964 resultados para Insect Repellents
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The alkali metal salts of 1,5-hexadien-3-ols undergo accelerated Cope rearrangements to the enolates of δ, ε-unsaturated carbonyl compounds. The generality of the rearrangement was investigated in numerous systems, particularly acyclic cases, and the effect of changes in substituents, counterions, solvents, and geometrical structures were noted and discussed. Applications of this methodology in synthesis included the synthesis of the insect pheromone frontalin, the preparation of selectively monoprotected 1,6-dicarbonyl compounds from 4-methoxy- and 4-phenylthio-1,5-hexadien-3-ols, and the construction of complex ring structures such as a D-homo-estratetraenone derivative.
Thermochemical estimates of the energetics of anionpromoted alkoxide fragmentations were made, and in all cases heterolytic cleavage was favored over hemolytic cleavage by 8.5-53 kcal/mol. The implication of these and other thermochemical estimates is that the anionic oxy-Cope rearrangement occurs via a concerted mechanism rather than a dissociation-recombination process. The concepts of anion-induced bond weakening were successfully applied to an accelerated [1,3]-shift of a dithiane fragment in a cyclohexenyl system. Trapping experiments demonstrated that > 85% of the [1,3]-shift occurred within a solvent cage. Attempts at promoting an intramolecular ene reaction using the potassium salts of 2,7-octadien-1-o1 and 2,8-nonadien-1-o1 were unsuccessful. A general review of anion-promoted bond reorganizations and anion substituent effects is also presented.
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The zooplankton and macrobenthic communities of Lake Victoria were sampled by lift net and Ponar grab, respectively. The zooplankton comprised copepods and cladocerans, rotifers and aquatic insect larvae. Most taxa exhibited wide distribution in the lake, with the exception of rotifers which were rare in deep offshore waters. The main components in the macro-benthos were chaoborid and chironomid larvae and molluscs. Caridina nilotica (Roux) and other groups were rare in the samples. Zooplankton density ranged from 100000 or more to 4 million ind. m2 and increased from the shallow inshore to deep offshore waters. Numerical dominance of cyclopoids and nauplius larvae was a common feature at all stations sampled. Most macrobenthic taxa were also widely distributed, although chaoborid and chironomid larvae were rare in the samples. Rastrineobola argentea (Pellegrin) and larval Lates niloticus (L.) ate mainly cyclopoid copepods, while cichlids showed a strong preference for adult insects. High ecological stability of the cyclopoids, and the zooplankton community in general, despite radical ecosystem changes in recent years, coupled with what appears to be high predation pressure, offers good prospects for the pelagic fishery in the lake.
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The majority of water mites found in freshwater belong to the Hydrachnellae, a group which exhibit striking morphological diversity. This paper reviews work on the structure, morphology and taxonomy. The role of water mites as predators, their life history and their parasitic associations with aquatic insect or freshwater mollusc hosts is discussed along with the distribution of water mites in the British Isles.
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Part I
Phenol oxidase is the enzyme responsible for hardening and pigmentation of the insect cuticle. In Drosophila, phenol oxidase is a latent enzyme. Enzyme activity is produced by the interaction of a number of protein components. A minimal activation scheme consisting of six protein components, designated Pre S, S activator, S, P. P' and Ʌ1 is described. Quantitative assays have been developed for the S activator, S, P and P' proteins and these components have been partially purified. Experiments describing the interactions of the six components have been conducted and a model for the activation of phenol oxidase in a minimal system is proposed. Possible mechanisms of the reactions between the constituents of the activating system and potential regulatory mechanisms involved in phenol oxidase production and function are discussed.
Part II
A method has been developed for the partial purification of insulin from human serum. A procedure for the determination of the electrophoretic mobility of serum insulin on polyacrylamide gels is described. An electrophoretic analysis of insulin isolated from a normal subject is reported and in addition to a major band, the existence of a number of minor bands of immunoreactive insulin is described. A comparison of the electrophoretic patterns of insulin isolated from normal and diabetic subjects was carried out and indications that differences between them may occur are reported.
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Blowflies are insects of forensic interest as they may indicate characteristics of the environment where a body has been laying prior to the discovery. In order to estimate changes in community related to landscape and to assess if blowfly species can be used as indicators of the landscape where a corpse has been decaying, we studied the blowfly community and how it is affected by landscape in a 7,000 km(2) region during a whole year. Using baited traps deployed monthly we collected 28,507 individuals of 10 calliphorid species, 7 of them well represented and distributed in the study area. Multiple Analysis of Variance found changes in abundance between seasons in the 7 analyzed species, and changes related to land use in 4 of them (Calliphora vomitoria, Lucilia ampullacea, L. caesar and L. illustris). Generalised Linear Model analyses of abundance of these species compared with landscape descriptors at different scales found only a clear significant relationship between summer abundance of C. vomitoria and distance to urban areas and degree of urbanisation. This relationship explained more deviance when considering the landscape composition at larger geographical scales (up to 2,500 m around sampling site). For the other species, no clear relationship between land uses and abundance was found, and therefore observed changes in their abundance patterns could be the result of other variables, probably small changes in temperature. Our results suggest that blowfly community composition cannot be used to infer in what kind of landscape a corpse has decayed, at least in highly fragmented habitats, the only exception being the summer abundance of C. vomitoria.
