小径竹对亚高山暗针叶林优势 树种林窗更新的影响

在亚高山岷江冷杉林中选取面积≤50m2,50~150m2,>150m2的林窗,每种类型内均包含3种小径竹盖度(≤20%、20%~50%、>50%),共调查林窗9个,并调查包含这3种小径竹盖度的三块林下对照样地,研究了该类森林林窗更新与小径竹生长的关系。结果表明:(1)无论林窗大小,林窗内的更新幼苗数量都比林下的多,林窗更新是岷江冷杉群落更新的主要途径;(2)所选林窗均为发育早期,林窗对更新树种的种类组成和数量的影响主要表现在幼苗上。糙皮桦幼树及幼苗数量随林窗面积的增加而急速增加,它的更新更需要较大的林窗;(3)不同小径竹盖度下幼苗的密度呈现显著性变化,小径竹的生长明显抑制了森林幼苗的更新及填充的进程;(4)华西箭竹的分散程度随林窗面积的增大而降低,而平均高度和基径则有增加的趋势。     

四川茂县土地岭大熊猫走廊带植被恢复格局及其与干扰的关系

通过样带调查和TWINSPAN、DCCA分析,从植物种、植物群落及其多样性与环境关系方面,研究了岷江上游土地岭大熊猫走廊带恢复植被的干扰状况。结果表明：应用TWINSPAN分类,并结合优势种组成、干扰状况分析及DCCA排序,可将植被划分为6个群落类型,同时划分出响应型、迟钝型、中度干扰忍耐型和重度干扰忍耐型4类干扰响应的植物类型。以样方物种和以样方多样性指数的DCCA分析结果基本一致,物种及群落的空间分布呈明显的聚集格局,反映其与环境因子间的密切关系。DCCA排序图上,海拔差、坡形、与公路距离、坡度及道路条数对群落和物种分布有明显的影响,与干扰相关性最大的坡度、样地道路数目、与公路间的距离3个因子反映了植被的干扰梯度。干扰对土地岭恢复植被影响显著,干扰降低了群落的物种多样性,同时阻碍了演替进程。     

FGF8在脊椎动物早期胚胎发育中的调控作用

成纤维细胞生长因子8 (fibroblast growth factor 8,FGF8)是成纤维细胞生长因子家族的成员之一,是一种组织发育过程中的重要分泌性调控信号分子,参与脊椎动物的多种组织器官的发生与发育.早期胚胎细胞通过表达FGF8在组织和器官发育、血管发生、血细胞生成、附肢发生和伤口愈合等方面发挥着重要作用.FGF8不但可以在细胞外通过胞内信号通路,而且也可以进入细胞内部发挥生物学功能.本文就FGF8在脊椎动物神经系统、内脏器官、肢体发育及不对称发育等组织、器官发育中的调控作用予以阐述.     

不同N端序列长度匍枝根霉△6-脂肪酸脱氢酶重组子的表达

克隆并在酵母中表达两个不同N段序列长度的匍枝根霉△6-脂肪酸脱氢酶重组子,其中长序列的重组子LYRnD6D是从匍枝根霉中克隆的△6-脂肪酸脱氢酶基因,编码459个氨基酸,N端序列为MSTLDRQSIFTIKELESISQRIHDG-DEEAMKFIII;短序列重组子SYRnD6D是预测的匍枝根霉△6-脂肪酸脱氢酶基因的ORF序列,N端序列为MKFIIIDKKVY,编码430个氨基酸;两个重组子均具有△6-脂肪酸脱氢酶保守的组氨酸序列和HPGG序列,长序列的N端比短序列长29个氨基酸残基(MSTLDRQSIFTIKELESISQRIHDGDE-EA)。两个重组子在缺陷型酵母中均得到了的表达,产生了γ-亚麻酸。利用酶的相对活力比较两个重组子在同一温度下的稳定性,长序列重组子的酶在15℃下反应4h后相对活力仍有74%,而短序列酶的相对活力只有43%,所以长序列重组子酶在低温下比短序列酶稳定性高,是因为长序列多出的氨基酸序列增加了酶的稳定性。     

Vegetation restoration patterns and their relationships with disturbance on the Giant Panda Corridor of Tudiling, Southwest China

