Tetrazolium Testing of Shrubs

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

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 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. Germination, viability and the tz test

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: www.nsl.fs.fed.us