Plant morphophysiological and anatomical factors associated with nitrous oxide flux from wheat (Triticum aestivum)

Experiments were conducted to study the dynamics of nitrous oxide (N?O) emission from wheat varieties viz., Sonalika, HUW 468, HUW 234 and DBW 14 grown in alluvial soils of North Bank Plain Agroclimatic Zone of Assam, India. Attempts were made to find out the relationship of N?O emission with plant morphophysiological, anatomical and soil properties. N?O fluxes from wheat varieties ranged from 40 μg N?O-N m?2 h?1 to 295 μg N?O-N m?2 h?1. Soil organic carbon and soil temperature have shown significant relationship with N?O flux. The rate of leaf transpiration recorded from the wheat varieties at different growth stages exhibited a positive correlation with N?O emission suggesting that movement of N?O along with the transpirational water flow may be an important mechanism of N?O transport and emission through wheat plants. Anatomical investigation by scanning electron microscope revealed that N?O emission has relationship with stomatal frequency of leaf and leaf sheaths. Variety HUW 234 with the highest stomatal frequency of leaf and leaf sheath also recorded higher seasonal N?O emission compared to other varieties. Seasonal N?O emission (E(sif)) of the varieties ranged from 3.25 to 3.81 kg N?O-N ha?1. Significant variations in E(sif) values were recorded within the varieties.     

Biophysical characterization and molecular modeling of the coordinative-intercalative DNA monoadduct of a platinum-acridinylthiourea agent in a site-specifically modified dodecamer

The guanine-N7 monoadduct of [Pt(en)Cl(ACRAMTU)](NO₃)₂ (PT-ACRAMTU; en=ethane-1,2-diamine, ACRAMTU=1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea), a dual metalating/intercalating cytotoxic agent, was generated in a double-stranded dodecamer, d(CCTCTCG*TCTCC/GGAGACGAGAGG) (III*), and isolated by preparative reverse-phase high-performance liquid chromatography (HPLC). The adduct was characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), circular-dichroism spectropolarimetry (CD), UV-melting curves, and NMR spectroscopy. In addition, a molecular mechanics/restrained molecular dynamics (MM/rMD) study was performed for this adduct using the AMBER force field. Monoadduction of the sequence leads to a pronounced increase in melting temperature, T_m=T_m(III*)–T_m(III)=9.7 °C. Because there is complete enthalpy–entropy compensation, binding occurs without noticeable thermodynamic destabilization. This feature and the CD (induced-ligand circular dichroism) and NMR (upfield shifts of aromatic acridine proton signals) data are indicative of a unique, nondenaturing dual-binding mode that involves partial intercalation of the acridine chromophore. An energy-minimized AMBER model of III* demonstrates that platination of G7-N7 of guanine in the major groove and partial insertion of the acridine moiety into the C6G19/G7C18 base step on the 5 face of the modified purine base is feasible and supportive of the experimental results. Differences in the biophysical properties between III* and duplexes containing adducts of the clinical-drug cisplatin are outlined, and possible biological consequences are discussed.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00775-004-0534-3Abbreviations ACRAMTU 1-[2-(acridin-9-ylamino)ethyl]-1,3-dimethylthiourea - dGuo 2-deoxyguanosine - dGuo* [Pt(en)(ACRAMTU-S)(dGuo-N7)]³⁺ - en ethane-1,2-diamine - ICD Induced circular dichroism - MALDI-TOF MS Matrix-assisted laser desorption ionization time-of-flight mass spectrometry - MM Molecular mechanics - PIPES 1,4-piperazinediethanesulfonic acid - PT-ACRAMTU [Pt(en)Cl(ACRAMTU)](NO₃)₂ - rMD Restrained molecular dynamics     

High frequency plant regeneration of Cymbopogon martinii (Roxb.) Wats by somatic embryogenesis and organogenesis

Embryogenic callus cultures were obtained upon repeated sub-culture of non-embryogenic callus from nodal segments of Cymbopogon martinii (Roxb.) Wats. Murashige and Skoog's medium supplemented with 1mg/l 2,4-dichlorophenoxyacetic acid and 0.5 mg/l kinetin and Linsmaier and Skoog's medium supplemented with 2mg/l 2,4-dichlorophenoxyacetic acid and 0.4 mg/l kinetin were used as maintenance media for non-embryogenic and embryogenic cultures, respectively. Plant regeneration occurred through organogenesis in MS basal media containing 2 mg/l kinetin, 1 mg/l 6-benzylaminopurine, 0.2 mg/l biotin, 0.2 mg/l Ca-pantothonate and 0.1 mg/l napthalene acetic acid. Embryogenesis was induced in LS medium supplemented with 1 mg/l kinetin, 0.5 mg/l 6-benzylaminopurine and 0.1 mg/l 3-indole acetic acid. Plant regeneration at high frequency was recorded both through organogenesis and embryogenesis in different passages of long term callus cultures.Abbreviation MS Murashige and Skoog medium - LS Linsmair and Skoog medium - BAP 6-benzylaminopurine - kin kinetin - 2,4-D 2,4-Dichlorophenoxyacetic acid - IAA Indole-3-acetic acid - CH Casein hydrolysate - CaP calcium pantothonate - NAA napthalene acetic acid     

