Sensitivity of terpene emissions to drought and fertilization in terpene-storing Pinus halepensis and non-storing Quercus ilex

We studied the effects of water stress, fertilization and time course on foliar volatile terpene emission rates by Quercus ilex and Pinus halepensis in a garden experiment. The terpenes mostly emitted by both species were α -pinene, β -pinene, β -myrcene and Δ³-carene. P. halepensis emission rates (average 31.45 μg g⁻¹ DM h⁻¹) were similar to those of Q. ilex (average 31.71 μg g⁻¹ DM h⁻¹). The effects of drought (reduction to one-third of full watering) and fertilization (250 kg N ha⁻¹, 250 kg P ha⁻¹, or both) were different depending on the species: the drought treatment significantly increased the terpene emissions from Q. ilex by 33%, and the fertilization treatments reduced the terpene emissions from P. halepensis by 38%. Terpene emission rates increased with time course in parallel to raising summer temperatures in P. halepensis and Q. ilex , whose emission rates were temperature related (r = 0.42 and r = 0.68, respectively) and light related (r = 0.32 and r = 0.57, respectively). There was a positive relationship for P. halepensis , and a negative relationship for Q. ilex, between emission rates and relative water contents. No relationship was found between emission rates and N or P foliar concentrations. The results of this study show complex species-specific responses with stronger and faster short-term responses in terpene-non-storing than in storing species and indicate that terpene emissions may significantly change in the warmer, drier and more fertilized conditions predicted for the next decades in the Mediterranean region.     

Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions

The seasonal pattern of terpene content and emission by seven Mediterranean woody species was studied under field conditions. Emission rates were normalized at 30°C and 1000 μmol·m·s PFD (photosynthetic photon flux density). Bupleurum fruticosum, Pinus halepensis, and Cistus albidus stored large amounts of terpenes (0.01-1.77% [dry matter]) with maximum values in autumn and minimum values in spring. They emitted large amounts of terpenes (2-40 μg·g DM·h), but with no clear seasonal trend except for Cistus albidus, which had maximum values in spring and minimum values in autumn. The nonstoring species Arbutus unedo, Erica arborea, Quercus coccifera and Quercus ilex also emitted large amounts of terpenes (0-40 μg·g DM·h) and also tended to present maximum emission rates in spring, although this trend was significant only for A. unedo. At the seasonal scale, emission rates did not follow changes in photosynthetic rates; instead, they mostly followed changes in temperature. From autumn to spring, the least volatile monoterpenes such as limonene were emitted at highest rates, whereas the most volatile monoterpenes such as α-pinene and β-pinene were the most emitted in summer. The monoterpene emission rates represented a greater percentage of the photosynthetic carbon fixation in summer (from 0.51% in Arbutus unedo to 5.64% in Quercus coccifera) than in the rest of the seasons. All these seasonality trends must be considered when inventorying and modeling annual emission rates in Mediterranean ecosystems.     

Pinus Halepensis and Quercus Ilex Terpene Emission as Affected by Temperature and Humidity

The short-term relationships of monoterpene emission with temperature and relative humidity were studied in Pinus halepensis L. and Quercus ilex L. seedlings grown in air-conditioned chamber. In P. halepensis terpene emission rate increased with temperature (from 15 to 35 °C) and relative humidity (from 40 - 60 to 65 - 95 %). In Q. ilex, a terpene non-storing species, it increased with temperature only at high relative humidities but not at relative humidities lower than 60 %. This revised version was published online in July 2006 with corrections to the Cover Date.     

Implications of foliar terpene content and hydration on leaf flammability of Quercus ilex and Pinus halepensis

