基于根部年轮与导管特征的黄土高原苜蓿生长衰退分析

紫花苜蓿作为黄土高原退耕还林还草工程的重要人工草本物种,对控制水土流失、植被固碳和生态环境改善等方面都发挥着重要生态作用;但是苜蓿草地在黄土高原普遍出现生长不可持续的特征,在第6年左右植被出现明显生长衰退现象。本研究在黄土高原4个降水梯度(280、400、500 mm和550 mm)的地点采集紫花苜蓿和自然对照草本物种:委陵菜的根部年轮样品,并分析了紫花苜蓿与委陵菜的年轮宽度和导管大小随年龄的变化趋势特征及与气候要素的相关关系。研究结果表明:在气候暖干化环境下,紫花苜蓿和委陵菜的年轮宽度随年龄增加都有不断下降的趋势,且在降水量偏低样点下降更为显著,这是由于植株在降水量偏低地点易遭受严重水分胁迫,以致无法满足生长所需的水分而造成根部生长速率明显减缓。紫花苜蓿根部导管大小随年龄增加均有明显下降趋势,在降水量偏低的样点下降趋势更加显著;这表明水分胁迫随年龄增加逐渐加剧,紫花苜蓿导管大小逐年下降以致不能满足自身生长的水分需求,植被生长呈衰退趋势,且在降雨偏低地区,苜蓿生长衰退出现时间较早。自然草本委陵菜根部导管大小随年龄增加均有明显上升趋势且在降水量偏低样点上升趋势更显著,这表明委陵菜通过增大根部导管大小、增加输水能力来满足随年龄增加不断上升的水分需求,这也说明委陵菜导管结构特征较好的适应了黄土高原干旱半干旱环境,生长处于可持续发展状态。     

黄土高原多年生草本物种根部导水结构及空间分异特征

植物茎干导水系统起着植株水分长距离输导功能,深入了解植物导水解剖结构和功能对于认识植物水分、养分输导和分配策略具有重要意义,然而相关研究还是主要集中在木本乔、灌木物种上,而对于多年生草本物种的相关研究还未引起人们的重视。以黄土高原多年生草本物种为研究对象,在黄土高原沿降雨梯度(250—530 mm)布设12个采样点,采集了30种多年生草本物种的主根解剖材料,并分析了该地区草本物种根部导管解剖结构及空间分异特征。研究结果表明1)多年生草本物种根部导管特征参量具有较大的变异性,在固定测量范围内导管数量、导管直径、导管分数、总水分传导效率的变化范围分别为25—295个、24.46—54.58μm、2.42%—33.16%、0.034—25.357 kg m~(-1) MPa~(-1) s~(-1)。2)多年生草本根部导管直径、导管分数和导水效率均沿降雨量的增加呈不断下降趋势,其中以导水效率下降趋势最为明显(R=-0.3—-0.362,P0.05),这表明水分条件是限制黄土高原草本物种根部导水特征空间变异的主要因素。3)多年生草本根部导管直径和导水效率以半荒漠分布为主的蒺藜科草本物种中数值最高,其次是人工种植为主的豆科草本物种,而以自然分布为主的菊科草本物种的导管参量数值最低,这表明黄土高原不同类群草本物种的导水特征和输水策略存在较大差异性。     

黄土高原多年生草本根部导水策略空间异质性特征

根据多年生草本根部导管解剖结构特征,分析了黄土高原两个气候区草本物种导水结构特征及导水策略对干旱气候条件的适应性特征。结果表明,黄土高原半干旱区(年降雨量小于400 mm)草本物种平均年龄较大(7年),理论导管直径(33μm)、导管面积(680μm²)和导水效率(1.56 kg m^-1 MPa^-1 s^-1)数值较高,而导管数量(65个)和导管分量(6.2%)数值较低;黄土高原半湿润区(年降雨量大于400 mm)草本物种平均年龄较小(5年),理论导管直径(27μm)、导管面积(550μm²)和导水效率(1.12 kg m^-1 MPa^-1 s^-1)数值较低,而导管数量(85个)和导管分量(7.5%)数值较高。黄土高原半干旱区草本物种的导管直径较大、单位面积内的导管数量较少,因而导水效率较高,在干旱胁迫条件下趋向于采取效率优先的导水策略;黄土高原半湿润区草本物种的导管直径较小、单位面积内的导管数量较多,因而导水效率较低...     

