Producing Plants From Seed
Paul A. Thomas and Bodie. V. Pennisi
The University of Georgia
2005 Plant Propagation Workshop
Southeast Greenhouse Conference
No Two Seeds Are Alike
Seed Collecting
Provenance : A seed’s origin, in
terms of climate and geographical
location. This can
Have profound effects on seed
germination and the plant’s
survival. Example: Hemlocks
grown from southern North
Carolina seed sources are more
heat tolerant than Hemlocks grown
from Pennsylvania seed sources.
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!
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
Heritage
Varieties
Vegetables and
flowers that were
grown and passed
on through many
generations by
families.
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
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.
Fleshy Berry Seed
Extraction Methods
• Fermentation
• Flotation
• Blender Separation
• Screen-Press Separation
• Gravity Separators
• Hand Separation
• Sifting
• Drying (Heating Pine Cones)
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
o
o
temperature between 0 and 50 C.
Seed Storage
o
Moist Storage @35 to 50 F
o
Dry Storage @ 35 to 50 F*
o
o
Cold Storage @ 0 F, –18 C *
o
Cryopreservation @ -196 C *
*** at 3 – 8% Moisture
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
SEED STORAGE
Recalcitrant Seed – Short-term Viability
Tropical – Store warm and moist (ASAP)
Coffee, Cocoa, Mango, Macadamia, Avocado, Tea
Subtropical – Store cool and moist (ASAP)
Maple, Oak, Elm, Poplar, Salix,
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
Life Expectancy Of Selected Seeds
Sugar Maple
English Elm
Cocklebur
White Clover
Sensitive Plant
Indian Lotus
Artic Lupine
2 weeks
26 weeks
16 years
90 years
200 years
1,040 years
10,000 years
Testing Viability - Simplified
Handling Tiny Seeds
Mix Seed with Sand
Seed Coatings
•Fungicides/Rhyzobia
•Polycoating
•Pre-germinated
Important Information
Directions
Planting Depth
Expiration Date
Source
More Information
Lot Number
Germination
Percentage
Scientific Name
The Cycle of Life
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.
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!
Advantages of Seed Dormancy
• Favors seedling survival
• Creates a seed bank
• Seed dispersal (birds)
• Synchronizes germination with seasons
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.
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.
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)
Exogenous Dormancy
• Physical – Impermeable seed coat : Scarification
• Mechanical – Seed covering restricts radical : Removal
• Chemical – Inhibitors in seed coat : Removal / Leaching
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
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
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
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
Germination Of Lettuce
Preconditioning Seeds
(for more uniform germination)
Methods:
Mechanical scarification
Soaking In Water
Acid Scarification
Moist Chilling / Freezing
Double Dormancy
Mechanical Scarification
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.
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.
Moist Stratification
Cold or Warm
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.
Clean & Organized Environment
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.
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.
Electric Heating Tapes
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!
Fungicides
BanRot!
Follow The Label Directions!
Seedling Production Options
Community Pot
Seeding Box
Plug Tray
Fabric Matt
Hydroseeding
Direct Broadcast
Sowing Success
•Proper seed bed
•Proper planting season
•Proper pretreatment
•Proper seed handling
•Proper sowing depth
•Proper sowing rate
•Proper post-sowing care
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
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!
Gardener
by Ann North
Some of the seeds of hope
Planted tentatively in the fall
Have not come up
They lie stillborn and unrealized
Somewhere in the spring soil
Decaying
The Strongest and best ones
Pushed up though the leaves
And layers of cold, hard resistance
Right into clear blue air
And stand there nakedly green
Breathing
It's always that way with growing things
Never knowing at the start
Which will make it and which will fail
But the thing to hold fast to
Never to lose faith in, is simply,
Sowing