997 resultados para Artemisia genus


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本工作研究植物源CH4排放,即植物本身生成的CH4,不是厌氧微生物代谢产生的。目前对植物是否直接排放甲烷仍然存在很大争议:一方面实验中观测到的植物甲烷排放率差异较大;另一方面对植物甲烷排放内在机理仍不清楚。本文以旱生植物冷蒿(Artemisia frigida)为对象,测定冷蒿甲烷排放,分析冷蒿甲烷排放的可能存在的外界干扰因素。实验结果表明,冷蒿确实能够排放甲烷,冷蒿甲烷生成可能与活性氧代谢有关。 冷蒿是一种典型的旱生植物,其生长的典型草原中,土壤透气性好并表现为大气甲烷的汇。土壤孔隙间的甲烷浓度不高于大气甲烷浓度,能够通过植物根系进入植物体内的土壤甲烷量十分有限,植物组织又缺乏吸附甲烷的能力,很难在植物体内累积甲烷。因此,一些实验研究中所提出的植物蒸腾作用和细胞壁吸附作用对冷蒿的甲烷排放并没有显著影响。我们研究在实验室条件下冷蒿能否排放甲烷,无论是野外生长的冷蒿,还是室内无菌培养的冷蒿,都有明显的甲烷排放。通过研究植物呼吸作用与甲烷排放之间的相关性,我们发现两者有明显的线性关系。植物在应对环境胁迫时,呼吸电子传递链发生紊乱,导致活性氧的积累,这可能是植物所排放甲烷的主要来源。进而,我们通过活性氧添加实验证实包括超氧阴离子(•O2-),羟基自由基(•OH)和过氧化氢(H2O2)在内的多种活性氧都能够促进冷蒿的甲烷排放,而抗氧化酶CAT则对冷蒿的甲烷排放具有抑制效果,我们认为这种抑制效果是通过对ROS的清除来实现的。冷蒿体内能够不断产生甲烷的途径可能需要活性氧的参与,植物体内自由基水平的高低,很可能决定了这种植物能否排放甲烷。因此,我们对比了四种植物体内的抗氧化酶活性。我们在抗氧化酶活性高的物种中没有测得甲烷的排放,而冷蒿和小叶锦鸡儿两种有明显甲烷排放的植物,其三种抗氧化酶活性均较低。由此我们认为,植物体内的活性氧与植物细胞内的某些成分发生反应并产生甲烷的过程很可能是植物体内清除活性氧,降低过氧化毒害的一种适应机制。

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本文利用电子显微镜和光学显微镜研究了国产的蒿属花粉代表种和常见种共66种4变种,根据花粉外壁纹饰可将其分为六大类型:1、具刺状突起,排列不密集,刺间具颗粒状纹饰(类型—I)。2、刺状突起较类型—I稍为密集,没有或有少许颗粒状纹饰(类型—II)。3、具刺状突起,排列不密集,但刺间无颗粒状纹饰,较粗糙(类型—III)。4、刺状突起较类型—I稍为密集,刺间具发育的小芽胞状或颗粒状纹饰,小芽孢状突起顶部有的还可见有一小穿孔存在(类型-IV)。5、具微刺状突起,排列极稀,刺间较为平滑(类型—V)。6、刺状突起有大小之分,大刺较尖,还有颗粒状纹饰(类型—VI)。其中类型—I占绝对优势,其次为类型—II,类型—V和类型VI为较特殊的类型。 本文还对蒿属邻近属(即蒿自然群中的其它属)各属代表种花粉作了详细的研究,并和蒿属花粉作了比较。结果表明:按外壁纹饰可将蒿自然群分为两大类型:1、具明显的刺状纹饰。其中包括:亚菊属、女蒿属、百花蒿属。2、具退化状小刺。其中包括:蒿属、茶蒿属、线叶菊属、画笔菊属、喀什菊属、栉叶蒿属、绢蒿属。经研究我们认为在花粉形态上蒿自然群是一相互关联的有机整体,并从花粉形态的角度出发,文中讨论了紊蒿属和百花蒿属的分属问题,作者认为它们独立成两个单种属的意见较为妥当。

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The timing and order of divergences within the genus Rattus have, to date, been quite speculative. In order to address these important issues we sequenced six new whole mitochondrial genomes from wild-caught specimens from four species, Rattus exulans, Rattus praetor, Rattus rattus and Rattus tanezumi. The only rat whole mitochondrial genomes available previously were all from Rattus norvegicus specimens. Our phylogenetic and dating analyses place the deepest divergence within Rattus at ∼3.5 million years ago (Mya). This divergence separates the New Guinean endemic R. praetor lineage from the Asian lineages. Within the Asian/Island Southeast Asian clade R. norvegicus diverged earliest at ∼2.9 Mya. R. exulans and the ancestor of the sister species R. rattus and R. tanezumi subsequently diverged at ∼2.2 Mya, with R. rattus and R. tanezumi separating as recently as ∼0.4 Mya. Our results give both a better resolved species divergence order and diversification dates within Rattus than previous studies.

