2012 Seed Germination Workshop

Paul A. Thomas

The University of Georgia

Teacher Training Conference

Producing Plants From Seed

About SeedsAbout Seeds

No Two Seeds Are Alike

Three Types Of Seed Sources

Fleshy Fruits: Fleshy Fruits: Berries, Figs

Dry Fruits: Dry Fruits: Grains, Grasses

Dry Seeds / Dehiscent Pods: Dry Seeds / Dehiscent Pods: Cones/Pods

Heritage Heirloom Varieties

Vegetables and flowers Vegetables and flowers that were grown and that were grown and passed on through many passed on through many generations by families.generations by families.

Seedlings match parent Seedlings match parent plants closely.plants closely.

Landraces – Populations of plants – Populations of plants maintained over hundreds of years by maintained over hundreds of years by farmers by holding over some of the farmers by holding over some of the seed crop. This seed crop. This allowed for local allowed for local specialization and specialization and great differences great differences in genetic makeupin genetic makeup

Terms To Know

Cross Pollination – Pollen from one plant – Pollen from one plant fertilizes the embryo sac of another plant fertilizes the embryo sac of another plant within the species. within the species.

Self Pollination – The pollen from a plant is – The pollen from a plant isable to fertilize the embryo sac on the same able to fertilize the embryo sac on the same plant and produce a viable embryo.plant and produce a viable embryo.

Terms To Know

Provenance : A seed’s origin, in A seed’s origin, in terms of climate and geographical terms of climate and geographical location. This canlocation. This canHave profound effects on seed Have profound effects on seed germination and the plant’s germination and the plant’s survival. Example: Hemlocks survival. Example: Hemlocks grown from southern North grown from southern North Carolina seed sources are more Carolina seed sources are more heat tolerant than Hemlocks grown heat tolerant than Hemlocks grown

from Pennsylvania seed sources.from Pennsylvania seed sources.

Seed Collecting

Seed Collecting

Seeds collected from hybrid vegetables Seeds collected from hybrid vegetables and flowers s rarely look anything and flowers s rarely look anything like the parent plant due to the random like the parent plant due to the random reassortment of genetic material, and reassortment of genetic material, and the random sources of pollen. Native the random sources of pollen. Native species tend to be more stable, but also species tend to be more stable, but also have variation between generations.have variation between generations.

To get a clone, try vegetative propagation!To get a clone, try vegetative propagation!

Seed Cleaning / Separation

For many dry seed, simply For many dry seed, simply crush dried material and crush dried material and blow gently, transferring blow gently, transferring the seed from hand to hand.the seed from hand to hand.

Cleaning seed reduces Cleaning seed reduces disease and weed seed disease and weed seed from growing along with from growing along with your selectionyour selection

Seed Deterioration

Seeds lose half their storage life for Seeds lose half their storage life for every 1% increase in seed moisture every 1% increase in seed moisture between 5 and 14%.between 5 and 14%.

Seeds lose half their storage life for Seeds lose half their storage life for every 5 degrees C increase in storage every 5 degrees C increase in storage temperature between 0temperature between 0ooand 50and 50ooC.C.

Life Expectancy Of Selected Seeds

Sugar MapleSugar Maple 2 weeks 2 weeksEnglish ElmEnglish Elm 26 weeks 26 weeksCockleburCocklebur 16 years 16 yearsWhite CloverWhite Clover 90 years 90 yearsSensitive PlantSensitive Plant 200 years 200 yearsIndian LotusIndian Lotus 1,040 years 1,040 yearsArtic Lupine 10,000 yearsArtic Lupine 10,000 years

Recalcitrant Seed – These seeds are able – These seeds are able to germinate without dessicating. These to germinate without dessicating. These seeds lose viability after drying and must seeds lose viability after drying and must be planted quickly. be planted quickly. Oak, Maple, Coffee

Orthodox Seed – The seeds dessicate – The seeds dessicate after reaching full development to allow after reaching full development to allow the seed to be quiescent or dormant until the seed to be quiescent or dormant until conditions are right to germinate. conditions are right to germinate. Beans

Terms To Know

Orthodox Seed

Short-Lived – Store dry and cold (Under 1 yr) – Store dry and cold (Under 1 yr)Vinca, Pansy, Begonia

Medium - Lived - Store dry and cold ( 2-5 years) - Store dry and cold ( 2-5 years)Marigold, Petunia, Coleus

