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Phase relations in the subsolidus area of the MgO–P2O5–Cr2O3 system were reinvestigated. The reactions were carried out by the method of multi-stage calcination of samples in the temperature range of 350–1150 °C. As a result of the conducted research, a new pyrophosphate with the formula Mg5Cr2 (P2O7)4 was discovered. This compound, crystallizing in the orthorhombic system, most likely exhibits the Fe52+Fe23+ (P2O7)4 structure. The infrared spectrum of the new pyrophosphate was presented. Mg5Cr2 (P2O7)4 melts incongruently at 1330 °C depositing Mg3Cr4 (PO4)6. The developed division of the MgO–P2O5–Cr2O3 system into subsidiary subsystems differs significantly from the one known from the literature. First of all, unlike in the literature, it takes into account the existence of the compound just discovered, as well as the other two phosphates, i.e. Mg3Cr4 (PO4)6 and Cr2P4O13. The melting points of mixtures of phases coexisting in the equilibrium state were estimated by the pyrometric method. All phosphates (V) with mixed cations, i.e. Mg5Cr2 (P2O7)4, Mg3Cr4 (PO4)6 and MgCr2 (P2O7)2, were tested for their use for colouring lead-free glaze fired once at 1050 °C. It turned out that the investigated phosphates act as dyes and ceramic layers of good quality and interesting colours were obtained. The optimal concentration of the applying phosphates was close to 3 mass%. [ABSTRACT FROM AUTHOR]

A study was conducted to further develop our understanding of antimony (Sb) uptake in plants. Unlike other metal(loid)s, such as silicon (Si), the mechanisms of Sb uptake are not well understood. However, SbIII is thought to enter the cell via aquaglyceroporins. We investigated if the channel protein Lsi1, which aids in Si uptake, also plays a role in Sb uptake. Seedlings of WT sorghum, with normal silicon accumulation, and its mutant (sblsi1), with low silicon accumulation, were grown in Hoagland solution for 22 days in the growth chamber under controlled conditions. Control, Sb (10 mg Sb L−1), Si (1mM) and Sb + Si (10 mg Sb L−1 + 1 mM Si) were the treatments. After 22 days, root and shoot biomass, the concentration of elements in root and shoot tissues, lipid peroxidation and ascorbate levels, and relative expression of Lsi1 were determined. When mutant plants were exposed to Sb, they showed almost no toxicity symptoms compared to WT plants, indicating that Sb was not toxic to mutant plants. On the other hand, WT plants had decreased root and shoot biomass, increased MDA content and increased Sb uptake compared to mutant plants. In the presence of Sb, we also found that SbLsi1 was downregulated in the roots of WT plants. The results of this experiment support the role of Lsi1 in Sb uptake in sorghum plants.

The research presented in this study aimed to document the variability of synthetic lead antimonate pigments known as Naples yellow in selected artworks by Czech landscape painters from the turn of the 20th century. Spectra obtained through Raman spectroscopy show considerable difference in the position of main band maximum (from 110 to 145 cm−1) characteristic of cubic pyrochlore structure Pb2Sb2O7—the major phase of the Naples yellow pigment. In several samples, hexagonal PbSb2O6 with main band at 655 cm−1 was identified as a dominant phase, a finding that is somewhat surprising because PbSb2O6 has been generally considered a minor admixture to cubic Pb2Sb2O7. Reference pigment samples were synthesised under known conditions, and their spectra were collected in order to get more comparative material. Also, commercially available Naples yellow pigments were characterised in the same way. We observed considerable differences of the obtained spectra caused by the presence of admixtures and diverse production conditions. The diversity of Naples yellow and the corresponding Raman spectra makes their identification problematic. Presented data thus may serve as a reference material in the identification process. [ABSTRACT FROM AUTHOR]

Effect of beauvericin on root cell transmembrane electric potential (EM), electrolyte leakage and respiration of roots were studied in two maize cultivars (Zea mays L.) with different susceptibility to this toxigenic metabolite produced by Fusarium. Beauvericin treatment induced rapid and significant depolarisation of membrane potentials of the outer cortical cells of maize roots of tolerant cv. Lucia. The range of depolarisation was dose dependent with maximum depolarisation of 55 mV (55 ± 7 mV, n = 7) at 200µM beauvericin. In contrast, membrane potentials of beauvericin susceptible cv. Pavla was only slightly depolarised by identical concentrations of beauvericin and the value of depolarisation represented only half of the value of tolerant cv. Lucia (27 ± 6 mV, n = 8). The values of membrane potentials of root cells of tolerant cv. Lucia were higher (137 ± 9 mV, n = 26) and more electrogenic (60 ± 2 mV, n = 3) than in susceptible cv. Pavla (125 ± 7 mV, n = 28), (47 ± 2 mV, n = 3), respectively. Our results confirmed that 2 h treatment with 50µM beauvericin does not cause irreversible changes in plasma membrane H+-ATPase, because fusicoccin, an H+-ATPase activator diminished the depolarizing effect of beauvericin on the EM. Further experiments revealed beauvericin-induced increase of membrane conductivity in root cells of Pavla but not in root cells of Lucia. Time-coarse experiments showed that 25µM beauvericin induced slight, but significant inhibition of root respiration in both cultivars during the first two hours of treatment, and the inhibition was higher in cv. Lucia than in cv. Pavla. The depolarisation of EM in the outer cortical cells of maize roots may be the result of a cumulative effect of beauvericin on ATP supply, activity of H+-ATPase and mainly on the permeability of plasmalemma. Increased beauvericin tolerance in maize might be associated with the increased ability of tolerant plant to maintain normal ion fluxes and membrane potentials across the plasmalemma of root cells in the presence of beauvericin.

The effect of osmotic stress on oxidative injury, compatible solutes content and water relations was investigated in two maize cultivars (Zea mays L. cv. Ankora - drought-sensitive and cv. Nova - drought-tolerant). Relative water content in leaves of both cultivars decreased after drought treatment, leaf water loss of sensitive cv. Ankora was higher than that of cv. Nova. The 24 h water stress induced by 0.3M sorbitol (-1.4 MPa) resulted in a damage of cell membranes. Lipid peroxidation rose in all studied organs of cv. Ankora and electrolyte leakage in roots of cv. Ankora was much higher than in cv. Nova. Similarly, proline content increased significantly in all studied organs of cv. Ankora. Content of soluble sugars increased in all studied organs of both cultivars, but the mesocotyl of cv. Nova accumulated the highest amount of sugars. The electrolyte leakage was the highest in the roots of both cultivars. Osmotic stress had deep influence predominantly on the roots of both cultivars. It is apparent that stress impact on the drought-sensitive cv. Ankora was deeper than on the drought-tolerant cv. Nova.

Natural non-metallics, including granitoide and quartz sands, often contain iron which decreases the whiteness of these raw materials. Insoluble Fe3+ in these samples could be reduced to soluble Fe2+ by bacteria of Bacillus spp. and Saccharomyces spp. The leaching effect, observed by the measurement of Fe2+concentration in a solution, showed higher activities of a bacterial kind isolated from the Bajkal lake and also by using of yeast Saccharomyces sp. during bioleaching of quartz sands. However, allkinds of Bacillus spp. isolated from the Slovak deposit and from Bajkal lake were very active in the iron reduction during bioleaching of the feldspar raw material. This metal was efficiently removed from quartz sands as documented by the Fe2O3 decrease (from 0,317 % to 0,126 %) and from feldpars raw materials by the Fe2O3 decrease (from 0,288 % to 0,115 %) after bioleaching. The whiteness of these non-metallics was increased during a visual comparison of samples before and after bioleaching but samples contain selected magnetic particles. A removal of iron as well as a release of iron minerals from silicate matrix should increase the effect of the magnetic separation and should give a product which is suitable for industrial applications.