Photosynthetic characteristics of the terrestrial blue-green alga, Nostoc flagelliforme

Photosynthetic responses of rewetted Nostoc flagelliforme to CO2, desiccation, light and temperature were investigated under emersed conditions in order to characterize its ecophysiological behaviour in nature. Net photosynthesis increased to a maximum rate at about 30 % water loss, then decreased, while dark respiration always decreased with the progress of desiccation. Light-saturated photosynthesis and dark respiration were significantly reduced at 8 degreesC, but remained little affected by changes of temperature within the range of 15-35 degreesC. Photosynthetic efficiency (alpha) was maximal at the beginning of desiccation and then reduced with increased water loss. Saturating irradiance for photosynthesis was about 194-439 mu mol quanta m(-2) s(-1), being maximal at about 30 % water loss. No photoinhibition was observed at irradiances up to 1140 mu mol m(-2) s(-1). Light compensation points were about 41-93 mu mol m(-2) s(-1). Photosynthesis of N. flagelliforme was CO2-limited at the present atmospheric CO2 level. The CO2-saturated photosynthesis increased with increase of irradiance (190-1140 mu mol m(-2) s(-1)) and temperature (8-25 degreesC) and decreased significantly with water loss (0-75 %). Photosynthetic affinity for CO2 was sensitive to temperature and irradiance. The CO2 compensation point (Gamma) increased significantly with increased temperature and was insensitive to irradiance. Desiccation did not affect Gamma values before water loss exceeded 70 %. Photorespiratory CO2 release did not occur in N. flagelliforme at the current atmospheric CO2 level.

KINETICS OF SIZE-FRACTIONATED AND DISSOLVED ALKALINE-PHOSPHATASE IN A FARM POND

Nutrient addition bioassays were conducted in 10 L carboys with water from a eutrophic farm pond. The four bioassay treatments each conducted in triplicate were control (no nutrients added), +N (160 mu mol L(-1) NH4Cl), +P (10 mu mol L(-1) KH2PO4), and N+P (160 mu mol L(-1) NH4Cl and 10 mu mol L(-1) KH2PO4). The size fractionated (0.2-0.8, 0.8-3, > 3 mu m) contents of the carboys were analyzed after 7 d for alkaline phosphatase activity (APA) and chlorophyll-a content. Chlorophyll data suggested P deficiency in ammonium and control mesocosms and no P deficiency with phosphate additions. Pond water also was collected in June, August, October, and March for measurement of APA. In water from the pond, the greatest V-max of APA usually was associated with microorganisms in the size classes between 0.8-3 mu m. In mesocosm experiments, the N+P treatment increased V-max of dissolved and particulate associated APA in the 0.2-0.8 mu m size range and in dissolved form. The V-max of APA in the largest size-fraction (> 3 mu m) increased markedly with P deficiency (+N treatment) and decreased in the P-enrichment treatment. The patterns of APA and chlorophyll associated with different size fractions often varied independently among different treatments and seasons and not always as a function of P deficiency, indicating the difficulty of attempting to normalize APA to phytoplankton biomass or chlorophyll. The Michaelis half saturation constant of APA in the pond water showed no strong trends with varied seasons or size fraction.

旱地农业发展中若干生物学问题的探讨

植物抗旱节水生物学是发展旱地农业和缺水区农业的重要学科基础,当前面临的主要问题包括:在研究路线上,如何正确处理分子水平研究与整体性研究之间的关系,以促进两者的互补;在研究目标上,如何做到抗旱性、水分利用效率、产量性状的有效结合,以实现高产高效;在研究成果应用中,如何切实加强学科交叉,以尽快取得实际效果。在论述上述问题的同时,对当前半干旱和半湿润地区与抗旱节水生物学有关的几个实践中的科技难点作了介绍,并提出建议。

六盘山不同森林群落地被物的持水特性

在森林生态系统中,地被物由林下枯落物、苔藓层以及表层土壤的根系组成(Kosugiet al.,2001;程金花等,2003)。在动物、微生物以及环境温湿度的作用下,地被物不断分解,补充了土壤养分含量(刘洋等,2006)。地被物在地表形成一层结构疏松的毡层,不仅能够减小雨水对地面的冲击,阻滞和分散降水,还增加了地表粗糙度,能够阻滞地表径流,吸收和储存降水,促使水分缓慢入渗,在防止土壤侵蚀和保持水土方面发挥了重要作用(张洪江等,2003)。此外,研究还发现,地被物层能够减少土壤蒸发(Schaapet al.,1997),缓解表层土温变化,影响冬季土壤的冻结过程(Sharratt,1997),同时又是林下种子萌发和幼苗更新的制约因素之一(班勇等,1995)。目前,国内外地被物研究主要集中于枯落物的凋落动态(张冀等,2001;杨玉盛等,2001;郑征等,2005)、苔藓层和枯落物的持水特性(Naethet al.,1991;薛立等,2005;叶吉等,2004;Zhanget al.,2006)、枯落物分解及养分归还(王瑾等,2001;Chandiniet al.,2002;魏晶等,2004;邵玉琴等,2004)、枯落...

