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Published on: January 16, 2014
Magnesium-isotope fractionation during plant growth
Jay R Black1, Emanuel Epstein, William D Rains
1Department of Geology, University of California, One Shield Avenue, Davis, California 95616, USA. jayblack@ucla.edu
Environmental Science & Technology
|November 27, 2008
Summary
Wheat plants preferentially absorb heavy magnesium isotopes, leading to isotope enrichment in seeds and exudates. This suggests agricultural harvesting may alter soil magnesium bioavailability over time.
Area of Science:
- Biogeochemistry
- Plant Physiology
- Isotope Geochemistry
Background:
- Magnesium is vital for numerous enzymes and biogeochemical cycles.
- Stable magnesium isotopes (24Mg, 25Mg, 26Mg) offer insights into these cycles.
- Magnesium isotope fractionation in higher plants remains largely unstudied.
Purpose of the Study:
- To investigate magnesium stable-isotope distribution in wheat (Triticum aestivum L.) throughout its growth cycle.
- To determine how wheat plants fractionate magnesium isotopes under controlled conditions.
- To assess the implications of plant magnesium isotope uptake for soil biogeochemistry.
Main Methods:
- Wheat plants were cultivated hydroponically with limited nutrient supply.
- Plants were monitored through senescence, with some detopped for exudate collection.
- Magnesium isotopic composition was measured in various plant tissues (chlorophylls, seeds, shoots, roots, leaves), exudates, and the nutrient solution.
Main Results:
- Wheat plants established an isotopic equilibrium with the available nutrient solution.
- Plants showed enrichment in heavy magnesium isotopes (25Mg, 26Mg) in a mass-dependent manner as they matured.
- Seeds and exudates exhibited the most significant heavy isotope enrichment.
Conclusions:
- Wheat plants exhibit a preference for heavier magnesium isotopes during growth and maturation.
- This selective uptake suggests a potential difference in magnesium bioavailability between agricultural and natural soils.
- Periodic harvesting may deplete soils of heavy magnesium isotopes, impacting future nutrient availability.
