9th-13rd July, 2018: 19th International Symposium on Iron Nutrition and Interactions in Plants, Taipei, Taiwan

[Z. Klencsar]

The "19th International Symposium on Iron Nutrition and Interactions in Plants" was held during the days July 9 - 13, 2018, at the Academia Sinica in Taipei, Taiwan. On the conference Ferenc Fodor presented the latest results achieved in connection with the effects of nanoferrihydrite and nano-Mn-Zn-ferrite colloid suspensions and that of insoluble nano FeCo powder on cucumber plants. The work was summarized in an abstract as given below.

Iron uptake from manufactured nanomaterials: obscured mechanism, controversial effect

Fruzsina Pankaczi 1, Zsuzsanna Farkas 1, Viktória Halasy 1, Sylva Larsson 1,2, Sára Pólya 1, Brigitta Müller 1, Krisztina Kovács 3, Zoltán Klencsár 4, Zoltán May 5, Zoltán Sándor 5, Ervin Gy. Szabó 5, László Szabó 5, Ernő Kuzmann 3, Zoltán Homonnay 3, Gyula Tolnai 6, Ádám Solti 1, Ferenc Fodor 1*

1 Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
2 Department of Chemistry, Faculty of Mathematics and Science, University of Jyväskylä, Jyväskylä, Finland
3 Department of Analytical Chemistry, Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary
4 Centre for Energy Research, Hungarian Academy of Sciences, Budapest, Hungary
5 Research Centre for Natural Sciences, Hungarian Academy of Sciences, Budapest, Hungary
6 Kondorosi út 8/A., 1116 Budapest, Hungary

*ferenc.fodor@ttk.elte.hu

Transition metals in nanomaterials such as iron, manganese or zinc are essential microelements for plants. When these metals are present in suboptimal concentration for the plants, deficiency syndromes develop that causes reduced crop production or poor fruit quality. Low mineral content of plant products has a major role in human malnutrition. Most stable Fe-chelates for the correction of Fe deficiency are not biodegradable and expensive so applying manufactured nanomaterials may serve as a cheap and eco-friendly alternative. Newly designed, transition metal containing nanomaterials stabilized in colloid suspension have been characterised and then applied in hydroponic cultures to cucumber model plants in a wide range of concentration. The uptake and distribution of the elements from the nanomaterials and their utilization were investigated by microXRF mapping, ICP-MS, enzyme activity tests, gene expression measurements and the changes in some basic physiological parameters were followed. Nanoferrihydrite and nano-Mn-Zn-ferrite colloid suspensions with 3-8 nm particle size applied in 0.01-0.02 mM concentration and at slightly acidic pH proved to be a good source of Fe, Mn and Zn in various experimental conditions. Mn-Zn-ferrite has also been tested at pH 7.5 and Fe deficient cucumber plants showed a significant recovery after 3 days of application in terms of chlorophyll concentration and photosynthetic efficiency but not at pH 8.5. Mn and Zn deficient plants also showed recovery upon addition of the ferrite. Ferric chelate reductase assays showed that it is not the normal reduction-based uptake pathway that plays a role in the iron utilization of these nanoparticles. Analysis of root ferric chelate reductase expression pointed out a quick utilisation of Fe content of the nanoferrihydrite particles. Elevated concentrations of the nanoferrite at the millimolar range as compared to equal concentrations of micronutrient salts proved to be significantly less toxic. However, another nanomaterial, an insoluble nano FeCo powder applied to the nutrient solution of cucumber in high concentration causes severe chlorosis due to cobalt toxicity, pointing on that the composition of the nanoparticles is highly important for their bioactivity.

Keywords: nanomaterial, ferrite, ferrihydrite, fertilizer, ferric chelate reductase, toxicity

This work was supported by the National Research, Development and Innovation Office, Hungary (NKFIH) K115784, 115913, 124159 and VEKOP-2.3.3-15-2016-00008. Á. Solti was also supported by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (BO/00207/15/4).