黄耆属草本植物根部导管结构对环境因子的响应

干旱半干旱区植物的导水解剖结构对环境条件的适应性具有重要生态学意义。本研究采用石蜡切片法获取了中国干旱半干旱区4种黄耆属草本植物——斜茎黄耆(Astragalus adsurgens)、黄耆(Astragalus membranaceus)、乳白黄耆(Astragalus galactites)和草木樨状黄耆(Astragalus melilotoides)根部导管解剖结构的特征，分析了导管解剖性状对环境因子(温度和降水)的响应特征。结果发现，黄耆属草本物种的导管解剖性状(导管数量、导管分数、平均导管面积、平均水力传导率和水力直径)具有较大的变异特征。随着降水和温度的增加，导管数量显著下降，而导水效率相关的性状(水力直径、平均导管面积和平均水力传导率)则具有上升趋势。这表明在降水量和温度较低地区，较多的导管数量和较小的导管面积导致黄耆属草本采取导水安全优先策略；在降水量和温度较高的地区，较少的导管数量和较大的导管面积导致黄耆属草本采取导水效率优先策略。黄耆属草本根的解剖性状与温度的相关性均高于其与降水的相关性，表明温度可能是影响其导管解剖结构的主要气候因子。     

三峡水库消落带植被高程梯度分异及其对生境胁迫的响应

三峡水库蓄水运行形成的极端生境胁迫深刻改变了消落带植被结构和功能。在消落带横向断面高程梯度上,植被生境具有典型的空间异质性。选取三峡水库典型自然恢复消落带,通过野外调查和室内分析,揭示了消落带自然演替植被的群落构成、物种多样性和生物量随高程梯度的分异特征,系统分析了极端淹水、侵蚀-沉积、土壤环境等生境胁迫类型对消落带植被高程梯度分异的影响。结果表明：①研究消落带适生植被以草本为主,共有15科25种23属,其中禾本科种类较多,但单属单种、单优群落现象明显;一年生和多年生草本分别占52%和48%,且一年生草本多在消落带上部定居,多年生草本主要在消落带下部聚集。②物种多样性指数与高程呈正相关趋势,在145-150m范围内较低,在160-170m范围内较高。③植被生物量为199.68-1211.2g/m²,总体呈现随高程增加而显著增加的趋势;受多种生境因子的复合胁迫影响,生物量随高程存在局部波动。④水库水位变动形成淹水时长、出露时令、淹水强度等是影响消落带植被生物量高程梯度分异的主导因子;侵蚀/沉积过程改变土层厚度、根层土壤持水能力和肥力条件,对植被生长产生重要影响;土壤水分和氮是植被生长的限制性因子。因此,优势生境适宜性物种选育、土壤基质保育和植被格局功能优化是三峡水库消落带植被恢复和生态功能重建的重要任务。     

锡林浩特多年生草本根部导管性状与植株生态策略的相关特征

干旱半干旱区植物的木质部输水系统对维持植物生长发育有重要作用。以中国干旱半干旱区的草本植物为研究对象,旨在探究草本物种根系导管解剖结构与植物生长之间的关系。用石蜡切片法,将在锡林浩特草原采集的草本物种的主根样品制作成切片,得到固定面积内导管解剖结构参量(导管数量、导管分数、平均导管面积、平均水力传导率和水力直径),然后用逐步回归法和Pearson相关分析各导管解剖性状与植物生长特征(年龄、生长速率和平均高度)之间的关系。结果发现(1)生长速率与导管数量(R=-0.494,P<0.01)和导管分数(R=-0.255,P<0.05)显著负相关,与平均导管面积(R=0.274,P<0.05)、平均水力传导率(R=0.263,P<0.05)和水力直径(R=0.245,P<0.05)显著正相关,表明生长快的草本具有大而少的导管,需要较高的水分传输能力,而生长慢的草本具有小而多的导管,水力安全性较高;(2)植株的高度与导管数量(R=-0.354,P<0.01)显著负相关,与平均导管面积(R=0.293,P<0.05)、平均水力传导率(R=0.289,P&l...     

