景观生态学的学科前沿与发展战略

根据美国景观生态学2001年年会关于景观生态学的关键议题和研究领域特别专题的讨论，综合16位国际知名专家所发表的关于深化理论、整合协调和方法改进等方面的意见，深入论述了景观生态学的6项关键议题和10个优先研究领域。包括通过景观镶嵌体的生态流，土地利用和土地覆被变化的过程、机制，非线性动态和景观复杂性，尺度转换方法论的发展，景观指标与生态过程，人类活动与景观生态，景观格局的优化，景观保育与可持续性，资料获取与准确性评价。并对构建中国景观生态学的理论框架提出了初步的想法，即发展以格局——过程关系为中心的生态空间理论，以人类活动有序化为中心的景观生态建设理论，以发挥景观多重价值为中心的景观规划理论。  

景观生态学中的十大研究论题

近年来 ,景观生态学在理论、方法及应用诸方面均取得了长足发展。但作为一个迅速发展中的学科 ,景观生态学尚面临着许多新的问题和挑战。基于两次相关论题的国际研讨会 ,概述当今景观生态学十大研究论题 ,以促进国内该学科的全面发展。  

六种木本植物水分利用效率和其小生境关系研究

北京山区落叶阔叶林优势种的水分利用效率(WUE)与其所在地的气候条件有很密切的关系,特别是大气相对湿度、太阳辐射强度、饱和水汽压亏缺(VPD)和温度.辽东栎、山杏、大叶白蜡、北京丁香、荆条和核桃楸等植物在整个生长季水分利用效率的变化幅度在3.76～4.95 mmolCO2.mol1H2O之间,平均水分利用效率为4.428±0.386 mmo1 CO2.mol-1H 2O,水分利用效率以山杏最高,核桃楸最低.在整个生长季中,这些植物在早春时水分利用效率高于生长旺期.另外,同种植物生长在于旱瘠薄生境上的水分利用效率高.  

植物氮代谢及其环境调节研究进展

氮代谢是植物的基本生理过程之一，也是参与地球化学循环的重要组成部分，植物氮素同化的主要途径是经过硝酸盐还原为铵后直接参与氨基酸的合成与转化，期间硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酰胺合酶(GOGAT)、天冬酰胺转氨酶(AspAT)等关键酶参与了催化和调节，以氨基酸为主要底物在细胞中合成蛋白质，再经过对蛋白质的修饰、分类、转运及储存等，成为植物有机体的组成部分，同时与植物的碳代谢等协调统一，共同成为植物生命活动的基本过程，文中概述了植物氮素同化的途径、几种关键酶的特性和调控机制，简述了氮素代谢的信号传导、植物细胞蛋白质的形成、转运、储存和降解过程，基于水分胁迫等关键生态因子对氮代谢的影响及其调节机制的评述，强调了未来需加强研究的7个方面。  

Stability of Bovine Adrenal Medulla Cells in Culture

The functional stability of primary cultures of adrenal medulla cells was investigated. Isolated cells were prepared by treatment of bovine adrenal glands with collagenase followed by purification on Percoll density gradients and were maintained in Dulbecco's medium containing 10% fetal calf serum. Within 12 h after plating on plastic culture dishes, the cells became firmly attached and exhibited good survival for periods of time up to 3 weeks, as indicated by their morphology using light and electron microscopy, by maintenance of their content of catecholamines, tyrosine hydroxylase, dopamine-beta-hydroxylase, and phenylethanolamine N-methyltransferase, and their ability to respond to secretagogues. During the first 10 days to 2 weeks in culture there was little or no change in any of these parameters. During the 3rd week there were progressive losses of catecholamine and enzyme activities and increased vacuolization of medullary cells. The cells synthesized protein and RNA with no apparent loss in activities over the period studied, but did not incorporate [3H]thymidine into PCA-precipitable material. The cells responded to secretagogues and secretory antagonists similarly to isolated perfused adrenal glands. The studies described here demonstrate that primary cultures of adrenal medulla cells provide an excellent experimental system for obtaining more detailed information on stimulus-secretion coupling and other functional aspects of the adrenal medulla.  

