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Iron (Fe) sources available for plants in the rhizospheric solution are mainly a mixture of complexes between Fe and organic ligands, including phytosiderophores (PS) and water-extractable humic substances (WEHS). In comparison with the other Fe sources, Fe-WEHS are more efficiently used by plants, and experimental evidences show that Fe translocation contributes to this better response. On the other hand, very little is known on the mechanisms involved in Fe allocation in leaves. In this work, physiological and molecular processes involved in Fe distribution in leaves of Fe-deficient Cucumis sativus supplied with Fe-PS or Fe-WEHS up to 5 days were studied combining different techniques, such as radiochemical experiments, synchrotron micro X-ray fluorescence, real-time reverse transcription polymerase chain reaction and in situ hybridization. In Fe-WEHS-fed plants, Fe was rapidly (1 day) allocated into the leaf veins, and after 5 days, Fe was completely transferred into interveinal cells; moreover, the amount of accumulated Fe was much higher than with Fe-PS. This redistribution in Fe-WEHS plants was associated with an upregulation of genes encoding a ferricIII-chelate reductase (FRO), a Fe2+ transporter (IRT1) and a natural resistance-associated macrophage protein (NRAMP). The localization of FRO and IRT1 transcripts next to the midveins, beside that of NRAMP in the interveinal area, may suggest a rapid and efficient response induced by the presence of Fe-WEHS in the extra-radical solution for the allocation in leaves of high amounts of Fe. In conclusion, Fe is more efficiently used when chelated to WEHS than PS and seems to involve Fe distribution and gene regulation of Fe acquisition mechanisms operating in leaves. [ABSTRACT FROM AUTHOR]

A technology for remediation of mine tailings, based on air oxidation of added Fe(II) in solution, was tested by chemical extraction and growing pea (Pisum sativum) plants in a greenhouse experiment. Tailings, from a mine site (Cave del Predil, Italy) with high content of Pb and Zn, were saturated with a 0.5M FeSO4 solution and then air-dried. The acidity released by Fe(II) oxidation was successively neutralized by Ca(OH)2. This treatment was repeated 6 times. Cd, Cu, Ni, Mn, Pb and Zn mobility was assessed by Ca(NO3)2 extraction, and their bio-available fraction either by DTPA-extraction or by plant test. Mobility of Cd, Pb and Zn decreased at the end of 6 cycles by 48, 66 and 67%, respectively, whereas Cu, Mn and Ni were below detection limits. In treated mining tailings, DTPA-extractable Cu, Pb and Zn after 6 cycles of treatment showed a marked decrease of 50, 65 and 38%, respectively. Conversely, extractable Mn and Ni, although present at very low concentrations, slightly increased their bioavailability, and that of Cd did not change significantly. Pea dry matter yield increased significantly after 4 and 6 treatment cycles. Metal concentration in plant tissue at the end of 6 cycles showed a decrease for Cd (53%), Cu (9%), Mn (8%), Pb (35%) and Zn (26%), but a slight increase for Ni. [ABSTRACT FROM AUTHOR]

In membrane treatment of wastewater containing proteins, humic acid influences the rate and extent of fouling. Cations may increase the tendency of foulants to precipitate due to the changes in intermolecular electrostatic interactions. In this paper, we investigated the effect of cations, including ionic charge and size of hydrated ion, on ultrafiltration of the solutions containing the mixture of HA and bovine serum albumin (BSA). All experiments were carried out in an Amicon batch stirred cell using Amicon XM50, XM300, YM 100 ultrafiltration membranes with molecular weight cut-offs of 50 kDa, 300 kDa and 100 kDa, respectively, and Sartorius microfiltration membranes with a nominal pore size of 0.2 μm. Humic substances were extracted from a commercial sample of sphagnum peat from Northern Ireland (Bulrush). In the presence of Ba2+ cations, the HA rejection in the solutions containing HA and BSA was higher compared to the solutions containing Na+ cations. Unlike monovalent cations, divalent cations interact specifically with natural organic matter (NOM) and form metal humic complexes. The binding of divalent cations with natural organic matter is responsible for the development of a dense layer on the membrane surface. Metal cations may also act as a bridge between humic acid and protein. These phenomena result in a higher deposition of substances on the membrane surface leading to lower flux and higher rejection in the presence of divalent metal cations. In addition to the charge, the size of cation plays a role in the deposition process. The solutions containing MgCl2·6H2O are characterizing by higher flux and lower rejection compared to the solution containing BaCl2·2H2O at all ultrafiltration membranes. This phenomenon may be attributed to the size of Mg2+ and Ba2+ ions. [ABSTRACT FROM AUTHOR]

Climate change has strong impacts on soil conservation and agricultural productivity, with severe consequences on smallholders in developing countries, but virtually no research has been carried out so far on this issue. Therefore, it is necessary to foster the implementation of participatory projects to help communities deal with new difficulties. Sustainable soil management can reduce and even reverse land degradation, helping farmers to adapt to climate change effects. Progress toward sustainability cannot be implemented in small rural communities regardless of local knowledge, which can be addressed using participatory techniques. To this purpose the choice and use of indicators is essential to carry out correct assessments of soil vulnerability integrating local and technical knowledge. The purpose of this review was to study how the problem of building a set of integrated indicators to assess soil quality has been addressed so far and which participatory techniques have been more successfully employed, analyzing studies carried out in rural communities of developing countries. We found out that there is a lack of participated studies dealing with environmental issues. Those that do so address them only indirectly, being centered on present agricultural problems. The studies rarely feature a collaboration with social science experts, consequently the use of participatory techniques lacks protocols and a standardized nomenclature to help in the transfer and generalization of experiences. Women are rarely involved and nearly exclusively in African countries: this could be related to social and cultural conditions, but needs more attention. Different aspects need to be improved to help the implementation of a successful approach in future projects. This review provides a tool to facilitate future interdisciplinary research on integration of local and scientific knowledge and will help to devise more successful strategies to tackle the challenges posed by climate change to smallholders in developing countries. [ABSTRACT FROM AUTHOR]