川西箭竹群落生态学研究

箭竹是大熊猫的主食竹，主要分布在亚高山地带，是亚高山森林下层重要的优势层片。对箭竹生态学研究主要集中在种群结构、生长、更新、生物生产力、繁殖特性及其在亚高山森林系统水土保持、养分平衡等生态功能发挥中的作用等几方面。而有关箭竹层片对整个森林生态系统养分循环动态过程和机理、箭竹种群生活史动态格局、开花机理、人为干扰下箭竹群落及森林群落更新的过程等方面的研究相对滞后。建议加强箭竹层片在亚高山针叶林生态系统结构和养分循环动态过程中的作用，箭竹克隆生长过程与森林群落更新过程的互动机理、箭竹种群生活史过程中养分源库动态、人为干扰下箭竹克隆种群更新过程与森林更新过程互动等方面的研究。     

干旱条件下植物生长适应策略研究进展

受全球气候变化和人类活动的影响,干旱环境缺水现状正越来越严重,干旱区正在扩散。如何抑制这种蔓延趋势,逐步改善干旱区环境是当前亟待解决的全球性难题。基于多年来对干旱条件下植物物候节律、形态生长特性和资源利用策略等植物生长适应机制以及植被调控的研究结论,提出在今后的理论研究或植被实践中加强干旱条件下植物物候特征及其生理机制、全球气候变化下干旱环境植物的生长适应策略响应和以生长适应机制为基础的干旱环境植被调控实践等方面的研究,以通过深入了解干旱条件下植物的生长适应策略及其机制,指导干旱地区的植被实践,遏止干旱环境不断恶化的趋势。     

道路对若尔盖高寒草地植被的影响研究

对国道213线若尔盖高寒湿地花湖段道路周围的植被进行了调查,沿道路按照一定的景观格局,在道路两边设置垂直于道路的样线,沿样线在距离道路10m、50m和200m的地方设置样地.共布置样线19条,样地57个,测量样方130个.道路段地处亚高山草甸地带,主要植被类型是矮型嵩草和杂类草草甸.道路周围的植物群落根据聚类分析可分为8个群丛,其中85%的群落类型为长叶火绒草——长毛风毛菊——鹅绒委陵菜——小嵩草群落（Assoc.Lenotopodium-Saussurea-Potentilla-Kobresia）,7%为鹅绒委陵菜——平车前——二裂委陵菜群落（Assoc.Potentilla anserinc-Plantago——Potentilla bifurca）.施工区植物种类共计约110种,隶属于29科73属,未发现濒危物种存在.区系组成上,以北温带分布物种为主,占总数的55%,其次为世界分布物种,占25.7%,菊科、禾本科和毛茛科植物种类最多,占物种总数的36.8%.整个路段植物物种丰富度值为27.8±8.2,其中以牧民夏棚定居点附近的物种丰富度最低,其它地段较高;湿地物种丰富度中等;物种丰富度最高的出现在红星乡牧场.整个道路段附近植物多样性指数（Shannon-Wiener指数）为1.95±0.48,分布式样与丰富度类似.在红星乡冬牧场和花湖地段靠近道路的样地多样性指数最高,在湿地保护站以南道路段,多样性指数也基本上以道路边最高.物种丰富度并未表现出明显的梯度,显示出道路对植被的匀质化作用.土地使用（冬牧场和夏牧场）类型差异对植被类型和生物量有显著的影响.但是由于道路存在的时间较长以及放牧的存在使道路效应的表现不很明显.     

盐胁迫对植物的影响及植物的抗盐机理

盐是影响植物生长和产量的主要环境因子之一,根据国内外最新的研究资料,从盐胁迫对植物的生长、水分关系、叶片解剖学、光和色素及蛋白、脂类、离子水平、抗氧化酶及抗氧化剂、氮素代谢、苹果酸盐代谢、叶绿体超微结构的影响,及影响光合作用的机制等方面入手,对植物盐胁迫研究现状及进展情况进行了综述,旨在为开展植物抗盐机理研究、选育培育耐盐植物新品种提供依据。     

嫁接用苗生长状态无损测量技术的研究

利用机器视觉技术对蔬菜幼苗的生长特征信息进行了无损检测,该研究技术是定量化研究植物生长规律的关键技术之一,并为蔬菜自动化生产过程中的嫁接、移栽、间苗等作业提供必要的技术理论依据.该研究通过在温室内设计了一套计算机视觉系统,对多株群体蔬菜苗的生长进行了长时间、连续、快速的无损检测,并利用VB6.0编制了图像处理软件,提取了蔬菜幼苗的外部形态特征,经过图像处理软件分析得到蔬菜幼苗的日生长变化规律,发现蔬菜苗在夜间的生长率明显高于白天.研究表明,采用机器视觉及图像处理技术可以快速、准确地监测出蔬菜幼苗的外部形态特征量,能够对蔬菜生长状态进行直观测量,实现对蔬菜幼苗生长规的定量化研究,为蔬菜生产过程中相关作业的自动化提供可靠的理论依据.     

