樟子松人工林原产地与不同自然降水梯度引种地土壤和植物叶片生态化学计量特征

降水格局是影响陆地生态系统结构和过程的重要环境要素,尤其对于干旱/半干旱地区,降水变化是植物生长驱动的关键生态因子。目前,针对降水变化对陆地生态系统C、N、P等元素生物地球化学循环过程影响开展了大量研究。然而,关于沙地樟子松重要引种地科尔沁沙地自然降水梯度下沙地樟子松人工林土壤、植物生态化学计量特征的研究未见报道。因此,本研究以樟子松原产地红花尔基和引种地科尔沁沙地自然降水梯度下4个典型沙地樟子松人工林为对象,研究樟子松引种地降水变化对土壤(0—10,10—20 cm和20—40 cm)和植物(1年和2年生叶)生态化学计量特征的影响。研究结果发现:(1)与红花尔基原产地樟子松人工林相比,科尔沁沙地引种的樟子松人工林土壤C、N、P元素含量显著降低;(2)科尔沁沙地自西向东,随降水量增加,沙地樟子松人工林土壤C、N、P含量以及C∶P和N∶P表现为逐渐增加趋势,而土壤C∶N呈减少趋势;(3)随着降水量增加,樟子松叶C含量呈下降趋势,叶N含量和N∶P比值呈增加趋势,植物叶P含量无一致性规律;(4)樟子松叶片P含量与土壤C、N、P含量呈极显著正相关关系,而叶片C和N含量与土壤C、N、P含量无显著相关性。研究表明,沙地樟子松引种地科尔沁沙地土壤C、N、P养分比较缺乏,且随着降水增加土壤N养分限制降低,而土壤P养分限制增加。本研究从生态化学计量特征角度,为今后开展科尔沁沙地不同降水梯度条件下引种樟子松人工林提供理论依据。     

Synthesis and profiling of benzylmorpholine 1,2,4,5-tetraoxane analogue N205: Towards tetraoxane scaffolds with potential for single dose cure of malaria

A series of aryl carboxamide and benzylamino dispiro 1,2,4,5-tetraoxane analogues have been designed and synthesized in a short synthetic sequence from readily available starting materials. From this series of endoperoxides, molecules with in vitro IC50s versus Plasmodium falciparum (3D7) as low as 0.84?nM were identified. Based on an assessment of blood stability and in vitro microsomal stability, N205 (10a) was selected for rodent pharmacokinetic and in vivo antimalarial efficacy studies in the mouse Plasmodium berghei and Plasmodium falciparum Pf3D70087/N9 severe combined immunodeficiency (SCID) mouse models. The results indicate that the 4-benzylamino derivatives have excellent profiles with a representative of this series, N205, an excellent starting point for further lead optimization studies.     

Microcystins: Synthesis and structure–activity relationship studies toward PP1 and PP2A

Microcystins are highly toxic cyanotoxins responsible for plant, animal and human poisoning. Exposure to microcystins, mainly through drinkable water and contaminated food, is a current world health concern. Although it is quite challenging, the synthesis of these potent cyanotoxins, analogs and derivatives helps to evaluate their toxicological properties and to elucidate their binding mechanisms to their main targets Protein Phosphatase-1 (PP1) and -2A (PP2A). This review focuses on synthetic approaches to prepare microcystins and analogs and compiles structure–activity relationship (SAR) studies that describe the unique features of microcystins that make them so potent.     

Quinoxaline derivatives as potential antitrypanosomal and antileishmanial agents

Continuous efforts have been made to discover new drugs for the treatment of Chagas’ disease, human African trypanosomiasis, and leishmaniasis. We have previously reported the synthesis and antileishmanial and antitrypanosomal (Y strain) properties of 2,3-disubstituted quinoxalines. Considering their promising antiparasitic potential, the present study was conducted to expand our search and take advantage of high-throughput assays to investigate the effects of quinoxaline derivatives against Leishmania donovani, Trypanosoma brucei, and Trypanosoma cruzi (Tulahuen strain). These compounds were active against the kinetoplastid parasites that were evaluated. The 2-chloro-3-methylsulfoxylsulfonyl and 2-chloro-3-methylsulfinyl quinoxalines were the most potent, and some of these derivatives were even more active than the reference drugs. Although the 2,3-diaryl-substituted quinoxalines were not active against all of the parasites, they were active against T. brucei and intracellular amastigotes of T. cruzi, without interfering with mammalian cell viability. These compounds presented encouraging results that will guide our future studies on in vivo bioassays towards the mode of action.     