干湿交替过程中土壤胀缩特征的实验研究

土壤胀缩是土壤在干燥、湿润交替变化过程中所表现出的土壤容积随含水量改变的现象。本文通过测定4种土壤脱水和吸水过程中的土柱高度和直径的变化,分析了胀缩过程中土壤容积与含水量的关系及土壤的胀缩特征。结果显示:三直线模型能够很好地拟合4种土壤的收缩、膨胀过程;土壤收缩、膨胀曲线各段的特征值均小于1,这说明土壤胀缩过程中土壤容积的变化速率小于含水量的变化速率;4种土壤胀缩过程中几何因子rs大于1而小于3,且收缩初期几何因子rs等于1,表明土壤的胀缩是各向异性的,并且在土壤收缩的最初阶段只有垂直收缩。

西藏产雪莲花的化学成分研究

本学位论文报道了作为传统藏药材广泛使用的西藏产雪莲花化学成分的研究。论文由五章组成，第一章是三种西藏产雪莲花的化学成分的系统分离纯化和结构鉴定；第二章为西藏产雪莲花化学成分的液-质及串联质谱联用分析；第三章提出了以HPLC和TLC为检测方法的雪莲花药材质量标准草案；第四章给出了对西藏产雪莲花挥发油化学成分的气-质联用分析结果；第五章概述了雪莲花的化学成分及药理研究进展。 第一章包括三个部分。第一部分报道了绵头雪莲花(Saussurea laniceps Hand.-Mazz.)全草乙醇提取物化学成分的分离鉴定。采用正相硅胶柱层析及凝胶柱层析等分离方法，从西藏产绵头雪莲花的乙醇提取物中共分离鉴定出15个化合物。其中11个化合物为首次从该植物中分离得到，当中2个化合物系在凤毛菊属植物中首次发现。第二部分报道了水母雪莲花(Saussurea medusa Maxim.)全草乙醇提取物的化学成分。采用正、反相硅胶柱层析及凝胶柱层析等分离方法，共分离鉴定出15个化合物，其中1个为新化合物，另有4个化合物为首次从该植物中分离得到。新化合物结构通过质谱和一维及二维核磁共振等波谱解析方法及碱水解反应确定为巴豆酰基-高车前苷(M-7)。第三部分报道了三指雪莲花 (Saussurea tridactyla Sch.-Bip. ex Hook. f.)全草乙醇提取物的化学成分。采用正相硅胶柱层析及凝胶柱层析等分离方法，共分离鉴定出7个化合物，其中1个化合物为首次从该植物中分离得到。 第二章也包括三个部分。首先是采用液-质联用(HPLC-DAD-ESI-MSn)分析方法，对7个西藏不同产地的三指雪莲花化学成分进行了分析，通过与标准品的 UV和MS数据比较，共鉴定出14个峰，并对其中8个共有成分进行了定量测定。其次是关于八种西藏产雪莲花化学成分的液-质联用(HPLC-DAD-ESI-MSn)分析，通过与标准品的UV和MS数据比较，共鉴定出15个峰，并对其中8个共有成分进行了定量检测。最后通过对八种西藏产雪莲花主要化学成分的多级串联质谱(ESI-MSn)分析，快速、灵敏地鉴定出10个黄酮和3个香豆素化学成分。 第三章同样包括三个部分。首先是以绵头雪莲花中主要香豆素成分东莨菪素和伞形花内酯为对照品，通过TLC定性检测和HPLC含量测定，草拟出较严谨的药材质量标准。其次是将绵头雪莲花、三指雪莲花和雪兔子作为一个药材看待，草拟了以东莨菪素和伞形花内酯的TLC检测为指标的药材质量标准。最后是针对水母雪莲花，以主要黄酮成分芹菜素-7-O-b-D-葡萄糖苷为对照品作TLC检测，并草拟出该药材的质量标准草案。 第四章报道了西藏产雪莲花挥发油的化学成分分析。采用传统水蒸气蒸馏法分别从八种雪莲花全草中提取挥发油，利用气相色谱-质谱联用技术分别从水母雪莲花、绵头雪莲花、槲叶雪莲花、云状雪兔子、拉萨雪兔子、小果雪兔子、雪兔子和三指雪莲花中分别鉴定出83、83、56、34、21、20、24和20个化学成分，分别占其挥发油总量的70.7%、76.0%、82.2%、55.4%、49.7%、70.4 %、76.2%和 76.7%。 第五章为综述，总结和概括了雪莲花的化学和药理研究进展。 The dissertation reports the investigation of the chemical constituents of the genus Saussurea. Quite a lot of species in this genus are traditional Tibetan medicinal plants, and hence have been widely used in traditional Tibetan medicine. This dissertation consisted of five chapters. The first chapter is on the chemical constituents of three Saussurea plants. The second section is about the analysis of chemical constituents of Saussurea plants using HPLC-MS and ESI-MS/MS. In the third chapter, we proposed quality-control standards for the Genus Saussurea based on TLC (thin layer chromatography) and HPLC. The fourth chapter is about chemical compositions of the essential oil from the whole plant of Saussurea plants. The last chapter reviews the research progress of the Genus Saussurea. The first chapter consists of three parts. The first part is about chemical constituents of ethanol extracts from whole plant of Saussurea laniceps Hand.-Mazz. Fifteen compounds were isolated by column chromatography on normal phase silica gel and Sephadex LH-20. Among them, eleven compounds were isolated from this plant for the first time, and two compounds were isolated from Genus Saussurea for the first time. The second part is about chemical constituents of ethanol extracts from whole plant of Saussurea medusa Maxim. Fifteen compounds were isolated by column chromatography on normal phase, reversed phase silica gel and Sephadex LH-20. Five of them were isolated from this plant for the first time, and there is one new flavonoid glucoside which was identified as 6″-O-crotonoyl-homoplantaginin (M-7) based on the evidence of one- and two-dimensional nuclear magnetic resonance, mass spectrometry analysis, and alkaline hydrolysis reaction. The last part is about chemical constituents of ethanol extracts from whole plant of Saussurea tridactyla Sch.-Bip. ex Hook. f.. Seven compounds were isolated by column chromatography on normal phase silica gel and Sephadex LH-20. There is one compound which was isolated from this plant for the first time. The second chapter consists of three parts. In the first part, we analyzed the chemical constituents of S. tridactyla collected from seven different places in Tibet using HPLC-DAD-ESI-MSn. Fourteen peaks in the HPLC were identified by comparison of UV and MS spectra with those of authentic compounds, among which eight common peaks were quantified. In the second part, we analyzed the chemical constituents of eight Saussurea species using HPLC-DAD-ESI-MSn method. Fifteen peaks in the HPLC were identified by comparison of UV and MS spectra with those of authentic compounds and eight main peaks of them were quantified. In the last part, we analyzed the chemical compounds of the above eight Saussurea plants directly by ESI-MS/MS. Thirteen major compounds, including 10 flavonoids and 3 coumarins were easily rapidly identified. The third chapter consists of three parts. In the first part, we proposed a comparative high quality-control standard for S. laniceps, based on quality detection by TLC and quantity analysis by HPLC using two major compounds (umbelliferone and scopoletin) as standard compounds. In the second part, in viewing S. laniceps, S. tridactyla and S. gossypiphora as the members of one family of medicinal herbs, we suggested a quality-control standard based on the TLC detection of the two major compounds (umbelliferone and scopoletin). In the last part, we proposed a quality-control standard for S. medusa based on the TLC detection of its major component (apigenin 7-O-glucoside). The four chapter analyzed the chemical constituents of essential oil of eight Saussurea species. The essential oils were extracted from the whole plants of these samples with water stream distillation. By GC-MS analysis, we identified eighty-three compounds from S. medusa, eighty-three from S. laniceps, fifty-six from S. quercifolia, thirty-four from S. aster, twenty-one from S. kingii, twenty from S. simpsoniana, twenty-four from S. gossypiphora, and twenty from S. tridactyla respetively, which accounted for 70.7%, 76.0%, 82.2%, 55.4%, 49.7%, 70.4 %, 76.2% and 76.7% of the total essential oil, respectively. The last chapter reviews the research progress of the Genus Saussurea.

