摘要：
The ZnO nanorods (diameter of 40 nm and 100 nm) were modified with Ru(dcbpy)(2)(NCS)(2) (RuN3), and their responses to formaldehyde were measured at room temperature. All the results showed that the responses to formaldehyde of modified ZnO were higher than that of bare ZnO; especially the responses of modified ZnO nanorods with diameter of 40 nm-5 ppm formaldehyde was about 200% higher than that of bare ZnO. The UV-vis absorption spectrum and transient photovoltage analysis showed that the high responses of modified ZnO mainly arose from the strong photocatalytic oxidizing effect induced by the increasing of the absorption and photo-generated electron-hole separation. Our results demonstrate that the modification of RuN3 is a promising approach on improving the formaldehyde responses of ZnO nanorods. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
摘要：
The volatile microbial metabolite 2-methylisoborneol (2-MIB) is a root cause of taste and odor issues in freshwater. Although current evidence suggests that 2-MIB is not toxic, this compound degrades water quality and presents problems for water treatment. To address these issues, cyanobacteria and actinomycetes, the major producers of 2-MIB, have been investigated extensively. In this study, two 2-MIB producing strains, coded as Pseudanabaena sp. and Planktothricoids raciborskii, were used in order to elucidate the genetic background, light regulation, and biochemical mechanisms of 2-MIB biosynthesis in cyanobacteria. Genome walking and PCR methods revealed that two adjacent genes, SAM-dependent methyltransferanse gene and monoterpene cyclase gene, are responsible for GPP methylation and subsequent cyclization to 2-MIB in cyanobacteria. These two genes are located in between two homologous cyclic nucleotide-binding protein genes that may be members of the Crp-Fnr regulator family. Together, this sequence of genes forms a putative operon. The synthesis of 2-MIB is similar in cyanobacteria and actinomycetes. Comparison of the gene arrangement and functional sites between cyanobacteria and other organisms revealed that gene recombination and gene transfer probably occurred during the evolution of 2-MIB-associated genes. All the microorganisms examined have a common origin of 2-MIB biosynthesis capacity, but cyanobacteria represent a unique evolutionary lineage. Gene expression analysis suggested that light is a crucial, but not the only, active regulatory factor for the transcription of 2-MIB synthesis genes. This light-regulated process is immediate and transient. This study is the first to identify the genetic background and evolution of 2-MIB biosynthesis in cyanobacteria, thus enhancing current knowledge on 2-MIB contamination of freshwater.
摘要：
The study was conducted to investigate the effects of applying different concentrations of the macronutrients K+,Ca2+,and Mg2+on the responses of contrasting rice(Oryza sativa L.)genotypes under salt stress.A solution culture experiment was conducted in a phytotron at the International Rice Research Institute(IRRI),under controlled temperature and humidity and natural sunlight.When subjected to salt stress of 100 mmol L-1 using NaCl,the salt tolerant genotypes FL478 and IR651,accumulated less Na+and maintained lower ratios of Na+/K+,Na+/Ca2+,and Na+/Mg2+than the sensitive genotypes IR29 and Azucena.These tolerant genotypes also had higher concentrations of K+in their shoots and greater root and shoot biomass and green leaf area.Tolerant genotypes also maintained much lower concentration of Na+and lower and more favorable ratios of Na+/K+,Na+/Ca2+,and Na+/Mg2+in their active and developing tissues.Salt tolerance and shoot and root growth of both tolerant and sensitive genotypes were enhanced considerably when higher concentrations of Ca2+and Mg2+were applied in culture solution.The concentration of Na+and the ratios of Na+/K+,Na+/Ca2+,and Na+/Mg2+ in shoots also declined significantly.The beneficial effects of higher calcium were greater than that of magnesium and application of higher concentration of K+seems to have minor effects.Responses to salinity in rice can therefore be considerably enhanced through proper nutrient management,by increasing the concentrations of nutrient elements that have favorable effects such as Ca2+and Mg2+.Calcium is particularly more effective than both magnesium and potassium,and can be applied at relatively larger quantities in salt affected soils.
