竹子扩张对阔叶林物种多样性的影响:两竹种的叠加效应

研究了不同扩张强度下毛竹和肿节少穗竹对江西武夷山常绿阔叶林群落结构和物种多样性的影响.结果表明: 毛竹、肿节少穗竹扩张都会不同程度地改变阔叶林群落结构与物种组成,两者同时高强度扩张时(毛竹30～50 ind·100 m^-2,肿节少穗竹300～500 ind·100 m^-2),群落的乔∶灌(密度比)由2∶8变成1∶9,竹∶木(密度比)由0∶10变成9∶1.毛竹、肿节少穗竹扩张对阔叶林物种多样性影响的主效应显著,毛竹主要影响乔木层,肿节少穗竹主要影响灌木层,但两种竹子的交互作用不显著.两种竹子同时扩张对群落生物多样性的影响存在叠加效应,尤其是高强度扩张使群落Shannon指数下降91.3%.毛竹与肿节少穗竹同时低强度扩张时,两者相互影响不大,但当达到一定密度后两者会相互竞争排斥.这表明,当常绿阔叶林同时遭受毛竹、肿节少穗竹扩张时,虽然二者交互作用不明显,但会通过叠加效应影响木本植物,导致阔叶林群落简单化.     

外源GA3对毛竹实生苗茎秆生长及CesA基因表达的影响

以毛竹实生苗为试验材料,研究不同浓度外源GA₃（0,0.1,0.5,1 μmol·L^-1）对毛竹生长及CesA基因表达的影响。结果表明,与未经GA₃处理相比,施用外源GA₃后,毛竹实生苗茎节间和纤维细胞显著伸长,初生壁纤维素合成相关基因PeCesA2和PeCesA6相对表达量明显上调,次生壁相关基因PeCESA4和PeCESA4-1显著下调,傅里叶红外光谱分析（FTIR）,发现毛竹茎秆纤维素特征峰强度（1 060,1 160及1 373 cm^-1）随着GA₃浓度升高而逐渐增强,表明施用外源GA₃能够影响毛竹茎秆CesA基因表达,PeCesA2和PeCesA6的表达与外源GA₃促进纤维细胞伸长的过程存在一定联系。     

Allocation to floral structures in Thalictrum pubescens (Ranunculaceae), a cryptically dioecious species

Females of Thalictrum pubescens produce stamens that contain sterile pollen, whereas males are both functionally and morphologically unisexual. This study examines the investment in stamen production by females of T. pubescens by comparing the female structures with those of their fully functional male counterparts. Stamens from females had the same biomass and contained the same amount of nitrogen and phosphorus as stamens from males. Anther size was the same in males and females, but filaments were longer in stamens from males. Females produced more pollen per anther than males, and pollen size was the same in both sexes. Within flowers, there was a positive correlation between the amount of pollen per anther and the length of anthers in males, but not in females. This would be expected if males growing in better environmental conditions or with greater vigour invested more resources in pollen production, thereby increasing fitness. Females, who receive no fitness benefits from increased pollen production, did not show this pattern. There was also evidence of a trade-off within female flowers between the number of stamens and the number of pistils. This trade-off was noted in conditions when variance among plants was reduced, namely in the field during a year when flower size was particularly small and in a previous glasshouse study. Therefore, it appears that when environmental variance is low, stamens are produced at the expense of producing more pistils, and hence seeds. In conclusion, stamen production does not appear to be inconsequential to females of Thalictrum pubescens.     