花椒主效化感物质分离鉴定及化感作用研究

近年来，随着对作物重茬障碍原因的深入研究，植物的化感作用越来越受到国内外众多学者的重视。花椒（Zanthoxy piperitum.）为芸香科植物，是一种收益早、用途广、价值高的经济树种，是川西干旱河谷地区的重要经济作物，其连作障碍也倍受关注，系统研究花椒化感作用将有助于理解和最终解决花椒连作障碍问题。本文首先通过萃取、层析等方法分离花椒主效化感成分；通过外加不同浓度的花椒叶水浸液研究了对土壤氮素养分循环的影响；研究了花椒叶水浸液对苜蓿生理生化、光合作用、氮素养分吸收的影响，并对外施氮肥对这种化感影响的缓解作用做了研究；研究了花椒化感潜力对全球变化——UV-B增强辐射的响应。主要研究结果如下： 1．用不同极性的有机溶剂对花椒叶水浸液浓缩浸膏萃取、柱层析，结合生物活性检测，分离得到主效化感作用组分的一种化感物质——对甲氧基苯酚。采用该物质纯品进行生物活性检测，证明其具有化感作用。 2．花椒叶水浸液处理土壤30天后，土壤硝态氮、铵态氮、无机氮（硝态氮＋铵态氮）与对照相比，随着花椒叶水浸液浓度的增加呈现降低的趋势，其中土壤铵态氮含量显著降低，而硝态氮含量的变化则不显著，无机氮含量也显著降低。土壤脲酶和蛋白酶的活性与无机氮含量的变化趋势相同。随着花椒叶水浸液浓度的增加，氨化细菌数量显著降低，固氮菌的数量变化不显著，硝化细菌和反硝化细菌数量有减少的趋势。60天后，硝态氮含量、铵态氮含量、无机氮随水浸液浓度增加的变化趋势与30天时相似；随着花椒叶水浸液浓度的增加，氨化细菌、固氮菌的数量显著减少，硝化细菌数量、反硝化细菌数量仍呈减少趋势；土壤脲酶、蛋白酶活性与第30天的变化趋势相同。第60天与第30天的结果相比，相同水浸液浓度处理的硝态氮、铵态氮、无机氮均有下降的趋势，但除了25g.L－1水浸液处理的外，其它相同浓度的处理间差异均不显著；除了12.5 g.L的处理外土壤脲酶活性均呈增强的趋势；蛋白酶活性都有不同程度的增加；花椒叶水浸液处理的土壤硝化细菌和反硝化细菌数量呈增加趋势。 3．随着花椒叶水浸液浓度的增加，显著抑制了苜蓿根长、地上地下生物量、叶绿素含量、叶片中可溶性蛋白的含量，净光合速率。苜蓿体内四种抗氧化酶（POD、SOD、CAT、APX） 活性随着水浸液浓度的增加而降低，而丙二醛含量则增加。苜蓿氮初级同化相关酶硝酸还原酶（NR）、谷氨酰合成酶(GS)、谷氨酸脱氢酶（GDH）的活性随着水浸液浓度的增加受到不同程度的影响。总的来说，苜蓿硝酸还原酶、谷氨酰合成酶的活性受到抑制，而谷氨酸脱氢酶活性的变化则比较复杂，根呈先降低后增加的趋势，叶片则无显著变化。外施两种不同浓度的硝酸铵氮肥后，对12.5、25 g.L－1花椒叶水浸液处理的苜蓿化感作用有显著的缓解作用，表现在株高、生物量、光合作用等方面，大多达到与对照（0 g.L－1）未施氮肥无显著差异的水平，而对50 g.L－1水浸液处理的苜蓿幼苗，虽有一定的缓解作用，但这种作用均未达到与对照（0 g.L－1）未施氮肥时无显著差异的水平。 4． UV-B增强辐射处理花椒后，花椒的化感潜力显著增强。花椒叶片内UV-B吸收物质的含量和总酚含量均显著增加。 In recent years, with profound research on the reasons of continuous cropping obstacles, allelopathy received increasing attention to many scholars at home and abroad. Zanthoxy bungeanum as a Rutaceae plant is a high economic value species which gains early and uses widely. Zanthoxylum is an important economic crop in the arid valley of western Sichuan region, and its not even has received much concern for the continuous cropping obstacles. The systematic study of allelopathy of Zanthoxylum will contribute to the understanding and final settlement of this issue. The major allelopathic composition was separated through the extraction, chromatography combined with other methods. The impact on soil nutrient cycling was also studied through the addition of different concentrations of water extracts of Zanthoxylum. Furthermore, the effects of water extracts of Zanthoxylum leaves on alfalfa leaf physiological and biochemical indexes, photosynthesis, soil enzymes and nutrient uptake of nitrogen and the mitigation of allelopathy through using external fertilizer were studied to put forward scientific resolvent for Zanthoxylum continuous cropping obstacles .The response of allelopathic potential of Zanthoxylum to global change - UV-B enhanced radiation was studied . The main findings are as follows: 1. Through extraction with different polar organic solvents on concentrated water extract of Zanthoxylum leaf and then using column chromatography combined with detection of biological activity, one of the main allelopathic components- methoxy-phenol was isolated. The biological activity testing of the pure material of methoxy-phenol proved that it does have allelopathic potential. 