大兴安岭呼中林区火烧迹地粗木质残体特征

对大兴安岭呼中林区不同年份火烧迹地的粗木质残体特征进行了研究.结果表明：呼中林区火烧迹地粗木质残体贮量在24.87～180.98 m³·hm^-2,其中倒木和枯立木分别为6.03～93.91 m³·hm^-2和15.29～138.37 m³·hm^-2,且不同年份火烧迹地之间差异显著;倒木、枯立木所占比例分别为24.26％～86.00％和14.01％～75.4％,且不同年份火烧迹地之间差异显著;倒木和枯立木的优势径级分别为2.50～20 cm和1.50～15 m, 优势长度分别为2.50～15 cm和5～20 m;随着火烧迹地的恢复,粗木质残体贮量的动态变化不明显.粗木质残体特征与火前林分条件和火烧强度密切相关.     

西双版纳热带季节雨林的生物量及其分配特征

 根据3块1 hm² 样地的调查资料,利用123株样木数据建立以胸径(D)为单变量的生物量预测方程。采用样木回归分析法(乔木层、木质藤本)和样 方收获法(灌木层、草本层), 获取西双版纳热带季节雨林的生物量,并分析了其组成和分配特征。结果表明,西双版纳热带季节雨林的总生物 量为423.908±109.702 Mg•hm^－2(平均值±标准差,n=3) ,其中活体植物生物量占95.28%,粗死木质残体占4.07%,地上凋落物占 0.64%。在 其层次分配方面：乔木层优势明显,占98.09%±0.60%;其次为木质藤本,占0.83%±0.31%;灌木层和草本层生物量均小于木质藤本的生物量; 附生植物最低,仅为0.06%±0.03%。总生物量的器官分配以茎所占比例最高,达68.33%;根、枝、叶的比例分别为18.91%、11.07%和1.65 %。 乔木层生物量的径级分配主要集中于中等径级和最大径级。大树(D＞70 cm)具有较高的生物量,占整个乔木层的43.67%±12.67%。树种分配方 面,生物量排序前10位的树种占乔木层总生物量的63.43%±4.09%,生物量集中分配于少量优势树种。西双版纳热带季节雨林乔木层叶面积指数 为6.39±0.85。西双版纳热带季节雨林乔木层的地上生物量位于世界热带湿润森林的中下范围。     

大兴安岭呼中林区粗木质残体贮量及其环境梯度

对大兴安岭呼中林区主要植被类型、兴安落叶松不同林型内粗木质残体贮量进行对比研究,并利用除趋势典范对应分析对其环境梯度进行定量分析.结果表明：云杉林粗木质残体贮量较高,为0.20 m³·hm^-2,且不同植被类型之间呈显著性差异;兴安落叶松不同林型粗木质残体贮量在0～0.28 m³·hm^-2,其中偃松群落最高,为0.28 m³·hm^-2,泥炭藓-杜香-落叶松林最低（0）,且各林型之间差异不显著.粗木质残体贮量分布格局较复杂,受多因素交叉影响;海拔、坡位等地形因子和林分年龄、郁闭度等林分条件是影响森林粗木质残体贮量的主要环境因子,二者综合作用表达了该地区森林粗木质残体贮量的空间生态梯度.     

鼎湖山季风常绿阔叶林粗死木质残体的研究

在3次样地调查的基础上对鼎湖山季风常绿阔叶林内粗死木质残体的贮量、输入量进行了研究,并通过比较林窗范围内土壤养分含量,初步评述了粗死木质残体在森林生态系统养分循环中的作用。研究结果表明:1)季风常绿阔叶林粗死木质残体的贮量为25.278t·hm~(-2),立木、倒木、大枝所占的比例分别为32.02％、49.62％和18.36％;2)1994～1999年间群落的死亡率为24％·a~(-1),死亡个体以胸径小于5cm的为主,粗死木质残体的平均输入量为4.128t·hm~(-2)·a~(-1);3)倒木主体所在的样方土壤有机质和速效钾的含量较高。     

武夷山甜槠林粗死木质残体的贮量、动态及其功能评述

 本文对武夷山甜槠林76龄成熟林内粗死木质残体的贮量、增枯量和分解量等进行了研究,对不同林龄甜槠林粗死木质残体的贮量动态进行了对比分析,并初步评述了它们在森林生态系统养分循环中的作用。研究结果表明：(1)甜槠林成林粗死木质残体贮量为7.349t·hm-2,增枯量为1.425t·hm-2·a-1,分解量为0.512t·hm-2·a-1;(2)随着林龄增长,不同林龄甜槠林的粗死木质残体贮量呈“S”型动态模式,至58龄阶段达到最大值,其后渐趋稳定;(3)粗死木质残体是甜槠林生态系统中较为重要的组成部分,其各养分元素贮量占该系统生物量分室总贮量的0.09%～1.91%,由增枯量实现的各养分元素归还量占养分元素归还总量的l.94%～4.48%。     