外来物种每年给非洲造成数十亿美元损失

据国际自然资源保护联盟前些日的报告 ,外来物种在非洲蔓延迅速 ,严重破坏了生物多样性和经济发展 ,每年造成的经济损失多达数十亿美元。报告的主要起草人霍华德在报告的发表仪式上说 ,目前了解的外来物种给非洲造成的破坏可能只是冰山一角 ,这些物种对非洲生态和经济发展的影响可能比估计的要大得多。而在全球 ,外来物种入侵给各国造成的经济损失每年要超过40 0 0亿美元。据介绍 ,外来物种指的是那些离开原有进化环境进入新环境的植物、动物和微生物。由于外来物种在新环境中没有天敌 ,繁殖迅速 ,抢夺其它物种的养分和生存空间 ,从而造成其…     

升高CO2浓度和温度对针叶林的影响以及在川西亚高山针叶林研究中的展望

以CO2浓度和温度升高为主要特征的全球气候变化受到了世界各国科学家们的普遍关注。目前已经有大量关于森林生态系统对全球变化响应的研究报道和综述性文章,涉及分子、生理生态、种群和群落生态以及区域和全球尺度等微观和宏观领域的研究内容,因而要想对森林生态系统对全球变化的响应研究进行全面的综述是相当困难的。因此,本文只简要评述了森林生态系统对升高CO2浓度和温度响应研究中的诸如CO2浓度和温度升高对森林生长和生产力的影响、森林生态系统物种组成和多样性对升高CO2浓度和温度的响应、植被变化与全球碳循环的互动以及气候变化与森林生态系统生物地球化学循环的关系等几个热点问题。川西亚高山针叶林区为我国的第二大林区,地处高山峡谷地带,是全球变化的敏感地带。相对简单的植物群落结构、较低的物种丰富度和多样性、巨大的冷冻土壤碳库、不同演替阶段和功能的植物群落组合以及分布于林线附近的邻接效应等为研究针叶林系统对升高CO2浓度和温度的响应提供了良好的天然实验室。针叶林生产力、植物群落物种组成和多样性以及土壤碳氮过程等对升高CO2浓度和温度的响应对于预测未来气候变化下针叶林系统的生态过程具有重要意义。     

若尔盖郎川公路建设区有毒有害植物扩散及生态安全性评价

通过大量的野外考察和文献资料分析,研究了朗川公路建设区沿线天然草地有毒有害植物种类、分布、群落结构及安全性。结果表明,由于人为干扰改变了天然植物群落物种间的竞争格局,具有较强竞争力的有毒有害物种得以扩散,在群落中作用增强,在群落中优势度逐渐上升。在各等级样方中,Shannon-Wiener物种多样性指数和Pielou均匀度指数随着有毒有害物种分盖度的增加呈现出先增后减再回升的趋势,Simpson优势度指数则随着有毒有害物种的分盖度增加而逐渐降低。此外,工程建设中采取草皮移植措施在一定程度上取得了成效,已恢复的边坡群落比较稳定,根据不同研究结果表明割取草皮厚度及大小与草皮恢复后的植物群落结构密切相关。     

基于策略多样性熵指标的无人机群智系统激发-汇聚程度度量方法研究

新一代无人机群系统的重要特征是具有群体智能,是一类典型的群智激发汇聚系统.目前,多智能体强化学习技术展现出较强优势,是构建新一代自主智能无人机群系统的重要方法.但多智能体强化学习的训练过程尚处于“黑盒”状态,缺乏对群体智能的激发和汇聚程度的有效度量手段.针对这一问题,从多智能体强化学习中智能体的策略出发,以策略多样性度量无人机群在多智能体强化学习的训练过程中的激发-汇聚程度.为了对策略的多样性进行度量,借鉴物种多样性和信息论中的相关概念,明确了策略多样性的内涵包括丰富和均匀程度两方面,提出了“策略距离二次熵”和“动作分布信息熵”这两种策略多样性的计算方法.设计了无人机群突防场景对本文所提出的策略多样性指标和两种计算方法的有效性和有用性进行了验证,并通过敏感程度分析对两种计算方法进行了对比.实验结果表明这两种计算方法在该场景中均能有效区分策略多样性的变化,且两种计算方法间具有一致性,从而验证了策略多样性指标及其计算方法的有效性.在有用性方面,验证了策略多样性与奖赏之间的关联关系,以及环境的动态改变与策略多样性之间的相互影响和关联关系,体现了策略多样性在认知群智系统,指导群智激发汇聚过程上...     