2. Thirty days after treating soil with water extract of Zanthoxylum leaf, as compared with the control, the contents of soil nitrate, ammonium, nitrate plus ammonium nitrogen showed a trend of decrease with the increase of the concentration of water extract whereas the content of ammonium nitrogen showed a significant reduction, and the content of nitrate did not change significantly, the content of nitrate plus ammonium nitrogen also showed a significant (P <0.05) redction. The activity of soil urease and protease showed the same trend as the content of nitrate nitrogen plus ammonium nitrogen. With the increase in the concentration of water extract, the number of ammonification bacteria significantly reduced but nitrogen-fixing bacteria did not change significantly and there was a decreasing trend in the number of nitrifying bacteria and denitrifying bacteria. Sixty days after the treatment, with the increase in solution concentration of water extract of Zanthoxylum leaf, the content of nitrate、 ammonium nitrogen, nitrate plus ammonium nitrogen showed a similar change trend to 30 days’; the number of ammonification bacteria, nitrogen-fixing bacteria significantly reduced ; the number of nitrifying bacteria, denitrifying bacteria was still an downward trend; the activity of soil urease and protease showed the same trend as the 30th days’. Compared to the results of the 30th days’, the content of nitrate, ammonium, nitrate plus ammonium nitrogen showed a decrease trend between the treatment of same concentration, but there was no significant difference except the treatment of 25g.L-1 between the same concentration; the activity of soil urease showed enhanced trend except the treatment of 12.5 g.L-1; the activity of protease increased to varying degrees; the number of ammonification bacteria、 nitrifying bacteria and denitrifying bacteria were growing while nitrogen-fixing bacteria reduced.. 3. With the increase of the concentration of water extract of Zanthoxylum leaf, the water extract significantly inhibited the root length, aboveground biomass, content of chlorophyll and soluble protein in leaf and net photosynthetic rate. The activity of four antioxidant enzymes (POD, SOD, CAT, APX) reduced with the increase in concentration of the water extract but the content of MDA increased. The activity of enzymes related to primary nitrogen assimilation such nitrate reductase (NR), glutamyl synthetase (GS), glutamate dehydrogenase (GDH) were subject to different degrees with an increase in the concentration of water extracts. In general, the activity of nitrate reductase, glutamyl synthetase were inhibited, while change in the activity of glutamate dehydrogenase was more complex. The activity of glutamate dehydrogenase in leaf was first reduced and then increase,but did not change significantly in root. After using two external different concentrations of nitrogen fertilizer, there was a significant mitigation in inhibiton in plant height, biomass, photosynthesis, etc. in the treatment of 12.5,25 gL-1 of water extract of Zanthoxylum leaf, and most of these indexes showed no significant difference with the control (0 g.L-1, no external fertilizer was added) .Although there showed a certain degree of ease in the treatment of 50 g.L-1 , there was still a significant difference compared with the control (0 gL-1) in which no external fertilizer was used. 4.The allelopathic potential of Zanthoxylum positively responded to enhanced UV-B significantly. The content of UV-B absorbing compounds and the total phenol also significant increased.