We investigated the implications of foliar hydration and terpene content on leaf flammability in two widely distributed forest species of the Mediterranean basin, Quercus ilex, which does not store terpenes, and Pinus halepensis, a terpene-storing species. The experiments were carried out in plants grown under different water regimes that generated a wide range of foliar hydration and terpene contents. We monitored the temperatures and time elapsed to reach the smoke, pyrolysis and flame phases. Smoke appeared much earlier (37 versus 101 s) and at lower temperatures (96 versus 139 degrees C) in Quercus ilex than in Pinus halepensis. Quercus ilex reached pyrolysis earlier than Pinus halepensis (278 versus 338 s) but at the same temperature (365-371 degrees C). There were no significant differences in time elapsed nor in temperature for flammability (386-422 s; 505-487 degrees C in both species). Quercus ilex had lower water hydration than Pinus halepensis (41 versus 100%) and the leaf content of terpenes in Quercus was three orders of magnitude lower. The results of this study show no differences in the flame phase between the two species and the absence of a significant relationship between temperature and elapsed time of the different flammability phases in relation to monoterpene content; thus indicating that the role of monoterpenes in flammability phases is smaller than that of the water content. This, however, does not exclude the effects of terpene content on plant combustibility and fire propagation once fires start.     

Influence of intra- and inter-specific Interference on Terpene Emission by Pinus Halepensis and Quercus Ilex Seedlings

Seedlings of two common Mediterranean trees, Pinus halepensis L. and Quercus ilex L., were grown alone and together with seedlings of the same or of the other species in the same pot during one year to test the effects of intra- and inter-specific interference on terpene emission. Light, nutrients and water were amply supplied. There were higher emission rates in P. halepensis than in Q. ilex. The emission increased when the neighbour was a pine and decreased when the neighbour was a holm oak. Volatile organic compound and terpene emission rates followed inverse trends to foliar biomass or growth, which decreased when the neighbour was a pine. This revised version was published online in July 2006 with corrections to the Cover Date.     

Induction of terpene biosynthesis in dinoflagellate symbionts of Caribbean gorgonians

This report describes a series of experiments designed to determine if terpene biosynthesis is inducible in two families of marine terpenes, pseudopterosins from the gorgonian coral Pseudopterogorgia elisabethae and fuscol from Eunicea fusca. Since we have recently shown that terpene biosynthesis is not under the control of the invertebrate host, but rather occurs within a dinoflagellate preparation, we examined the terpene content of the dinoflagellate symbiont following a decrease in UV/vis radiation as well as in response to the addition of methyl jasmonate, salicylic acid and gibberellic acid. We demonstrated that pseudopterosin and fuscol biosynthesis can be markedly increased through the addition of the plant bioactive substances. We also demonstrated that, while the terpene content of P. elisabethae increases in response to decreased UV/vis light, this is due primarily to an increase in the concentration of the dinoflagellate rather than simply an induction of terpene biosynthesis.     

山西五鹿山白皮松群落乔灌层的种间分离

种间分离的研究对于揭示种间相互作用、群落组成与动态具有重要意义。为了探讨五鹿山自然保护区白皮松林内物种间的关系及其共存机制,运用ArcGIS软件、N×N最近邻体列联表及其2×2列联表截表的方法、Pielou的分离指数,Hegyi单木竞争指数对山西五鹿山白皮松群落55个样方内的15种乔木和灌木的种间分离规律及9种乔木的种内种间竞争关系进行研究,并根据种间分离情况以及物种对环境的适应方式,将样地中15个物种划分为3个生态种组。结果表明:(1)该群落中随机毗邻种对占绝大多数(80%),正分离种对较少(16.19%),负分离种对极少(3.81%),群落趋于稳定。(2)种间分离在不同种之间存在着一定的差异,正分离常发生在群落中的建群种或优势种之间;而负分离常发生在群落中的优势种和一些伴生种之间。(3)物种的种间分离状况与其种内种间竞争及物种的空间分布格局具有密切的关系,正分离常常发生在种内竞争大于种间竞争呈聚集分布的优势种或建群种之间;而负分离常常发生在种间竞争大于种内竞争的优势种和伴生种之间,且同一生态种组内的物种种间竞争较不同生态种组间激烈。(4)种间分离与群落的生境异质性和物种的生态需求也具有密切的关系,即两个具有不同生境要求的物种之间常常发生正分离;而具有相同或相似生境要求的物种之间常常发生负分离。(5)白皮松群落内物种的总体分离规律为全面不分离。(6)由生境异质性和物种间不同的生态适应性引起的种内种间关系是维持五鹿山自然保护区白皮松群落稳定共存的机制。     