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Neste trabalho utilizou-se a técnica fluorescência de raios X usando radiação síncrotron (SR-TXRF) para estudar, quantitativamente, o transporte de cloro, potássio e cálcio na hemolinfa, urina e túbulos de Malpighi (TM) em ninfas de quinto estágio do Rhodnius prolixus (R. prolixus), considerando a excreção destes elementos em diferentes dias após o repasto sanguíneo. R. prolixus é um dos principais vetores do Trypanosoma cruzi, agente causador da doença de Chagas. R. prolixus fornece um sistema modelo particularmente útil porque seus TMs tanto secretam quanto reabsorvem íons a taxas elevadas. Os TMs filtram a hemolinfa e secretam um líquido que é muitas vezes comparado com a urina primária em vertebrados. Os resultados obtidos mostram que a concentração de potássio na urina é substancialmente maior do que na hemolinfa. A concentração de cloro na hemolinfa é menor do que na urina, mas a diferença não é tão marcada como no caso do potássio. No caso do Rhodnius é razoável interpretar a elevada concentração de potássio na urina como adaptativo para o problema de excreção imediato do inseto. A concentração de cálcio nos TMs é substancialmente maior em comparação com os valores encontrados na hemolinfa e urina. Este resultado mostra que o cálcio é retido no corpo do R. prolixus e pouco eliminado. Os resultados obtidos estão coerentes com a literatura. Avaliou-se também o efeito no transporte de Cl, K e Ca após um repasto de sangue de coelho contaminado com HgCl2 de modo a avaliar o efeito da presença deste metal tóxico no balanço iônico nos fluidos de excreção urina e hemolinfa e também pelo principal órgão de transporte, os túbulos de Malpighi. As excreções de Cl e K pela urina são afetadas pela ingestão. Este resultado é esperado levando-se em consideração a ingestão de excesso de Cl através do HgCl2. O transporte de Cl, K e Ca na hemolinfa do Rhodnius prolixus não é afetada pela ingestão de HgCl2. Nos túbulos de Malpighi, as altas concentrações de Ca obtidas foram comparáveis àquelas encontradas nos insetos controle. Pode-se concluir que SR-TXRF é um método muito promissor para análises diretas, rápidas e confiáveis para a quantificação simultânea de elementos envolvidos na regulação do transporte e em todo o sistema excretor de insetos. Além disso, o estudo do transporte e a excreção de elementos no inseto Rhodnius prolixus abrem oportunidade para a maior compreensão de efeitos da poluição em espécies de invertebrados.
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Background: Chagas disease is caused by Trypanosoma cruzi, and humans acquire the parasite by exposure to contaminated feces from hematophagous insect vectors known as triatomines. Triatoma virus (TrV) is the sole viral pathogen of triatomines, and is transmitted among insects through the fecal-oral route and, as it happens with T. cruzi, the infected insects release the virus when defecating during or after blood uptake. Methods: In this work, we analysed the occurrence of anti-TrV antibodies in human sera from Chagas disease endemic and non-endemic countries, and developed a mathematical model to estimate the transmission probability of TrV from insects to man, which ranged between 0.00053 and 0.0015. Results: Our results confirm that people with Chagas disease living in Bolivia, Argentina and Mexico have been exposed to TrV, and that TrV is unable to replicate in human hosts. Conclusions: We presented the first experimental evidence of antibodies against TrV structural proteins in human sera.
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An investigation was conducted into the food and feeding habits of Synodontis nigrita from the Osun River near Epe, Lagos, Nigeria. The food items in the stomach of the S. nigrita covered a wide spectrum, ranging from various types of plankton to invertebrates and plants. A seasonal variation was also noted in the stomach contents of S. nigrita over the period of investigation. The predominant food items found in the stomach were Polycystis spp., Closterium spp., Oedogonium spp., plant tissues, insect parts and detritus. This suggests that S. nigrita is an omnivore.
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The apple snail, Pomacea canaliculata, was imported into Japan and cultured extensively for food in the early 1980s. Not long after, escaped or discarded snails became feral and started feeding on rice seedlings and other aquatic plants. This was especially noted in Kyushu in southern Japan. Snails are still proliferating, but the area of damaged rice is not increasing as fast, mainly because of the success of snail control. Currently, the most effective methods of avoiding damage to rice are keeping water shallow, transplanting older seedlings and, in some cases, using molluscicides or repellents. However, these methods have almost no effect on damage by snail feeding when rice fields are flooded. The apple snail is believed to be the most important obstacle to the spread of direct-sowing culture of rice in Kyushu. The Ministry of Agriculture, Forestry and Fisheries has launched a national project for the integrated management of the snail under direct sowing culture of rice in Kyushu. The Ministry of Agriculture, Forestry and Fisheries has launched a national project for the integrated management of the snail under direct-sowing rice culture. Some recent results from this project are briefly reviewed in this paper.