西方生态学近况

本文对美英等西方英语国家的近期生态学研究的研究趋向、流行概念，研究方式、前沿领域及新方法、新技术进行了综述分析，近期、西方英语国家的生态学理论研究中最受重视的问题是：在一定时空尺度上生物物种组成和各物种种群丰盛度的动态规律和特征，以及决定这种规律和特征的内在机制。这些机制包括：个体发育、生理、行为和遗传过程对生物与非生物环境的反应及这些过程对自身所在的种群、种落和栖息地的影响；种内种间相似或相异个  

用于全球变化研究的中国植物功能型划分

 植物功能型(Plant functional types, PFTs)作为沟通植物的结构和功能与生态系统属性的桥梁，随着全球变化与植被的关系研究的深入而受到广泛重视。植物功能型的划分依赖于研究的背景、尺度和要解决的问题。为了区域尺度全球变化研究的需要，该文提出了一个基于植物关键特征的植物功能型划分方法。该方法首先选择了6项植物特征，包括3项冠层特征：木本-草本、常绿-落叶和针叶-阔叶，以及3项生理特征：光合途径(C3 / C4)、植物的水分需求和热量需求，作为划分植物功能型的关键特征；然后，先根据植物冠层特征划分得到5个基本类型，再根据水分和热量条件进行详细划分，得到29种备选类型；需要时，再根据研究目的从这29种备选类型中选择所需类型。根据这个方法，在充分考虑了我国季风气候条件下特有的水热配置和高海拔环境对植物的形态和功能特征影响的基础上，从备选类型中选择了一套适合中国气候和植被特征的植物功能型体系。这套体系包括18类植物功能型，其中含7类‘树’功能型、6类‘灌木’功能型和5类‘草’功能型，另根据需要设置2类‘裸地’功能型。并且根据植物的生理生态特征和中国植被的地理分布确定了用于限制植物功能型分布的气候因子，这些气候因子包括绝对最低温度、最暖月平均温度、有效积温、年最热月平均温和最冷月平均温之差、湿润指数、年均降水量。应用表明，这套植物功能型可用于模拟我国植被在当前气候条件下的分布。该研究为发展适于我国的植被模型和区域气候模型、评估全球变化对我国植被的影响及植被变化对气候的反馈作用提供依据与参数。  

Regulation of sucrose and starch metabolism in potato tubers in response to short-term water deficit

To investigate the effect of water stress on carbon metabolism in growing potato tubers (Solanum tuberosum L.), freshly cut and washed discs were incubated in a range of mannitol concentrations corresponding to external water potential between 0 and −1.2 MPa. (i) Incorporation of [¹⁴C]glucose into starch was inhibited in water-stressed discs, and labeling of sucrose was increased. High glucose overrode the changes at low water stress (up to −0.5 MPa) but not at high water stress. (ii) Although [¹⁴C]sucrose uptake increased in water-stressed discs, less of the absorbed [¹⁴C]sucrose was metabolised. (iii) Analysis of the sucrose content of the discs confirmed that increasing water deficit leads to a switch, from net sucrose degradation to net sucrose synthesis. (iv) In parallel incubations containing identical concentrations of sugars but differing in which sugar was labeled, degradation of [¹⁴C]sucrose and labeling of sucrose from [¹⁴C]glucose and fructose was found at each mannitol concentration. This shows that there is a cycle of sucrose degradation and resynthesis in these tuber discs. Increasing the extent of water stress changed the relation between sucrose breakdown and sucrose synthesis, in favour of synthesis. (v) Analysis of metabolites showed a biphasic response to increasing water deficit. Moderate water stress (0–200 mM mannitol) led to a decrease of the phosphorylated intermediates, especially 3-phosphoglycerate (3PGA). The decrease of metabolites at moderate water stress was not seen when high concentrations of glucose were supplied to the discs. More extreme water stress (300–500 mM mannitol) was accompanied by an accumulation of metabolites at low and high glucose. (vi) Moderate water stress led to an activation of sucrose phosphate synthase (SPS) in discs, and in intact tubers. The stimulation involved a change in the kinetic properties of SPS, and was blocked␣by protein phosphatase inhibitors. (vii) The amount of ADP-glucose (ADPGlc) decreased when discs were incubated on 100 or 200 mM mannitol. There was a strong correlation between the in vivo levels of ADPGlc and 3PGA when discs were subjected to moderate water stress, and when the sugar supply was varied. (viii) The level of ADPGlc increased and starch synthesis was further inhibited when discs were incubated in 300–500 mM mannitol. (ix) It is proposed that moderate water stress leads to an activation of SPS and stimulates sucrose synthesis. The resulting decline of 3PGA leads to a partial inhibition of ADP-glucose pyrophosphorylase and starch synthesis. More-extreme water stress leads to a further alteration of partitioning, because it inhibits the activities of one or more of the enzymes involved in the terminal reactions of starch synthesis. Received: 26 August 1996 / Accepted: 5 November 1996