Plant and Cell Physiology Advance Access first published online on December 10, 2008
This version published online on December 12, 2008
Plant and Cell Physiology, doi:10.1093/pcp/pcn192
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52Fe Translocation in Barley as Monitored by a Positron-Emitting Tracer Imaging System (PETIS): Evidence for the Direct Translocation of Fe from Roots to Young Leaves via Phloem
1 Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
2 Central Research Laboratory, Hamamatsu Photonics K.K., Hamamatsu, Shizuoka 434-0041 Japan
3 Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, Gunma 370-1292, Japan.
Corresponding author: Naoko K. Nishizawa Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan Tel&Fax: +81-3-5841-7514 e-mail: annaoko{at}mail.ecc.u-tokyo.ac.jp
| Abstract |
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The real-time translocation of iron (Fe) in barley (Hordeum vulgare L. cv. Ehimehadaka no. 1) was visualized using the positron-emitting tracer 52Fe and a positron-emitting tracer imaging system (PETIS). PETIS allowed us to monitor Fe translocation in barley non-destructively under various conditions. In all cases, 52Fe first accumulated at the basal part of the shoot, suggesting that this region may play an important role in Fe distribution in graminaceous plants. Fe-deficient barley showed greater translocation of 52Fe from roots to shoots than did Fe-sufficient barley, demonstrating that Fe deficiency causes enhanced 52Fe uptake and translocation to shoots. In the dark, translocation of 52Fe to the youngest leaf was equivalent or higher than that under the light condition, while the translocation of 52Fe to the older leaves was decreased, both in Fe-deficient and Fe-sufficient barley. This suggests the possibility that the mechanism and/or pathway of Fe translocation to the youngest leaf may be different from that to the older leaves. When phloem transport in the leaf was blocked by steam treatment, 52Fe translocation from the roots to older leaves was not affected, while 52Fe translocation to the youngest leaf was reduced, indicating that Fe is translocated to the youngest leaf via phloem in addition to xylem. We propose a novel model in which root-absorbed Fe is translocated from the basal part of the shoots and/or roots to the youngest leaf via phloem in graminaceous plants.
Keywords: barley - Fe translocation - phloem - positron emitting tracer - real time imaging - xylem
4These authors contributed equally to this work.
(Received September 16, 2008; Accepted December 4, 2008)
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