Fractionation of stable zinc isotopes in the field-grown zinc hyperaccumulator Noccaea caerulescens and the zinc-tolerant plant Silene vulgaris.
Stable Zn isotope signatures offer a potential tool for tracing Zn uptake and transfer mechanisms within plant-soil systems. Zinc isotopic compositions were determined in the Zn hyperaccumulator  Noccaea caerulescens  collected at a Zn-contaminated site (Viviez), a serpentine site (Vosges), and a noncontaminated site (Sainte Eulalie) in France. Meanwhile, a Zn-tolerant plant ( Silene vulgaris ) was also collected at Viviez for comparison. While δ(66)Zn was substantially differentiated among  N. caerulescens  from the three localities, they all exhibited an enrichment in heavy Zn isotopes of 0.40-0.72‰ from soil to root, followed by a depletion in heavy Zn from root to shoot (-0.10 to -0.50‰). The enrichment of heavy Zn in roots is ascribed to the transport systems responsible for Zn absorption into root symplast and root-to-shoot translocation, while the depletion in heavy Zn in shoots is likely to be mediated by a diffusive process and an efficient translocation driven by energy-required transporters (e.g., NcHMA4). The mass balance yielded a bulk Zn isotopic composition between plant and soil (Δ(66)Zn(plant-soil)) of -0.01‰ to 0.63‰ in  N. caerulescens , indicative of high- and/or low-affinity transport systems operating in the three ecotypes. In  S. vulgaris , however, there was no significant isotope fractionation between whole plant and rhizosphere soil and between root and shoot, suggesting that this species appears to have a particular Zn homeostasis. We confirm that quantifying stable Zn isotopes is useful for understanding Zn accumulation mechanisms in plants.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.
Ye-Tao
YT
Tang
Christophe
C
Cloquet
Thibault
T
Sterckeman
Guillaume
G
Echevarria
Jean
J
Carignan
Rong-Liang
RL
Qiu
Jean-Louis
JL
Morel
D019607:Brassicaceae / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D029751:Silene / Q000378:metabolism*; D015032:Zinc / Q000032:analysis / Q000378:metabolism*; D015033:Zinc Isotopes / Q000032:analysis / Q000378:metabolism*
D015033:Zinc Isotopes; D015032:Zinc