九寨沟湖泊湿地植物群落与植物地理研究

九寨沟湖泊湿地在维持九寨沟的生态平衡中起着重要的作用，在旅游产业的发展下，湿地生态系统及生物多样性面临着较大的威胁。尽管九寨沟湿地具有重要的生态价值，但目前对其研究尚比较薄弱。湿地植物群落和植物地理研究可以为湿地资源的可持续利用和监测保护提供科学依据。作者从2004年8月到2007年11月对九寨沟湿地的植物物种组成、地理分布、优势植物群落的结构、生长动态、湿地土壤种子库进行了调查研究。主要结果如下： 1. 九寨沟湿地物种组成、地理分布特点及湿地植物群落特点 九寨沟湿地共有苔藓植物8科13属16种，维管植物为48科107属199种。九寨沟湿地植物的地理成份较为丰富，维管植物在科级水平上有7种地理分布型（变型），在属级水平上有13种地理分布型（变型）， 在种级水平上共有29种地理分布型（变型）。九寨沟湿地植物以温带成份和我国特有成份为主，同时兼有热带、亚热带成份和环极—高山成份。九寨沟湿地植物的分布表现出明显的垂直地带性和水平地带性。湿地植物群落可划分21个群落类型，不同植物群落类型的物种多样性及物种组成存在较大的差异。九寨沟湿地植物的物种多样性和群落多样性以及较高的生产力特征，是维持其湿地生态景观多样性和稳定性的基础。 2. 土壤、水环境、海拔等对湿地植物的分布及生物多样性的影响 九寨沟湿地土壤、水等环境因子存在较大的差异。帕米尔苔草和宽叶香蒲等群落的凋落物较多，土壤有机碳、土壤总磷较高，可能是九寨沟湿地的重要土壤碳库。 九寨沟湿地植物沿水环境梯度的分布规律表现为：沉水植物（轮藻—篦齿眼子菜，水苦荬，杉叶藻）——挺水植物（水木贼，芦苇，宽叶香蒲）——湿生草本（苔草、节节草、披散木贼）——湿生灌木（柳灌丛，小檗灌丛）等。海拔也影响湿地植物的物种组成。 水深对物种多样性有影响，水深与物种丰富度负相关。随着水深的增加，水木贼、芦苇、杉叶藻、宽叶香蒲等群落的物种多样性下降；在长期淹水和季节性淹水的地方，水木贼群落物种多样性存在显著差异。土壤总氮与水木贼群落物种丰富度正相关。 3. 土壤营养元素、水环境对植物生长的影响 水深影响湿地植物生物量的分配。芦苇无性系分株在47 cm水深的环境中单株平均生物量最大；在干滩地中（地面水深0 cm），叶生物量百分比最大，而茎生物量百分比最小，茎的生物量百分比和生长速率随水深的增加而增加；在较干的滩地生境中，开花率、花序的生物量百分比明显大于水较深的生境。 水深与水木贼地上生物量负相关，但水木贼地上生物量在长期淹水和季节性淹水的地方没有显著的差异。在水浅的地方，杉叶藻、水木贼、芦苇等植物群落中，其他伴生物种的生物量占样方总生物量的百分比较大。 土壤有机碳、土壤总氮、土壤总磷等对湿地植物生物量的影响比较大：宽叶香蒲地上生物量与土壤总磷正相关；水木贼地上生物量与土壤总氮正相关；杉叶藻地上生物量与土壤有机碳正相关。 水深、土壤营养成分对湿地植物高度、密度等有影响。水木贼的平均高度在季节性淹水的地方比长期淹水的地方低，平均密度在长期淹水的地方比季节性淹水的地方低；除了5月份，其他观察月份水木贼的密度都与水深负相关，同时与土壤有机碳正相关。另外，芦苇密度与土壤有机碳含量正相关，宽叶香蒲密度与水深负相关，帕米尔苔草高度与土壤有机碳负相关。 4. 优势植物群落的动态变化 在优势植物群落中，优势种的高度、密度、盖度、生物量等在群落中占绝对优势。除五花海，水木贼群落的物种组成、高度、生物量在两年间没有显著的变化。芦苇群落的物种丰富度在近两年有所增加。 湿地植物生长表现为明显的季节动态，生长的峰值大多在7月－8月。优势植物群落的物候与水文周期有关。湿地植物群落的物种组成和密度，可以作为对湿地监测和保护的生物指示。 5. 九寨沟湿地土壤种子库特征及其在湿地生物多样性恢复中的作用 水深和现存植被物种丰富度可以解释湿地土壤种子库的变化。水深可以解释表层物种丰富度45%的变化。现存植被物种丰富度可以分别解释10 cm土层、2－5 cm土层及5－10 cm土层土壤种子库45%、48%和25%的变化。 湿地土壤种子库的密度为0－15945粒m-2, 种子库中共发现23个物种。现存植被优势物种和种子库优势物种不同。各层土壤种子库密度和物种丰富度并不存在显著的差异，但第二层土壤种子库密度最大。海拔、现存植被优势种盖度、土壤总磷、土壤总氮、土壤有机碳对湿地土壤种子库的密度和垂直结构没有影响。土壤种子库物种丰富度小于地上植被物种丰富度。湿地土壤种子库与地上植被的相关性不大。在浅水区域，湿地土壤种子库在湿地植被恢复中有一定作用。但在深水区域，保护现存植被更重要。 The lakeshore wetlands are valuable ecological units of the Jiuzhaigou lakes. Pressure for travel industry development pose a continuing and severe threat to the biodiversity-support function of the wetland system. Despite the ecological importance of wetlands in Jiuzhaigou, they are so far poorly studied. Both general plant communties and biogeographical studies are needed in order to attain basis for sustainable use the wetland resources and adequate protection of these areas. The present study was undertaken to examine aquatic plants distribution and the species compositon, structure and growth dynamics of their communities with variations of environmental factors along altitudes, water depth and soil properities gradients in Jiuzhaigou. Analysis of field survey data collected during August 2004 and November 2007 in lakeshore wetlands in Jiuzhaigou National Nature Reserve, Sichuan, China. The results were as following: (i) Species composition and biogeography in wetland vegetation 8 families, 13 genus, 16 species of moss and 48 families, 107 genus and 199 species of vascular plants in Jiuzhaigou wetlands were found. The floristic compositions were abundunt. Ten geographical distribution types at family level, 13 geographical distributions types at generic level and 29 geographical distribution types at specific level in vascular plants were found. Most species in Jiuzhaigou wetlands are temperate elements and Chinese endemic elements, with a few of tropical and subtropical and some circumarctic elements. And the plant distributions show clear vertical and horizontal patterns. There were 21 major wetland plant community types. Species composition and species richness in different plant communities are different. The species diversity and plant community diversity and their high biomass are the basis for the diversity and stability of wetland landscapes in Jiuzhaigou. (ii) Water depth, soil nutrients and altitudes influence on the species diversity and plant distribution. Total phosphorous and organic cabon in soil were higher in C. pamiernensis and T. latifolia communities, where are important cabon reservoirs in Jiuzhaigou wetlands. Along gradients of water depth, among populations of the dominant plant species present: submerged macrophytes (Chara vulgaris, Potagemonton pectinatus, Veronica anagalis-aquatica，Hippuris