不同光照处理下青藏高原克隆植物黄帚橐吾(Ligulariavirgaurea)种子大小对其幼苗生长的影响

以高寒草甸克隆植物黄帚橐吾为实验材料,通过遮荫网模拟植被遮荫,研究种子大小与萌发及幼苗生长能力的关系和幼苗对光照条件的反应。结果表明：（1）在自然光照下,黄帚橐吾种子大小对种子萌发的影响显著,大种子的萌发率高于小种子。遮荫生境下,大、小种子萌发率有所降低,但遮荫对小种子萌发的影响比大种子显著。小种子的萌发率下降了近1/8,而大种子的萌发率仅下降了1/11。（2）黄帚橐吾种子大小对幼苗生物量积累影响显著,大种子幼苗总生物量（TB）大于小种子幼苗的。但生物量的分配与播种时间相关,播种后60 d,在自然光照条件下,大种子幼苗对根生物量的分配大于小种子幼苗,而对叶生物量的分配则正好相反。在遮荫环境中,大、小种子幼苗普遍对根的生物量分配增加,大种子幼苗根冠比（R/S）大于小种子幼苗。（3）黄帚橐吾种子大小对幼苗的生长也有明显影响。在自然光照下,小种子幼苗的相对生长速率（RGR）较大于大种子幼苗,但叶面积比率（LAR）、叶面积干质量比（SLA）、叶干质量（LWR）差别不明显。在遮荫条件下,幼苗的LAR、SLA、LWR显著增加,但大、小种子幼苗间差异不显著,幼苗的RGR减小,小种子幼苗的减小趋势大于大种子幼苗。     

高寒草场橐吾属植物幼苗对低温的应答

分别在适宜和模拟低温胁迫下,测定了青藏高原3种橐吾属植物幼苗生物量的分配模式、相对生长率(RGR)、可溶性糖含量及膜渗漏率,并计算半致死温度(LT50),旨在了解这3种植物幼苗的生长特性、对低温胁迫的忍受力及其种间差异,探讨3种橐吾幼苗对高寒环境的适应能力。结果表明:3种植物的萌发初期,子叶迅速伸展,而后根/冠比快速增加,相对生长率在萌发后10~15 d达到峰值,根/冠比与生物量的累积呈极显著正相关关系;经4℃低温处理后,3种植物幼苗的存活率均超过70%,RGR峰值降低且滞后出现,回归分析表明RGR降低量的64%是由根部生物量的降低引起的;黄帚橐吾、箭叶橐吾及掌叶橐吾的LT50值分别为-8.24、-8.14、-7.28℃,表明3种植物幼苗均能够忍受苗期短暂的低温胁迫而实现种群更新;经-5℃低温处理,三者叶片中的可溶性糖含量分别增加3.61、2.90、1.61倍,而游离脯氨酸分别增加2.57、4.40、37.68倍,表明3种橐吾各自通过不同的代谢调节机制提高自身抗寒能力。总之,3种橐吾属植物均具有良好的适应青藏高原高寒气候环境的生活史对策。     

高寒草场优势杂草黄帚橐吾水浸液对牧草的化感作用

研究了高寒草场中主要毒杂草——黄帚橐吾水浸液对同域分布的5种牧草的化感作用.将反应指数(RI)相加平均后分为一、二、三级敏感指数,分别评价不同测定指标、不同发育期和物种水平对化感作用的敏感性;从供体角度对相应RI值做同样处理,以综合评价不同水浸液及其不同浓度的化感效应.结果表明,5种牧草对黄帚橐吾化感作用的敏感性从强到弱依次为早熟禾>大雀麦>中华羊茅>羊茅>垂穗披碱草;牧草种子萌发期的敏感性强于幼苗生长期,尤以萌发指数受化感作用的影响明显.黄帚橐吾根、叶水浸液对牧草生物测定结果大多达到显著差异水平,物种水平的化感效应均表现为抑制作用,说明雨水淋溶是黄帚橐吾向环境中释放化感物质的途径之一.黄帚橐吾根部化感效应强于叶片,可能与其地下种间激烈的资源竞争有关.化感作用在增强黄帚橐吾生存竞争力、扩大种群和入侵草场中起着不容忽视的作用,可能是黄帚橐吾单优势种群落形成和草场退化的原因之一.     