不同浓度亚硒酸钠溶液对水杉种子萌发的影响

硒元素是植物生长所需的微量元素。在水杉母树主要生长所在地恩施境内形成立体的硒资源环境,而该区的水杉群落天然更新困难,林下鲜见更新幼苗或幼树。因此,结合硒资源,研究硒元素与水杉种子萌发的相互关系对水杉的天然更新繁育具有重要意义。为了揭示硒元素对水杉种子发芽的影响,该研究通过测定不同环境条件(温度:20、25、30 ℃; 光照:12 h光照/12 h黑暗、24 h全黑暗; 是否浸种)下原生水杉种子的萌发率,筛选出最适萌发条件,并在此条件下采用不同浓度(0、0.25、0.5、1.0、2.0、4.0、8.0、16.0 mg·L^-1)的亚硒酸钠对水杉种子进行处理,观察其萌发的变化。结果表明:当使用浓度为0.25 mg·L^-1的亚硒酸钠溶液处理水杉种子时,种子的发芽率、发芽势和发芽指数都为最高,分别为34.0%、29.0%、13.9; 当亚硒酸钠浓度大于0.25 mg·L^-1时,水杉种子的发芽率、发芽势和发芽指数开始随着浓度的增加而降低,在亚硒酸钠浓度为16.0 mg·L^-1时,三个指标都达到最低值,分别为0.5%、0%、0.025。由此可知,低浓度(0～0.25 mg·L^-1)的亚硒酸钠处理对水杉种子的萌发有一定的促进作用,而高浓度(>0.25 mg·L^-1)的亚硒酸钠处理对水杉种子的萌发则有一定的抑制作用。     

Effects of leaf nutrient concentration and resorption on leaf falling time of dominant broadleaved species in a montane region of eastern Liaoning Province,China

凋落物是森林生态系统养分的重要来源, 叶片脱落时间是影响其分解的关键因素。东北温带森林中蒙古栎(Quercus mongolica)落叶时间较其他树种晚, 在山脊等贫瘠立地叶片甚至第二年春天才脱落。我们假设: 相对于其他树种, 蒙古栎叶片养分元素含量过高、再吸收时间长, 导致叶片延迟脱落。为验证假设, 除蒙古栎外, 选择了落叶时间居中的色木槭(Acer mono)和落叶较早的胡桃楸(Juglans mandshurica)为对象, 持续监测叶片从成熟至凋落过程中叶片养分元素含量, 包括大量元素: 氮(N)、磷(P)、钾(K)、钙(Ca)和镁(Mg), 微量元素: 铁(Fe)、铜(Cu)、锰(Mn)和锌(Zn); 并分析养分再吸收率。结果表明: 蒙古栎成熟叶养分元素含量介于对照树种之间; 凋落叶N、P和K含量低于对照树种, Fe和Mn含量高于对照树种, 其余元素含量介于对照树种之间。该结果不支持“蒙古栎叶片养分含量过高”假设。蒙古栎叶片N、P和K再吸收率高于对照树种, 再吸收率高低与其落叶时间完全一致; 叶片Cu和Zn再吸收率与对照树种无显著差异; 叶片其余元素未发生再吸收, 其累积率与对照树种无显著差异; 说明养分再吸收与养分含量无关, 可能与树种的种专一性相关, 可能会影响叶片脱落时间。由于蒙古栎多生长在贫瘠土壤, 其成熟叶无法积累更多养分; 为避免叶片脱落后养分进入土壤被其他物种利用, 将养分尽量回收储存于自身, 即蒙古栎叶片养分再吸收过程较长, 叶片脱落较晚。生长在极端贫瘠立地的蒙古栎叶片次年春天才落叶, 可能是由于再吸收一直在进行, 来不及脱落而保留至新生长季开始。落叶晚的树种养分再吸收率高、有利于自身养分保存, 更能适应贫瘠土壤, 反之亦然。     

