Revisiting the iron pools in cucumber roots: identification and localization
- 348 Downloads
Fe deficiency responses in Strategy I causes a shift from the formation of partially removable hydrous ferric oxide on the root surface to the accumulation of Fe-citrate in the xylem.
Iron may accumulate in various chemical forms during its uptake and assimilation in roots. The permanent and transient Fe microenvironments formed during these processes in cucumber which takes up Fe in a reduction based process (Strategy I) have been investigated. The identification of Fe microenvironments was carried out with 57Fe Mössbauer spectroscopy and immunoblotting, whereas reductive washing and high-resolution microscopy was applied for the localization. In plants supplied with 57FeIII-citrate, a transient presence of Fe-carboxylates in removable forms and the accumulation of partly removable, amorphous hydrous ferric oxide/hydroxyde have been identified in the apoplast and on the root surface, respectively. The latter may at least partly be the consequence of bacterial activity at the root surface. Ferritin accumulation did not occur at optimal Fe supply. Under Fe deficiency, highly soluble ferrous hexaaqua complex is transiently formed along with the accumulation of Fe-carboxylates, likely Fe-citrate. As 57Fe-citrate is non-removable from the root samples of Fe deficient plants, the major site of accumulation is suggested to be the root xylem. Reductive washing results in another ferrous microenvironment remaining in the root apoplast, the FeII-bipyridyl complex, which accounts for ~30 % of the total Fe content of the root samples treated for 10 min and rinsed with CaSO4 solution. When 57FeIII-EDTA or 57FeIII-EDDHA was applied as Fe-source higher soluble ferrous Fe accumulation was accompanied by a lower total Fe content, confirming that chelates are more efficient in maintaining soluble Fe in the medium while less stable natural complexes as Fe-citrate may perform better in Fe accumulation.
KeywordsCucumis sativus L. Ferritin Hydrous ferric oxides Iron uptake Mössbauer spectroscopy
Electron energy loss spectroscopy
The authors wish to thank Frits Bienfait for the discussion on the bypridyl method. This work was supported by the Hungarian National Science Fund grants National Research, Development and Innovation Office—NKFIH PD 111979, PD 112047 and K 115913. The authors gratefully acknowledge the support by the project LO1305 of the Ministry of Education, Youth and Sports of the Czech Republic. This work (Á.S.) was also supported by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (BO/00207/15/4).
- Cseh E, Váradi G, Fodor F (1994) Effect of Fe-complexes and N-forms on the Fe absorption, uptake and translocation of cucumber plants. Bot Kozl 81:47–55Google Scholar
- Kovács K, Kuzmann E, Fodor F, Homonnay Z, Machala L, Vértes A (2010) Low temperature 57Fe Mössbauer study of cucumber root. J Phys: Conf Ser 217:012019Google Scholar
- Pechousek J, Jancik D, Frydrych J, Navarik J, Novak P (2012) Setup of Mössbauer spectrometers at RCPTM. In: AIP conference proceedings, Olomouc, vol 1489, pp 186–193Google Scholar
- Rellán-Álvarez R, Giner-Martínez-Sierra J, Orduna J, Orera I, Rodríguez-Castrillón JÁ, García-Alonso JI, Abadía J, Álvarez-Fernández A (2010) Identifi cation of a tri-iron(III), tri-citrate complex in the xylem sap of iron-deficient tomato resupplied with iron: new insights into plant iron long-distance transport. Plant Cell Physiol 51(1):91–102CrossRefPubMedGoogle Scholar
- Rodriguez-Lucena P, Benedicto A, Lucena JJ, Rodriguez-Castrillon JA, Moldovan M, Alonso JIG, Hernandez-Apaolazaa L (2010) Use of the stable isotope 57Fe to track the efficacy of the foliar application of lignosulfonate/Fe3+ complexes to correct Fe deficiencies in cucumber plants. J Sci Food Agr 91:395–404CrossRefGoogle Scholar
- Szilágyi ÁP (2007) Study of iron-chelates in solid state and aqueous solutions using Mossbauer spectroscopy. Dissertation, Eötvös Lorand University, Budapest, HungaryGoogle Scholar
- Vértes A, Korecz L, Burger K (1979) Mössbauer spectroscopy. Elsevier, AmsterdamGoogle Scholar