黄帚橐吾挥发物的化感作用及其主要成分分析

研究了青藏高原东部高寒草场上广布的菊科毒杂草--黄帚橐吾(Ligularia virgaurea)挥发物的化感作用,并运用气相色谱-质谱方法对其挥发物主要化学成分进行了分析.结果表明,黄帚橐吾挥发物对所有5种受试牧草种子的萌发速度指数和最终萌发率均产生抑制作用,其中对垂穗披碱草和大雀麦的种子萌发抑制较为显著,而对早熟禾和羊茅影响较小.黄帚橐吾挥发物中主要含有2-甲基-庚烷(9.84%)、3-甲基-庚烷(8.25%)、庚烷(7.93%)、4-甲基-1-异丙基-双环[3,1,0]己-2-烯(7.79%)、3-甲基-己烷(6.38%)、2-甲基-己烷(5.54%)、D-苧烯(.70%)等18种化合物,占总挥发物的68.24%,其中单萜类化合物含量占总挥发物的16.58%,因此萜类化合物是其主要的化感活性物质,并通过挥发途径释放后影响到受体植物种子的萌发.黄帚橐吾挥发物的化感作用对增强其生存竞争力和种群增长起着重要作用.     

黄帚橐吾对高寒草甸凋落物分解及氮释放的影响

受过度放牧等干扰因素的影响,黄帚橐吾(Ligularia virgaurea)在高寒草甸逐渐扩张成为优势种而被称为“退化指示种”,从而威胁生态系统功能和养分循环。然而,黄帚橐吾扩张引起的凋落物比例增多,对分解及养分释放的影响尚不清晰。凋落物分解连结着生态系统碳、氮循环,对于系统功能维持具有重要意义。本试验在三江源区黄帚橐吾为优势种的高寒草甸中,设置黄帚橐吾和其他物种凋落物的多梯度混合分解试验,测定黄帚橐吾和其他物种凋落物的重量损失和氮释放,分析黄帚橐吾生物量增多对凋落物分解的影响。结果表明：(1)分解1年后,黄帚橐吾重量损失及氮素释放较其他物种更缓慢;(2)随着黄帚橐吾生物量比例的增加,凋落物整体重量损失及氮素释放显著降低;(3)混合凋落物中黄帚橐吾能限制其他物种的分解,这种拮抗效应进一步延缓了混合凋落物的分解。综上,高寒草甸黄帚橐吾扩张引起的凋落物生物量增多通过延缓凋落物分解及氮释放,阻碍土壤养分输入,进而对草地碳氮循环过程产生不利影响。     

不同生境下黄帚橐吾（Ligularia Virgaurea）个体大小依赖的繁殖分配

 研究了不同生境和密度下黄帚橐吾(Ligularia virgaurea)个体大小依赖的繁殖分配。结果表明无论在种群水平还是在个体水平上,黄帚橐吾都表现出：1) 在不同的生境和种群密度中,个体大小与繁殖体大小均不相同,其排列顺序依次为沙地＞坡地＞滩地、裸地＞非裸地、低密度＞高密度;2) 繁殖分配和单株种子均重在不同生境和种群密度中,其差异程度均从不显著(p>0.05)到极显著(p<0.01)不等;3) 繁殖体大小与个体大小在不同生境和种群密度中均呈极显著的正相关关系(p<0.01);4) 单株种子均重与个体     

光照条件对蒙古栎幼苗生长特性和光合特征的影响

为了研究不同光照条件下蒙古栎幼苗的生长过程,本文通过控制实验,模拟设计4种不同的光照条件:全光照(FS)、轻度遮荫(LS)、中度遮荫(MS)和重度遮荫(SS),对蒙古栎幼苗的形态特征、光合特性和生物量分配进行比较研究。结果表明:中度遮荫和重度遮荫条件下蒙古栎幼苗的比叶面积显著大于全光照和轻度遮荫,不同光照条件下苗高无显著差异,全光照条件下蒙古栎幼苗的地径显著大于中度遮荫和重度遮荫,同时,全光照条件下的主根长度和根径显著大于3种遮荫条件,而轻度遮荫和中度遮荫又显著大于重度遮荫;最大净光合速率表现为轻度遮荫全光照中度遮荫重度遮荫的趋势,表观量子效率在全光照与轻度遮荫时显著大于中度遮荫和重度遮荫,暗呼吸速率无显著差异;全光照下单株总生物量和根系生物量最高,轻度遮荫和中度遮荫次之,重度遮荫最低;叶片生物量和茎生物量差异较小;不同器官生物量分配表现为根叶茎,并且根生物量所占比重在68%~76%之前;全光照、轻度遮荫和中度遮荫的根冠比显著高于重度遮荫。     

