2005 Plant Propagation Workshop

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2005 Plant Propagation Workshop
Producing Plants From Seed

• Paul A. Thomas and Bodie. V. Pennisi
• The University of Georgia

Southeast Greenhouse Conference
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No Two Seeds Are Alike
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Seed Collecting
Provenance A seeds
origin, in terms of climate and geographical
location. This can Have profound effects on seed
germination and the plants survival. Example
Hemlocks grown from southern North Carolina seed
sources are more heat tolerant than Hemlocks
grown from Pennsylvania seed sources.
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Seed Collecting
Seeds collected from hybrids rarely look like
the parent plant due to the random reassortment
of genetic material, and the random sources of
pollen. Native species tend to be more stable,
but also have variation between generations. To
get a clone, try vegetative propagation!
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Terms To Know
Landraces Populations of plants maintained
over hundreds of years by farmers by holding
over some of the seed crop. This allowed for
local specialization and great differences in
genetic makeup
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Heritage Varieties Vegetables and flowers that
were grown and passed on through many generations
by families.
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Terms To Know
Inbred Lines Progeny from identical lines that
are homozygous. These are then used to make
hybrids Hybrid Lines The progeny of two or
more inbred lines
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Seed Cleaning / Separation
Cleaning seed reduces disease and weed seed
from growing along with your selection
For many dry seed, simply crush dried material
and blow gently, transferring the seed from
hand to hand.
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Fleshy Berry Seed
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Extraction Methods

• Fermentation
• Flotation
• Blender Separation
• Screen-Press Separation
• Gravity Separators
• Hand Separation
• Sifting
• Drying (Heating Pine Cones)

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Seed Deterioration

• Seeds lose half their storage life for
• every 1 increase in seed moisture
• between 5 and 14.
• Seeds lose half their storage life for
• every 5 degrees C increase in storage
• temperature between 0oand 50oC.

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Seed Storage
Moist Storage _at_35 to 50oF Dry Storage _at_ 35 to
50oF Cold Storage _at_ 0oF, 18oC
Cryopreservation _at_ -196oC at 3
8 Moisture
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Terms To Know
Recalcitrant Seed These seeds are able to
germinate without dessicating. These seeds lose
viability after drying and must be planted
quickly. Oak, Maple, Coffee Orthodox Seed
The seeds dessicate after reaching full
development to allow the seed to be quiescent or
dormant until conditions are right to germinate.
Beans
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SEED STORAGE
Recalcitrant Seed Short-term Viability Tropica
l Store warm and moist (ASAP) Coffee, Cocoa,
Mango, Macadamia, Avocado, Tea Subtropical
Store cool and moist (ASAP) Maple, Oak, Elm,
Poplar, Salix,
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• Orthodox Seed
• Short-Lived Store dry and cold (Under 1 yr)
• Vinca, Pansy, Begonia
• Medium - Lived - Store dry and cold ( 2-5 years)
• Marigold, Petunia, Coleus
• Long - Lived Store dry and cold ( 5-200 years)
• Morning Glory, Zinnia, Hollyhock

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Life Expectancy Of Selected Seeds
Sugar Maple 2 weeks English Elm
26 weeks Cocklebur 16 years White
Clover 90 years Sensitive Plant
200 years Indian Lotus 1,040
years Artic Lupine 10,000 years
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Testing Viability - Simplified
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Handling Tiny Seeds
Mix Seed with Sand
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Seed Coatings

• Fungicides/Rhyzobia
• Polycoating
• Pre-germinated

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Important Information
Directions
Planting Depth
Expiration Date
Source
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More Information
Lot Number
Germination Percentage
Scientific Name
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The Cycle of Life
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1. Imbibed water stimulates Gibberellin
synthesis. 2-3. Gibberellins diffuse to the
aleurone layer and stimulate the synthesis of
enzymes. 4-5. Enzymes break down the starch and
the sugars are transported to the developing
embryo.
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Seed and Plant Dormancy
Dormancy is the condition In which seeds will
not Germinate even when most of the
environmental conditions are permissive for
germination. There are many types of dormancy!
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Advantages of Seed Dormancy

• Favors seedling survival
• Creates a seed bank
• Seed dispersal (birds)
• Synchronizes germination with seasons

