TetrazoliumTetrazolium Testing of Testing of ShrubsShrubs

Victor VankusVictor Vankus

USDA Forest ServiceUSDA Forest Service

National Seed LaboratoryNational Seed Laboratory

www.nsl.fs.fed.uswww.nsl.fs.fed.us

TopicsTopics

Describe the tz test and general proceduresDescribe the tz test and general procedures Special considerations for shrubsSpecial considerations for shrubs Germination, Viability and the Tz testGermination, Viability and the Tz test Benefits of using Tz/Problems associated Benefits of using Tz/Problems associated

with the testwith the test Wrap-upWrap-up

What is a TZ test?What is a TZ test?

Index or measure of the respiration Index or measure of the respiration process inside living cells, tissue and process inside living cells, tissue and seed.seed.

An estimate of viability at one point An estimate of viability at one point in time.in time.

An estimate of what may or may not An estimate of what may or may not happen in the future.happen in the future.

Method Overview and Method Overview and ConsiderationsConsiderations

Pure SeedPure Seed PreconditioningPreconditioning Preparation for StainingPreparation for Staining StainingStaining Preparation for EvaluationPreparation for Evaluation EvaluationEvaluation ReportingReporting

Pure SeedPure Seed

What is the pure seed unit?What is the pure seed unit?

PreconditioningPreconditioning

Water ContentWater Content

Preparation for StainingPreparation for Staining

Expose the TissueExpose the Tissue

StainStain

38° C., hours or days?38° C., hours or days? Surface area exposed Surface area exposed Degree of dormancyDegree of dormancy

Preparation for EvaluationPreparation for Evaluation

Expose the EmbryoExpose the Embryo

EvaluationEvaluation

Staining patternsStaining patterns TurgidityTurgidity

ReportReport

Report tz test result as a range or as Report tz test result as a range or as a single number?a single number?

Tz test alone or with a germination Tz test alone or with a germination test result?test result?

What does an estimated viability test What does an estimated viability test result mean?result mean?

Is the tz test result used as part of a Is the tz test result used as part of a Pure Live Seed calculation?Pure Live Seed calculation?

Considerations for ShrubsConsiderations for Shrubs

Seed anatomySeed anatomy MaturityMaturity DormancyDormancy

CornusCornus embryo embryo EndocarpEndocarp Seed coatSeed coat

CotyledonsCotyledons EndospermEndosperm HypocotylHypocotyl RadicleRadicle

ViburnumViburnum embryo embryo

EndocarpEndocarp Seed coatSeed coat EndospermEndosperm EmbryoEmbryo

AcerAcer embryo embryo

PericarpPericarp Seed coatSeed coat CotyledonsCotyledons HypocotylHypocotyl RadicleRadicle

CephalanthusCephalanthus embryo embryo

PericarpPericarp Seed coatSeed coat EndospermEndosperm CotyledonsCotyledons HypocotylHypocotyl RadicleRadicle

IlexIlex embryo embryo

EndospermEndosperm EmbryoEmbryo

ParthenocissusParthenocissus embryo embryo

EndospermEndosperm CotyledonsCotyledons HypocotylHypocotyl RadicleRadicle

PrunusPrunus embryo embryo

EndocarpEndocarp Seed coatSeed coat CotyledonsCotyledons EpicotylEpicotyl HypocotylHypocotyl RadicleRadicle

RhusRhus embryo embryo

EndocarpEndocarp Seed coatSeed coat CotyledonsCotyledons

RadicleRadicle HypocotylHypocotyl

RibesRibes embryo embryo

Seed coatSeed coat EndospermEndosperm CotyledonsCotyledons HypocotylHypocotyl RadicleRadicle

SerenoaSerenoa embryo embryo

EndocarpEndocarp Seed coatSeed coat EndospermEndosperm EmbryoEmbryo

CeltisCeltis embryo embryo

EndocarpEndocarp Seed coatSeed coat

CotyledonsCotyledons HypocotylHypocotyl RadicleRadicle

Considerations for ShrubsConsiderations for Shrubs

Seed anatomySeed anatomy MaturityMaturity DormancyDormancy

Considerations for ShrubsConsiderations for Shrubs Seed anatomySeed anatomy MaturityMaturity DormancyDormancy

Influence of Seed Health and Influence of Seed Health and Genetics on germination.Genetics on germination.