High polyphenol oxidase activity and low titratable acidity in browning bamboo tissue culture

Summary Tissue browning that frequently results in the early death of bamboo shoots in vitro correlated directly with polyphenol oxidase (PPO, EC 1.10.3.1) activity and inversely with titratable acidity. It was unrelated to the level of endogenous phenols. During the course of culture, timing of PPO activity paralleled that of explant browning. Browning was highest among shoots cultured in a medium of pH 8, which was consistent with the pH optinum of the bamboo enzyme. The pH optimum was first determined with the crude enzyme, then verified with two purified isozymes. Stability of the bamboo PPO was also highest at pH 10. PPO activities of the severely browning Dendrocalamus latiflorus, the moderately browning Phyllostachys nigra, and the relatively non-browning Bambusa oldhamii were inhibited strongly by ascorbic acid, cysteine, sodium diethyldithiocarbamate, and sodium sulfite. But characterization of bamboo PPO according to enzyme inhibitors was not possible because enzyme extracts of the three species gave varied responses to the traditional substances. Nutrient medium addenda of some PPO inhibitors, namely ascorbic acid, cysteine, kojic acid, and thiourea, mainly enhanced browning. However, ferulic acid at 3 mM and lower concentrations reduced the number of brown shoots per culture, although not the percentage of cultures that browned. Polyvinylpyrrolidone failed completely to suppress browning. The two purified isozymes showed different temperature optima for PPO activity: 60°C and 65°C. The purified isozymes displayed a substrate preference for dopamine, or a cathecol oxidase characteristics.     

河南玉兰属一新变种

对毛玉兰新变种Yulaniadenudata(Desr.)D.L.Fuvar.pubescensD.L.Fu,T.B.ZhaoetG.H.Tian,var.nov.进行了描述。该变种具有离生单雌蕊密被短柔毛或疏被短柔毛,果密被淡灰色细疣点特征,与玉兰原变种Y.denudata(Desr.)D.L.Fuvar.denudata具有离生单雌蕊无毛,果褐色、具白色皮孔特征相区别。     

Extensive sharing of chloroplast haplotypes among European birches indicates hybridization among Betula pendula, B. pubescens and B. nana

Extensive sharing of chloroplast haplotypes among the silver birch, Betula pendula Roth., the downy birch, B. pubescens Ehrh., and the dwarf birch, B. nana L., was discovered using polymerase chain reaction-restriction fragment length polymporphism markers. The geographical component of the genetic variation was stronger than the species component: the species were not significantly different while 11% of the variation could be attributed to differentiation between the two main regions studied, Scandinavia and western Russia. All haplotypes occurring in more than 2% of the individuals were shared among the species and the introgression ratios were quite large: 0.79 between B. pubescens and B. pendula and 0.67 between B. pubescens and B. nana. The data also indicate that B. pendula individuals are more similar to sympatric B. pubescens than to B. pendula individuals from nearby forests. However, this trend is not as pronounced when B. pubescens is considered, suggesting that introgression is not symmetrical. The haplotype sharing among the three Betula species is most likely caused by hybridization and subsequent cytoplasmic introgression.     

不同生境中柔毛淫羊藿形态特征及其有效成分差异分析

采用高效液相色谱法和紫外分光光度法分别测定了不同生境中柔毛淫羊藿的有效成分,并运用one-way ANOVA统计分析了不同生境中柔毛淫羊藿有效成分的差异以及形态参数和生物量的差异。结果表明:3个生境中,相对光照强度较低的生境,其形态参数和植株各个部位的生物量均要低于光照强度相对较强的生境,但3个生境中的整体叶形基本一致;三个生境中淫羊藿总黄酮和淫羊藿苷含量在光照强度较高的生境中要大于光照较低的生境;柔毛淫羊藿植株各个部位的有效成分大小为叶>根>茎;在不同生境中柔毛淫羊藿叶片的黄酮和淫羊藿苷含量都能达到用药标准,其余的部位则不能达到用药标准。因此在人工栽培柔毛淫羊藿时,应模拟野外生长条件,以期提高柔毛淫羊藿质量,替代和保护野生资源。     