vulgaris), emergent macrophytes (Equisetum fluviatile, Phragamites australis, Typha latifolia), helophytes (Carex pamirensis )and shrubs (Salix sp., Berberis sp. ). Altitudes influence on the assemblage of plant communities. Water depth negatively correlated with species richness. Specie richness showed differences between permanently flooded sites and seasonally flooded sites in E. fluvatile communities. And total nitrogen in soil was negatively correlated with species richness in E. fluviatile communities. Altitudes show no significant influence on species richness, but in fact, through our analyses, they do have influence on the assemblage of wetland plants. (iii) Water depth, soil nutrients influence on the plant growth Water depth influences the biomass allocation in Phragmities australis. The average aboveground biomass of a single ramet (4.2 g) was the largest in the habitat with water level 47 cm above the soil surface. At the habitat with water level under soil surface 15 cm (－15 cm), the leaf biomass percentage (of the total ramet biomass) was the largest (46.1%), and the height and percentage of ramose ramets ( with branches on stem )(of the total ramets in a plot) were found obviously different. The deeper in water, the larger the biomass percentage and growth rate of stems were. The flowering rate and biomass of panicles were greater in shallow water than those in deep water. Water depth negatively correlated with aboveground biomass of E. fluviatile. However, above-ground biomass of E. fluviatile showed no significant difference between permanently flooded sites and seasonally flooded sites. But in shallow water, more biomasses of accompanying species were found in dominant plant communities such as H. vulgaris communities, E. fluviatile communities and P. australis communities. Water depth, soil nutrients influence on shoot density and shoot length of wetland plants. The shoot density of E. fluviatile was correlated to water depth in all growth months. Annual average density was significantly lower at permanently flooded sites than at seasonally flooded sites. But the annual average shoot length was significantly lower at seasonally flooded sites than at permanently flooded sites. (iv) Growth dynamics of dominant communities in Jiuzhaigou wetland The shoot length and shoot density, coverage and biomass of domiant species were dominated in plant communities. The species composition increased in P. australis communities in recent two years. The species richness in E. fluviatile communities showed no difference between 2005 and 2007. The above-ground biomass and shoot density in Five－flower Lake from July 2005 to July 2007 were significantly different, while in other sites, the differences were not significant. Shoot height, shoot density and above-ground biomass showed significant seasonal changes in all sites. Growth dynamics correlated with the cycle of water levels in lakes. Most plants growth parameters peaked at July or August. The biomass of T. latifolia peaked in August. But the shoot length of T. latifolia in deeper water peaked in July. The shoot length of E. fluviatile increased significantly from May to August except in seasonally flooded sites in Arrow-bamboo Lake. The species composition of communities and shoot density can be used as bioindicators in Jiuzhaigou wetland. (v) Soil seed bank in Jiuzhaigou wetland and its role in vegetation restoration Seed density in all soil layer samples was negatively correlated to water depth. Water depth can explain 45% variance of species richness in surface layer in sediment. Species richness in extant vegetation can explain 45%, 48%, 25% variance of species richness in total 10 cm and in 2－5 cm and 5－10 cm layer sediment respectively. Mean seed densities in wetlands ranged from 0 to 15945 m–2. A total of 23 species germinated in seed bank. The dominant species in seed bank and extant vegetation showed great difference. The total number of species and seedlings that germinated in different layers was not significantly different. But the second layer had the greatest seed density. In shallow water, seed bank can contribute to vegetation restoration, while in deeper water, protection of extant vegetation may be a better strategy.

