1. Tetrazolium Testing of Shrubs
Victor Vankus
USDA Forest Service
National Seed Laboratory

2. 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

3. 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.

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

5. Pure Seed
What is the pure seed unit?

6. Preconditioning
Water Content

7. Preparation for Staining
Expose the Tissue

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

9. Preparation for Evaluation
Expose the Embryo

10. Evaluation
Staining patterns
Turgidity

11. 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?

12. Considerations for Shrubs
Seed anatomy
Maturity
Dormancy

13. Cornus embryo Endocarp Seed coat Cotyledons Endosperm Hypocotyl
Radicle

14. Viburnum embryo
Endocarp
Seed coat
Endosperm
Embryo

15. Acer embryo
Pericarp
Seed coat
Cotyledons
Hypocotyl
Radicle

16. Cephalanthus embryo Pericarp Seed coat Endosperm Cotyledons Hypocotyl
Radicle

17. Ilex embryo
Endosperm
Embryo

18. Parthenocissus embryo
Endosperm
Cotyledons
Hypocotyl
Radicle

19. Prunus embryo
Endocarp
Seed coat
Cotyledons
Epicotyl
Hypocotyl
Radicle

20. Rhus embryo
Endocarp
Seed coat
Cotyledons
Radicle
Hypocotyl

21. Ribes embryo
Seed coat
Endosperm
Cotyledons
Hypocotyl
Radicle

22. Serenoa embryo
Endocarp
Seed coat
Endosperm
Embryo

23. Celtis embryo
Endocarp
Seed coat
Cotyledons
Hypocotyl
Radicle

24. Considerations for Shrubs
Seed anatomy
Maturity
Dormancy

25. 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

26. 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

27. 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.

28. 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.

29. 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

30. 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

31. 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.

32. 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

33. 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.

34. 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.

35. 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

36. 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.

37. This presentation and a list of references can be found on the National Seed Laboratory website at: