Evaluation of terrestrial plants extracts for uranium sorption and characterization of potent phytoconstituents

Sorption capacity of four plants (Funaria hygrometrica, Musa acuminata, Brassica juncea and Helianthus annuus) extracts/fractions for uranium, a radionuclide was investigated by EDXRF and tracer studies. The maximum sorption capacity, i.e., 100% (complete sorption) was observed in case of Musa acuminata extract and fractions. Carbohydrate, proteins, phenolics and flavonoids contents in the active fraction (having maximum sorption capacity) were also determined. Further purification of the most active fraction provided three pure molecules, mannitol, sorbitol and oxo-linked potassium oxalate. The characterization of isolated molecules was achieved by using FTIR, NMR, GC-MS, MS-MS, and by single crystal-XRD analysis. Of three molecules, oxo-linked potassium oxalate was observed to have 100% sorption activity. Possible binding mechanism of active molecule with the uranyl cation has been purposed.     

光照强度对小麦苗期草酸氧化酶活性的影响

以小麦品种‘烟优361’(Triticum aestivum L.cv.Yanyou 361)萌发4 d幼苗为试验材料,分析了草酸氧化酶(OxO)在幼苗中的定位和表达,以及光照强度处理对小麦幼苗OxO活性的影响。实验结果显示,萌发后小麦幼苗的OxO分布在子叶与根的连接处和成熟的根中,其活性随光照强度的增加而下降;200μmol.m-2.s-1的强光显著抑制了OxO活性,该处理培养4 d幼苗的OxO活性仅为40μmol.m-2.s-1光照培养条件下的18.7%;强光还缩短OxO在苗期的表达时间,抑制了OxO的mRNA表达量。同时,光照强度还能影响小麦幼苗中H2O2的含量,200μmol.m-2.s-1处理幼苗的H2O2的含量显著下降,其培养4 d的幼苗H2O2含量仅为40μmol.m-2.s-1光照强度培养条件下的18.0%。研究发现,光照强度可通过调节OxO的活性和表达量来控制H2O2的产量,从而影响幼苗的生长发育。     

光呼吸代谢物乙醇酸、乙醛酸和草酸对烟草叶片硝酸还原的影响

乙醇酸、乙醛酸和草酸能明显促进烟草(Nicotiana rustica)叶片在黑暗中的硝酸还原,光呼吸抑制剂a-羟基吡啶甲烷磺酸能消除前二者的促进作用而不能完全消除草酸的作用。草酸+NAD~+能显著促进离体的硝酸还原。烟叶提取液加入草酸和NAD~+后生成NADH和CO_2认为活体内由乙醛酸氧化生成的草酸是经脱氢生成NADH供硝酸还原之用。未能证明在烟叶内存在乙醇酸脱氨酶,因此排除由乙醇酸直接脱氢以还原硝酸的可能。     

The beneficial effect of aluminium and the role of citrate in Al accumulation in Melastoma malabathricum

* Here we investigated the beneficial effect of aluminium (Al) on the development of the Al accumulating plant Melastoma malabathricum. * Seedlings of M. malabathricum were cultivated in a nutrient solution containing 0.5 mM Al and compared with barley (Hordeum vulgare). In addition, roots of M. malabathricum were divided into one part growing in a nutrient solution, and the other part growing in a calcium solution. Al (0.5 mM) was applied to either solution. * Al-induced improvements of the root activity contributed to a growth enhancement in M. malabathricum. Al exposure without nutrients did not increase root growth and Al accumulation in the leaves. The beneficial effect, however, was induced by the combination of Al and nutrients. * We suggest that without nutrients roots are not able to synthesize an adequate amount of citrate that is required for transporting Al to the leaves. High Al levels in the plant tissues and/or an interaction of Al with particular nutrient elements in the apoplast of root cells appear to be essential to exert the beneficial effect of Al.     

Aerobic reduction of manganese oxide by Salmonella sp. strain MR4

A new isolate of Salmonella, strain MR4, reduced Mn(IV)O₂ at 2.3 mM under aerobic conditions by about 83% over 24 h. Direct contact of cells to MnO₂ was not necessary as the cell-free spent medium produced a similar amount of Mn(II). Pyruvate (1.6 mM) and oxalate (0.8 mM) were identified in the culture medium and presumed to have a role in Mn(II) production in this microorganism.     

Cell and calcium oxalate crystal growth is coordinated to achieve high-capacity calcium regulation in plants

Summary Crystal idioblasts are cells which are specialized for accumulation of Ca²⁺ as a physiologically inactive, crystalline salt of oxalic acid. Using microautoradiographic, immunological, and ultrastructural techniques, the process of raphide crystal growth, and how crystal growth is coordinated with cell growth, was studied in idioblasts ofPistia stratiotes. Incorporation of⁴⁵Ca²⁺ directly demonstrated that, relative to surrounding mesophyll cells, crystal idioblasts act as high-capacity Ca²⁺ sinks, accumulating large amounts of Ca²⁺ within the vacuole as crystals. The pattern of addition of Ca²⁺ during crystal growth indicates a highly regulated process with bidirectional crystal growth. In very young idioblasts,⁴⁵Ca²⁺ is incorporated along the entire length of the needle-shaped raphide crystals, but as they mature incorporation only occurs at crystal tips in a bidirectional mode. At full maturity, the idioblast stops Ca²⁺ uptake, although the cells are still alive, demonstrating an ability to strictly regulate Ca transport processes at the plasma membrane. In situ hybridization for ribosomal RNA shows young idioblasts are extremely active cells, are more active than older idioblasts, and have higher general activity than surrounding mesophyll cells. Polarizing and scanning electron microscopy demonstrate that the crystal morphology changes as crystals develop and includes morphological polarity and an apparent nucleation point from which crystals grow bidirectionally. These results indicate a carefully regulated process of biomineralization in the vacuole. Finally, we show that the cytoskeleton is important in controlling the idioblast cell shape, but the regulation of crystal growth and morphology is under a different control mechanism.Abbreviation SEM scanning electron microscopy     

Structural features of mycorrhizal associations in two members of the Monotropoideae, Monotropa uniflora and Pterospora andromedea

Species in the subfamily Monotropoideae (family Ericaceae) are achlorophyllous and myco-heterotrophic. They have become highly specialized in that each plant species is associated with a limited number of fungal species which in turn are linked to autotrophic plants. This study provides an updated and comprehensive examination of the anatomical features of two species that have recently received attention with respect to their host-fungal specificity. Root systems of Monotropa uniflora and Pterospora andromedea collected from the field were characterized by light microscopy and scanning electron microscopy. All roots of both species were associated with fungi, each root having a well-developed mantle, paraepidermal Hartig net, and intracellular fungal pegs within epidermal cells. The mantle of M. uniflora was multi-layered and numerous outer mantle hyphae developed into cystidia of two distinct morphologies. Large calcium oxalate crystals were present, primarily on the mantle surface. The outer mantle of P. andromedea was more loosely organized, lacked cystidia, and had smaller plate-like as well as cylindrical crystals on the surface and between outer mantle hyphae. Fungal pegs in M. uniflora originated from inner mantle hyphae that penetrated the outer tangential wall of epidermal cells; in P. andromedea, these structures were initiated either from inner mantle hyphae or Hartig net hyphae and penetrated radial walls of epidermal cells. With respect to function, fungal pegs occurred frequently in both host species and, although presumed to be the sites of active nutrient exchange, no direct evidence exists to support this. Differences between these two monotropoid hosts, resulting from the mycorrhizal fungi with which each associates, are discussed.     

Role of glutathione on renal mitochondrial status in hyperoxaluria

Role of glutathione on kidney mitochondrial integrity and function during stone forming process in hyperoxaluric state was investigated in male albino rats of Wistar strain. Hyperoxaluria was induced by feeding ethylene glycol (EG) in drinking water. Glutathione was depleted by administering buthionine sulfoximine (BSO), a specific inhibitor of glutathione biosynthesis. Glutathione monoester (GME) was administered for supplementing glutathione. BSO treatment alone or along with EG, depleted mitochondrial GSH by 40% and 51% respectively. Concomitantly, there was remarkable elevation in lipid peroxidation and oxidation of protein thiols. Mitochondrial oxalate binding was enhanced by 74% and 129% in BSO and BSO + EG treatment. Comparatively, EG treatment produced only a 33% increase in mitochondrial oxalate binding. Significant alteration in calcium homeostasis was seen following BSO and BSO + EG treatment. This may be due to altered mitochondrial integrity and function as evidenced from decreased activities of mitochondrial inner membrane marker enzymes, succinate dehydrogenase and cytochrome-c-oxidase and respiratory control ratio and enhanced NADH oxidation by mitochondria in these two groups. NADH oxidation (r = -0.74) and oxalate deposition in the kidney (r = -0.70) correlated negatively with mitochondrial glutathione depletion. GME supplementation restored normal level of GSH and maintained mitochondrial integrity and function, as a result of which oxalate deposition was prevented despite hyperoxaluria. These results suggest that mitochondrial dysfunction resulting from GSH depletion could be a contributing factor in the development of calcium oxalate stones.