Novel synthesis of highly active Pt/C cathode electrocatalyst for direct methanol fuel cell

A 40 wt% Pt/C cathode electrocatalyst with controlled Pt particle size of similar to 2.9 nm showing better performance than commercial catalyst for direct methanol fuel cell was prepared by a polyol process with water but without using stabilizing agent.

Controlled release of urea encapsulated by starch-g-poly(L-lactide)

This paper presented a new approach for preparing a new type of slow-release membrane-encapsulated urea fertilizer with starch-g-PLLA as biodegradable carrier materials. By solution-casting and washing rapidly with water the urea was individually encapsulated within the starch matrix modified by L-lactide through in situ graft-copolymerization.

Stabilization of poly(lactic acid) by polycarbodiimide

Polycarbodiimide (CDI) was used to improve the thermal stability of poly(L-lactic acid) (PLA) during processing. The properties of PLA containing various amounts of CDI were characterized by GPC, DSC, rheology, and tensile tests. The results showed that an addition of CDI in an amount of 0.1-0.7 wt% with respect to PLA led to stabilization of PLA at even 210 degrees C for up to 30 min, as evidenced by much smaller changes in molecular weight. melt viscosity, and tensile strength and elongation compared to the blank PLA samples. In order to examine the possible stabilization mechanism, CDI was reacted with water, acetic acid, L-lactic acid, ethanol and low molecular weight PLA. The molecular structures of the reaction products were measured with FTIR.

