Tetrazolium Testing of Shrubs Victor Vankus USDA Forest Service National Seed Laboratory www.nsl.fs.fed.us

Topics Describe the tz test and general procedures Special considerations for shrubs Germination, Viability and the Tz test Benefits of using Tz/Problems associated with the test Wrap-up

What is a TZ test? Index or measure of the respiration process inside living cells, tissue and seed. An estimate of viability at one point in time. An estimate of what may or may not happen in the future.

Method Overview and Considerations Pure Seed Preconditioning Preparation for Staining Staining Preparation for Evaluation Evaluation Reporting

Pure Seed What is the pure seed unit?

Preconditioning Water Content

Preparation for Staining Expose the Tissue

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

Preparation for Evaluation Expose the Embryo

Evaluation Staining patterns Turgidity

Report Report tz test result as a range or as a single number? Tz test alone or with a germination test result? What does an estimated viability test result mean? Is the tz test result used as part of a Pure Live Seed calculation?

Considerations for Shrubs Seed anatomy Maturity Dormancy

Cornus embryo Endocarp Seed coat Cotyledons Endosperm Hypocotyl Radicle

Viburnum embryo Endocarp Seed coat Endosperm Embryo

Acer embryo Pericarp Seed coat Cotyledons Hypocotyl Radicle

Cephalanthus embryo Pericarp Seed coat Endosperm Cotyledons Hypocotyl Radicle

Ilex embryo Endosperm Embryo

Parthenocissus embryo Endosperm Cotyledons Hypocotyl Radicle

Prunus embryo Endocarp Seed coat Cotyledons Epicotyl Hypocotyl Radicle

Rhus embryo Endocarp Seed coat Cotyledons Radicle Hypocotyl

Ribes embryo Seed coat Endosperm Cotyledons Hypocotyl Radicle

Serenoa embryo Endocarp Seed coat Endosperm Embryo

Celtis embryo Endocarp Seed coat Cotyledons Hypocotyl Radicle

Considerations for Shrubs Seed anatomy Maturity Dormancy

Considerations for Shrubs Seed anatomy Maturity Dormancy Influence of Seed Health and Genetics on germination. Stress factors Environmental conditions present as seed develops Maturity at harvest/dispersal Storage conditions, length in storage Processing Age Genetic factors Ecology/plant evolution dormancy conditions required for germination

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration High vigor Seed health vigor Medium vigor Low vigor none

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration Degree of dormancy and conditions required for germ.

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration Degree of dormancy and conditions required for germ.

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration High vigor Seed health vigor Medium vigor low degree of dormancy, broad range of germ. conditions Low vigor none little variation between tz and germination

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration High vigor Seed health vigor Medium vigor little or no dormancy, secondary dormancy, with initial broad range of conditions for germination, narrow range over time Low vigor none potential for variation between tz and germination

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration High vigor Seed health vigor Medium vigor physiological dormancy, initial narrow range of conditions for germination, broader range over time Low vigor none potential variation between tz and germination.

Relationship between age, seed health, range of conditions required for germination Seed mature at dispersal Age Expiration High vigor Seed health vigor Medium vigor physiological dormancy and embryo immaturity, narrow range of conditions for germination Low vigor none potential for significant variation between tz and germination

Germination, viability and the tz test Germination is the transformation of the embryo into a seedling. Seed viability is a term used to describe the potential of a seed to germinate under certain conditions. Tz is a measure of seed viability, an estimate of the total germination potential.

Benefits of using Tz Useful during collection, processing, storage, with a germination test to determine plant production value of a seed lot. Advantages: Ability to test dormant seed When used to supplement germination test results to further explain or determine dormancy, rating for vigor, diagnosing causes of seed deterioration.

Problems associated with Tz test Disadvantages: Requires experience Cost State seed laws Uniformity between analysts and testing laboratories Inability to provide useful information with regard to dormant seed

Wrap-up Understand the tool, what a tz test is. Benefits, limitations, when to use tz test. Tz is a science and an art, many shades of gray.

This presentation and a list of references can be found on the National Seed Laboratory website at: www.nsl.fs.fed.us