Calcium isotope fractionation during plant growth under a limited nutrient supply

Potassium and Calcium Isotopic Fractionation by Plants (Soybean [Glycine max], Rice [Oryza sativa], and Wheat [Triticum aestivum])

“…This would tend to make the stems lighter than both the leaves and roots. The adsorption of light Ca (low δ 44 Ca) into cell walls lining xylem pathways has been suggested as the mechanism for isotopic fractionation between roots and shoots,(45, 18,19)and would be consistent with a positive ε 3 . This light Ca loss during transport would cause the Ca carried in the xylem to become progressively enriched in heavy isotopes, making the leaves generally higher in δ 44 Ca than stems.…”

“…Excess Ca sequestered as Ca-oxalate nodules could enhance this fractionation, as Ca-oxalate derived from leaves has been shown to have lower δ 44 Ca than the free-Ca in leaves. (18,19) Mechanisms of K and Ca Transport in Plants The model described above is nonspecific with regard to the transport mechanisms and source of isotopic fractionation. A number of different mechanisms have been called upon to explain isotopic fractionation within plants (17)(18)(19)(28)(29)(30)(31)(32)45,46) including adsorption or ligand binding, transport processes across cellular membranes some of which involve transporter proteins, and diffusion within plant fluids involving differences in diffusivity between isotopes.…”

Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments

“…measured 44 Ca of leaves and tissues of Metrosideros trees fromHawaii and found preferential absorptions of40 Ca by roots and stem tissues which were fractionated by -1.0 to -2.0 ‰. AlsoSchmitt et al (2013) found preferential uptake of40 Ca by the roots of bean plants. Isotope fractionation of Ca found in coral skeleton of the present study is similar to the fractionations suggested for Ca transmembrane transport from these studies, supporting the concept ofBöhm et al (2006) that Ca isotope fractionation in corals occurs during Ca transport through membranes.…”

Factors controlling the chemical composition of colloidal and dissolved fractions in soil solutions and the mobility of trace elements in soils

“…This may indicate that Ca and Mn are weakly complexed with OC and may be exchangeable between the colloidal and dissolved fractions and between the dissolved fraction and the vegetation, with the rhizosphere situated at 30 cm in depth. Once they are in the dissolved fraction, Ca and Mn may be used as nutrients in biotic processes (Dijkstra and Smits, 2002;Schmitt et al, 2013).…”