植物逆境胁迫耐受性启动子的研究进展

逆境胁迫如干旱、极端温度、损伤等非生物胁迫和病虫害等生物胁迫严重影响植物的生长发育及产量。逆境胁迫耐受性启动子能够接受逆境条件下的诱导信号,激活植物体内胁迫应答基因的表达,使植物感知并适应逆境。本文对逆境胁迫耐受性启动子的克隆及功能研究情况进行综合分析,主要包括抗旱、耐盐、耐高温、抗冻、耐损伤、抗病和抗虫基因启动子。     

气候变化对内蒙古中东部沙地-湿地镶嵌景观的影响

利用小波分析和遥感技术相结合的方法,研究了气候变化对1961—2005年内蒙古中东部沙地-湿地镶嵌景观的影响.结果表明：1961—2005年,研究区年均气温呈直线上升趋势,增温率为0.32 ℃·（10 a）^-1,年降水量变化呈现30 a的长周期和15 a的短周期,年均风速呈下降趋势,10 a的风速减小率为0.26 m·s^-1;研究区东南部存在一个气候变化恒定区域,由此恒定区向西北进入浑善达克沙地腹地,向东逐步进入科尔沁沙地腹地;2010年以前,研究区仍将维持气温升高、降水偏少、风速减小的趋势;受气候暖干化的影响,浑善达克沙地及其周围湿地的总面积呈逐年缩小趋势,随着沙地内部植被的退化,流动沙地不断扩大、湿地萎缩、湖泊干涸,而相应的固定和半固定沙地面积则明显减少.     

Formation of ice microparticles in cryoprotective solutions

The formation of ice microparticles in 0.2-mm thin layers of aqueous solutions of cryoprotective agents cooled to temperatures reaching–196°C was studied. The shape and size of ice microparticles were determined by cryomicroscopy. At temperatures below 0°C, the formation of solid ice masses was observed; further cooling caused ice fracturing induced by emerging thermomechanical stresses and the formation of microparticles. The shape and size of the particles depended on the composition of the frozen solution and on the rate of cooling. The components of cryoprotective solutions (cryoprotectants, egg yolk, sugars, and lipids) significantly changed the shape and size of the ice microparticles.     

Individual optimization: Mechanisms shaping the optimal reaction norm

In general, optimal reaction norms in heterogeneous populations can be obtained only by iterative numerical procedures (McNamara, 1991; Kawecki and Stearns, 1993). We consider two particular, but biologically plausible and analytically tractable cases of individual optimization to gain insight into the mechanisms which shape the optimal reaction norm of fecundity in relation to an environmental variable or an individual trait. In the first case, we assume that the quality of the environment (e.g. food abundance) or the quality of the individual (e.g. body size) is fixed during its entire life; it may also be a heritable individual trait. In the second case, individual quality is assumed to change randomly such that the probability distribution of quality in the next year is the same for the parent and for her offspring. For these two cases, we obtain analytical expressions for the shape of the optimal reaction norm, which are heuristically interpretable in terms of underlying selective mechanisms. It is shown that better quality may reduce the optimal fecundity. This outcome is particularly likely if better quality increases a fecundity-independent factor of parental survival in a long-lived species with fixed quality. This revised version was published online in July 2006 with corrections to the Cover Date.     

新疆塔里木柯坪地区上奥陶统凯迪阶串管海绵类化石及其滤食选择性探讨北大核心

奥陶纪是串管海绵早期演化的一个关键阶段,记录了该类群的首次大规模辐射演化事件(属级分类单元达15个)。然而,现有大部分奥陶系串管海绵的报道来自澳大利亚东部和北美等地,在中国至今仅发现了两个属,与前述地区相比研究程度偏低。早期研究主要基于形态学特征对串管海绵进行系统分类描述,对其滤食策略知之甚少,因此制约了对此类海绵在奥陶纪底栖生态系统作用的相关探讨。本文系新疆塔里木柯坪地区奥陶纪串管海绵的首次系统古生物学报道,详细描述凯迪阶(上奥陶统)印干组中保存完好的阔室丛花海绵(Corymbospongia amplia)化石的形态学特征,并通过研究标本外壁微孔孔径的大小分布,探讨其滤食选择性。海绵外壁微孔孔径的分析表明:小型和微型浮游生物可能是其食物的主要来源,而多细胞浮游动物因个体尺寸大于海绵外壁微孔,不能被阔室丛花海绵捕获。本研究为奥陶纪串管海绵古生态学及其地球生物学意义的探讨提供了进一步的依据。