2012 Seed Germination Workshop Paul A. Thomas The University of Georgia Teacher Training Conference Producing Plants From Seed

About Seeds

No Two Seeds Are Alike

Three Types Of Seed Sources Fleshy Fruits: Fleshy Fruits: Berries, Figs Dry Fruits: Grains, Grasses Dry Seeds / Dehiscent Pods: Cones/Pods

Heritage Heirloom Varieties Vegetables and flowers that were grown and passed on through many generations by families. Seedlings match parent plants closely.

– Populations of plants 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 Terms To Know

– Pollen from one plant Cross Pollination – Pollen from one plant fertilizes the embryo sac of another plant within the species. – The pollen from a plant is Self Pollination – The pollen from a plant is able to fertilize the embryo sac on the same plant and produce a viable embryo. Terms To Know

A seed’s origin, in terms of climate and geographical location. This can 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 hybrid vegetables and flowers s rarely look anything 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!

Seed Cleaning / Separation For many dry seed, simply crush dried material and blow gently, transferring the seed from hand to hand. Cleaning seed reduces disease and weed seed from growing along with your selection

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 0 o and 50 o C.

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

– These seeds are able Recalcitrant Seed – These seeds are able to germinate without dessicating. These seeds lose viability after drying and must be planted quickly. be planted quickly. Oak, Maple, Coffee – The seeds dessicate Orthodox Seed – The seeds dessicate after reaching full development to allow the seed to be quiescent or dormant until conditions are right to germinate. conditions are right to germinate. Beans Terms To Know

Orthodox Seed – Store dry and cold (Under 1 yr) Short-Lived – Store dry and cold (Under 1 yr) Vinca, Pansy, Begonia - Store dry and cold ( 2-5 years) Medium - Lived - Store dry and cold ( 2-5 years) Marigold, Petunia, Coleus – Store dry and cold ( years) Long - Lived – Store dry and cold ( years) Morning Glory, Zinnia, Hollyhock

SEED STORAGE Recalcitrant Seed – Short-term Viability – Store warm and moist (ASAP) Tropical – Store warm and moist (ASAP) Coffee, Cocoa, Mango, Macadamia, Avocado, Tea – Store cool and moist (ASAP) Subtropical – Store cool and moist (ASAP) Maple, Oak, Elm, Poplar, Salix,

Seed Storage Moist to 50 o F Dry 35 to 50 o F* Cold 0 o F, –18 o C * -196 o C * *** at 3 – 8% Moisture *** at 3 – 8% Moisture

Expiration Date Planting Depth Directions Important Information Source

GerminationPercentage Lot Number Scientific Name More Information

Fungicides/RhyzobiaFungicides/Rhyzobia PolycoatingPolycoating Pre-germinatedPre-germinated Seed Coatings

Enhanced Seed Park’sSeed

Testing Viability - Simplified

The Cycle of Life

THE GERMINATION PROCESS How Germination Works Water is usually the key factor in starting the germination process.

1. Imbibed water stimulates Gibberellin synthesis Gibberellins diffuse to the aleurone layer and stimulate the synthesis of enzymes Enzymes break down the starch and the sugars are transported to the developing embryo.

About Dormancy

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

Relative Hormone Level 14 o C Days of Cold Stratification Triphasic Changes In Seed Hormone Balance Overwintering of Seeds in the ground (Inhibits)

Types of Dormancy in Seed – The seeds are able to Germinate upon Quiescent – The seeds are able to Germinate upon imbibition of water at permissive temperatures. – Seeds cannot germinate 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. – An additional level of Secondary Dormancy – An additional level of Protection to prevent germination. Can be induced under very unfavorable conditions such as drought or cold, etc.

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

- Factors outside Secondary Dormancy - Factors outside the seed induce dormancy after the seed was previously non-dormant. seed was previously non-dormant. High (Thermo-dormancy) Soil Temperatures (Thermo-dormancy) Types of Dormancy in Seed - Any combination Double Dormancy - Any combination of 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 : A type of dormancy 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

Types Of Photoperiodic Response Short Day Plants – Single Cycle……….Rice Requires only one short day cycle to initiate the photoperiodic response. Long Day Plants – Single Cycle………….Dill Requires only one long day cycle to initiate the photoperiodic response. Day Neutral Plants………………………………Cucumber Flower 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 nm 660 nm Pr Pfr (Slow) Far Red Light Bright Sun Quiescence Germination Long hours of bright spring sun stimulates formation of Pfr and germination begins!

(Fast) Dark Reversion Red Light 740 nm 660 nm Pr Pfr (Slow) Far Red Light Germination Quiescence Far-red light, such as is found under lots of vegetation, prevents germination. Seeds wait for sun!

(Fast) Dark Reversion Red Light 740 nm 660 nm Pr Pfr (Slow) Far Red Light Germination Quiescence Darkness maintains Pr and quiescence. Buried seed won’t germinate until brought to the surface! Darkness

Techniques

Germination Environment Moisture / Humidity Temperature Range Light Level and Quality Aeration (Oxygen in Soil) Soil pH and Nutrition Air Movement

Technique Berry Roll Cracking Scratching Freezing Moist Chilling Hot Soaking Irradiation You can use a blender!

Irradiation Germination Of Lettuce

Fleshy Berry Seed

Handling Tiny Seeds Some seeds can be smaller than the tip of a pin. They can also be very expensive. A very careful approach is often needed to be efficient and successful planting tiny seeds

Handling Tiny Seeds Mix Seed with Sand

Preconditioning Seeds (for more uniform germination) Mechanical scarification Soaking In Water Acid Scarification Moist Chilling / Freezing Double Dormancy Methods:

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 110 O F Let soak for a few hours. Stir often. Do not re-heat the water. Plant ASAP.

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 hours is a very common soaking period.

Thermo-hydro-Limitations Time ! 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 Pot Seeding Box Plug Tray Fabric Matt Hydroseeding Direct Broadcast

Clean & Organized Environment

Fungicides BanRot! Follow The Label Directions!

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.

Germination Chambers

Relative Growth Rate 14 o C 22 o C 30 o C Degrees Fahrenheit Preferred Night Temperature 15 o C 10 o C

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.

Types Of Heating Technology Hot Water Tubes Electric Mats

Electric Heating Tapes

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! Mist Benches

Light Levels Affect Seedlings! As with mature plants, if cuttings are placed in too low light conditions, they will get leggy and may abort leaves. Even if they all live, the final quality of the adult plant is in question. Which plant will be thicker and more branched? Which would you buy?

Constantly Wet and/or Stagnant Air Condition Affects Seedlings The leaf surface of seedlings benefits from brief periods of surface dryness, especially at night. Air movement, especially as new root initials form, is essential for root development.

Experiment One: The Seed Environment ABC D E F Light Vermiculite Dark A=Asclepias, B=Catchfly, C=Black Eye, D=FoxGlove, E=Lettuce, F=Old Seed Control Extract

Experiment Two: Germination Techniques A B C D E F PreSoak A=Blueberry, B=PoleBean, C=Lemon, D=Cherry, E=FoxGlove, F=Locust Freeze PreSoakScratch Crack sand Scratch

Experiment Three: The Seed Environment ABC DE F Lime Control Iron Sulfate No Fertilizer Fertilizer A=Bean, B=Corn, C=Pumpkin, D=Cosmos, E=Burmuda, F=Marigold

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 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 Sowing Gardener by Ann North