塔克拉玛干沙漠腹地柽柳年轮宽度对地下水埋深的响应

【目的】柽柳作为干旱荒漠生态系统的典型物种,研究其年轮宽度对地下水响应的保护有重要价值。【方法】研究基于沙漠腹地达理雅博依绿洲地下水埋深资料,利用年轮测定方法分析不同地下水埋深状况下柽柳年轮宽度的变化,探讨其与地下水埋深变化的关系。【结果】样地一地下水埋深随时间逐年增加,埋深范围是1.2～2.6 m,柽柳的年轮宽度在2001-2020年呈显著增加趋势,变化范围为0.98～5.80 mm,年轮宽度年际间差异显著;样地二地下水埋深随时间增长呈现先增加后减小的趋势,埋深范围是2.7～4.5 m,柽柳年轮宽度在1977-2020年整体呈正弦函数变化,范围为1.46～4.41 mm,年轮宽度年际间差异性不显著;样地一柽柳标准年表振幅范围是0.502～1.641,大于样地二柽柳标准年表振幅范围为0.577～1.331。【结论】样地一地下水埋深向着柽柳生长适宜的范围增加时,有利于柽柳的生长,表现为年轮宽度增加,样地二的柽柳年轮宽度变化和地下水埋深之间无显著相关性。     

灌木年轮生态学研究进展

灌木年轮资料的生态学价值逐渐受到人们关注,灌木年轮数据逐步被用于揭示灌丛植被年际生长对气候响应的敏感性研究中,目前用于灌木年轮学研究的主要灌木种已近70种。灌木年轮材料拓宽了传统以乔木树种为主的树轮研究网络,丰富了树木年轮学的研究范围和研究对象,在揭示灌丛生态系统结构、功能、服务的时间变化特征上具有重要生态学价值。本文收集整理了1996—2021年间的灌木年轮学研究成果,综述灌木年轮学在生理学、气候学、生态学、水文学领域的研究进展。阐述了不同环境胁迫条件下灌木生长和木质部解剖特征;揭示了不同气候条件下灌木物种径向生长的主要限制性因素,以及基于灌木年轮材料记录的区域气候波动历史;评估了灌木物种径向生长和种群动态的气候和非气候因素驱动的灌丛生态系统变化特征;论述了灌木年轮资料在重建区域水文要素变化历史方面的研究。在全球气候变暖不断加剧的背景下,我国灌木年轮学研究应着重关注干旱半干旱区不同水分条件下灌木物种径向生长对干旱胁迫的响应规律,以及在气候变化背景下灌木物种空间分布及其气候响应敏感性的转型特征方面研究。     

Drought effects on the plasticity in vessel traits of two endemic Magnolia species in the tropical montane cloud forests of eastern Mexico

本文旨在探讨气候变化如何影响两种特有墨西哥木兰的导管性状可塑性和其每年的年轮宽度。尽管如此，很少有研究评估干旱对墨西哥东部热带山地云林导管性状的影响。通过生长年轮的数字图像，我们对所研究的墨西哥木兰树种的径向生长率、树龄和导管性状可塑性进行了评估，比较了两种墨西哥木兰树种在干旱年和非干旱年的导管密度、水力直径和传导面积百分比。本研究首次对墨西哥两个热带山地云林中的两个濒危木兰树种(Magnolia vovidesii 和M. schiedeana)的多孔木质部导管性状对长期气候变化的可塑性进行了分析。结果发现，当比较干旱和非干旱年份时，温度和降水量与年轮宽度的差异密切相关。扩散型多孔木质导管解剖结构具有很高的可塑性，这与所研究的两种木兰树种的温度和/或水的有效性有关。我们的结论是，与非干旱年份相比，对干旱年份的解剖学适应导致了导管性状的大量减少；这些可塑的适应性在植物长期环境胁迫下的水分运输以及生存的安全性方面起着重要的作用。     

干旱区多枝柽柳的生长特性

多枝柽柳是分布最为广泛的柽柳属植物之一。也是维持干旱区荒漠生态系统的关键植物种。本研究运用树轮年代学和树干解析方法。对额济纳地区不同生境条件下多枝柽柳的年轮生长、高生长和地径生长等方面的特征进行初步探讨。多枝柽柳每年形成1个年轮。树盘偏心生长极为普遍．完整树轮大多在10龄以内区域,10龄以外都呈单个或多个不完整年轮生长区。多枝柽柳单枝在1～4年高生长缓慢．4～8龄之间属于快速生长期,10年以上生长速率急剧下降。不同地下水位条件下三组样本径生长年增长速率达到极大值的年龄分别为21、56和74年,水环境条件是影响多枝柽柳径向生长的主要因素。同一年年轮宽度随枝高呈减小趋势。多枝柽柳边材的树轮数一般在3～5轮之间,进入老龄阶段有增加趋势。边材宽度随年龄增长逐渐减小。     

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。     

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.     

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.     

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.