Book with abstracts from the COST Action 0905 meeting in ... - UMB

ZINC FLUXES INTO THE DEVELOPING BARLEY GRAIN: USE OF
STABLE ZN ISOTOPES TO SEPARATE ROOT UPTAKE FROM
REMOBILIZATION IN PLANTS WITH CONTRASTING ZN STATUS
Josefine Nymark Hegelund, Pai Pedas, Michaela Schiller, Soeren Husted, Jan K.
Schjoerring
Plant and Soil Science Section, Department of Agriculture and Ecology, Faculty of Life Sciences,
University of Copenhagen, Thorvaldsensvej 40, 1871 Frederiksberg C, Denmark.
Key words: Barley, grain, isotope, flux, root, remobilization, zinc
Improved knowledge on Zn fluxes in plants is important for the development of agronomic
and genetic strategies to address the problems of Zn deficiency in humans. Zn import into
developing grain is the result of two processes integrated over time: translocation of Zn
absorbed de novo from the root medium and remobilization of Zn from vegetative tissues.
Little information is available on the relative importance of these two Zn pathways in
plants and how they are affected by the nutritional Zn status of the plant. Here we used the
stable isotope 67 Zn to characterize and quantify fluxes of Zn uptake and remobilization in
barley plants with different Zn status. Barley plants were grown in complete nutrient
solutions with 3 different zinc levels, i.e. 100 nM (low Zn), 1500 nM (medium Zn) or 5000
nM Zn (high Zn).
When grain development reached 15 days after pollination, the Zn concentration was in all
treatments changed to 1500 nM 67 Zn and plants were harvested after 6 h, 24 h or 48 h. The
short exposure time was chosen to minimize the remobilization of new 67 Zn from leaves to
the spike. Zn concentrations and isotope ratios were determined using Inductively Coupled
Plasma-Mass Spectrometry (ICP-MS). During the 48 h experimental period plants, with
low Zn status absorbed a total of 1760 nmol Zn which was 2.8- and 4- fold more than that
in medium and high Zn status plants. Stems and spikes 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 (