光照强度与埋深对外来植物曼陀罗幼苗生长的影响

光照强度与埋深是诸多环境因素中影响外来植物幼苗出土与生长的主要因素。为了探查外来植物幼苗对光照强度与埋深的生长响应, 以曼陀罗(Datura stramonium L.)为实验材料, 分别研究两种光照强度 (100%光照和35%光照)和五种种子埋深 (1、3、5、7和9 cm)处理对曼陀罗幼苗生长特征的影响。结果表明: (1)100%光照强度处理下曼陀罗幼苗的叶片总生物量、根冠比(R/S)、相对生长速率(RGR)和总生物量显著高于35%光照强度处理。相反, 幼苗的总叶面积、比叶面积(SLA)和叶面积比(LAR)和叶片生物量比(LMR) 显著低于35%光照强度处理。(2)曼陀罗幼苗的出土率、首苗出土所需时间、株高、根长、总生物量及相对生长速率(RGR)等指标均在埋深3 cm处理获得最大值, 埋深大于或低于3 cm均导致上述指标下降, 埋深7 cm处理呈现最小值; 埋深对幼苗根冠比(R/S)无显著影响, 但显著增加地下下胚轴长度。这表明曼陀罗幼苗更偏好入侵光照强度较高和较低埋深(≤3 cm)的环境, 遮阴或过深的埋深不利于曼陀罗幼苗出土和生长。因此, 提出曼陀罗入侵农田的防控建议为: 1)在曼陀罗种子结实前进行铲除, 从源头控制曼陀罗蔓延; 2)早春作物播种前进行深耕, 将土壤里的曼陀罗种子翻耕到深层土壤中。     

典型黄帚橐吾型退化草地形成过程中土壤和植被特征

为深入了解典型毒草型退化草地形成的过程，本文对青藏高原原生草地上黄帚橐吾逐渐扩张形成典型毒草型退化草地过程中植被和土壤特征进行研究。结果表明：黄帚橐吾型退化草地形成过程中，黄帚橐吾种群密度、株高、盖度和生物量均增加；相比原生草地，退化草地的总地上生物量增加113.9%,土壤全氮、铵态氮、有机碳和速效磷含量分别增加61.0%、77.9%、45.3%和78.8%,土壤微生物生物量碳、氮分别增加42.1%和47.4%,而土壤硝态氮含量和物种丰富度分别减少40.1%和28.5%,除黄帚橐吾以外其他植物的生物量减少45.7%。黄帚橐吾极强的种间抑制能力、形态可塑性、高效的养分蓄积能力和利用效率是其成功扩张的关键，促进了黄帚橐吾型退化草地的形成。     

黄帚橐吾种群扩张对土壤理化特性与微生物功能多样性的影响

黄帚橐吾(Ligularia virgaurea)是高寒草甸退化的指示物种, 其种群扩张已严重影响了草地生态系统的经济服务功能, 但目前仍不明确土壤微生物是否参与了黄帚橐吾的种群扩张。该研究依托兰州大学高寒草甸试验站, 选择了4个不同密度的黄帚橐吾斑块, 分析了黄帚橐吾种群扩张对该草甸土壤微生物功能多样性的影响。结果显示: 黄帚橐吾种群扩张虽然提高了土壤微生物活性, 但降低了土壤速效氮浓度。各斑块间土壤微生物Shannon指数、碳源利用种类、均一度指数均无显著差异, 但高密度斑块的土壤微生物碳源利用结构与对照斑块有显著差异。表明黄帚橐吾分布地土壤微生物功能多样性的改变所引起的土壤氮素限制是黄帚橐吾种群数量急剧增加的机制之一。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.     

2018年中国植物科学若干领域重要研究进展

2018年中国植物科学继续呈现快速发展的态势, 我国科学家在国际植物科学主流学术刊物发表论文数量大幅增加, 取得了多项具有重要影响的成果。调控植物生长-代谢平衡实现可持续农业发展入选2018年度中国科学十大进展; 中国被子植物区系进化历史研究入选2018年度中国生命科学十大进展。以水稻为代表的农作物和果蔬等经济作物研究在国际上已呈现出明显的优势, 若干领域已从“追赶”状态跨越到“领跑”地位。该文对2018年中国科学家在植物科学若干领域取得的重要研究成果进行了概括性评述, 旨在全面追踪和报道当前中国植物科学领域的发展前沿和热点, 展示中国科学家所取得的杰出成就。     

我国葫芦科植物离体培养研究进展

葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义。综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望。     

2018年中国植物科学若干领域重要研究进展

2018年中国植物科学继续呈现快速发展的态势, 我国科学家在国际植物科学主流学术刊物发表论文数量大幅增加, 取得了多项具有重要影响的成果。调控植物生长-代谢平衡实现可持续农业发展入选2018年度中国科学十大进展; 中国被子植物区系进化历史研究入选2018年度中国生命科学十大进展。以水稻为代表的农作物和果蔬等经济作物研究在国际上已呈现出明显的优势, 若干领域已从“追赶”状态跨越到“领跑”地位。该文对2018年中国科学家在植物科学若干领域取得的重要研究成果进行了概括性评述, 旨在全面追踪和报道当前中国植物科学领域的发展前沿和热点, 展示中国科学家所取得的杰出成就。     