Human activities such as deforestation, cultivation, and overgrazing have contributed to the destruction of forest ecosystems in the upper Minjiang River basin for a long time, which has led to the reduction in forest coverage and biodiversity. On the Giant Panda Corridor of Tudiling in this basin, the effects of the existing disturbance regimes on plant communities after the vegetation restoration in the 1980s were assessed, and the community composition, the species diversity and their relationships with environmental factors significantly associated with the disturbance were analyzed using the transect sampling method, the two-way indicator species analysis (TWINSPAN) and the detrended canonical correspondence analysis (DCCA). The results were as follows: communities could be classified into six types, and species were clustered into four functional groups (responsive to disturbance, retarded disturbance, resistant to intermediate disturbance, and resistant to heavy disturbance) based on both TWINSPAN and DCCA. DCCA with species composition of plots is similar to that with species diversity of plots. The communities were separated into distinct groups along the DCCA axis, and this pattern was significantly correlated with environmental factors. Elevation differences, shape, slope, distance to roads, and the number of paths in the plots had an evident influence on the distribution of the species and communities. Environmental factors including slope, distance to roads, and the number of paths revealed the gradient of disturbance among the communities along the DCCA axis. High disturbance intensity caused significantly lower species diversity and inhibited the regeneration of vegetation compared with the more diverse undisturbed communities. Artificial restoration was more effective than natural restoration in maintaining high species diversity. The process of succession was inhibited in natural restoration because of the failure of tree establishment, growth, and survival during regeneration.     

应用RAPD分析技术研究生姜青枯病的土壤防治

利用随机扩增多态性技术(RAPD)研究生姜连作地、施加有机肥后的生姜连作地及新开地中土壤微生物多样性与生姜青枯病的关系, 结果发现, 连作地的青枯病发病率为100%, 新开地没有发病, 而施加有机肥的连作地生姜青枯病发病率降至37%。发现施加有机肥连作地的真菌、放线菌数量增加, 平板上不同菌落形态的真菌、细菌、放线菌增加明显。多样性指数分析发现Shannon指数、Simpson指数等均显著增加。随机扩增条带出现连作地的条带丰富度较少、新开地的条带最多、施加有机肥连作地的RAPD条带明显多于连作地, 接近新开地, 并出现了一些连作地没有的特异条带。结果表明, 施加有机肥可以改善土壤微生物群落结构。     

Theoretical studies on identity SN2 reactions of lithium halide and methyl halide: A microhydration model

Reactions of lithium halide (LiX, X = F, Cl, Br and I) and methyl halide (CH₃X, X = F, Cl, Br and I) have been investigated at the B3LYP/6-31G(d) level of theory using the microhydration model. Beginning with hydrated lithium ion, four or two water molecules have been conveniently introduced to these aqueous-phase halogen-exchange S_N2 reactions. These water molecules coordinated with the center metal lithium ion, and also interacted with entering and leaving halogen anion via hydrogen bond in complexes and transition state, which to some extent compensated hydration of halogen anion. At 298 K the reaction profiles all involve central barriers ΔE _cent which are found to decrease in the order F > Cl > Br > I. The same trend is also found for the overall barriers (ΔE _ovr ) of the title reaction. In the S_N2 reaction of sodium iodide and methyl iodide, the activation energy agrees well with the aqueous conductometric investigation.     

棘腹蛙消化道脂肪酶的分布及pH和温度对脂肪酶活力的影响

采用聚乙烯醇橄榄油乳化液水解法,测定了棘腹蛙消化道不同部位的脂肪酶活力,研究了pH和温度对脂肪酶活力的影响。结果显示,棘腹蛙消化道不同部位脂肪酶活力依次为回肠>直肠>十二指肠>胃>食道。pH和温度显著影响脂肪酶的活力,二者对脂肪酶活力影响的关系曲线均呈现为单峰型,食道、胃和肠道脂肪酶活力的最适pH值分别为5.0、5.0和7.5,最适温度均为35℃。     

莲藕染色体上荧光原位杂交方法的初探

用酶解滴片法制备莲的染色体标本片,在传统的荧光原位杂交(FISH)的方法上进行改进,得到了一种适合于莲的高效荧光原位杂交方法,为莲的分子细胞遗传学研究提供技术上的帮助。     

Comparative analysis of five varieties in <Emphasis Type="Italic">Perilla frutescens</Emphasis> (L.) Britton by 45S rDNA FISH and 5S rDNA sequences

In this study, the relationships of five varieties in Perilla frutescens (L.) Britton were analyzed. All the varieties showed the same chromosome number 2n = 40, and the banding patterns of PI-DAPI staining and the FISH results of 45S rDNA probe were on the same site of the chromosome pair. The 5S rRNA gene spacers were ranged from 413 bp in P. frutescens var. purpurascens and 408 bp in var. frutescens. The varieties analyzed here were clustered into two clades according to the phylogenetic analysis. The sequence identity of 96% between var. auriculato-dentata and var. arguta suggested they could be considered the same variety. The article is published in the original.