智能双通道交通流系统中的先进信息反馈策略

尽管智能车辆交通流之实时交通信息的动力学行为已经被详细地研究,但寻找一个可以应用于实际双通道选择交通流之管理与控制的有效的信息反馈策略仍然是交通科学当务之急的一个重要问题.最近,一些实时反馈信息策略已经被提出,如旅行时间信息反馈策略(TTFS)、平均速度信息反馈策略(MVFS)和堵塞系数信息反馈策略(CCFS),以上3种策略中的最佳策略(堵塞系数信息反馈策略.CCFS)仍然有进一步改善之余地.文中提出一种称为车辆数反馈策略(VNFS)的新的交通信息控制策略.策略之关键在于只反馈每条通道上最前面某一路段的车辆数目信息.模拟计算表明这一新策略在整个双通道交通系统的通行流量和通行速度上表现出了很高的优越性.     

Mycorrhizas and root architecture

Summary Roots function dually as a support system and as the nutrient uptake organ of plants. Root morphology changes in response to the soil environment to minimize the metabolic cost of maintaining the root system, while maximizing nutrient acquisition. In response to nutrient-limiting conditions, plants may increase root fineness or specific root length (root length per gram root weight), root/shoot ratio, or root hair length and number. Each of these adaptations involves a different metabolic cost to the plant, with root hair formation as the least costly change, buffering against more costly changes in root/shoot ratio. Mycorrhizal symbiosis is another alternative to such changes. Plants with high degrees of dependence on the symbiosis have coarser root systems, less plasticity in root/shoot ratio, and develop fewer root hairs in low-fertility soils. In nutrient-limited soils, plants highly dependent on mycorrhiza reduce metabolic cost by developing an even more coarse or magnolioid root system, which is less able to obtain nutrients and thus creates a greater dependence of the plant on the symbiosis. These subtle changes in root architecture may be induced by mycorrhizal fungi and can be quantified using topological analysis of rooting patterns. The ability of mycorrhizal fungi to elicit change in root architecture appears to be limited to plant species which are highly dependent upon mycorrhizal symbiosis.     

Inheritance of phenotypic plasticity in soft chess,Bromus mollis L. (Gramineae)

Summary Phenotypic plasticity, measured by the phenotypic variation of a genotype living under diverse environments, was shown to be under genetic control in annual grass,Bromus mollis. Genetic polymorphism and phenotypic plasticity appear to be alternative strategies of adaptation in plant populations.     

Cell density-induced changes in lipid composition and intracellular trafficking

Cell density is one of the extrinsic factors to which cells adapt their physiology when grown in culture. However, little is known about the molecular changes which occur during cell growth and how cellular responses are then modulated. In many cases, inhibitors, drugs or growth factors used for in vitro studies change the rate of cell proliferation, resulting in different cell densities in control and treated samples. Therefore, for a comprehensive data analysis, it is essential to understand the implications of cell density on the molecular level. In this study, we have investigated how lipid composition changes during cell growth, and the consequences it has for transport of Shiga toxin. By quantifying 308 individual lipid species from 17 different lipid classes, we have found that the levels and species distribution of several lipids change during cell growth, with the major changes observed for diacylglycerols, phosphatidic acids, cholesterol esters, and lysophosphatidylethanolamines. In addition, there is a reduced binding and retrograde transport of Shiga toxin in high density cells which lead to reduced intoxication by the toxin. In conclusion, our data provide novel information on how lipid composition changes during cell growth in culture, and how these changes can modulate intracellular trafficking.     

Dual action of the active oxygen species during plant stress responses

Adaptation to environmental changes is crucial for plant growth and survival. However, the molecular and biochemical mechanisms of adaptation are still poorly understood and the signaling pathways involved remain elusive. Active oxygen species (AOS) have been proposed as a central component of plant adaptation to both biotic and abiotic stresses. Under such conditions, AOS may play two very different roles: exacerbating damage or signaling the activation of defense responses. Such a dual function was first described in pathogenesis but has also recently been demonstrated during several abiotic stress responses. To allow for these different roles, cellular levels of AOS must be tightly controlled. The numerous AOS sources and a complex system of oxidant scavengers provide the flexibility necessary for these functions. This review discusses the dual action of AOS during plant stress responses.     

