Cortical development in roots of the aquatic plant Pontederia cordata (Pontederiaceae)

Adventitious roots of marsh-grown Pontederia cordata were examined to determine cortical development and structure. The innermost layer of the ground meristem forms the endodermis and aerenchymatous cortex. The outermost layer of the early ground meristem undergoes a precise pattern of oblique and periclinal cell divisions to produce a single or double layer of prohypodermis with an anchor cell for each radial file of aerenchyma cells. At maturity, endodermal cell walls are modified only by narrow Casparian bands. The central regions of the ground meristem become proaerenchyma and exhibit asymmetric cell division and expansion. They produce an aerenchymatous zone with barrel-shaped large cells and irregularly shaped small cells traversing the aerenchyma horizontally along radii; some crystalliferous cells with raphides are present in the aerenchyma. The walls of the hypodermis are modified early by polyphenols. The outermost layer of the hypodermis later matures into an exodermis with Casparian bands that are impermeable to berberine, an apoplastic tracer dye. The nonexodermal layer(s) of the hypodermis has suberin-modified walls. Radial files of aerenchyma are usually connected by narrow protuberances near their midpoints, the aerenchyma lacunae having been produced by expansion of cells along walls lining intercellular spaces. We are terming this type of aerenchyma development, which is neither schizogenous nor lysigenous, "differential expansion."     

Adjustment of foliage structure and function to a canopy light gradient in two co-existing deciduous trees. Variability in leaf inclination angles in relation to petiole morphology

 Foliar inclination angles, petiole morphology and dry matter partitioning between assimilative and support biomass were studied in shade-intolerant Populus tremula L. and shade-tolerant Tilia cordata Mill. along a natural light gradient across the canopy. The leaves of sub-canopy species T. cordata were on average exposed to lower irradiances, and they were also more horizontal with greater blade inclination angles (ϕ_B, defined as the angle between the leaf fall-line and the horizon; ϕ_B was positive for the leaves inclined upwards, and negative for the leaves inclined downwards) than those in P. tremula. Seasonal average daily integrated quantum flux density (Q _int, mol m^–2 day^–1) and ϕ_B were not related in T. cordata, and only a weak negative effect of Q _int on ϕ_B was detected in P. tremula. Nevertheless, when both species were pooled, there was a strong negative relationship between Q _int and ϕ_B, implying that the leaves became progressively vertical with increasing height in the canopy. Interspecific differences in foliage inclination were mainly related to petiole morphology, in particular to petiole length, rather than to contrasting biomass investment patterns between assimilative and support tissues within the leaf. It was suggested that more horizontal leaves, resulting from the species-specific structure of petioles, partly explain the superior performance of shade-tolerant T. cordata in the understory and the sub-canopy. Received: 13 November 1997 / Accepted: 6 March 1998     

黑曲霉3.795glaA基因及其5'调控区的克隆和序列分析

黑曲霉Ｔ２１是由黑曲霉３．７９５经诱变育种获得的糖化酶高产菌株,为阐明其高产的分子机制,由黑曲霉３．７９５克隆了糖化酶结构基因及其５′旁侧序列,并与黑曲霉Ｔ２１的相应序列进行了比较．由黑曲霉３．７９５菌丝体分离染色体ＤＮＡ,Ｓｏｕｔｈｅｒｎ杂交分析表明,糖化酶结构基因位于～２．５ｋｂ的ＥｃｏＲⅠ－ＥｃｏＲⅤ染色体ＤＮＡ片段上,在此ＥｃｏＲⅠ位点上游约１．０ｋｂ处有一ＳａｌⅠ位点．为构建糖化酶结构基因及其５′旁侧序列的基因组文库,该染色体ＤＮＡ分别用ＥｃｏＲⅠ＋ＥｃｏＲⅤ和ＥｃｏＲ＋ＳａｌⅠ消化,琼脂糖凝胶电泳分离并回收长度在１．０ｋｂ左右和２．５ｋｂ左右的ＤＮＡ片段,分别与ｐＵＣ１９载体连接后转化入Ｅ．ｃｏｌｉＤＨ５．用原位杂交方法筛选到了携带糖化酶基因编码区及其１５０５ｂｐ５′旁侧序列的阳性克隆．对克隆片段的ＤＮＡ序列进行了测定并与黑曲霉Ｔ２１的相应序列进行了比较,结果表明,在糖化酶基因编码区及其１５０ｂｐ３′非编码区内,未发现碱基差异,但在－３４０～－１５０５的５′上游区内发生了９个位置的碱基变化,包括缺失、插入和替换．这些结果表明,黑曲霉Ｔ２１与３．７９５的糖化酶产量的差异与其结构基因无关,但可能与其     