Limitations on orchid recruitment: not a simple picture

Mycorrhizal fungi have substantial potential to influence plant distribution, especially in specialized orchids and mycoheterotrophic plants. However, little is known about environmental factors that influence the distribution of mycorrhizal fungi. Previous studies using seed packets have been unable to distinguish whether germination patterns resulted from the distribution of appropriate edaphic conditions or the distribution of host fungi, as these cannot be separated using seed packets alone. We used a combination of organic amendments, seed packets and molecular assessment of soil fungi required by three terrestrial orchid species to separate direct and indirect effects of fungi and environmental conditions on both seed germination and subsequent protocorm development. We found that locations with abundant mycorrhizal fungi were most likely to support seed germination and greater growth for all three orchids. Organic amendments affected germination primarily by affecting the abundance of appropriate mycorrhizal fungi. However, fungi associated with the three orchid species were affected differently by the organic amendments and by forest successional stage. The results of this study help contextualize the importance of fungal distribution and abundance to the population dynamics of plants with specific mycorrhizal requirements. Such phenomena may also be important for plants with more general mycorrhizal associations.     

Differential ecophysiological responses to seasonal drought of three co-existing oak species in northern Greece

Oaks (Quercus spp.) represent the most important broadleaf genus with respect to forest-shaping tree species in the Mediterranean. Considering future climate scenarios (increased drought conditions), the identification of drought tolerant oak species is of great importance for future forest management in this region. The objective of the study was the comparison of physiological status of three economically and ecologically valuable oak species (Quercus ilex, Quercus frainetto and Quercus pubescens) co-existing in natural coppice stands in NE Greece, in response to seasonal drought stress. Measurements were conducted between June and September 2016, every 15–20 days until leaf falling. The parameters studied were predawn leaf water potential and fast chlorophyll fluorescence induction curves (OJIP test), chlorophyll content, and relative water content. Meteorological data from the area were also collected. Photosynthetic parameters such as performance indices (PI_abs and PI_tot) reacted to summer drought conditions, with Q. frainetto showing the lowest values. The discrepancy between species increased with duration of drought period. Q. frainetto revealed the lowest predawn water potential values. The results indicate that Q. frainetto is less suitable for future forestry applications in the studied climate/elevation zone than Q. pubescens and Q. ilex.     

Population genetic effects of urban habitat fragmentation in the perennial herb Viola pubescens (Violaceae) using ISSR markers

BACKGROUND AND AIMS: Fragmentation of natural habitats can negatively impact plant populations by leading to reduced genetic variation and increased genetic distance as populations become geographically and genetically isolated from one another. To test whether such detrimental effects occur within an urban landscape, the genetic structure of six populations of the perennial herb Viola pubescens was characterized in the metropolitan area of Greater Cincinnati in southwestern Ohio, USA. METHODS: Using three inter-simple sequence repeat (ISSR) markers, 51 loci amplified across all urban populations. For reference, four previously examined agricultural populations in central/northern Ohio and a geographically distant population in Michigan were also included in the analysis. KEY RESULTS: Urban populations retained high levels of genetic variation (percentage of polymorphic loci, P(p) = 80.7 %) with similar genetic distances among populations and an absence of unique alleles. Geographic and genetic distances were correlated with one another, and all populations grouped according to region. Individuals from urban populations clustered together and away from individuals from agricultural populations and from the Michigan population in a principle coordinates analysis. Hierarchical analysis of molecular variance (AMOVA) revealed that most of the genetic variability was partitioned within populations (69.1 %) and among groups (22.2 %) of southwestern Ohio, central/northern Ohio and Michigan groups. Mean F(st) was 0.308, indicating substantial population differentiation. CONCLUSIONS: It is concluded that urban fragmentation does not appear to impede gene flow in V. pubescens in southwestern Ohio. These results are consistent with life history traits of this species and the possibility of high insect abundance in urban habitats due to diverse floral resources and nesting sites. Combined with the cleistogamous breeding system of this species, pollinator availability in the urban matrix may buffer populations against detrimental effects of habitat fragmentation, at least in larger forest fragments. Consequently, it may be inappropriate to generalize about genetic effects of fragmentation across landscapes or even across plant species with different pollination systems.