugs to Cell Packs

Bedding Plant Plug Culture, Small Growers

Seedling Plug Transplanter, Small Growers

Bedding Seed Planting, Bergen’s Greenhouse, MN

Bedding Plant Plug Culture

Stage 4 plugs

Bedding plant plug transplanter

Culture of bedding plant cell packs

Flood irrigation

Floor Irrigated Greenhouse

Flood irrigation

Bedding Plant Cell Packs

Containerized Bedding Plants Ready to Be Marketed

Bergen’s Greenhouse, Forest Lakes, MN

Gerten’s Greenhouse, MN

Use of Spores in Fern Propagation – Staghorn Fern

Spore germination under high temperature and humidity

Production of ornamental ferns from spore culture

Close-up of fern seedlings grown from spores

Alocacia

Seed Propagation for Trees

II. Vegetative Propagation

• Use of Apomictic Seeds

• Use of Specialized Vegetative Structures

• Adventitious Root Induction (Cuttings)

• Layering

• Grafting

a. Use of Apomictic Seeds

• Apomixis = Development of seeds from

maternal tissue inside ovule

• Some apomictic seeds are formed from

megaspore mother cells

• Apomictic seeds produce plants that are

genetically identical as maternal plants

• Examples: Mango, Kentucky bluegrass, Citrus

How is Apomictic Seed Formed?

Asexual seed formation from maternal tissues around zygotic

embryo inside an ovule

Apomictic seeds can be formed from nucellar tissues, egg mother

cell, flower heads (bulbils)

Found in Kentucky bluegrass, dandelion, citrus, Alliums

Nucellar embryos in Citrus

b. Specialized Vegetative Structures

• Runners (Stolons)

• Bulbs

• Corms

• Rhizomes

• Off-Shoots

• Stem Tubers

• Tuberous Roots

• Root Suckers

Runners (Stolons)

• Above-ground running stems

• New plants are formed on each node

• Examples: Strawberry, Spider Plant, Buffalograss

Strawberry Buffalograss

Bulbs

A specialized underground organ consisting of a basal

plate, growing points, flower primordia, and fleshy scales

Found in monocots

Tunicate bulbs - Onion, tulip, garlic, hyacinth

Non-tunicate bulbs – Easter lily, Oriental lily

Bulblets, bulbils, stem bulblets

Scaly Bulbs: Easter Lily

Anther Removal on Easter Lily Flowers

Anthers intact Anthers removed

Pollen germination on stigma triggers ethylene release

Yellow color stain makes the flowers unsightly

Corms: Gladiolus

Rhizomes Laterally grown underground stems

Iris, ginger, lily of the valley, orchid

Offshoots

Lateral shoots, often with roots at the base,

produced on main stems which can be separated and

grown as independent plants

Examples: Pineapple (slip), dendrobium, cymbidium

Stem Tuber

Tuber is a swollen, modified stem structure that

functions as an underground storage organ

Examples: potato, caladium, Jerusalem artichoke

Use of eyes in potato propagation

Tuberous Roots

b. Cutting Propagation

• Detached stems and roots are used to

induce adventitious roots or shoots

• Woody Plants• Hardwood cuttings

• Softwood cuttings

• Semi-hardwood cuttings

• Single-node cuttings

• Root Cuttings• Problem with phenotype conversion in chimeric

plants

Hardwood and Semi-hardwood Cuttings

1 2 3

4 5 6

1-Stock plant nursery, 2-making cuttings, 3-bundles of cuttings, 4-IBA

treatment, 5-rooting in artificial mix, 6-outdoor misting system for rooting

Influence of IBA on Rooting-Cordia parvifolia

1-Control, 2-50% ethanol, 3-100 ppm, 4-1000 ppm, 5-2000 ppm, 6-4000 ppm,

7-6000 ppm, 8-8000 ppm, 9-10000 ppm IBA

Cutting Propagation in Jojoba

• Regular Stem Cuttings

– Use 4-5 nodes

– Semi-hardwood cuttings

• Single Node Cuttings

– Double-eye single node cuttings

– Single-eye single node cuttings

Single Node Cuttings of Jojoba

5-node

Single Node Cuttings

DE SE

DE SE

Cutting Propagation in Jojoba

Clonally Propagated Jojoba FieldBakersfield, CA

Shoftwood Cuttings - Hydrangea

Use of Butterfly and Single Node Cuttings

Softwood Cuttings-Peach

Herbaceous Cuttings - Carnation

Pauk Ecke’s Poinsettia Greenhouse

Leaf Cuttings-African Violet, Piggyback Plant

Chimeras

A plant that is composed of tissues of more than

one genotype

Chimera (Greek Word)

A mythological monster, having a lion’s head, a

goat’s body and a serpent’s tail

Chimera

Periclinal Chimera

Three Types of Chimeras

Examples of Chimeric Plants

Chrysanthemum Rose

Propagation by Grafting

• Requirements for Success– Compatibility between stock and scion

– Alignment of cambium layers

– Prompt handling

• Grafting Methods– Cleft grafts

– Whip-and-Tongue

– Side grafts

– Budding

– Inarching

– Bridge Grafts

– Topworking

Cleft Graft

Whip Graft, Whip-and-Tongue Graft

Whip Graft Whip-and-Tongue Graft

Side Grafts

Budding

Grafted Plants

Bridge Graft and Inarching

Rejuvenating old fruit trees

Repair damage on the tree trunk

Bridge Graft Inarching

Topworking• Scions are grafted on branches of mature trees• Used to change cultivars on old fruit trees

Use of Herbaceous Grafting

1. Virus Indexing

2. Synthetic Plants

3. Construction of Genetic Chimeras

4. Improved Crop Performance

5. Research in Plant Physiology

6. Enhancement of Esthetic Value

Various grafting methods in vegetables with or

without rootstock root systems

Cucurbits (watermelons, melons, cucumbers, squashes, etc.)

Solanaceous crops (tomatoes, peppers, eggplants, paprika, etc.)

Grafted Cactus Production

Position of grafting

Tomatoes, grafted onto tomato rootstock (left) or on potato (right)

Eggplant/potatoTomato/eggplant

Cabbage/Radish Chinese

cabbage/Radish

Herbaceous Grafts

Cultivation of Grafted Vegetables in Korea and Japan.

J a p a n K o r e a

Field+Tunnel Greenhouse Field+Tunnel Greenhouse

Crop Total Grafted Total Grafted Total Grafted Total Grafted

(ha) (%) (ha) (%) (ha) (%) (ha) (%)

Watermelon 14,017 92 3,683 98 13,200 90 21,299 98

Cucumber 10,160 55 5,440 96 1,728 42 5,964 95

Melons 6,142 0 8,258 42 1,047 83 9,365 95

Tomato 6,549 8 7,141 48 258* 0 4,752 15

Eggplant 11,815 43 1,785 94 650* 0 413 10

Pepper* 2,684 – 1,468 5 75,574 0 5,085 25

Robotic Grafting Machine

Seedling Grafting on Vegetable Plugs

Herbaceous Grafts

※ After placing the scion on

the top of rootstock to match

the vascular bundle, thread or

clips are used to hold the

position.

Cut

Diameter of scion: 10 mm.

Vascular bundle

Hylocereus trigonus, the most popular

rootstock for cactus grafting

* Standard rootstock length : 9 cm long

* Diameter of rootstock: 30~ 35 mm

G

F

H

Care of grafted watermelon seedlings in a commercial

greenhouse

Commercial Cactus Greenhouse in Korea