典型草原植物叶片金属元素吸收对氮添加的响应

为深入探讨氮沉降影响草原植物金属养分吸收及其与土壤养分的耦合关系,以内蒙古典型草原4种主要物种为研究对象,设置0、5、10、15 g N/(m^(2)·yr)4个氮添加处理,分析不同施氮量对草原物种及群落水平植物叶片盐基、微量元素含量和储量的影响。结果表明:(1)杂类草比禾本科植物具有更高的养分浓度;(2)不同金属养分对氮沉降的响应具有高度的物种特异性;植物群落叶片盐基元素含量对氮添加无显著响应且与土壤盐基离子相关性较低;随氮添加量的增加,叶片中Mn、Cu含量增加,但Fe含量降低,草原植物微量元素失衡严重主要受土壤微量养分有效性和元素拮抗作用的影响;(3)植物金属元素地上储量的饱和阈值出现在10 g N/(m^(2)·yr);优势物种地上生物量对氮添加的非线性响应是驱动植物元素地上储量变化的主要机制。

沙漠苔藓结皮层土壤风化淋溶特征探讨

土壤风化淋溶作用对土壤形成、发育具有特别重要的影响,而流动风沙土固定的显著特征就是地表形成生物土壤结皮层(BSC),并影响其养分循环和维管植物群落发育。因此,探讨BSC土壤风化淋溶变化特征对进一步认识BSC生态功能及其和风沙土发育的关系具有现实意义。采用野外典型样地取样和室内分析方法,研究了沙漠区人工固沙植被不同年龄下BSC土壤风化淋溶系数变化。结果表明,随着BSC形成时间的增加,BSC各盐基(SiO2除外)氧化物含量总体呈现出增加的趋势,并且高于对照风沙土;BSC土壤ba值逐渐增加,盐基淋溶较弱,并引起MgO、CaO含量的增加;相对于风沙土,BSC层土壤μ值、Saf值或Sa值逐渐降低,风化程度较强。干旱风沙环境下,BSC土壤存在着盐基淋溶和风化过程,其数据变化值则随着BSC形成时间增加而变好,成土作用明显,保肥能力强。

Effects of tachyplesin and n-sodium butyrate on proliferation and gene expression of human gastric adenocarcinoma cell line BGC-823

AIM： To investigate the effects of tachyplesin and n-sodium butyrate on proliferation and gene expression of human gastric adenocarcinoma cell line BGC-823. METHODS： Effects of tachyplesin and n-sodium butyrate on proliferation of BGC-823 cells were determined with trypan blue dye exclusion test and HE staining. Effects of tachyplesin and n-sodium butyrate on cell cycle were detected by flow cytometry. Protein levels of c-erbB-2, c-myc, p53 and p16 were examined by immunocytochemistry. RESULTS： The inhibiting effects were similar after 2.0 mg/L tachyplesin and 2.0 mmol/L n-sodium butyrate treatment, the inhibitory rate of cellular growth was 62.66% and 60.19% respectively, and the respective maximum mitotic index was decreased by 49.35% and 51.69% respectively. Tachyplesin and n-sodium buD/rate treatment could markedly increase the proportion of cells at G0/G1 phase and decrease the proportion at S phase. The expression levels of oncogene c-erbB-2, c-myc, and mtp53 proteins were down-regulated while the expression level of tumor suppressor gene p16 protein was up-regulated after the treatment with tachyplesin or n-sodium buD/rate. The effects of 1.0 mg/L tachyplesin in combination with 1.0 mmol/L n-sodium butyrate were obviously superior to their individual treatment in changing cell cycle distribution and expression of c-erbB-2, c-myc, mtp53 and p16 protein. The inhibitory rate of cellular growth of BGC-823 cells after combination treatment was 62.29% and the maximum mitotic index wasdecreased by 51.95%. CONCLUSION： Tachyplesin as a differentiation inducer of tumor cells has similar effects as n-sodium butyrate on proliferation of tumor cells, expression of correlative oncogene and tumor suppressor gene. It also has a synergistic effect on differentiation of tumor cells.

Enhancement of NH_4^+ Uptake by NO_3^- in Relation to Expression of Nitrate-Induced Genes in Rice (Oryza sativa) Roots

This study aimed to survey the expression of genes involved in rice N uptake and aasimilatory network and to understand the potential molecular mechanisms responsible for the NO3^-enhanced NH4^＋ uptake. By using quantitative real-time polymerase chain reaction （PCR）, the genes related to N nutrition, including ammonium transporters （AMTs） and ammonium assimilatory enzymes （GS and GOGAT）, were transcriptionally analyzed in rice plants grown in the absence and presence of NO4^- in the NH4^＋-containing medium. The results showed that NH4^＋ uptake by rice was enhanced by the NO3^- supply to the medium. At the same time and in parallel, the amount of transcripts of seven genes （OsAMT1;1, OsAMT1;2, OsAMT4;1, OsGLNP, OsGLU1, OsGLT1, and OsGLTP） was increased in rice roots, but the expression of two genes （OsGLN1;1 and OsGLN1;P） was decreased and that of OsAMT1;3 remained without change. Up- or downregulation of these genes involved in NH4^＋ uptake and assimilation correlated with the increase in NH4^＋ uptake in the presence of NO3^- in rice roots.

Tribological characteristics and self-repairing effect of hydroxy-magnesium silicate on various surface roughness friction pairs

Tribological characteristics and self-repairing effect of hydroxy-magnesium silicate (HMS) dispersed in lubricant oil on steel-to-steel friction pairs with various surface roughness were analyzed.The friction-reduction,anti-wear and self-repairing performance of various surface roughness friction pairs were examined by friction testing machine.An operation comparison was made between SJ10W-40 lubricant with and without HMS.The surface morphology and elementary composition of the grinding cracks were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS).The results show that the lubrication state changes from boundary lubrication into mixed lubrication after operation in lubricant with HMS.The friction-reduction,anti-wear and self-repairing performance of the friction pairs with various surface roughness are distinctly different.There is a repairing film whose material is different from substrate material on the grinding cracks.In addition,Si,Mg,O,Al and other elements are deposited on the repairing film which contains nanocrystals of these elements.And HMS self-repairing material possesses superior performance of friction-reduction,anti-wear and self-repairing effects.