Long - Lived – Store dry and cold ( 5-200 years) – Store dry and cold ( 5-200 years)Morning Glory, Zinnia, Hollyhock

SEED STORAGE

Recalcitrant Seed – Short-term Viability

Tropical – Store warm and moist (ASAP) – Store warm and moist (ASAP)Coffee, Cocoa, Mango, Macadamia, Avocado, Tea

Subtropical – Store cool and moist (ASAP) – Store cool and moist (ASAP)Maple, Oak, Elm, Poplar, Salix,

Seed Storage

Moist Storage @35 to 50Moist Storage @35 to 50ooFF

Dry Storage @ 35 to 50Dry Storage @ 35 to 50ooFF**

Cold Storage @ 0Cold Storage @ 0ooF, –18F, –18ooC C **

Cryopreservation @ -196Cryopreservation @ -196ooC C **

*** *** at 3 – 8% Moistureat 3 – 8% Moisture

Expiration DateExpiration Date

Planting DepthPlanting Depth

DirectionsDirections

Important Information

SourceSource

Germination Germination PercentagePercentage

Lot NumberLot Number

Scientific NameScientific Name

More Information

•Fungicides/RhyzobiaFungicides/Rhyzobia

•PolycoatingPolycoating

•Pre-germinatedPre-germinated

Seed Coatings

EnhancedSeed

Park’s Park’s SeedSeed

Testing Viability - Simplified

The Cycle of Life

THE GERMINATIONPROCESS

How Germination WorksHow Germination Works

Water is usually the key Water is usually the key factor in starting the factor in starting the

germination process. germination process.

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..

About DormancyAbout Dormancy

Seed and Plant Dormancy

Dormancy is the condition Dormancy is the condition In which seeds will not In which seeds will not Germinate… even when Germinate… even when most of the environmental most of the environmental conditions are permissive conditions are permissive for germination. There are for germination. There are many types of dormancy!many types of dormancy!

Advantages of Seed Dormancy

• Favors seedling survivalFavors seedling survival

• Creates a seed bankCreates a seed bank

• Seed dispersal (birds)Seed dispersal (birds)

• Synchronizes germination with seasonsSynchronizes germination with seasons

Rel

ativ

e H

orm

one

Lev

el

14oC

Days of Cold Stratification

Triphasic Changes In Seed Hormone BalanceOverwintering of Seeds in the ground

0

25

50

75

100

43 50 57 65 72 79 86 93 100

ABA

Cytokinin

Gibberellin

(Inhibits)(Inhibits)

Types of Dormancy in Seed

Quiescent – The seeds are able to Germinate upon – The seeds are able to Germinate upon imbibition of water at permissive temperatures. imbibition of water at permissive temperatures.

Primary Dormancy – Seeds cannot germinate – Seeds cannot germinateeven if immediate conditions are right. This form of even if immediate conditions are right. This form of dormancy delays germination until season, or otherdormancy delays germination until season, or othermacro-environmental issues are right for survival.macro-environmental issues are right for survival.

Secondary Dormancy – An additional level of – An additional level of Protection to prevent germination. Can be induced under Protection to prevent germination. Can be induced under very unfavorable conditions such as drought or cold, etc. very unfavorable conditions such as drought or cold, etc.

Exogenous Dormancy - Imposed by - Imposed by factors outside the embryo. factors outside the embryo. Seed coat.

Endogenous Dormancy – Imposed by – Imposed by factors within the embryo. factors within the embryo. Underdeveloped embryo.

Types of Dormancy in Seed

• Physical – Impermeable seed coat : Scarification

• Mechanical – Seed covering restricts radical : Removal

• Chemical – Inhibitors in seed coat : Removal / Leaching

Exogenous 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

Endogenous Dormancy

Secondary Dormancy - Factors outside - Factors outsidethe seed induce dormancy after the the seed induce dormancy after the seed was previously non-dormant. seed was previously non-dormant. High Soil Temperatures (Thermo-dormancy) (Thermo-dormancy)

Types of Dormancy in Seed

Double Dormancy - Any combination - Any combination of endogenous and exogenous factorsof endogenous and exogenous factors

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

Double 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

Secondary Dormancy

Photodormancy

Photodormancy : A type of dormancy : A type of dormancy where the ability of the seed to germinate where the ability of the seed to germinate is controlled by the wavelengths and is controlled by the wavelengths and durations of light received by the embryo.durations of light received by the embryo.

Lettuce, Butterflyweed, Tobacco

Types Of Photoperiodic Response

Short Day Plants – Single Cycle……….RiceRequires only one short day cycle to initiate the photoperiodic response.