Phytochemical analysis and genetic characterization of six Hypericum species from Serbia

The secondary metabolite contents and genetic profiles of six Hypericum species (H. barbatum Jacq., H. hirsutum L., H. linarioides Bosse, H. maculatum Crantz, H. rumeliacum Boiss. and H. tetrapterum Fries), collected from different locations in Serbia, have been analyzed. Methanol extracts of the aerial parts of the plants were obtained by accelerated solvent extraction (ASE) at 40 degrees C and 100 bar, and analyzed for five pharmacologically important standard constituents (hyperoside, quercitrin, pseudohypericin, hyperforin and hypericin) by LC-MS/MS. The highest content of hypericin and pseudohypericin was observed in the H. barbatum extract, while the highest content of hyperforin and quercitrin was found in the H. tetrapterum extract and the highest content of hyperoside in the H. maculatum extract. A literature survey shows that the above six Hypericum species, with the exception of H. maculatum, have not been previously genetically profiled. In order to correlate the chemical constituents of the species under investigation with their genetic factors, genetic profiling of these species was undertaken using the random amplification of polymorphic DNA (RAPD) and single sequence repeat (SSR) profiles of the above selected plants. Among the 52 random primers used for the initial screening, only 10 yielded polymorphic RAPD profiles. A total of 111 polymorphic markers were generated using these primers. The SSR analysis shows that 8 out of the 10 primers used were polymorphic. The correlation among the species under investigation using the two genetic markers was performed using Jaccuard's coefficients of similarity and a high correlation (r=0.99) was obtained. The main conclusion from the above data is that there exists a stronger correlation for secondary metabolite contents with RAPD data than with SSR data among the six Hypericum species from Serbia.     

Fragrance chemistry,nocturnal rhythms and pollination "syndromes" in Nicotiana

GC-MS analyses of nocturnal and diurnal floral volatiles from nine tobacco species (Nicotiana; Solanaceae) resulted in the identification of 125 volatiles, including mono- and sesquiterpenoids, benzenoid and aliphatic alcohols, aldehydes and esters. Fragrance chemistry was species-specific during nocturnal emissions, whereas odors emitted diurnally were less distinct. All species emitted greater amounts of fragrance at night, regardless of pollinator affinity. However, these species differed markedly in odor complexity and emission rates, even among close relatives. Species-specific differences in emission rates per flower and per unit fresh or dry flower mass were significantly correlated; fragrance differences between species were not greatly affected by different forms of standardization. Flowers of hawkmoth-pollinated species emitted nitrogenous aldoximes and benzenoid esters on nocturnal rhythms. Four Nicotiana species in section Alatae sensu strictu have flowers that emit large amounts of 1,8 cineole, with smaller amounts of monoterpene hydrocarbons and alpha-terpineol on a nocturnal rhythm. This pattern suggests the activity of a single biosynthetic enzyme (1,8 cineole synthase) with major and minor products; however, several terpene synthase enzymes could contribute to total monoterpene emissions. Our analyses, combined with other studies of tobacco volatiles, suggest that phenotypic fragrance variation in Nicotiana is shaped by pollinator- and herbivore-mediated selection, biosynthetic pathway dynamics and shared evolutionary history.     

Lead and copper effects on lipid metabolism in cultured lichen photobionts with different phosphorus status

We evaluated the ability of heavy metals (copper, lead) to alter lipid metabolism in four algal lichen photobionts following short term exposure. Metal concentrations (10 microM) were equivalent to environmentally relevant levels that have been reported to have effects on intact algae. The algae were grown under normal or deficient phosphate conditions to assess any interactions with the heavy metal stress. Given the frequent sensitivity of lichens to copper and lead, there were surprisingly small changes on lipid metabolism, as assessed by radiolabelling from [1-14C]acetate. The main effects, which were seen in a number of cases, were an overall inhibition of total lipid labelling and a relative increase in the labelling of triacylglycerols in the non-polar fraction. Both of these changes can be viewed as reflecting general toxicity of heavy metals. The Coccomyxa photobiont species were more sensitive than Trebouxia species, which fits with the general distribution of the latter in lichens inhabiting harsh environments.     

