Download Basic Plant Propagation: Helping the Birds and Bees Reproduce

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Basic Plant Propagation: Helping the Birds
and Bees Reproduce Plants
Robert R. Tripepi
Plant Science Division
University of Idaho
Moscow, ID 83844-2339
Reference:
Plant Propagation: Principles and Practices. 2011. H. T. Hartmann, D. E. Kester, F. T.
Davies Jr., and R. L. Geneve. 8th Edition, Prentice-Hall, Inc., Englewood Cliffs, NJ.
Objectives:
1. Define plant propagation
2. Explain the difference between sexual and asexual propagation
3. Describe seed dormancy and heirloom plants
4. Describe selected asexual/vegetative propagation techniques
Definition:
Plant propagation is the art and science of multiplying plants by sexual or asexual
means
Sexual Propagation
1. Sexual reproduction occurs when the male sperm from pollen unites with the female
egg in a flower and a seed is produced
2. Each part of a seed has a specific function to help ensure that a healthy new plant
will emerge from the seed
SEEDS
1. The seed is a living entity which contains the embryo and everything necessary
(including root and shoot) for a new plant
2. Major method by which plants reproduce in nature
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3. One of the most efficient and widely used propagation methods
Selected Seed Dormancies
1. Physical dormancy: hard seed coat
 Treat with concentrated acid, hot water, sand paper or file coat
2. Chemical dormancy: chemical present
 Wash seeds or remove seed coat
3. Morphological dormancy: immature embryo
 Relieve by warm stratification
4. Physiological dormancy: alter embryo physiology
 Use cold stratification selectively
Seed Stratification – procedures involved:
1. Warm temperatures: ~70F for several weeks
2. Cold temperatures: ~40F for 2 to 24 weeks, depending on type of dormancy
3. Seeds must be stored moist
4. Seeds must have oxygen, be aerated
5. Note the time requirements
Black Chokecherry classification
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Family:
Genus:
Species epithet:
Variety:
Rosaceae
Prunus
virginiana
melanocarpa
Botanical variety = Subspecies
 different from the species and reproduces from seed with most all of the parent
characteristics
Heirloom Plants
1. Open pollinated seeds - pollination between plants is unrestricted
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2. Plants are actually varieties and are called Heirloom or Heritage plants
3. Plants from seeds will be true-to-type with minor variations
4. Seeds can be collected and saved if desired
5. To retain heirloom varieties, plants must be grown in isolation
6. Age of the heirloom variety differs but many sources say before the advent of
commercial hybrid seeds – early 1950s
Hybrids
1. Plants obtained from a cross between two different species, varieties, or genotypes
2. Hybrids will not breed true-to-form from their own seeds.
3. Collecting seeds is debatable??
Cultivars
1. NOT synonymous with variety
2. Maintained under cultivation
a. Sexual propagation – cross two inbred parent plants
b. Asexual propagation
3. Cultivar examples
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Favorite tomato cultivar: ‘Early Girl’
 Sexual propagated (hybrid) cultivar – crossed two inbred parent plants
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Favorite apple cultivar: ‘Granny Smith’
 Asexually propagated since seeds are considered hybrids
Asexual Propagation…
“Vegetative reproduction, i.e., multiplication that does not involve the seed cycle.”
1. Clonal propagation – one genotype is reproduced
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2. Genetic information stays the same
3. Methods
a. Cuttings – stem, leaf or root
b. Layering – air layering, & four other types
c. Specialized structures – tubers, bulbs, rhizomes, tuberous roots, and corms
d. grafting and budding
e. tissue culture – micropropagation
TYPES OF CUTTINGS:
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Stem cuttings
Root cuttings
Leaf cuttings
Leaf-bud cuttings
Types of Stem Cuttings
1. Hardwood – taken fall to late winter
a. Deciduous – 4 to 10 inches long
b. Evergreen – conifer (needle-leaf) 4 to 8 inches long
c. Broadleaf evergreen cuttings – 4 to 8 inches long
2. Semi-hardwood – cuttings taken in late summer (late July to mid-August)
3. Softwood cuttings – cuttings taken in June made from new, non-woody stems
4. Herbaceous cuttings – cuttings taken from non-woody plants anytime of year
Parts of a Stem Cutting
1. Nodes – growing points on the cutting
a. Must have a minimum of a two nodes but three or four are better
b. At least one node should be in the rooting medium, but two might be better in the
medium
c. Avoid allowing foliage to touch or be buried in the rooting medium
d. Have at least one bud above the rooting medium, but two buds are better
2. Three types of hardwood cuttings include:
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a. straight - uses only the recent past growth on the cutting. This type of cutting is
used most often and generally gives the best
results.
