Fractionation of Metal Stable Isotopes by Higher Plants

Abstract

Higher plants induce chemical reactions in the rhizosphere, facilitating metal uptake by roots. Fractionation of the isotopes in nutrients such as calcium, iron, magnesium, and zinc produces a stable isotope composition in the plants that generally differs from that of the growth medium. Isotope fractionation also occurs during transport of the metals within most plants, but its extent depends on plant species and on the metal, in particular, on the metal's redox state and what ligand it is bound to. The metal stable isotope variations observed in plants create an isotope signature of life at the Earth's surface, contributing substantially to our understanding of metal cycling processes in the environment and in individual organisms.

Testing the limits of micro-scale analyses of Si stable isotopes by femtosecond laser ablation multicollector inductively coupled plasma mass spectrometry with application to rock weathering

“…To resolve Si isotope signals from isobaric interferences (mainly N-O moleculars) the ion optics were operated in medium mass resolution mode (mass resolving m/m power at 5%, 95% intensity limits >6000). Moveable Faraday detectors with 10 11 Ω amplifiers were precisely positioned to obtain interference-free flat-top peak shoulders for simultaneous detection of all three stable Si isotopes. Faraday cups L2, C, and H2 were used for simultaneous measurements of 28 Si, 29 Si, and 30 Si, respectively.…”

“…At the same time, new applications for LA-ICP-MS have arisen in the form of metal and metalloid stable isotope ratios in oceanography [8], environmental sciences [9], plant physiology [10], igneous petrology [11], and cosmochemistry [12], for example. These elements are subject to minor shifts in their relative isotope ratios that mostly amount to only a few permil (‰) or less per mass unit.…”

Stable Isotopes of Transition and Post-Transition Metals as Tracers in Environmental Studies

“…As pointed out by von Blanckenburg et al (2009), the metabolic processes that control the behavior of metals in plants can be envisaged as a gigantic geochemical pump that continuously moves metals between reservoirs. As plants move metals from soils into roots and along the transpiration stream, the metals are cycled through a variety of chemical species via processes that can lead to isotope fractionation.…”

Fe isotope fractionation caused by translocation of iron during growth of bean and oat as models of strategy I and II plants

“…The use of stable iron isotopes has now been recognized (e.g. Walczyk and von Blanckenburg 2002;Walczyk and von Blanckenburg 2005;Guelke and von Blanckenburg 2007;Álvarez-Fernández 2006;Stuerup et al 2008, von Blanckenburg et al 2009). In studies of iron uptake stable iron isotopes can be used in two different ways: (1) isotope fractionation studies, utilizing minute natural shifts in the isotopic abundances of iron isotopes as driven by binding form and reaction kinetics; and (2) and tracing studies, using compounds enriched in a specific nonradioactive isotope.…”

“…Non-complete oxidative phytoferritin fixation during storage would result in light residual Fe(II)-NA. Also ligand exchange and change of the redox state during loading of iron to the phloem, transport inside it or unloading from the phloem can cause iron isotope fractionation (von Blanckenburg et al, 2009). As it has been shown that iron is transported as Fe 2+ into the cell's vacuole and is stored probably as Fe(III)-complexes (Kim et al 2006), it can be assumed that the mobilization of iron involves a reduction step and can therefore result in isotope fractionation favoring a relative accumulation of lighter iron isotopes in the soluble iron pool.…”