Structural disorder in plant proteins: where plasticity meets sessility

Plants are sessile organisms. This intriguing nature provokes the question of how they survive despite the continual perturbations caused by their constantly changing environment. The large amount of knowledge accumulated to date demonstrates the fascinating dynamic and plastic mechanisms, which underpin the diverse strategies selected in plants in response to the fluctuating environment. This phenotypic plasticity requires an efficient integration of external cues to their growth and developmental programs that can only be achieved through the dynamic and interactive coordination of various signaling networks. Given the versatility of intrinsic structural disorder within proteins, this feature appears as one of the leading characters of such complex functional circuits, critical for plant adaptation and survival in their wild habitats. In this review, we present information of those intrinsically disordered proteins (IDPs) from plants for which their high level of predicted structural disorder has been correlated with a particular function, or where there is experimental evidence linking this structural feature with its protein function. Using examples of plant IDPs involved in the control of cell cycle, metabolism, hormonal signaling and regulation of gene expression, development and responses to stress, we demonstrate the critical importance of IDPs throughout the life of the plant.     

Spatiotemporal asymmetric auxin distribution: a means to coordinate plant development

The plant hormone auxin plays crucial roles in regulating plant growth development, including embryo and root patterning, organ formation, vascular tissue differentiation and growth responses to environmental stimuli. Asymmetric auxin distribution patterns have been observed within tissues, and these so-called auxin gradients change dynamically during different developmental processes. Most auxin is synthesized in the shoot and distributed directionally throughout the plant. This polar auxin transport is mediated by auxin influx and efflux facilitators, whose subcellular polar localizations guide the direction of auxin flow. The polar localization of PIN auxin efflux carriers changes in response to developmental and external cues in order to channel auxin flow in a regulated manner for organized growth. Auxin itself modulates the expression and subcellular localization of PIN proteins, contributing to a complex pattern of feedback regulation. Here we review the available information mainly from studies of a model plant, Arabidopsis thaliana, on the generation of auxin gradients, the regulation of polar auxin transport and further downstream cellular events. Received 10 March 2006; received after revision 26 June 2006; accepted 9 August 2006     

Bacterial phytotoxins: Mechanisms of action

Many species of phytopathogenic procaryotes produce toxins that appear to function in disease development. The affect the plant in different ways, the end result of which is the elicitation of chlorosis, necrosis, watersoaking, growth abnormalities or wilting. The most extensively studied toxins cause chlorosis. They specifically inhibit diverse enzymes, all critical to the plant cell. This inhibition results in a complex series of metabolic dysfunctions ultimately resulting in symptom expression. Substances causing growth abnormalities consist of known phytohormones and other compounds with plant hormone-like activities, but which have no structural relationship to the known hormones. The former act in the usual manner but, because of their elevated levels and imbalances, the host's regulatory mechanisms are overwhelmed and abnormal growth results (hyperplasia, shoot or root formation); the mechanisms of action of the latter group are unknown. High molecular weight, carbohydrate-containing substances, also acting in unknown ways, cause tissue watersoaking or wilting. Likewise, we know little about toxins causing necrosis except for syringomycin which affects ion transport across the plasmalemma.     

Behavioral and neuronal mechanisms of cricket phonotaxis

Summary The auditory communication of crickets provides a model system for the analysis of the neuronal mechanisms underlying complex behavior. The song of male crickets attracts females. The necessary and sufficient parameter of the song for the female phonotaxis has been determined by a quantified behavioral analysis. Neuronal correlates of this pattern recognition exist in the cricket brain and give rise to a hypothesis on the mechanism of song pattern recognition. Causal relationships between the orientation of a cricket during phonotaxis and the activity of single identified neurons were found by monitoring and deactivating single neurons during behavior. The different roles of various identifield neurons for sound localization have been tested by this method. The plasticity of the auditory system at both the behavioral and at the neuronal level has been studied after ampytation of one ear, and a mechanism for sound localization with only one ear is proposed.     

The molecular mechanism of zinc and cadmium stress response in plants

When plants are subjected to high metal exposure, different plant species take different strategies in response to metal-induced stress. Largely, plants can be distinguished in four groups: metal-sensitive species, metal-resistant excluder species, metal-tolerant non-hyperaccumulator species, and metal-hypertolerant hyperaccumulator species, each having different molecular mechanisms to accomplish their resistance/tolerance to metal stress or reduce the negative consequences of metal toxicity. Plant responses to heavy metals are molecularly regulated in a process called metal homeostasis, which also includes regulation of the metal-induced reactive oxygen species (ROS) signaling pathway. ROS generation and signaling plays an important duel role in heavy metal detoxification and tolerance. In this review, we will compare the different molecular mechanisms of nutritional (Zn) and non-nutritional (Cd) metal homeostasis between metal-sensitive and metal-adapted species. We will also include the role of metal-induced ROS signal transduction in this comparison, with the aim to provide a comprehensive overview on how plants cope with Zn/Cd stress at the molecular level.