摘要：
To define the molecular response of Acidithiobacillus ferrooxidans under pH up-shift, temporal gene expression profiles were examined by using whole-genome DNA microarrays for A. ferrooxidans. Approximately 30% of the 3,132 genes represented on the microarray were significantly upregulated over a 160-min period, while about 14% were significantly downregulated. Our results revealed that A. ferrooxidans showed potential self-protection and self-regulation performance in response to pH up-shift stress. Many genes involved in regulation of membrane components were differentially expressed under the pH up-shift stress. Likewise, most of genes involved in phosphate metabolism, sulfur assimilation, and CO2 fixation were obviously induced. Conversely, the transcription of a polyphosphate kinase gene (AFE1210) associated with phosphate storage was significantly repressed, which probably stemmed from the depletion of polyphosphate. Besides, most of the genes involved in hydrogen uptake were significantly induced, whereas many genes involved in nitrogen fixation were obviously repressed, which suggested that hydrogen uptake and nitrogen fixation could contribute to cytoplasmic pH homeostasis.
摘要：
BACKGROUND, AIM, AND SCOPE: Ferro-cyanide is one of the commonly found species at cyanide-contaminated soils and groundwater. Unlike botanical metabolism of KCN via the beta-cyanoalanine pathway, processes involved in the plant-mediated assimilation of ferro-cyanide are still unclear. The objective of this study was to investigate a possible mechanism involved in uptake and assimilation of ferro-cyanide by plants. MATERIALS AND METHODS: Detached roots of plants were exposed to ferro-cyanide in a closed-dark hydroponic system amended with HgCl(2), AgNO(3), LaCl(3), tetraethylammonium chloride (TEACl), or Na(3)VO(4), respectively, at 25 +/- 0.5 degrees C for 24 h. Total CN, free CN(-), and dissolved Fe(2+) were analyzed spectrophotometrically. Activity of beta-cyanoalanine synthase involved in cyanide assimilation was also assayed using detached roots of plants in vivo. RESULTS: Dissociation of ferro-cyanide [Fe(II)(CN)(6)](-4) to free CN(-) and Fe(2+) in solution was negligible. The applied inhibitors did not show any significant impact on the uptake of ferro-cyanide by soybean (Glycine max L. cv. JD 1) and hybrid willows (Salix matsudana Koidz x alba L.; p > 0.05), but rice (Oryza sativa L. cv. JY 98) was more susceptible to the inhibitors compared with the controls (p < 0.05). However, TEACl had the most severe effect on the assimilation of ferro-cyanide by soybean, hybrid willows, and maize (Zea mays L. cv. PA 78; p < 0.01), whereas AgNO(3) was the most sensitive inhibitor to rice (p < 0.01). No measurable difference in beta-cyanoalanine synthase activity of roots exposed to ferro-cyanide was observed compared with the control without any cyanides (p > 0.05), whereas roots exposed to KCN showed a considerable increase in enzyme activity (p < 0.05). CONCLUSIONS: Plants take up Fe(2+) and CN(-) as a whole complex, and in vivo dissociation to free CN(-) is not prerequisite during the botanical assimilation of ferro-cyanide. Ferro-cyanide is likely metabolized by plants directly through an unknown pathway rather than the beta-cyanoalanine pathway.
摘要：
The potential for photo-induced dissociation of ferri- and ferro-cyanide was investigated. The overall reactions followed first order kinetics, judged by the free cyanide analyzed in aqueous solution. The dissociation rates for ferri- and ferro-cyanide were mathematically described by the equations: C
(CN,t) = C
(CN,O)e1.3t
and C
(CN,t) = C
(CN,O)e0.39t
, respectively. In addition, photo-induced dissociation of both iron cyanides was enhanced under an alkaline environment than a neutral condition. Results from the temperature-dependent tests indicated that the dissociation rate of ferri- cyanide was significantly higher than that of ferro-cyanide at all treatment temperatures. The kinetic parameter, activation energy (E
a
) was also experimentally determined to be 12.02 and 12.32 kJ/mol for ferri- and ferro-cyanide, respectively. The results obtained suggest that both iron cyanides are susceptible to photo-dissociation and the rates are positively correlated to the change of temperatures. The information collectively also has important implications for waste management of iron cyanides as well as for risk assessment in a field trial.