盐胁迫对2种栎树苗期生长和根系生长发育的影响

以低浓度(50 mmol/L)和高浓度(150 mmol/L)NaCl处理弗吉尼亚栎(Quercus virginiana)和麻栎(Quercus acutissima)1年生幼苗,研究了2种栎树在盐胁迫下的生长、对盐分的敏感性和耐受性及其根系形态学参数变化以及根系对盐离子的吸收与积累。结果表明,高浓度盐胁迫明显抑制了2种栎树地上部生物量的积累(P0.05),而低浓度盐胁迫对弗吉尼亚栎地上部干重的影响不明显,但显著抑制了麻栎地上部干重(P0.05);2种栎树的根冠比在盐胁迫下呈增加趋势,特别是在高浓度盐胁迫下,2种栎树的根冠比明显增加(P0.05),盐胁迫下增加生物量在根部的分配是植物应对盐胁迫的方式之一。2种栎树根部生物量积累在盐胁迫下变化不明显,但2种栎树根系形态学参数在盐胁迫下的响应不同,弗吉尼亚栎根系总长度、总表面积和总体积在盐胁迫下均有不同程度增加,特别是在低浓度盐胁迫下,根系形态学参数明显增加(P0.05),但麻栎根系形态学参数有下降趋势,但与对照相比变化不明显;通过对不同径级根系总长的分析发现,弗吉尼亚栎根系总长度的增加主要是由于直径小于2 mm的细根总长的增加,细根长度的增加对于植物吸收水分和营养物质具有重要意义;通过对Na+和Cl-在根系的含量分析表明,盐胁迫下2种栎树根系盐离子的积累均有明显增加,但弗吉尼亚栎根系盐离子的含量在低浓度和高浓度盐胁迫下的差异不明显,而麻栎在高浓度盐胁迫下根系盐离子的含量明显高于弗吉尼亚栎。综合2种栎树盐胁迫下的生物量分配策略和根系形态学响应以及盐离子的积累规律,证明2种栎树尽管在生物量分配策略方面具有相同的特点,但根系的响应策略截然不同,弗吉尼亚栎在盐胁迫下能够扩大根系吸收范围,维持较高的K+/Na+比值,而麻栎在盐胁迫下根系由于吸收过多的盐离子,导致根系的生长发育受到抑制,影响了根系在逆境中的分布范围,从而在一定程度上避免了进一步的盐害。     

Characterization of four terpene synthase cDNAs from methyl jasmonate-induced Douglas-fir, Pseudotsuga menziesii

Numerous terpenoid compounds are present in copious amounts in the oleoresin produced by conifers, especially following exposure to insect or fungal pests. CDNA clones for many terpene synthases responsible for the biosynthesis of these defense compounds have been recovered from several conifer species. Here, the use of three terpene synthase sequences as heterologous probes for the discovery of related terpene synthase genes in Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco (Pinaceae), is reported. Four full-length terpene synthase cDNAs were recovered from a methyl jasmonate-induced Douglas-fir bark and shoot cDNA library. These clones encode two multi-product monoterpene synthases [a (-)-alpha-pinene/(-)-camphene synthase and a terpinolene synthase] and two single-product sesquiterpene synthases [an (E)-beta-farnesene synthase and a (E)-gamma-bisabolene synthase].     

Intraspecific shape variation in horseshoe crabs: The importance of sexual and natural selection for local adaptation

A morphometric analysis of the body shape of three species of horseshoe crabs was undertaken in order to infer the importance of natural and sexual selection. It was expected that natural selection would be most intense, leading to highest regional differentiation, in the American species Limulus polyphemus, which has the largest climatic differences between different populations. Local adaptation driven by sexual selection was expected in males but not females because horseshoe crab mating behaviour leads to competition between males, but not between females. Three hundred fifty-nine horseshoe crabs from nine populations, representing three species, were analyzed using a digitizer to position sixty morphometric landmarks in a three-dimensional space. Discriminant analysis revealed strong regional structuring within a species, which suggests strong philopatry, and showed the existence of geographically-based intraspecific variation. An admixture analysis showed regional intraspecific differentiation for males and females of L. polyphemus and males of the Asian horseshoe crab Carcinoscorpius rotundicauda, but not for females of C. rotundicauda and another Asian horseshoe crab, Tachypleus gigas. Differences in shape variation between sexes were tested with F-tests, which showed lower intrapopulation morphometric variation in males than females. These results indicate a lower degree of local adaptation on body shape in C. rotundicauda and T. gigas than in L. polyphemus and a lower degree of local adaptation in females than in males.     

