Zinc fluxes into developing barley grains: use of stable Zn isotopes to separate root uptake from remobilization in plants with contrasting Zn status

TY - JOUR

T1 - Zinc fluxes into developing barley grains

T2 - use of stable Zn isotopes to separate root uptake from remobilization in plants with contrasting Zn status

AU - Hegelund, Josefine Nymark

AU - Pedas, Pai

AU - Husted, Søren

AU - Schiller, Michaela

AU - Schjørring, Jan Kofod

PY - 2012/11

Y1 - 2012/11

N2 - Background and Aims: Zn imported into developing cereal grains originates from either de novo Zn uptake by the roots or remobilization of Zn from vegetative tissues. The present study was focused on revealing the quantitative importance of the two pathways for grain Zn loading and how their relative contribution varies with the overall plant Zn status. Methods: The stable isotope 67Zn was used to trace Zn uptake and remobilization fluxes in barley (Hordeum vulgare L.) plants growing in hydroponics at 0. 1 μM (low Zn), 1. 5 μM (medium Zn) or 5 μM Zn (high Zn). When grain development reached 15 days after pollination the Zn source was changed to an enriched 67Zn isotope and plants were harvested after 6 to 48 h. Zn concentrations and isotope ratios were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Results: Plants with low Zn status absorbed 3-fold more Zn than plants with medium or high Zn status when roots were exposed to an external concentration of 1. 5 μM 67Zn. Stems and ears were the primary recipients of the de novo incorporated Zn with preferential allocation to the developing grains over time. The leaves received in all cases a very small proportion (<5 %) of the newly absorbed Zn and the proportion did not increase over time. Zn fluxes derived from uptake and remobilization were almost equal in plants with low Zn status, while at high Zn status remobilization delivered 4 times more Zn to the developing grains than did root Zn uptake. Conclusions: Stable isotopes in combination with ICP-MS provided a strong tool for quantification of Zn fluxes in intact plants. The importance of Zn remobilization compared to de novo root absorption of Zn increased with increasing plant Zn status. Very little de novo absorbed Zn was translocated to the leaves during generative growth stages.

AB - Background and Aims: Zn imported into developing cereal grains originates from either de novo Zn uptake by the roots or remobilization of Zn from vegetative tissues. The present study was focused on revealing the quantitative importance of the two pathways for grain Zn loading and how their relative contribution varies with the overall plant Zn status. Methods: The stable isotope 67Zn was used to trace Zn uptake and remobilization fluxes in barley (Hordeum vulgare L.) plants growing in hydroponics at 0. 1 μM (low Zn), 1. 5 μM (medium Zn) or 5 μM Zn (high Zn). When grain development reached 15 days after pollination the Zn source was changed to an enriched 67Zn isotope and plants were harvested after 6 to 48 h. Zn concentrations and isotope ratios were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Results: Plants with low Zn status absorbed 3-fold more Zn than plants with medium or high Zn status when roots were exposed to an external concentration of 1. 5 μM 67Zn. Stems and ears were the primary recipients of the de novo incorporated Zn with preferential allocation to the developing grains over time. The leaves received in all cases a very small proportion (<5 %) of the newly absorbed Zn and the proportion did not increase over time. Zn fluxes derived from uptake and remobilization were almost equal in plants with low Zn status, while at high Zn status remobilization delivered 4 times more Zn to the developing grains than did root Zn uptake. Conclusions: Stable isotopes in combination with ICP-MS provided a strong tool for quantification of Zn fluxes in intact plants. The importance of Zn remobilization compared to de novo root absorption of Zn increased with increasing plant Zn status. Very little de novo absorbed Zn was translocated to the leaves during generative growth stages.

U2 - 10.1007/s11104-012-1272-x

DO - 10.1007/s11104-012-1272-x

M3 - Journal article

SN - 0032-079X

VL - 361

SP - 241

EP - 250

JO - Plant and Soil

JF - Plant and Soil

IS - 1-2

ER -