Long Day Plants – Single Cycle………….DillRequires only one long day cycle to initiate the photoperiodic response.

Day Neutral Plants………………………………CucumberFlower the same time under all day-lengths, least photoperiodic response.

Whereas many plants are photoperiodic,they do not all respond the same way.

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)

Far Red Light

Bright Sun

Quiescence Germination

Long hours of bright spring sun stimulatesformation of Pfr and germination begins!

(Fast)

Dark Reversion

Red Light

740 nm660 nm

PrPr PfrPfr

(Slow)

Far Red Light

Far Red Light

GerminationQuiescence

Far-red light, such as is found under lots of vegetation,prevents germination. Seeds wait for sun!

(Fast)

Dark Reversion

Red Light740 nm660 nm

PrPr PfrPfr

(Slow)

Far Red Light

GerminationQuiescence

Darkness maintains Pr and quiescence. Buried seed won’t germinate until brought to the surface!

DarknessDarkness

TechniquesTechniques

Germination Environment

Moisture / HumidityMoisture / HumidityTemperature RangeTemperature RangeLight Level and QualityLight Level and QualityAeration (Oxygen in Soil) Aeration (Oxygen in Soil) Soil pH and NutritionSoil pH and NutritionAir MovementAir Movement

Technique

• Berry Roll

• Cracking

• Scratching

• Freezing

• Moist Chilling

• Hot Soaking

• Irradiation

• You can use a blender!

IrradiationGermination Of Lettuce

Fleshy Berry Seed

Handling Tiny Seeds

Some seeds can be Some seeds can be smaller than the tip of smaller than the tip of a pin. They can also a pin. They can also be very expensive. A be very expensive. A very careful approachvery careful approachis often needed to be is often needed to be efficient and successfulefficient and successfulplanting tiny seedsplanting tiny seeds

Handling Tiny Seeds

Mix Seed with Sand

Preconditioning Seeds(for more uniform germination)(for more uniform germination)

Mechanical scarificationMechanical scarificationSoaking In WaterSoaking In WaterAcid ScarificationAcid ScarificationMoist Chilling / FreezingMoist Chilling / FreezingDouble Dormancy

Methods:

Mechanical Scarification

Acid Scarification

An alternative toAn alternative toscraping the seed scraping the seed coat is to use acid coat is to use acid to etch through to etch through the coat. Therethe coat. Thereare many referenceare many referencebooks that advisebooks that advisewhich acid andwhich acid andhow long to treat.how long to treat.

Hot Water Scarification

Water temperature should be over 110OF

Let soak for a fewhours. Stir often.

Do not re-heatthe water.

Plant ASAP.

Seed Soaking / Leaching

Seed soaking optimizes the amount of imbibed Seed soaking optimizes the amount of imbibed seeds and evens out the stage of imbibition by seeds and evens out the stage of imbibition by insuring 100% moisture availabilityinsuring 100% moisture availability

Soaking too long Soaking too long can cause anoxia can cause anoxia and reduced and reduced germination. 12-36germination. 12-36hours is a very hours is a very common soakingcommon soakingperiod.period.

Thermo-hydro-LimitationsTime !

• Each species has a requirement for how many hours the seed radical is exposed to a critical level of moisture and/or soil temperature.

• Example: Cold, saturated soil inhibits corn seedling radical growth after onset of germination.

• Local control: Use a heating pad and well drained soils!

Moist Stratification Cold or Warm

•Proper seed bedProper seed bed•Proper planting seasonProper planting season•Proper pre-treatmentProper pre-treatment•Proper seed handlingProper seed handling•Proper sowing depthProper sowing depth•Proper sowing rateProper sowing rate•Proper post-sowing careProper post-sowing care

Sowing Success

Seedling Production Options

Community PotCommunity PotSeeding BoxSeeding BoxPlug TrayPlug TrayFabric MattFabric MattHydroseedingHydroseedingDirect BroadcastDirect Broadcast

Clean & Organized Environment

Fungicides

BanRot!BanRot!

Follow The Label Directions!

Window-Box Propagation

Two clear halves of sweater/storage boxes taped Two clear halves of sweater/storage boxes taped together with duct tape as a hinge make ideal together with duct tape as a hinge make ideal propagation boxes!propagation boxes!

Place the box in a Place the box in a sunny window, and sunny window, and open it up for an hour open it up for an hour at night to replace airat night to replace airand dry off leaves.and dry off leaves.