Essential oil composition of Hypericum L. species from Southeastern Serbia and their chemotaxonomy

The essential oils of the aerial parts of nine species of Hypericum (Hypericum barbatum, Hypericum hirsutum, Hypericum linarioides, Hypericum maculatum, Hypericum olympicum, Hypericum perforatum, Hypericum richeri, Hypericum rumeliacum and Hypericum tetrapterum), collected from different locations in Southeast Serbia, were obtained by steam distillation and analyzed by GC and GC–MS. The essential oils investigated were characterized by a high content of non-terpene compounds and a low content of monoterpenes. The contents of non-terpenes, monoterpenes and sesquiterpenes in oils of the species H. barbatum, H. richeri and H. rumeliacum (section Drosocaprium) were similar and these oils were characterized by high contents of fatty acids. The oils of H. hirsutum and H. linarioides (section Taeniocarpium) contained a high percentage of n-nonane. There were similarities in contents of non-terpenes and sesquiterpenes in oils of species that belong to the section Hypericum (H. maculatum, H. perforatum and H. tetrapterum). The oil of H. olympicum differed from others by higher terpene content. A comparison was also carried out of the chemical composition of the essential oils from flower, leaf and stem of H. perforatum and it revealed that the highest concentration of non-terpene compounds was found in the flower and stem oil, while a high concentration of sesquiterpenes was characteristic for leaf oil. There were significant differences in the concentrations of the same compounds in the essential oils of H. maculatum, H. olympicum and H. perforatum, collected in different years from the same location which could be explained by seasonal differences. All data were statistically processed with principal component analysis and cluster analysis. The main conclusion from the above data is that genetic and environmental factors both play a role in determining the composition of essential oils of the Hypericum species studied.     

Effects of seed mass on seedling height and competition in European white oaks

The relationship between seed size and fitness in plants may depend on offspring density, especially in cases where seed size affects the outcome of competition. We investigated the relationship between seed mass, germination, intraspecific competition and seedling height in a glasshouse experiment on three European white oak species (Quercus robur, Q. petraea, Q. pubescens). Within offspring families, seed mass showed a moderate, but statistically significant effect on seedling height, i.e. seedlings from heavier seeds were slightly taller. In contrast, competition caused pronounced inequality in seedling height in pairs of competing seedlings, but in only 55.2% of all pairs the dominant competitor arose from the heavier seed. It is thus possible that a positive effect of seed mass on seedling growth can be mediated through the density of conspecific seedlings and that heterogeneity in offspring density will contribute to the maintenance of seed mass variation in oak populations.     

On the relative importance of the effects of selection and complementarity as drivers of diversity–productivity relationships in Mediterranean shrublands

Extensive research has been devoted to understanding the role of biodiversity as a driver of ecosystem functioning. However, no previous study has evaluated the relative contribution of complementarity and selection to productivity in shrublands. We have attempted to do this for a Mediterranean shrubland dominated by Quercus coccifera , Cistus albidus , Ulex parviflorus and Rosmarinus officinalis . We found a highly significant and linear positive relationship between productivity and species richness. No selection effect was apparent, but both the complementarity and net effects were highly significant. The magnitude of these effects increased from two to three species, but became non-significant in the four-species mixtures. Analysis of pairwise interactions revealed that legumes did not promote overyielding. Complementarity was mostly driven by Cistus , which always performed better when growing with other species than when growing with conspecifics. Our results are an addition to the still scarce literature dealing with diversity–productivity relationships in communities dominated by woody species, and show that methodologies commonly used to assess complementarity may not provide a precise estimation when a given species has negative effects on its conspecifics.     

