羊草草原枯枝落叶分解的研究——枯枝落叶分解与生态环境的关系

枯枝落叶的分解受生态环境的影响,枯枝落叶置于不同的生态环境下,其分解速率不同。例如,羊草(Leymus chinensis)在6种不同生境中的分解存在着明显差异。枯枝落叶位于地表和地下,其分解速率则不同,埋入地下的分解比位于地表的迅速。分解速率与土壤水分、地表温度和土壤pH呈指数正相关,与相对湿度呈线性正相关,它们对分解有积极的促进作用。通过生态因子对分解影响的综合分析表明,在羊草草原上,诸生态因子对枯枝落叶分解的重要性依次为:土壤水分、土壤pH、地表温度、相对湿度。     

羊草草原枯枝落叶分解的研究——主要优势植物的分解速率和损失率

分解速率和损失率从不同侧面反映了枯枝落叶分解动态,羊草草原主要优势植物,羊草（Leymus chinensis),拂子茅（Calamagrostis epigejos),减蓬（Suaeda glauca),碱茅（Puccinellia tenuiflora),五脉山黎豆（Lathyrus quinqueneruivs),碱蒿（Artemisia anethifolia)分解速率的季节变化动态近似倒“V”字型,损失率的季节变化呈S型,反了枯枝落叶的失重情况,枯枝落叶的化学组成成分是造成不同种植物间分解差异的主要原因,特别是C／N比与分解快慢有密切关系,分解初期,枯枝落叶的损失符合指数衰减模型,枯枝落叶损失95％所需时间,羊草群落约为8．8a,杂类草群落约为9．7a,碱茅群落约为7．1a,碱蓬群落约为4．7a。     

羊草草地枯枝落叶与分解者之间能量流动的研究

对羊草草地枯枝落叶和分解者之间的能量流动过程分析表明,每年因植物枯死输入到枯枝落叶的能量为3769.42kJ／m2／a;储存在枯枝落叶中的能量为：3424.10kJ／m2;每年被分解者所消耗的能量为1141.67kJ／m2／a,其中71.87%的能量用于呼吸作用。目前在羊草草地上,枯枝落叶和分解者之间的能量流动输入大于输出,能量处于积累阶段。当达到稳定状态时,储存在枯枝落叶中的能量为11305.61kJ／m2,分解者中的能量为1475.20kJ／m2。     

羊草草原枯枝落叶积累的研究──自然状态下枯枝落叶的积累及放牧、割草对积累量的影响

在自然状态下,羊草草原枯枝落叶积累季节动态是积累量从５月出现,随着时间推移呈指数形式递增,１０月末出现最大值。当枯枝落叶输入量和分解速率保持恒定时,积累量的年变化,随着时间的进展不断增加,最后达到稳定状态,量大积累量为５７２ｇ／ｍ￣２,达９５％稳定状态时间约为７─８ａ。放牧对枯枝落叶积累有明显的抑制作用,当放牧强度达７．５８羊（只）／ｈｍ￣２时,积累量比非放牧区减少近７４％。割草对枯枝落叶积累的影响也是显著的,随着割草频度增加,积累量明显减少,当一年内刈割３次,积累量减少８３％。刈割时间对积累量的影响表现在割草期的早晚,伴随刈割时间推迟,积累量逐渐减少。     

帽儿山森林落叶分解消耗与土壤动物关系的研究

１引言森林凋落物分解是森林生态系统物质循环和能量流动的重要环节,枯枝落叶分解是由多种因素作用的复杂过程．研究枯枝落叶在自然环境下的分解消耗及其与土壤动物的关系具有重要的生态学意义［４］,并对林业生产、营造人工林有一定的指导作用．在枯枝落叶分解研究中,...     