Heel
b. heel - uses a small, partial piece of older wood.
c. mallet - uses a short stem segment of older wood.
Cutting Treatments – can help certain species of plants to
root.
1. Use a rooting treatment if desired – contains an auxin
a. Indole-3-butyric acid (IBA)
Straight
b. Naphthaleneacetic acid (NAA)
c. Two forms of auxin can be used:
i.
liquid – easy to apply and use
ii. powder – easy to apply but must dibble a hole for the stem
d. Use an auxin concentration based on ease or difficulty of root formation
i.
low concentration – used on easy- to-root species
ii. higher concentrations – used on difficult-to-root species but AVOID TOO
HIGH concentrations
2. Wound a stem cutting at its bottom end by:
a. Making shallow slices
b. Slightly bruising the tissue
c. Peel small patches of tissue
Care of Stem Cuttings
1. Care depends on the type of stem cutting – are leaves present?
2. Usually must raise humidity for a while and then lower it gradually
Mallet
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3. Usually light is kept low for a while and then gradually raised
LAYERING
1. Layering is defined as adventitious roots forming on the plant part (stem) while it is
still attached to the parent plant
a. The layering is severed later and planted in a field or a pot
b. Usually think of layering for stems above or below ground
2. Nutrition of the stock plant
a. Advantage of layering in terms of nutrition – the layer is continuously supplied
with nutrients and water
b. Xylem tissue remains intact
3. Stem treatments – manipulate stems to form adventitious roots
a. Manipulate stems to form adventitious roots
b. The stem is usually wounded in some way including:
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girdling
notching
or partial breaking of stems
c. Cut is made on lower side of the stem
d. The cut slows or blocks downward movement of auxins and carbohydrates
4. Root promoting compounds
a. Stems must be wounded to get the compound into the tissue
b. Compound can be applied as a powder, liquid or lanolin paste
Air Layering
1. Is used for several reasons:
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a. Get larger size plants versus cuttings
b. Good for some difficult-to-root plants
c. Can be used on some indoor plants or landscape plants
2. Air layers can be made at different times of the year
a. For landscape plants, make in the spring from the previous
year’s growth or on semi-hardwood (new)
b. For indoor plants, done any time after several leaves have
developed
3. Steps include the following:
a. Girdle the stem or wound the stem with a slice or a notch
 if girdling the stem, make the wound about one inch long
b. If girdling the stem, be sure to remove ALL of the vascular cambium tissue in the
wound area
c. Any of the three types of wounds or cuts can be made on the stem
d. Apply a root promoting compound if desired
e. Keep the wound moist with moistened sphagnum moss that is wrapped in plastic
film
f. The air layer can be separated from the parent plant after roots can be seen
i.
may need from 4 weeks to 3 months depending on the plant species
ii. handle the rooted layer carefully – usually keep the severed layer in a high
humidity area for up to one week
Simple Plant Cloning
1. Division – the process of cutting the plant into sections for reproduction
 Example: crown division
2. Separation – the multiplication of plants by naturally detachable structures
 Examples: bulb scaling or bulb offsets
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Specialized Stems and Roots
A. Specialized structures used for vegetative propagation
B. TUBER - is a swollen, modified stem that functions as an underground storage
organ
1. A tuber has all the parts of a stem, and it is very swollen
a. A tuber has buds, leaf scars, and nodes
b. Eyes – are the buds on the tuber (stem)
c. A terminal bud is at the apical end (distal) part of the tuber
d. Tubers exhibit apical dominance – terminal bud opens first
2. The tuber is borne on an underground stolon
3. Examples: potato and caladium
4. The growth pattern is that the tuber forms the first year, has a dormant period, and
the grows the second year
a. The tuber is used as a food source and deteriorates as new shoots grow
b. Certain environmental conditions favor tuberization
5. Propagate tubers by division, with each piece containing at least one eye
6. Tubercles – are small tubers that form in aerial portions of the shoot
Summary
“It is the policy of the University of Idaho Cooperative Extension System that all persons
shall have equal opportunity and access to the programs and facilities without regard to
race, color, sex, religion, national origin, age, marital status, parental status, sexual
orientation, or disability.”
c:mydocs\Talks\INLA-16_Plant propagation.docx