摘要：
The ZnO nanorods with different diameters (similar to 300, 100, 40 nm) and nanoparticles (similar to 6 nm) were prepared, and their sensitivities to formaldehyde at room temperature were measured with and without the UV light irradiation (the intensity of light is 0.155 mW/cm(2)). The XRD, TEM and SEM were utilized to examine the size of crystal and the morphology of material. The transient photovoltage and photoluminescence spectra were utilized to investigate the photoelectric properties of ZnO. The ZnO nanorods with diameter of similar to 40 nm own the highest response to formaldehyde with the UV light illumination than that of other samples. It is attributed to the large surface-to-volume ratio and high photo-generated charge efficiency, which are two key parameters to determine the gas response. The transient photovoltage results further demonstrate that the photo-generated charge efficiency of gas sensing element decreases as the surface-to-volume ratio increases (i.e. the size of crystal decreases). Therefore, the particles with highest sensitivity are of a certain size, neither the largest nor the smallest tested. Our work may supply a direction to fabricate the high performance gas sensor with UV light illumination. (C) 2010 Elsevier B.V. All rights reserved.
关键词：
Later growth period;nitrogen loss in plant;nitrogen redistribution;nitrogen-use efficiency;oilseed rape
摘要：
To determine the relationship between nitrogen (N) redistribution of oilseed rape (Brassica napus L.) varieties and N-use efficiency during later growth stages, the differences in N-use efficiency between two varieties (X-36 and X-50) were studied using the 15N labeling method with sand culture under complete nutrient solution conditions. Results showed that X-36 had greater grain yield not because of greater N uptake but because of greater grain yield per unit N in the plant and N-harvesting index. The average proportion of N in the two varieties that was redistributed from the vegetative organs to the grain was 65.1%. The redistribution amount and the proportion of N absorbed at the stem elongation stage and redistributed into the grain of two varieties were the greatest; the least were amounts absorbed at the siliquing stage. The high-N-use-efficiency variety (X-36), when compared with the low-N-use-efficiency variety (X-50), had slower redistribution speed of N before the siliquing stage, which then became faster after the siliquing stage. The amount of N redistributed to the grains and its proportion were larger, whereas those toward the silique husk were smaller. The amount of N loss from the plant and its proportion were smaller, and the velocity of N loss was also slower. This explains why varieties with high N efficiency have high N-harvesting index. At the later growth stages, N redistribution in the vegetative organs will significantly affect N-use efficiency.
摘要：
Differences of nitrogen efficiency of oilseed rape (Brassica napus L.) cultivars and their physiological properties were studied in a pot experiment, and the ratio of seed yield with no nitrogen supplied to that with normal nitrogen supply was adopted as a nitrogen efficiency coefficient. Results showed that the nitrogen efficiency coefficient determined for eight oilseed rape cultivars varied from 0.37 to 0.69, the ratio of nitrogen uptake amounts per plant, nitrogen transfer velocity from stems and leaves to seeds, and nitrogen physiological efficiency of oilseed rape cultivars under nitrogen stressed condition differed from with normal nitrogen supply. The higher the nitrogen efficiency of a cultivar, the higher the ratio of N uptake in no nitrogen to with N supplied. Under low nitrogen-supplying conditions, high nitrogen efficiency cultivars had longer roots, more lateral roots, higher amounts of reuse of nitrate from stem and leaves, and higher nitrate reductase activities in leaves.