Factors limiting the microbial conversion of sterols to 17-ketosteroids in the presence of metal chelate inhibitors

Bioconversion of sterols to 17-ketosteroids by anArthrobacter species occurred in the presence of hydrophobic metal-chelating agents but the production of 17-ketosteroids (17-KS) was seriously limited by the rapis loss of the viability of cells in the presence of these inhibitors. Besides, the conversion was inhibited by 17-KS at concentrations of 500 ppm or more. The 17-KS formed consisted exclusively of l,4-androstadiene-3,17-dione (ADD) and 4-androstene-3, 17-dione (AD) and these were found in the extracellular medium predominantly in bound form or as molecular aggregates which may limit their accumulation. It was concluded that enhanced production of 17-KS could be achieved by protecting the viability of cells and by removing the steroid metabolites from the site of inhibition.     

A kinetic model for microbial growth on liquid hydrocarbons

A kinetic model is presented to explain microbial growth using liquid n-alkanes as substrate. The model is based on the assumption that growth occurs on the soluble alkane and that the metabolite produced by the growing cells helps the dissolution of liquid alkanes in the aqueous medium. Growth curves based on that model fit well with growth data for batch and continuous culture reported by various authors. The model also explains the differences between the relative length of exponential and linear phases of growth reported earlier.     

Predominant role of hydrocarbon solubilization in the microbial uptake of hydrocarbons

Using EDTA and proteolytic enzymes to suppress hydrocarbon solubilization, direct evidence is presented in support of the mechanism of liquid hydrocarbon uptake by microbial cells predominantly from the solubilized or accommodated substrate. EDTA (2-5mM) strongly inhibited growth of three yeast species and one bacterial species on n-hexadecane and the inhibition was removed by surfactant-emulsified and surfactant-solubilized alkane and also by excess addition of Ca(2+). EDTA had no inhibitory effect on the growth of the organisms on soluble substrates such as sodium acetate and nutrient broth or on n-pentane, a volatile alkane which was primarily transported by diffusion from gas phase. EDTA was shown to have no significant effect on the adsorption of cells on alkane drops. EDTA inhibition of growth was considered to be due to suppression of alkane solubilization, brought about by the solubilizing factor(s) produced by cells. It was shown that this chelating agent did not inhibit the growth of yeast on solubilized alkane but strongly inhibited its growth on alkane drops. It was demonstrated that adherent capacity of microbial cell to oil phase was closely related to the state of hydrocarbon emulsification and had no relationship to the ability of organisms to grow on hydrocarbon. Certain proteolytic enzymes inhibited the growth of yeast on alkane, presumably by digesting the alkane solubilizing protein, but not on glucose, and the inhibition was removed by a supply of surfactant-emulsified and surfactant-solubilized alkane. Specific solubilization of various hydrocarbon types during growth of the prokaryotic bacterial strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited by EDTA, and the inhibition was removed by excess Ca(2+). It was concluded that specific solubilization of hydrocarbons is an important mechanism in the microbial uptake of hydrocarbons.     

Comparative Utilization of Paraffins by a Trichosporon Species

Utilization of normal and isoparaffins, separately and in mixtures, by a Trichosporon sp. was investigated. From a mixture of normal paraffins and isoparaffins, the organism consumed straight-chain paraffins, leaving the branched paraffins relatively unchanged. When offered separately, the highest utilization of n-alkanes by the organism was obtained in the range of undecane to octadecane; n-pentadecane was poorly utilized. From a mixture of n-alkanes, the rate of consumption of shorter-chain alkanes, n-decane to n-dodecane, was found to be relatively faster and more uniform than that of longer-chain alkanes.     

Ascopore formation in yeasts during active growth on hydrocarbons

Summary Induction of ascospore formation in hydrocarbon utilizing ascosporogenous yeasts was observed during the growth of the yeasts on gas oil, diesel oil, white kerosene and n-alkanes. Studies of relationships between cell morphology and cell growth showed that ascospores were formed during the active growth phase on gas oil but not on glucose. Contact of yeast cells with hydrocarbons may be the possible reason for sporogenesis on hydrocarbons.     

Flavonoids from Millettia pulchra

Chemical examination of Millettia pulchra yielded (?)-maackiain, (?)-pterocarpin, (?)-sophoranone and the new compounds (6S, 6aS, 11aR)-6α-methoxypterocarpin, (6S, 6aS,11aR)-6α-methoxyhomopterocarpin, (2S)5,7,4′-trihydroxy-8,3′,5′-triprenylflavanone, (2R,3R)7,4′-dihydroxy-8,3′,5′-triprenyldihydroflavanol, 5,7,2′,4′-tetrahydroxy-6,3′-diprenylisoflavone and 5,7,4′-trihydroxy-2′-methoxy-6,3′-diprenylisoflavone.     

Clerodanes from solidago virgaurea

The isolation and structure determination of four known and eight new cis-clerodane lactones from the aerial parts of Solidago virgaurea are described.