Stable Hydrogen Isotope Fractionations during Autotrophic and Mixotrophic Growth of Microalgae
1Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20008.
Plant Physiology
|March 1, 1981
Summary
Hydrogen isotope effects reveal key steps in plant metabolism. Microalgae studies show light and dark reactions of photosynthesis influence hydrogen incorporation into carbohydrates and other organic molecules.
Area of Science:
- Biochemistry
- Plant Physiology
- Photosynthesis Research
Background:
- Isotope effects are crucial for understanding metabolic pathways in plants.
- Hydrogen (H) metabolism plays a vital role in photosynthesis and biosynthesis.
Purpose of the Study:
- To investigate hydrogen isotope effects in microalgae to elucidate critical steps in plant H metabolism.
- To determine how light and dark reactions of photosynthesis regulate H isotope discrimination.
Main Methods:
- Utilized precision isotope ratio mass spectrometry to study H isotope effects.
- Manipulated growth conditions of microalgae to analyze H isotope fractionation.
Main Results:
- Observed significant H isotope discrimination (-100 to -120 per thousand) between water and carbohydrates, regulated by photosynthetic light and dark reactions.
- Photosynthetic electron transport enriched the light H isotope in reductant pools for biosynthesis.
- Additional fractionation (-30 to -60 per thousand) occurred during protein and lipid biosynthesis, linked to glycolysis.
Conclusions:
- Hydrogen metabolism in photosynthesis is tightly coupled with dark biosynthetic reactions.
- The reductant pool, likely NADPH, serves as a critical link between photosynthetic and biosynthetic H metabolism.
- Isotope effects provide a powerful tool for dissecting complex metabolic pathways in plants.
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