摘要：
Two highly water-soluble amino acids,which derived fromβ-CDs,i.e.,glutamic acid-β-cyclodextrin(GluCD)and ethylene-diamine-β-cyclodextrin(EDCD),were synthesized and were examined for their effect on solubilization of anthracene(ANT),complexation of cadmium(Cd~(2+)),and elution removal of ANT and Cd~(2+)in soil.The results showed that GluCD and EDCD were powerful complexant for ANT and Cd~(2+).In the presence of 10 g/L GluCD and EDCD,the solubilization of ANT increased by 47.04 and 23.85 times compared to the control,respectively.GluCD resulted in approximately 90%complexation of Cd~(2+)while 70%complexation was observed for EDCD.Simultaneously,GluCD and EDCD could greatly enhance the elution removal of ANT and Cd~(2+)from soil.GluCD resulted in the highest elution effciency of ANT and Cd~(2+).With the addition of 10 g/L GluCD,53.5%of ANT and 85.6%of Cd~(2+)were eluted,respectively.The ANT had a negligible effect on the Cd~(2+)removal due to different complexing sites of ANT and Cd~(2+),while Cd~(2+)enhanced the ANT removal under the addition of GluCD because Cd~(2+)neutralized the-COOH group of GluCD.Adversely,the removal of ANT was decreased with Cd~(2+)under the addition of EDCD,this was due to the fact that Cd~(2+)enhanced the polarity of EDCD molecule and inhibited the complexation between ANT and EDCD.The study suggested that GluCD could be preferred and be successfully applied to remediation of heavy metals or organic compounds in contaminated soil
摘要：
In order to explore the mechanism of acute toxicity for pyrene to cyanobacterial organisms, the responses of Synechocystis sp. PCC 6803 photosystem II (PS II) under pyrene stress were studied. The results showed there was no significant difference about the oxygen evolution under 0.125 mg/L pyrene stress when compared with control, but it was significantly lower than control at 0.625 mg/L pyrene. Polyphasic chlorophyll-a fluorescence transients in cells of Synechocystis sp. PCC 6803 exhibited a typical increase including O, J, I, and P phases. Fluorescence yield at phases J, I and P declined slightly at 0.125 and 0.625 mg/L pyrene, and significantly lower than control at 3.125 mg/L. According to the parameters deviated from JIP-test, no modification was induced by pyrene both at the donor side and at the acceptor side of PS II, and the reaction centre of PS II is the primary damaging target. Based on the expressing of four key genes (psbA, psbB, psbC and psbO) of PS II, only psbA showed significant difference at 3.125 mg/L pyrene when compared with control.
摘要：
The removal of hexavalent and trivalent chromium from hydroponic solution by plants to changes in temperature was investigated. Pre-rooted hybrid willows (Salix matsudana Koidz x alba L.) were exposed to a nutrient solution spiked with potassium chromate (K2CrO4) or chromium chloride (CrCl3) for 4 days. Ten different temperatures were tested ranging from 11 to 32A degrees C. Total Cr in solutions and in plant materials were all analyzed quantitatively. The results revealed that large amounts of the applied Cr were removed from the hydroponic solution in the presence of the plants. Significantly faster removal of Cr(III) than Cr(VI) was achieved by hybrid willows from the hydroponic solutions at all temperatures (P < 0.01). The removal rates of both chemical forms of Cr by plants increased linearly with the increase of temperatures. The highest removal rate of Cr(VI) was found at 32A degrees C with a value of 1.99 mu g Cr/g day, whereas the highest value of Cr(III) was 3.55 mu g Cr/g day at the same temperature. Roots were the main sink for Cr accumulation in plants at all temperatures. Translocation of both chemical forms of Cr from roots to lower stems was only found at temperatures a parts per thousand yen24A degrees C. The temperature coefficient values (Q (10)) were 2.41 and 1.42 for Cr(VI) and Cr(III), respectively, indicating that the removal of Cr(VI) by hybrid willows was much more susceptible to changes in temperature than that of Cr(III). This information suggests that changes in temperature have a substantial influence on the uptake and accumulation of both chemical forms of Cr by plants.