人为干扰对大兴安岭北坡兴安落叶松林粗木质残体的影响

比较了兴安落叶松天然林和两种不同干扰类型兴安落叶松林(一次干扰林、二次干扰林)之间活立木蓄积、粗木质残体(CWD)蓄积和组成的差异.结果表明：天然林、一次干扰林和二次干扰林的活立木蓄积量分别为161.6、138.3和114.8 m³·hm^-2,粗木质残体的蓄积量分别为69.77、36.64和32.61 m³·hm^-2.天然林粗木质残体大部分径级在20～40 cm,其中倒木、枯立木分别占总材积的72%和28%;一次干扰林和二次干扰林粗木质残体大部分径级在10～30 cm,其中倒木、枯立木和伐桩分别占各自总材积的70%、14%、16%和57%、15%、28%.人为干扰造成兴安落叶松林粗木质残体蓄积减少,改变了粗木质残体的组成.     

人为干扰对大兴安岭北坡兴安落叶松林粗木质残体的影响

比较了兴安落叶松天然林和两种不同干扰类型兴安落叶松林(一次干扰林、二次干扰林)之间活立木蓄积、粗木质残体(CWD)蓄积和组成的差异.结果表明：天然林、一次干扰林和二次干扰林的活立木蓄积量分别为161.6、138.3和114.8 m³·hm^-2,粗木质残体的蓄积量分别为69.77、36.64和32.61 m³·hm^-2.天然林粗木质残体大部分径级在20～40 cm,其中倒木、枯立木分别占总材积的72%和28%;一次干扰林和二次干扰林粗木质残体大部分径级在10～30 cm,其中倒木、枯立木和伐桩分别占各自总材积的70%、14%、16%和57%、15%、28%.人为干扰造成兴安落叶松林粗木质残体蓄积减少,改变了粗木质残体的组成.     

丰林自然保护区阔叶红松林粗木质残体研究

粗木质残体(CWD)是森林生态系统的重要组成部分,对维持森林生态系统健康具有不可忽视的贡献.采用典型取样法在黑龙江丰林国家级自然保护区设置了17块20×20m的标准样地,拟对保护区内阔叶红松林中粗木质残体的贮量、形态组成、直径、长度及腐烂度等特征进行研究.研究结果表明:(1)CWD总贮量为75.1m³·hm^-2,其中倒木,枯立木和树桩的贮量分别为.24 m³·hm^-2,2.03m³·hm^-2和7.34m³ ·hm^-2.(2)倒木和枯立木的优势径级范围分别为11cm～20cm(占CWD总数的4%)和0-10cm(45%);倒木和枯立木的优势长度范围分别为0-5m (%)和m-10m(49%).(3)CWD腐烂度呈近正态分布,且主要分布在Ⅱ(28%),Ⅲ(35%)和Ⅳ(2%)腐烂等级上.     

鼎湖山黄果厚壳桂粗死木质残体的分解

通过建立时间序列法、测定粗死木质残体的密度变化,研究鼎湖山黄果厚壳桂粗死木质残体三个直径(5~10cm、10~20cm和20~30cm)的分解过程,探讨粗死木分解过程中C、N元素及其C/N比值与分解速率的关系。结果表明粗死木质残体的分解常数K值随直径的增加从0.2225a-1呈指数降低到0.1257a-1,由粗死木质残体在分解过程中密度变化得出三个直径从小到大分解95%所需的时间分别为13a、19a和24a;黄果厚壳桂粗死木质残体在分解过程中不存在时滞效应,其树皮和心材的分解速度也相近,用单因素数指数方程能准确反映黄果厚壳桂的分解过程;与高纬度地区比较,鼎湖山黄果厚壳桂粗死木残体的分解速率常数K值显著高于前者。还就粗死木残体基质组成和性质、气候与环境条件、生物等因素对粗死木分解速率的影响进行了详细的讨论。     

高山峡谷区暗针叶林木质残体储量及其分布特征

木质残体是高山峡谷区暗针叶林生态系统的重要组成元素,其分布在林窗、林缘和林下可能具有较大的差异,但一直缺乏必要关注。因此,以典型川西高山峡谷区岷江冷杉(Abies faxoniana)原始林为研究对象,研究了高山峡谷区暗针叶林木质残体的储量特征及其在林窗、林缘和林下的分布特征。结果表明,岷江冷杉原始林木质残体总储量达53.00 t/hm~2,且呈现林下的储量大于林窗和林缘的趋势。从林窗到林下木质残体的类型均以倒木为主,直径大于40 cm的木质残体储量占粗木质残体的74.55%—76.15%,林窗、林缘和林下Ⅲ和Ⅳ腐烂等级的粗木质残体储量之和分别占粗木质残体储量的50.02%、55.84%和62.90%。相对于林下和林缘,林窗内倒木和根桩的储量比例较小,但枯立木和细木质残体的储量比例较高。此外,林窗内较低腐烂等级粗木质残体的储量较高,而林下较高腐烂等级粗木质残体的储量显著高于林窗和林缘。这些结果为充分认识高山峡谷区暗针叶林生态系统林窗更新过程中木质残体相关的物质循环等关键生态过程提供了基础理论依据。     

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。     

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。     

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。     

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.