Effect of arbuscular mycorrhiza on inter- and intraspecific competition of two grassland species

We were interested in the role of arbuscular mycorrhiza (AM) in the competition between plants of different sizes. A pot experiment of factorial design was established, in which AM root colonization and competition were used as treatments. Five-week-old Prunella vulgaris seedlings were chosen as target plants (i.e. plants whose response to competition was studied) and the following (13 replicates of each) were used as neighbours: (1) a large, 10-week-old P. vulgaris, (2) two P. vulgaris seedlings, and (3) a large, 10-week-old Fragaria vesca. In the experiment where small neighbours were grown together with small target plants, competition did not reduce target plant weight significantly, compared to the other two treatments. The competitive effects of large neighbours were significant, regardless of species (both older neighbours reduced the weights of target plants similarly), but there was a clear difference between intra- and interspecific competition when plants were mycorrhizal. In intraspecific competition with a large neighbour, the target plant shoot weight was reduced 24% when inoculated with AM. Thus, AM amplified rather than balanced intraspecific competition. In interspecific competition with old F. vesca, the shoot weights of target plants were 22% greater when inoculated with AM than when non-mycorrhizal. The results showed that, for given soil condition, AM might increase species diversity by increasing competitive intraspecific suppression and decreasing the interspecific suppression of small plants by larger neighbours.     

4种鲟鱼养殖亲鱼群体遗传多样性分析

近年鲟鱼人工繁殖技术促进了鲟鱼养殖业的发展,但在选育初期未对后备亲鱼进行遗传背景分析,为了抑制种质资源退化和防止近交衰退,繁育场需要对现有后备亲鱼进行遗传背景分析.本文利用线粒体控制区(D-loop)部分序列对4种养殖鲟鱼后备亲鱼群体(共120个样本)的遗传多样性进行了分析.研究发现不同种鲟鱼D-loop部分序列长度不...     

Brassicaceae contain nortropane alkaloids

The report of cochlearine, the 3-hydroxybenzoate ester of tropine found in Cochlearia officinalis, Brassicaceae, initiated a screening for tropane alkaloids in Cochlearia species and for calystegines in further Brassicaceae. All ten Cochlearia species investigated contained cochlearine, tropine, and pseudotropine. Calystegines, nortropane alkaloids deriving from pseudotropine, were also identified in all Cochlearia species and accumulated up to 0.5% dry mass in leaves. Brassicaceae species of all major lineages of the family were analysed for calystegines. Of the 43 species included in the study, 18 accumulated calystegines of various structures. This is the first screening of Brassicaceae for products of the tropane alkaloid pathway, which is known as characteristic for plants of Solanaceae family. The identification of calystegines in all branches of the Brassicaceae family including Aethionema, a species at the basis of the family, suggests tropane alkaloids as secondary compound typical for Brassicaceae.     

Seasonal dynamics of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis as a response to abiotic factors and abundance of insect hosts

The seasonal dynamics of entomopathogenic nematodes (EPNs) of the genus Steinernema and Heterorhabditis were studied during one season in meadow and oak wood habitats, in the vicinity of Ceské Budejovice, Czech Republic. The influences of soil temperature, moisture, and abundance of suitable hosts on EPN dynamics were investigated. The host range of these nematodes, in both habitats was also observed. A total of four EPN species were found in both habitats. Steinernema affine was the dominant species both in oak wood and in meadow. Additionally, the oak wood habitat was inhabited by S. kraussei and S. weiseri; the meadow habitat by Heterorhabditis bacteriophora. The mean abundance of total EPN community was 28,000ind./m(2) in oak wood and 11,000ind./m(2) in meadow. The seasonal dynamics of entomopathogenic nematodes in both habitats were characterized by high nematode densities in the beginning of the season, followed by a rapid decrease, and then stabilization. EPN abundances did not show any apparent correlation with soil temperature and moisture, but they were negatively correlated with the abundance of suitable insect hosts. Inter- and intraspecific competition for limited nutrients (hosts) probably played a major role in EPN seasonal dynamics. Broad host range of entomopathogenic nematodes in both habitats was predominantly represented by dipteran and coleopteran larvae. Most common hosts belonged to the families Asilidae, Bibionidae, and Empididae (Diptera), as well as Carabidae and Curculionidae (Coleoptera).