箬叶多糖的分离纯化及其理化性质的研究

采用分步提取的方式从中药箬叶中分离得到８种多糖组分：酸性杂多糖ＦＳ、ＦＥ、ＦⅠ,β－Ｄ－葡萄糖醛酸聚糖ＦⅡ和四种半纤维素多糖α－Ｄ－木聚糖ＦⅢ－ａ、ＦⅢ－ｂ、ＦⅣ－ａ及ＦⅣ－ｂ．紫外光谱、红外光谱、凝胶色谱、元素分析等结果表明８种箬叶多糖为纯品．并采用纸层析,气相色谱分析确定其单糖组成．采用高效凝胶渗透色谱ＧＰＣ法测定了４种箬叶多糖ＦＥ、ＦⅠ、ＦⅢ－ａ及ＦⅣ－ａ的重均分子量Ｍｗ、数均分子量Ｍｎ,均为大分子,分子量分布较窄,纯度较高．     

C-型咽侧体抑制素(AST-C)和促前胸腺激素释放激素(PTTH)基因在家蚕脑组织中的时空表达分析

【目的】咽侧体抑制素在昆虫体内具有重要的调控功能。本研究比较了家蚕Bombyx mori C-型咽侧体抑制素(allatostatin C,AST-C)与促前胸腺激素释放激素(prothoracicotropic hormone,PTTH)基因在不同发育阶段家蚕脑组织中转录表达的模式及其在脑组织的表达定位,以期为家蚕AST-C的功能研究提供重要的线索。【方法】利用脑组织芯片数据分析比较AST-C和PTTH基因在家蚕脑组织中的发育表达特征,RT-PCR验证其芯片数据,分析AST-C在不同发育阶段家蚕中枢神经系统中的表达模式,并用全组织包埋原位杂交技术对AST-C和PTTH在脑组织的表达进行定位。【结果】AST-C和PTTH在不同发育阶段家蚕脑组织中有相似的转录表达模式,且都在脑组织外侧一对神经分泌细胞中表达。【结论】AST-C可能与PTTH以相同的转录表达模式共同参与家蚕的变态发育调控。     

松鼠分子生态学研究进展

松鼠由于受到非法猎捕、栖息地破坏及欧洲部分地区的北美灰松鼠生态入侵,导致种群数量锐减,现已被世界自然保护联盟(IUCN)列为近危种,我国吉林省已将其列入省重点保护野生动物名录.分子生物学研究方法的快速发展,尤其是基于mtDNA片段开展的相关研究,以及已筛选出并能应用于松鼠研究的微卫星位点的应用,使松鼠分子生态学研究不断深入.本文对松鼠的分子系统发育、遗传多样性和分子系统地理学等分子生态学内容进行了综述,并提出松鼠分子生态学未来研究的展望:进一步探讨松鼠与日本松鼠的系统分化关系;松鼠连续种群、隔离种群和集合种群的遗传多样性比较分析;利用核基因其他标记分析松鼠分子系统地理学问题;探讨亚洲是否存在第四纪冰期避难所.     

盐渍化胁迫下油葵对土壤原油污染的适应性及其改良措施

为了探究植物在盐渍化胁迫下对原油污染的适应性及改良措施,本研究以油葵作为研究对象,进行了原油-氯化钠-脱硫石膏盆栽正交试验和煤渣-沸石-脱硫石膏-锯沫盆栽正交试验.结果表明: 在盐渍化条件下,随着原油浓度的增大,油葵幼苗株高相对生长率(RGR)、地上生物量RGR、根氮磷比均显著减小,超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性呈先增加后显著降低的趋势;随着锯沫体积分数的加大,油葵株高RGR和地上生物量RGR均显著增加,SOD活性逐渐降低,说明锯沫在改良盐渍化原油污染土壤方面比煤渣、沸石和脱硫石膏效果显著.在盐渍化条件下,原油污染能够降低油葵幼苗的生长率,锯沫对改良原油污染有较好的效果.