森林枯叶分解过程中真菌的特性

枯枝落叶是森林土壤有机质的主要来源,枯枝落叶的分解对提高土壤肥力,增加树木的生产力是极其重要的。关于枯枝落叶的特性,有机质的积累和元素循环,枯枝落叶分解过程中的微生物学特性,死地被物和土壤中微生物的分布和活动,土壤中的生物化学动态与物质转化的关系,近年来很多学者对此有过报道。     

东北松嫩平原羊草群落的土壤呼吸与枯枝落叶分解释放CO2贡献量

根据静态气室法的测量结果 ,分析了羊草群落土壤呼吸量和枯枝落叶分解释放 CO2 量的季节动态 ,及其与地上生物量 ,枯枝落叶分解量及环境因子的关系。结果表明 :( 1 )在整个观测期内 ,羊草群落土壤呼吸的季节动态呈现单峰曲线 ,8月中旬达到最大值 1 3.2 7g C/( m2 · d)。 ( 2 )羊草群落土壤呼吸的季节变化规律与地上绿色体生物量的季节动态同步。( 3)羊草群落土壤呼吸的季节动态与枯枝落叶分解量的季节动态同步。 ( 4 )羊草群落土壤呼吸量与土壤 0～ 1 0 cm土壤含水量显著正相关。( 5 )地表枯枝落叶层直接排放 CO2 量的季节动态呈现逐渐递减的趋势 ,释放量平均为 -0 .87g C/( m2·d)。有减缓土壤向大气排放 CO2 的作用。 ( 6 )枯枝落叶分解释放 CO2 量同地表枯枝落叶量显著正相关。     

羊草草甸枯枝落叶的分解、积累与营养物质含量动态

通过数理统计,建立了枯枝落叶的分解和积累模型。枯枝落叶的消失率为0.4065g／g·a,消失量比率的季节变化符合于logisitic曲线,分解活动在5—9月份最活跃,这段时间的消失量约占全年消失量的90%。 分解作用冬季基本停止。羊草草甸在现有情况下,积累量达95%稳定状态大约需要8年。最大积累量约为572g／m2,在分解过程中,枯枝落叶中化学成分的含量和分解初期相比不断下降。氮、磷、钾较其它化学元素损失得快。纤维素分解较慢。各种化学成份损失的顺序是：K>P>N>Na>Ca>Mg>Fe>纤维素。     

羊草草原和大针茅草原氮素贮量及其分配

不同类型草原氮素贮量及其分配的研究,是草原生态系统物质循环研究的重要内容。它不仅有助于阐明草原生态系统物质循环的规律性,而且对于预测草原发育的方向和趋势,对于草原合理利用和提高草原生产力,都具有重要意义。在我国广大草原地区,草场退化日益严重的今天,研究生命的元素——氮素的循环,不仅有理论意义,而且有其重要现实意义。此项研究,在国际上作为IBP和MAB研究重要课题,受到普遍重视。在我国仅趋开始。本文是作者1979年对内蒙古锡林河流域羊车(Leymus chinensis)、小木草杂类草草原(简称羊草草原)和大针茅(Stipa grandis)草原氮素贮量及其分配研究的结果。     

红松洼的土壤螨——一群不为人知的小动物

正土壤动物,顾名思义,是指那些生活在土壤或落叶下的各种小动物的总称,包括蚯蚓、蚂蚁、线虫、蜘蛛、跳虫、螨类等很多种类。土壤动物通常能够促进枯枝落叶等自然界"垃圾"的分解,改善土壤结构,提高土壤肥力,对维系生态系统的健康运转具有重要意义。其中,土壤螨类是土壤动物中的重要组成部分。土壤螨类是红松洼自然生态系统的重要组成部分,也是红松洼草原重要的分解者,更是守卫     

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.     

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。     

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.     

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.     

Apoptosis in experimental myocardial infarction in situ and in the perfused heart in vitro

We report the appearance of apoptotic cells in experimental myocardial infarction (rabbit heart) in in situ and in vitro preparations. Apoptosis was recognized by intravital staining with Hoechst 33342 (Ho342), by nick-end labeling (TUNEL) and by DNA laddering. A steady rise in the relative number of apoptotic cardiomyocytes (apoptotic index) was noted in in situ preparations. Apoptosis was first noted 6 h after the onset of ischemia with its highest value occurring after 72 h. Apoptotic nuclei were absent in remote areas of the left and right ventricles. Apoptotic nuclei within the infarcted area showed diminished intensity of Ho342 fluorescence. Three days after ischemia, a border zone adjacent to the infarcted area consisting of apoptotic macrophages was recognized. A novel finding was the appearance of apoptotic cardiomyocytes in the isolated perfused ischemic heart. Occurring as early as 50 min after the onset of ischemia, a high apoptotic index was present adjacent to the ligature placed around the coronary artery. This observation provides the opportunity to selectively examine factors leading to apoptosis in the ischemic heart under controlled experimental conditions.     

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.