Works for almost allWorks for almost alltropical plants.tropical plants.

Germination ChambersGermination Chambers

Rel

ativ

e G

row

th R

ate

14oC

22oC

30oC

Degrees Fahrenheit

Preferred Night Temperature

0

25

50

75

100

43 50 57 65 72 79 86 93 100

Primula

Fern

Lantana

15oC

10oC

Root Zone HeatingRooting medium temperature, given control, may beRooting medium temperature, given control, may be

applied to speed up growth. A good example is usingapplied to speed up growth. A good example is using

heating pads under planted seed flats to speed heating pads under planted seed flats to speed

up germination or rooting. The right temperatureup germination or rooting. The right temperature

can take a can take a

week or month week or month

off of rooting off of rooting

schedule and schedule and

can take a few can take a few

days to a few weeks days to a few weeks

off of germination. off of germination.

Time is moneyTime is money..

Types Of Heating Technology

Hot Water TubesHot Water Tubes

Electric MatsElectric Mats

Electric Heating Tapes

We need to provide seedlings a film of water to We need to provide seedlings a film of water to reduce evaporation, and the loss of water. Tooreduce evaporation, and the loss of water. Toomuch water is as bad as too little water!much water is as bad as too little water!

Mist Benches

Light Levels Affect Seedlings!

As with mature plants, if cuttings are placed in too low As with mature plants, if cuttings are placed in too low light conditions, they will get leggy and may abort leaves.light conditions, they will get leggy and may abort leaves.

Even if they all live, Even if they all live, the final quality of the final quality of the adult plant is in the adult plant is in question. Which question. Which plant will be thicker plant will be thicker and more branched? and more branched? Which would you buy?Which would you buy?

Constantly Wet and/or Stagnant Air Condition Affects Seedlings

The leaf surface of The leaf surface of seedlings benefits from seedlings benefits from brief periods of surface brief periods of surface dryness, especially at dryness, especially at night. Air movement, night. Air movement, especially as new root especially as new root initials form, is essential initials form, is essential for root development.for root development.

Experiment One: The Seed EnvironmentExperiment One: The Seed Environment

AA BB CC

DD EE FF

LighLightt

VermiculiteVermiculite DarkDark

A=Asclepias, B=Catchfly, C=Black Eye, D=FoxGlove, E=Lettuce, F=Old SeedA=Asclepias, B=Catchfly, C=Black Eye, D=FoxGlove, E=Lettuce, F=Old Seed

Con

trol

Con

trol

Extr

act

Extr

act

Experiment Two: Germination TechniquesExperiment Two: Germination Techniques

AA BB

CC DD

EE FF

PreSoaPreSoakk

A=Blueberry, B=PoleBean, C=Lemon, D=Cherry, E=FoxGlove, F=LocustA=Blueberry, B=PoleBean, C=Lemon, D=Cherry, E=FoxGlove, F=Locust

FreezeFreeze PreSoaPreSoakk

ScratcScratchh

CrackCrack

sandsand

ScratcScratchh

Experiment Three: The Seed EnvironmentExperiment Three: The Seed Environment

AA BB CC

DD EE FF

LimLimee

ControlControl Iron SulfateIron Sulfate

No Fe

rtilizer

No Fe

rtilizer

Fert

iliz

er

Fert

iliz

er

A=Bean, B=Corn, C=Pumpkin, D=Cosmos, E=Burmuda, F=MarigoldA=Bean, B=Corn, C=Pumpkin, D=Cosmos, E=Burmuda, F=Marigold

Some of the seeds of hopeSome of the seeds of hope

Planted tentatively in the fallPlanted tentatively in the fallHave not come upHave not come up

They lie stillborn and unrealizedThey lie stillborn and unrealizedSomewhere in the spring soilSomewhere in the spring soil

DecayingDecayingThe Strongest and best onesThe Strongest and best onesPushed up though the leavesPushed up though the leaves

And layers of cold, hard resistanceAnd layers of cold, hard resistanceRight into clear blue airRight into clear blue air

And stand there nakedly greenAnd stand there nakedly greenBreathingBreathing

It's always that way with growing thingsIt's always that way with growing thingsNever knowing at the startNever knowing at the start

Which will make it and which will failWhich will make it and which will failBut the thing to hold fast toBut the thing to hold fast to

Never to lose faith in, is simply,Never to lose faith in, is simply, SowingSowing

Gardener by Ann North