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Why are Spartina grasses so successful? Adaptations to anoxia and hydrogen sulfide

Why are Spartina grasses so successful? Adaptations to anoxia and hydrogen sulfide. Ray Lee and Brian Maricle School of Biological Sciences Washington State University. Spartina alterniflora and Spartina anglica.

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Why are Spartina grasses so successful? Adaptations to anoxia and hydrogen sulfide

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  1. Why are Spartina grasses so successful? Adaptations to anoxia and hydrogen sulfide Ray Lee and Brian Maricle School of Biological Sciences Washington State University

  2. Spartina alterniflora and Spartina anglica • Saltmarsh grasses native to the Eastern U.S. (S. alterniflora) and British Isles (S. anglica). • Invasive species in Puget Sound and Willapa Bay in Washington State.

  3. Why are physiological studies of Spartina relevant? • Physiological processes are the link between environment and performance Metabolic Structural adaptations Growth reproduction Challenges opportunities Physiological processes Performance Environment

  4. Spartina are physiologically resilient and vigorous • Physiological tolerance • Wide range of salinities • Waterlogged soils • Anoxia • Hydrogen sulfide

  5. Distribution of hydrogen sulfide in sediments Oxidized zone No hydrogen sulfide Anoxic zone Hydrogen sulfide-rich

  6. Sulfide is a potent toxin to aerobic respiration • µM levels inhibit mitochondrial cytochrome c oxidase • Sulfide binds to hemoglobin forming sulfhemoglobin • Sulfide spontaneously reacts with oxygen producing hypoxic/anoxic conditions • Can be used as an energy source by sulfide-oxidizing bacteria

  7. Chemoautotrophic symbiosis • An adaptation to exploit sulfide-rich environments

  8. Tolerating anoxic sediments • Aerenchyma • Anaerobic metabolism • Alcohol dehydrogenase • Sulfide oxidation Spartina anglica root

  9. Functions of aerenchyma • Oxygen transport • Reduce cellular oxygen demands

  10. Root Ultrastructure 1 cm from root tip 2 cm from root tip

  11. Root Ultrastructure 4 cm from root tip 6 cm from root tip

  12. Root Ultrastructure 8 cm from root tip 10 cm from root tip

  13. The difference in root structure between treatments of Spartina alterniflora

  14. A comparison of root structure between treatments of Spartina anglica

  15. S. anglica respirometry experiments • Use automated flow-through respirometry system • Investigate oxygen transport

  16. Flow-through respirometry

  17. Root - high O2 uptake mitochondria O2 Root surface O2 O2 High oxygen consumption and/or low aerenchyma supply

  18. Root - low O2 uptake mitochondria O2 Root surface O2 O2 O2 O2 Low oxygen consumption and/or high aerenchyma supply

  19. Oxygen transport is more effective in S. anglica compared with S. alterniflora

  20. Checking for oxygen transport • A plant can be sealed into a flask of N2-flushed water. • An oxygen-sensing probe can be used to monitor the water--any increase in O2 must have come through the plant.

  21. Differences in oxygen transport between species Negative fluxes=uptake; positive fluxes=release; n=9, 11, 9, 9

  22. Sulfide volatilization mitochondria H2S Root surface H2S Occurs in S. anglica but not S. alterniflora

  23. Conclusions • Function of increased aerenchyma appears to be to reduce oxygen demands NOT increase oxygen transport • S. anglica has a highly effective oxygen AND sulfide transport system

  24. Questions • Can S. anglica grow better than S. alterniflora in anoxic/sulfidic conditions? • Can sulfide levels ever be so high that plants cannot deal with it? • What is the relationship between sulfide levels and effectiveness of eradication efforts?

  25. Acknowledgements • J. Doeller and D. Kraus (UAB) • S. Hacker (WSU Vancouver) • Kim Patten (WSU Long Beach) • Miranda Wecker • NSF, NOAA, WSU faculty seed grant

  26. Sox mechanism H2S Enzyme or Metal catalyst Root surface O2 O2 O2 mitochondria SOx

  27. Spartina alterniflora roots catalyze the oxygenation of sulfide

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