Stress factors

Environmental conditions present as seed developsMaturity at harvest/dispersalStorage conditions, length in storageProcessingAge

Genetic factors

Ecology/plant evolution dormancy conditions required for germination

Seed mature at dispersal

Age Expiration

High vigor

Medium vigor

Low vigo

r

none

Seed health vigor

Relationship between age, seed health, range of conditions required for germination

Seed mature at dispersal

Age Expiration

Relationship between age, seed health, range of conditions required for germination

Degree of dormancy and conditions required for germ.

Seed mature at dispersal

Age Expiration

Relationship between age, seed health, range of conditions required for germination

Degree of dormancy and conditions required for germ.

Seed mature at dispersal

Age Expiration

High vigor

Medium vigor

Low vigo

r

none

Seed health vigor

Relationship between age, seed health, range of conditions required for germination

low degree of dormancy,

broad range of germ. conditions

little variation between tz and germination

Seed mature at dispersal

Age Expiration

High vigor

Medium vigor

Low vigo

r

none

Seed health vigor

Relationship between age, seed health, range of conditions required for germination

potential for variation between tz and germination

little or no dormancy, secondary dormancy, with initial broad range of conditions for germination, narrow range over time

Seed mature at dispersal

Age Expiration

High vigor

Medium vigor

Low vigo

r

none

Seed health vigor

Relationship between age, seed health, range of conditions required for germination

potential variation between tz and germination.

physiological dormancy, initial narrow range of conditions for germination, broader range over time

Seed mature at dispersal

Age Expiration

High vigor

Medium vigor

Low vigo

r

none

Seed health vigor

Relationship between age, seed health, range of conditions required for germination

potential for significant variation between tz and germination

physiological dormancy and embryo immaturity, narrow range of conditions for germination

Germination, viability and theGermination, viability and the tz test tz test

Germination is the transformation of the Germination is the transformation of the embryo into a seedling. embryo into a seedling.

Seed viability is a term used to describe Seed viability is a term used to describe the potential of a seed to germinate under the potential of a seed to germinate under certain conditions. certain conditions.

Tz is a measure of seed viability, an Tz is a measure of seed viability, an estimate of the total germination potential.estimate of the total germination potential.

Benefits of using Tz Benefits of using Tz

Useful during collection, processing, storage, Useful during collection, processing, storage, with a germination test to determine plant with a germination test to determine plant production value of a seed lot.production value of a seed lot.

Advantages:Advantages: Ability to test dormant seedAbility to test dormant seed When used to supplement germination test results When used to supplement germination test results

to further explain or determine dormancy, rating to further explain or determine dormancy, rating for vigor, diagnosing causes of seed deterioration.for vigor, diagnosing causes of seed deterioration.

Problems associated with Tz Problems associated with Tz testtest

Disadvantages:Disadvantages: Requires experienceRequires experience CostCost State seed lawsState seed laws Uniformity between analysts and testing Uniformity between analysts and testing

laboratorieslaboratories Inability to provide useful information Inability to provide useful information

with regard to dormant seedwith regard to dormant seed

Wrap-upWrap-up

Understand the tool, what a tz test is.Understand the tool, what a tz test is.

Benefits, limitations, when to use tz Benefits, limitations, when to use tz test.test.

Tz is a science and an art, many Tz is a science and an art, many shades of shades of gray.gray.

This presentation and a list of references can be found on the

National Seed Laboratory website at:

www.nsl.fs.fed.us