Comparison of RAPD, STS, ISSR and AFLP molecular methods used for assessment of genetic diversity in hop (Humulus lupulus L.)

CoxI genomic and cDNA sequences from gymnosperms and angiosperms were used to study the effects of RNA editing on gene evolution and phylogenyre construction. In six gymnosperms harboring edited coxI gene the number of nucleotide substitutions at 1^st, 2^nd and 3^rd codon positions was similar. In contrast, in angiosperms, the number of nucleotide substitutions at 1^st and 2^nd codon positions was much lower than at the 3^rd. The coxI gene in long-lived gymnosperms evolved much faster than in annual angiosperms. This accelerated rate of nucleotide substitution in gymnosperms is due to accumulation of T-C substitutions at edited sites that can randomly appear at all three codon positions. Editing predominantly occurred at 1^st and 2^nd codon positions as a result of selection against non synonymous T-C substitutions and other types of mutations. The tree topologies for the investigated species based on genomic DNA data were in concordance with their taxonomic positions. The trees based on polymorphic edited sites agreed with trees derived from complete sequence information. This indicates that edited sites are reliable sources of phylogenetic information especially for species that contain many edited sites. However, the fast evolution rate of coxI gene in gymnosperms has caused the long branches in the phylogenetic trees. The inclusion of the species with a processed paralog i.e., edited form of the coxI gene, affected the topology of phylogenetic trees, especially when the taxon with a processed paralog was closely related to the other species analyzed. This revised version was published online in July 2006 with corrections to the Cover Date.     

黑松花粉与花粉管中的微管分布

应用免疫荧光标记法结合激光扫描共聚焦显微镜术对黑松花粉和花粉管中的微管骨架进行观察.结果表明:黑松萌发花粉内存在一密集的微管网络,在花粉粒中微管呈斜向或横向分布,在伸长的花粉管内微管呈轴向排列,并一直延伸至花粉管顶端.花粉管顶端区域的微管网络荧光特别明亮.在含秋水仙碱的培养基中萌发的黑松花粉,其花粉管形态明显异常,特别是花粉管顶端肿胀的频率显著提高.认为是秋水仙碱破坏了花粉管顶端区域的微管骨架而导致顶端肿胀的产生,这说明分布于裸子植物花粉管顶端的微管网络对于维持正常的花粉管顶端形态具有重要作用.裸子植物花粉管顶端的生长可能与被子植物不同,微管网络参与了引导顶端生长的方向.     

气象因子对树木生长量影响研究综述

全球气温出现明显的上升趋势以及它所导致的全球气候变化成为近年来研究的热点问题.从温度、降水、光照、蒸发量和风速等气象因子变量综述其对树木的年轮宽度、树高、解离管胞变化的影响.结果表明,温度与降水的影响在众多的气象因子变量中表现尤为突出,并且各气象因子对树木的生长表现出明显的滞后效应.简要的阐述相关的研究方法,并对今后的研究提出建议.     

黑松花粉体外萌发与花粉管生长的研究

应用荧光标记和激光扫描共聚焦显微镜术研究了黑松花粉和花粉管的形态结构,结果表明:黑松成熟花粉含2个退化的原叶细胞、1个生殖细胞和1个管细胞;花粉水合12 h后才开始萌发,花粉萌发后管细胞核移动进入花粉管内,而生殖细胞仍留在花粉粒内;伸长的花粉管可分淀粉粒区和透明区;花粉管内原生质的流动呈喷泉式;花粉管壁具纤维素层;年青的花粉管壁有胼胝质沉积,而较老的花粉管壁不具胼胝质层,花粉管内亦不具胼胝质塞;花粉管易于形成分枝,培养基中蔗糖浓度与分枝的形成有关;培养基中高浓度蔗糖可抑制花粉管的伸长.裸子植物在花粉结构、花粉萌发和花粉管的形态结构方面与被子植物存在较大差异.     

裸子植物应用于昆明园林的综合评价

【目的】对昆明市园林绿地裸子植物种植质资源和应用现状进行调查,为未来昆明市园林规划配置中裸子植物的应用提供参考及理论依据。【方法】对昆明45个园林绿地中裸子植物种类进行实地调查,以调查到的70种裸子植物为研究对象,从观赏价值、景观应用潜力及生态适应性3个方面,提出12个裸子植物综合评价指标,建立层次分析(AHP)评价模型,对昆明市裸子植物资源的园林应用综合价值进行评价,根据综合评价得分划分等级。【结果】权重值排序观赏价值(0.6833)生态适应性(0.1998)景观应用潜力(0.1168)。通过综合评价结果,得到裸子植物Ⅰ级(≥4)7种、Ⅱ级(3.5～4.0)23种、Ⅲ级(3.0～3.5)30种、Ⅳ级(3.0)10种。参考AHP的综合评价及各层次评价结果,推荐Ⅰ级资源作为林带的基调树和主景树大力开发使用,Ⅱ级资源可适当开发,Ⅲ级资源可选择具有价值的开发和利用,Ⅳ级资源树种暂不推荐开发利用。【结论】研究结果可为昆明市园林树种选择和园林应用提供科学参考,研究方法也可为其他特定生境植物筛选提供借鉴。     

Allelopathy of gymnospermous trees

The present paper reviews the available literature on the allelopathy of gymnosperms which constitute the famous boreal forests known for their high quality timber and other products of great commercial importance. Nineteen genera belonging to six of the seven taxonomic families of conifers comprising one of the most dominating and largest group of present day gymnosperms, are reported to show the phenomena of allelopathy. The available information signifies the role these mighty trees play in determining the understorey vegetation, ecological succession and forests dynamics besides causing regeneration problems to the donor trees. The allelochemicals, identified from these plants, responsible for such interactions have also been summarised. In most of the cases the leaching of phenolics from the litter predominantly of tree needles, which remain on the ground for a longer time due to slow decomposition rate, are held responsible for these interactions.