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Types of Dormancy in Seed
Quiescent The seeds are able to Germinate upon
imbibition of water at permissive temperatures.
Primary Dormancy Seeds cannot germinate even
if immediate conditions are right. This form of
dormancy delays germination until season, or
other macro-environmental issues are right for
survival. Secondary Dormancy An additional
level of Protection to prevent germination.
Can be induced under very unfavorable conditions
such as drought or cold, etc.
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Types of Dormancy in Seed
Exogenous Dormancy - Imposed by factors outside
the embryo. Seed coat. Endogenous Dormancy
Imposed by factors within the embryo.
Underdeveloped embryo.
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Types of Dormancy in Seed
Double Dormancy - Any combination of endogenous
and exogenous factors
Secondary Dormancy - Factors outside the seed
induce dormancy after the seed was previously
non-dormant. High Soil Temperatures
(Thermo-dormancy)
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Exogenous Dormancy

• Physical Impermeable seed coat Scarification
• Mechanical Seed covering restricts radical
  Removal
• Chemical Inhibitors in seed coat Removal /
  Leaching

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Endogenous Dormancy

• Morphological - Underdeveloped embryo Warm
  Stratification
• Physiological
• Non-Deep After Ripening Dry storage
• Photo-dormant Exposure to red light.
• Intermediate Embryo/coat separation Cold
  Stratification
• Epicotyl Epicotyl dormant Warm - Cold
  Stratification

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Double Dormancy
Morpho-physiological Some combination of
underdeveloped embryo and physiological dormancy
Cycles of warm and cold stratification.
Exo-Endodormancy Combination of exogenous and
endogenous dormancy conditions Sequential
combinations of dormancy releasing treatments,
Eg. Scarification followed by cold stratification
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Secondary Dormancy

• Thermo-dormancy - High temperatures induce
  dormancy
• Growth regulators or Cold stratification
• Conditional Change in ability to germinate is
  related to time of year.
• Chilling or Warm stratification

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Photodormancy
Photodormancy A type of dormancy where the
ability of the seed to germinate is controlled
by the wavelengths and durations of light
received by the embryo. Lettuce,
Butterflyweed, Tobacco
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Germination Of Lettuce
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Preconditioning Seeds (for more uniform
germination)
Methods
Mechanical scarification Soaking In Water Acid
Scarification Moist Chilling / Freezing Double
Dormancy
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Mechanical Scarification
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Acid Scarification
An alternative to scraping the seed coat is to
use acid to etch through the coat. There are
many reference books that advise which acid
and how long to treat.
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Hot Water Scarification
Water temperature should be over 110OF Let soak
for a few hours. Stir often. Do not re-heat the
water. Plant ASAP.
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Moist Stratification Cold or Warm
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Seed Soaking / Leaching
Seed soaking optimizes the amount of imbibed
seeds and evens out the stage of imbibition by
insuring 100 moisture availability
Soaking too long can cause anoxia and reduced
germination. 12-36 hours is a very common
soaking period.
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Clean Organized Environment
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Window-Box Propagation
Two clear halves of sweater/storage boxes taped
together with duct tape as a hinge make ideal
propagation boxes! Place the box in a sunny
window, and open it up for an hour at night to
replace air and dry off leaves. Works for almost
all tropical plants.
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Root Zone Heating
Rooting medium temperature, given control, may
be applied to speed up growth. A good example is
using heating pads under planted seed flats to
speed up germination or rooting. The right
temperature can take a week or month off of
rooting schedule and can take a few days to a
few weeks off of germination. Time is money.
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Electric Heating Tapes
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Mist Benches
We need to provide seedlings a film of water to
reduce evaporation, and the loss of water.
Too much water is as bad as too little water!
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Fungicides
BanRot!
Follow The Label Directions!
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Seedling Production Options
Community Pot Seeding Box Plug Tray Fabric
Matt Hydroseeding Direct Broadcast
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Sowing Success

• Proper seed bed
• Proper planting season
• Proper pretreatment
• Proper seed handling
• Proper sowing depth
• Proper sowing rate
• Proper post-sowing care

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Transplanting Seedlings

• Minimize root disruption!
• Never press on roots or handle roots!
• Never compact soil around roots
• Work quickly and gently
• Re - water in transplants in minutes

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Growing Out Seedlings

• Use low levels of fertilizer 50 ppm!
• Do not allow to become dry.
• Do not allow to stay saturated!
• Modify light levels according to species.
• Scout seedling several times a day!

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Gardener by Ann North

• Some of the seeds of hopePlanted tentatively
  in the fallHave not come upThey lie stillborn
  and unrealizedSomewhere in the spring
  soilDecayingThe Strongest and best onesPushed
  up though the leavesAnd layers of cold, hard
  resistanceRight into clear blue airAnd stand
  there nakedly greenBreathing
• It's always that way with growing thingsNever
  knowing at the startWhich will make it and which
  will failBut the thing to hold fast toNever to
  lose faith in, is simply,
• Sowing