Effects of drought stress on the osmotic adjustment and active oxygen metabolism of Phoebe zhennan seedlings and its alleviation by nitrogen application北大核心CSCD

Aims Two-year-old seedlings of Phoebe zhennan were used in this study to explore the responses of osmotic adjustment and active oxygen metabolism to drought stress and the mitigation effect of nitrogen application. Methods The soil water content was firstly adjusted to four treatment levels, i.e. 80% of field water holding capacity (80% FC), 50% FC, 30% FC and 15% FC, respectively. The physiological variables of plants were measured after one week, and then three nitrogen application rates, control (N0), medium nitrogen (MN) and high nitrogen (HN) were performed at an interval of 7 days for four times (7 d, 14 d, 21 d and 28 d, respectively). The same physiological variables were determined again one month after the accomplishment of nitrogen application. Important findings 1) The free proline (Pro) and soluble sugar (SS) contents in the leaves increased significantly with the aggravation of drought stress after 7 days of drought, but the content of soluble protein (SP) was firstly increased and then declined. The increase of Pro content was especially obvious under severe drought (15% FC). After nitrogen application, the content of Pro raise further, but the values varied in drought treatment. The SS contents under sufficient water supply (80% FC) and mild drought (50% FC) were decreased by MN, but it did not change significantly when supplied with HN despite the soil water content. After nitrogen application, the SP contents under 80% FC and 50% FC were lower than those of no exogenous N, while they were opposite response under 30% FC and 15% FC. 2) Before nitrogen application, with the aggravation of drought stress, the hydrogen peroxide (H2O2) content, superoxide dismutase (SOD) activity, catalase (CAT) activity increased significantly, and the peroxidase (POD) activity showed an up-down trend. After nitrogen application, the content of H2O2 was generally deceased at each water condition, with the maximum decrease at MN, while the HN treatment was not conducive to reduce the content of H2O2. The activities of three kinds of enzymes responded differently to the severity of drought and the level of nitrogen application. 3) Before nitrogen application, the content of malondial-dehyde (MDA) in leaves increased significantly when the soil water content declined to and below 50% FC. The relative electrical conductivity (REC) was decreased at first, and followed by significant increase. Except severe drought (15% FC) stress, the MDA content showed a decreasing trend at MN, but a rebound at HN. As regards severe drought stress, however, the content of MDA increased at both MN and HN, indicating that nitrogen application is not a good choice to alleviate the damage caused by severe drought stress. 4)Two-factor ANOVA revealed an obvious interaction between nitrogen application and drought stress. In conclusion, a proper amount of nitrogen (1.35 g·a–1 for each sapling) could somewhat alleviate drought stress no severer than 15% FC on seedlings of Phoebe zhennan, but excessive nitrogen at rate of or more than 2.70 g·a–1 per sapling is not recommended. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

不同斜生栅藻密度下布洛芬浓度对多刺裸腹溞生命表统计学参数的影响

以多刺裸腹溞为受试生物,在较低(0.5×10⁶ cells·mL^-1)、中等(1.0×10⁶ cells·mL^-1)和较高(2.0×10⁶ cells·mL^-1)的斜生栅藻密度下研究了不同浓度(0、0.45、0.9、1.8、3.6、7.2 和14.4 mg·L^-1)的布洛芬对多刺裸腹溞生命表统计学参数的影响.结果表明: 在较低和较高的食物密度下,布洛芬浓度分别对多刺裸腹溞的种群内禀增长率和生命期望具有显著性影响;但在3个食物密度下,布洛芬浓度对多刺裸腹溞的世代时间、净生殖率和总生殖率均无显著性影响.与对照组相比,在较低的食物密度下,暴露于0.45、0.9、3.6和14.4 mg·L^-1布洛芬溶液中的多刺裸腹溞的种群内禀增长率显著降低;在较高的食物密度下,暴露于3.6 和14.4 mg·L^-1布洛芬溶液中的多刺裸腹溞的生命期望显著延长.表明在较低的食物密度下,布洛芬对多刺裸腹溞的种群增长具有不利的影响;但在中等和较高的食物密度下其不利影响消失.在较高的食物密度下,布洛芬对多刺裸腹溞的存活具有促进作用;但在较低和中等食物密度下其促进作用并未出现.布洛芬对多刺裸腹溞部分生命表统计学参数的影响因食物密度的不同而异.     