2017年中国植物科学若干领域重要研究进展

2017年中国植物科学继续保持高速发展态势, 重大成果频出, 具体表现在中国植物学家在国际顶级学术期刊发表的文章数量平稳上升。中国植物科学领域的研究工作者成果精彩纷呈, 如新型广谱抗病机制的发现、水稻广谱抗病遗传基础及机制和疫霉菌诱发病害成灾机制研究等。2017年中国生命科学领域十大进展评选中, 有两项植物科学领域的研究成果入选。水稻生物学、进化与基因组学和激素生物学等领域学科发展突出。另外, 值得一提的是, 长期从事高等植物与代谢途径调控分子网络研究和水稻品种设计育种的李家洋院士的研究成果“水稻高产优质性状形成的分子机理及品种设计”荣获2017年国家自然科学一等奖。这一具有重大国际影响的开创性贡献标志着中国植物科学在该领域的国际科学前沿居于引领和卓越地位。该文对2017年中国本土科学家在植物科学若干领域取得的重要研究成果进行了系统梳理, 旨在全面追踪和报道当前中国植物科学领域发展的最新前沿动态, 与广大读者共同分享我国科学家所取得的辉煌成就。     

Morphine-potentiated platelet aggregation in in vitro and platelet plug formation in in vivo experiments

The detailed mechanisms underlying morphine-signaling pathways in platelets remain obscure. Therefore, we systematically examined the influence of morphine on washed human platelets. In this study, washed human platelet suspensions were used for in vitro studies. Furthermore, platelet thrombus formation induced by irradiation of mesenteric venules with filtered light in mice pretreated with fluorescein sodium was used for an in vivo thrombotic study. Morphine concentration dependently (0.6, 1, and 5 microM) potentiated platelet aggregation and the ATP release reaction stimulated by agonists (i.e., collagen and U46619) in washed human platelets. Yohimbine (0.1 microM), a specific alpha(2)-adrenoceptor antagonist, markedly abolished the potentiation of morphine in platelet aggregation stimulated by agonists. Morphine also potentiated phosphoinositide breakdown and intracellular Ca(2+) mobilization in human platelets stimulated by collagen (1 microg/ml). Moreover, morphine (0.6-5 microM) markedly inhibited prostaglandin E(1) (10 microM)-induced cyclic AMP formation in human platelets, while yohimbine (0.1 microM) significantly reversed the inhibition of cyclic AMP by morphine (0.6 and 1 microM) in this study. The thrombin-evoked increase in pH(i) was markedly potentiated in the presence of morphine (1 and 5 microM). Morphine (2 and 5 mg/g) significantly shortened the time require to induce platelet plug formation in mesenteric venules. We concluded that morphine may exert its potentiation in platelet aggregation by binding to alpha(2)-adrenoceptors in human platelets, with a resulting inhibition of adenylate cyclase, thereby reducing intracellular cyclic AMP formation followed by increased activation of phospholipase C and the Na(+)/H(+) exchanger. This leads to increased intracellular Ca(2+) mobilization, and finally potentiation of platelet aggregation and of the ATP release reaction.     

我国葫芦科植物离体培养研究进展

葫芦科植物包括多种瓜类蔬菜,对其进行离体培养研究具有重要的理论和实践意义.综述了国内在葫芦科植物器官培养、体细胞胚胎发生、花药培养、原生质体培养和体细胞杂交及离体遗传转化等方面取得的研究进展,并对葫芦科植物离体培养、遗传转化与育种的前景作了展望.     

Progress in glial cell studies in some laboratories in China

Glial cells in the central nervous system(CNS) consist of a heterogeneous population of cell types,each characterized by distinct morphological features,physiological properties,and specific markers.In contrast to the previous view that glial cells were passive elements in the brain,accumulating evidence suggests that glial cells are active participants in various brain functions and brain disorders.This review summarizes recent progress of glial cell studies from several groups in China,ranging from studie...     

Changes in aquatic vegetation in Rhine floodplain streams in Alsace in relation to disturbance

Abstract. Changes are described in aquatic vegetation in oligotrophic, groundwater-fed Rhine floodplain streams in Alsace (eastern France), resulting from disturbance. Disturbance factors include changes in nutrients, either permanent ones - effluent from a waste water treatment plant or trout hatcheries - or periodic ones: flooding. Regular inputs of high levels of phosphate and ammonia modified the macrophyte vegetation in these streams. The floristic composition, which was characteristic of oligotrophic waters upstream of the eutrophicated sector, changed to that of a eutrophic situation as originally found downstream. Periodic disturbance by floods which normally occur once a year, irregularly eutrophicates the small streams, causing the development of a mixture of eutrophic and oligotrophic species. Six macrophyte communities are distinguished, indicating different trophic levels. The aquatic vegetation is adapted to the variations of phosphate and ammonia levels. Hence, aquatic macrophytes can be used as bio-indicators of fluctuations in water nutrient levels in relation to the type of disturbance.