Transcript Chapter 14 - sullivan east ffa

Chapter 14
Techniques of Plant
Propagation
Among all the crafts of ornamental
horticulture, none exemplifies the
application of science to the profession
better than plant propagation.
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To promote the initiation and development
of new roots on cuttings it is necessary to
create an environment for the cutting base
that will:
– Support the cutting
– Retain moisture uniformly
– Drain away excess water uniformly
– Provide adequate aeration
– Not support weed seeds and other pests
– Pasteurize easily
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Materials that can be used in the
propagation medium:
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Natural soil
Sand
Peat moss
Sphagnum moss
perlite
Vermiculite
Fired clay
Vermiculite
Peat moss
Fired clay
Perlite
Steam pasteurization is used to eliminate
weeds seeds, nematodes, fungi, and other
soil-borne plant pathogens.
 Sand or peat moss are often added to the
growing medium to improve texture,
moisture retention, and drainage.
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The propagation structure must possess
the following characteristics:
– Sufficient light to permit seed germination.
– High humidity to reduce wilting of the cutting
until new roots can form and promote.
– Warmth to accelerate germination or rooting.
– Ventilation to reduce risk of disease once
roots have been formed.
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Certain areas of the greenhouse should be
designated as “propagation only” because
it requires higher temperatures and higher
humidity than typical greenhouse crops.
Seed suppliers usually provide the buyer
with information about the best time to
plant, any necessary treatments, and
follow-up culture information.
 Scarification is a process that breaks down
tough seed coats by rubbing them with
sandpaper, soaking them in hot water or
acid, or by a similar process.
 Common Scarification techniques:
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– Sandpaper
– Hot water bath
– Sulfuric acid bath
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Stratification- subjecting seeds to a required
period of low temperatures to induce growth.
 Double dormancy- when plants require both
scarification and stratification before they
germinate.
 Factors of good propagation:
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Good quality seed
Correct propagation medium
Correct planting technique
Appropriate lighting
Proper watering
Good drainage
Proper temperature
Adequate nutrients
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Planting techniques vary depending on
whether they are herbaceous or woody, and
whether they are to be transplanted or grown
at the planting site after germination.
Plugs are seedlings that retain their
undisturbed root system within a core of
media.
In the production of ornamentals plugs are
mostly used for bedding plants.
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The majority of growers prefer to use plugs over
seed propagation techniques because:
– Transplant shock and transplant times are reduced
– Plugs do not overcrowd as quickly and can be held
longer for transplant.
– Seed sowing can be automated and there is no need
to thin the seedlings after germination.
– Plugs can be transplanted automatically.
– Shorter production time allows more crops to be
produced.
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If plugs are kept too long in a growth chamber
they will stretch and overgrow.
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Cuttings are pieces of roots, leaves, or stems
that are removed from the parent plant and
placed in an environment that promotes their
development into total plants.
 Adventitious roots are initiated in herbaceous
plants from points just outside or between
vascular bundles. In woody plants they originate
next to and out from the vascular core. This is
significant in the “cutting process” because they
may form after cuttings are taken or may be
performed but dormant.
 The best cuttings result from healthy stock
plants that contain adequate nitrogen and high
carbohydrate levels.
Adventitious roots form more quickly on
stem cutting in the dark than in the light.
 Stem or root cuttings taken from young
plants root more quickly than cuttings
taken from older plants.
 When a species is difficult to root, better
results are usually obtained when
vegetative growth is selected for the
cuttings.
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Factors the propagator must consider to protect
cuttings:
– Moisture – helps rootless cuttings absorb water.
Usually created through a mist line.
– Temperature – controls the rate of root and shoot
development.
– Nutrition – influences the quality of cuttings
– Acidity/Alkalinity – affects the number and quality of
cuttings.
– Light quality and intensity – high light intensity is
important for good root production.
– Oxygen content – oxygen is important for developing
plants.
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Hardening-off is important because the gradual
adaptation of plants to environmental conditions
are more stressful than the present conditions.
 Plant graft – the union of parts from two or more
plants into a single plant.
 Much of the research into grafting has been
accomplished with citrus and fruit trees.
 While grafting can be done on both woody and
herbaceous plants, it is most common to woody
plants.
When the graft union is successful and the
two different plants become one, it is
termed a compatible graft.
 Delayed incompatibility – a graft may be
successful for years before suddenly
failing.
 Basic items required for grafting:
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– A knife
– Tying materials
– Grafting wax
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Budding is grafting using a single bud as the
scion. To bud a plant, you remove a piece of
bark and replace it with a similarly sized piece of
bark from another plant.
 Layering allows a new plant to form by creating
a new plant that is still attached to the parent
plant by a stem, and is sometimes the chosen
method because a new plant can be separated
after a root system develops.
 Compared to other methods of propagation,
layering is usually slower, more expensive, and
produces fewer plants per parent plant.
Layering
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Simple layering – a dormant one year branch is bent
to the ground and covered with soil excepting the tip.
Roots will begin to form in the underground segment.
Tip layering – a shoot from current growth is bent and
covered.
Mound layering – the parent plant is cut back to
ground level to encourage shoot growth. The new
shoots are covered with soil. Each shoot makes a
new plant.
Air layering – a young portion of stem is cut to induce
root formation. Sphagnum moss is wrapped around
the injured area, fastened on, and tied. When roots
form, the new plant is cut from the parent.
Serpentine layering – the branch being layered is
buries in many places, rising above the ground at
varying intervals.
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The twentieth century lead the beginning of new
propagation techniques known as tissue and
organ culturing. These techniques permit the
reproduction of certain species from embryos,
pollen grains, shoots tips, or undifferentiated
plant tissue.
 Totally sterile or aseptic conditions are essential
throughout the tissue and organ culturing
process.
 Tissue and organ culturing are comparatively
new propagation techniques.