Synthesis, extraction and electronic structure of Ce@C-2n

In view of the growing interest in endohedral lanthanide fullerenes, Ce, as a typical +4 oxidation state lanthanide element, has been systematically studied. The synthesis, extraction and electronic structure of Ce@C-2n are investigated. Soot containing Ce@C-2n was synthesized in high yield by carbonizing CeO2-containing graphite rods and are back-burning the CeC2-enriched cathode deposit in a DC are plasma apparatus. Ce@C-2n, dominated by Ce@C-82, can be efficiently extracted from the insoluble part of the soot after toluene Soxhlet extraction by pyridine at high temperature and high pressure in a closed vessel. About 60% Ce@C-2n (2n = 82,80,78,76) and 35% Ce@C-82 can be enriched in the pyridine extract. This fact is identified by desorption electron impact mass spectrometry (DEI MS). The electronic structure of Ce@C-2n is analyzed by using X-ray photoemission spectroscopy (XPS) of pyridine-free film. It is suggested that the encapsulated Ce atom is in a charge state close to +3 and was effectively protected from reaction with water and oxygen by the enclosing fullerene cage. Unlike theoretical expectation, the electronic state of Ce@C-82 is formally described as Ce+3@C-82(3-). (C) 1997 Elsevier Science Ltd.

Geochemistry of rare earth elements in cobalt-rich crusts from the Mid-Pacific M seamount

Rare earth elements (RFEs) and major elements of 25 cobalt-rich crusts obtained from different depths of Mid-Pacific M seamount were analyzed using inductively coupled plasma-atomic emission spectrometer and gravimetric method. The results showed that they were hydrogenous crusts with average Sigma REE content of 2084.69 mu g/g and the light REE (LREE)/heavy REE (HREE) ratio of 4.84. The shale-normalized PEE patterns showed positive Ce anomalies. The total content of strictly trivalent REEs increased with water depth. The Ce content and LREE/HREE ratios in Fe-Mn crusts above 2000 in were lower than those below 2000 m. The change in RE E with water depth could be explained by two processes: adsorptive scavenging by setting matters and behaviors of REE in seawater. However, the Ce abundance took no obvious correlation with water depth reflects the constant Ce flux. The Cc in crusts existed mainly as Ce(IV), implying that the oxidative-enriching process was controlled by kinetic factors.

中太平洋海区富钴结壳地球化学特征及成因机制

本文利用ICP-AES、EPMA、X-ray衍射等测试技术以及聚类分析和因子分析等多种数理统计方法，系统地对中太平洋海区富钴结壳的元素地球化学特征、矿物组成和微观组构进行了研究，并探讨了其成因机制，获得以下主要认识： 1中太平洋海区富钴结壳类型多样，均为水成成因，其矿物相主要由锰矿物相、铁矿物相和非金属矿物相组成；富钴结壳壳层发育多种原生和次生构造类型。 2磷酸盐化作用不仅强烈改变富钴结壳元素初始含量，而且造成富钴结壳某些元素间的相关性发生改变，这些敏感型元素对可用于指示富钴结壳是否发生磷酸盐化。在不同水深段内，未磷酸盐化型富钴结壳的主要元素随经向、纬向的变化趋势相似，表明其受水体化学障、表面生产力和物质来源等环境参数控制；而随水深的变化则具有区域一致性，表明水体化学具有区域成层性。 3未磷酸盐化富钴结壳稀土元素含量和轻重稀土分馏程度随水深发生规律变化，这种变化不仅与它们在海洋中的含量和行为有关，也与海洋背景颗粒的吸附有关；铈(Ce)在富钴结壳中基本上呈4价，且动力学因素控制了其富集过程，因此Ce异常不能用于指示富钴结壳形成环境的氧化程度。 4基于富钴结壳微层呈锯齿状且同一微层生长速率不同，提出了富钴结壳在各种基底表面生长以及后继发育过程受固液界面双电层控制的发育模式。在富钴结壳整个发育过程中，经历了从贫氧环境向富氧环境的转变，但微环境则呈富氧-低氧过程的交替。 关键词： 富钴结壳；中太平洋；元素地球化学；界面双电层

Determination for the different combined-form inorganic carbon in marine sediments

Marine sediment is the important sources and sinks of carbon. The inorganic carbon(IC) in marine sediments plays an important role in carbon cycling. In order to understand IC function in carbon cycling, sequential extraction method based on IC combined chemical strength difference were established to get five phases: NaCl phase (step I), NH3 - H2O phase (step II), NaOH phase (step III), NH2OH . HCl phase (step IV) and HCl phase(step V). The best extraction conditions were obtained by a series of experiments. Extractants were added into plastic centrifuge tubes in Step I - M, the capped tube were placed on a shaker table to keep the solids suspended for two hours. The suspended solution was separated by centrifugal, the residues were washed with water. The two supernatant were combined and the CO, was finally determined by volumetric analysis. The residues were transferred into conical flask in step IV and V, and then the extractants were added. The produced CO2 was adsorbed by saturated Ba(OH)(2) solution, and determined by volumetric analysis. This method for IC has a good precision in the analysis sediment samples.