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To date, a molecular phylogenetic approach has not been used to investigate the evolutionary structure of Trogoderma and closely related genera. Using two mitochondrial genes, Cytochrome Oxidase I and Cytochrome B, and the nuclear gene, 18S, the reported polyphyletic positioning of Trogoderma was examined. Paraphyly in Trogoderma was observed, with one Australian Trogoderma species reconciled as sister to all Dermestidae and the Anthrenocerus genus deeply nested within the Australian Trogoderma clade. In addition, time to most recent common ancestor for a number of Dermestidae was calculated. Based on these estimations, the Dermestidae origin exceeded 175 million years, placing the origins of this family in Pangaea.

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Currently there are ~3000 known species of Sarcophagidae (Diptera), which are classified into 173 genera in three subfamilies. Almost 25% of sarcophagids belong to the genus Sarcophaga (sensu lato) however little is known about the validity of, and relationships between the ~150 (or more) subgenera of Sarcophaga s.l. In this preliminary study, we evaluated the usefulness of three sources of data for resolving relationships between 35 species from 14 Sarcophaga s.l. subgenera: the mitochondrial COI barcode region, ~800. bp of the nuclear gene CAD, and 110 morphological characters. Bayesian, maximum likelihood (ML) and maximum parsimony (MP) analyses were performed on the combined dataset. Much of the tree was only supported by the Bayesian and ML analyses, with the MP tree poorly resolved. The genus Sarcophaga s.l. was resolved as monophyletic in both the Bayesian and ML analyses and strong support was obtained at the species-level. Notably, the only subgenus consistently resolved as monophyletic was Liopygia. The monophyly of and relationships between the remaining Sarcophaga s.l. subgenera sampled remain questionable. We suggest that future phylogenetic studies on the genus Sarcophaga s.l. use combined datasets for analyses. We also advocate the use of additional data and a range of inference strategies to assist with resolving relationships within Sarcophaga s.l.

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Understanding the evolutionary history and phylogenetic relationships between rare and common species is necessary for the effective management of rare species. The genus Cherax, a group of freshwater crayfish species, is of interest in this regard as a number of species are rare or have restricted distributions while other species are common and widespread. Here we describe the characterisation of three novel nuclear genes of the haemocyanin superfamily for phylogenetic reconstruction of the genus. All novel markers developed in this study amplified consistently in species from three divergent clades of the genus Cherax. The level of polymorphism found in these markers was consistently higher than that found in other nuclear genes previously used in invertebrate systematics, such as NaK ATP-ase. In combination, these markers will be useful to delineate phylogenetic relationships between rare and common Cherax species.

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The practical need to partition the world of viruses into distinguishable, universally agreed upon entities is the ultimate justification for developing a virus classification system. The Author of this Book is Andrew MQ King, Elliot Lefkowitz, Eric B. Carstens, Michael J. Adams Since 1971, the International Committee on Taxonomy of Viruses (ICTV) operating on behalf of the world community of virologists has taken on the task of developing a single, universal taxonomic scheme for all viruses infecting animals (vertebrate, invertebrates, and protozoa), plants (higher plants and algae), fungi, bacteria, and archaea.

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Barbadocladius n. gen. is erected and described in larval, pupal and adult stages for two species: B. andinus sp. nov. and B. limay sp. nov., from Andean streams. The larva is distinctive by virtue of the very large ventromental 'beard' and the anterior parapods with a 'sleeve' of hooklets in addition to apical pectinate claws. The pupa has hooklets on some tergal and sternal intersegmental membranes. The adult, reported only in teneral specimens has hairy eyes, no antennal apical strong seta, no acrostichals, bare and unmarked wings, cylindrical 4th tarsomere subequal in length to the 5th, pulvilli about half the claw length, and hypopygium with anal point, lacking a virga. Molecular phylogenetic analysis eliminates relationships directly to the Eukiefferiella complex (which also have pupal hooklets), or to the Cricotopus group (adults also with hairy eyes), suggesting instead a sister group relationship to a suite of predominantly austral genera of Orthocladiinae.

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The Australian species of the Orthocladiinae genus Cricotopus Wulp (Diptera: Chironomidae) are revised for larval, pupal, adult male and female life stages. Eleven species, ten of which are new, are recognised and keyed, namely Cricotopus acornis Drayson & Cranston sp. nov., Cricotopus albitarsis Hergstrom sp. nov., Cricotopus annuliventris (Skuse), Cricotopus brevicornis Drayson & Cranston sp. nov., Cricotopus conicornis Drayson & Cranston sp. nov., Cricotopus hillmani Drayson & Cranston, sp. nov., Cricotopus howensis Cranston sp. nov., Cricotopus parbicinctus Hergstrom sp. nov., Cricotopus tasmania Drayson & Cranston sp. nov., Cricotopus varicornis Drayson & Cranston sp. nov. and Cricotopus wangi Cranston & Krosch sp. nov. Using data from this study, we consider the wider utility of morphological and molecular diagnostic tools in untangling species diversity in the Chironomidae. Morphological support for distinguishing Cricotopus from Paratrichocladius Santo-Abreu in larval and pupal stages appears lacking for Australian taxa and brief notes are provided concerning this matter.