CO2浓度倍增影响转Bt水稻非靶标害虫褐飞虱的生长发育及取食行为

近年来,大气CO₂浓度升高等全球气候变化和转Bt作物非靶标害虫抗虫性等问题备受关注.大气CO₂浓度升高直接或间接地影响植食性昆虫,而迄今为止有关大气CO₂浓度升高对刺吸式昆虫(同时也是转Bt作物的非靶标害虫)的影响结论不一,且对其刺吸取食行为的影响研究少有报道.本研究利用智能人工气候箱设置CO₂浓度,研究大气CO₂浓度倍增(800 μL·L^-1)对转Bt水稻的非靶标害虫褐飞虱取食行为及其生长发育和繁殖等的影响.结果表明: 大气CO₂浓度倍增对褐飞虱卵和若虫历期、成虫体质量和寿命,以及4龄和5龄若虫的刺吸取食行为等都具有显著影响,但对其繁殖力影响不显著.与对照CO₂浓度(400 μL·L^-1)相比,倍增CO₂浓度处理下褐飞虱的卵和若虫历期及雌成虫寿命分别显著缩短了4.0%、4.2%和6.6%;长翅型成虫比例显著增加了11.6%;初羽化成虫体质量降低,且雌成虫体质量显著降低了2.2%;此外,倍增CO₂浓度处理下褐飞虱4龄和5龄若虫口针的刺探效率都显著增加;其中,N4b波的持续时间分别显著延长了60.0%和50.1%,频次分别显著增加了230.0%和155.9%.可见,CO₂浓度倍增可通过提高褐飞虱的刺吸取食而促进其生长发育,并缩短其世代历期、提高长翅成虫比例,最终导致大气CO₂浓度升高下转Bt水稻的非靶标害虫褐飞虱发生危害严重,并面临其迁飞扩散为害加重的风险.     

Responses of exchangeable base cations to continuously increasing nitrogen addition in alpine steppe: A case study of Stipa purpurea steppe北大核心CSCD

Aims Soil exchangeable base cations (BCs) play important roles in keeping soil nutrient and buffering soil acidification, which may be disturbed by anthropogenic nitrogen (N) input. Considering relatively limited evidence from alkaline soils, this study was designed to explore the effects of N addition on soil exchangeable BCs in a typical alpine steppe on the Qinghai-Xizang Plateau. Methods From May 2013, eight levels of N addition (0, 1, 2, 4, 8, 16, 24, 32 g·m-2·a-1) in the form of NH4NO3 were added in the alpine steppe, where soil is alkaline. During the following three years (2014-2016), we collected soil samples in mid-August in each year. By measuring the concentrations of exchangeable BCs, we examined their changes along the N addition gradient. We also explored the relationships between BCs and other plant and soil properties. Important findings Continuous N addition resulted in significant loss of exchangeable BCs, especially Mg2+ in all three years and Na+ in two years. The concentrations of BCs were found to be negatively related to above-ground biomass and the concentration of soil inorganic N (p < 0.05). These results indicated that increase in N availability stimulated plant growth, which in turn led to more uptake of BCs by plants. Moreover, enhanced NO3- leaching resulted in the loss of BCs due to the charge balance in soil solution. In addition, increased NH4+ displaced BCs binding to soil surface and made them easy to be leached out of soils. Different from acid soils, soil acidification caused by N deposition in alkaline soils is mainly buffered by calcium carbonate, having less effect on BCs. Our results suggest that N addition results in the loss of exchangeable BCs in alkaline soils, leading to poor buffering capacity and decreased plant productivity over long time period, which needs to be considered during grassland management in the future. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.