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A Inteligência de Enxame foi proposta a partir da observação do comportamento social de espécies de insetos, pássaros e peixes. A ideia central deste comportamento coletivo é executar uma tarefa complexa decompondo-a em tarefas simples, que são facilmente executadas pelos indivíduos do enxame. A realização coordenada destas tarefas simples, respeitando uma proporção pré-definida de execução, permite a realização da tarefa complexa. O problema de alocação de tarefas surge da necessidade de alocar as tarefas aos indivíduos de modo coordenado, permitindo o gerenciamento do enxame. A alocação de tarefas é um processo dinâmico pois precisa ser continuamente ajustado em resposta a alterações no ambiente, na configuração do enxame e/ou no desempenho do mesmo. A robótica de enxame surge deste contexto de cooperação coletiva, ampliada à robôs reais. Nesta abordagem, problemas complexos são resolvidos pela realização de tarefas complexas por enxames de robôs simples, com capacidade de processamento e comunicação limitada. Objetivando obter flexibilidade e confiabilidade, a alocação deve emergir como resultado de um processo distribuído. Com a descentralização do problema e o aumento do número de robôs no enxame, o processo de alocação adquire uma elevada complexidade. Desta forma, o problema de alocação de tarefas pode ser caracterizado como um processo de otimização que aloca as tarefas aos robôs, de modo que a proporção desejada seja atendida no momento em que o processo de otimização encontre a solução desejada. Nesta dissertação, são propostos dois algoritmos que seguem abordagens distintas ao problema de alocação dinâmica de tarefas, sendo uma local e a outra global. O algoritmo para alocação dinâmica de tarefas com abordagem local (ADTL) atualiza a alocação de tarefa de cada robô a partir de uma avaliação determinística do conhecimento atual que este possui sobre as tarefas alocadas aos demais robôs do enxame. O algoritmo para alocação dinâmica de tarefas com abordagem global (ADTG) atualiza a alocação de tarefas do enxame com base no algoritmo de otimização PSO (Particle swarm optimization). No ADTG, cada robô possui uma possível solução para a alocação do enxame que é continuamente atualizada através da troca de informação entre os robôs. As alocações são avaliadas quanto a sua aptidão em atender à proporção-objetivo. Quando é identificada a alocação de maior aptidão no enxame, todos os robôs do enxame são alocados para as tarefas definidas por esta alocação. Os algoritmos propostos foram implementados em enxames com diferentes arranjos de robôs reais demonstrando sua eficiência e eficácia, atestados pelos resultados obtidos.
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兰科植物传粉生物学的研究以往多集中于单个物种上,很少对两个以上的物种同时进行研究。但后一类研究对于理解一个地区或一个代表类群的传粉适应是大有裨益和非常必要的,毕竟单一种植物与其传粉者在一个居群或是一年中的相互关系所提供的有效信息是非常有限的。杓兰属Cypripedium L.是兰科植物中比较原始的类群,全世界约有50种;中国是杓兰属植物的分布中心,有30多种。但是,有关该属植物的传粉生物学研究集中在欧、美的种类,中国绝大部分物种尚未进行这方面的研究。本文通过对分布于四川省黄龙寺自然保护区的8种杓兰属植物的传粉生物学研究,探讨了该属植物的传粉机制、适应进化及生殖隔离等问题。 1. 杓兰属植物的繁育系统 虽然所研究的8种杓兰人工自交授粉均可以成功结实,但在自然条件下都必须依赖于昆虫才能结实成功,表明杓兰属植物的繁殖系统以异交授粉为主。 2. 杓兰属植物的传粉系统以及传粉系统的进化趋势 杓兰属植物一向被认为是典型的蜂类传粉物种,本文所包括的西藏杓兰C. tibeticum King ex Rolfe、离萼杓兰C. plectrochilum Franch.、绿花杓兰C. henryi Rolfe与褐花杓兰C. smithii Schltr.的传粉生物学研究也证明了这一点。但研究发现最进化的“无苞组”的3种杓兰,即无苞杓兰C. bardolphianum W. W. Smith et Farrer、小花杓兰C. micranthum Franch.与四川杓兰C. sichuanense Perner都是由蝇类传粉的,而黄花杓兰C. flavum P. F. Hunt et Summerh.则可由蜂类和蝇类共同传粉。结合杓兰的种间系统关系,本文认为杓兰属中存在从蜂类传粉系统向蝇类传粉系统的进化趋势。 3.杓兰属植物传粉系统的特化机制 传粉观察表明8种杓兰均有多种多样的访花昆虫,但只有1种或1类具有相同功能的昆虫能成为其传粉者。这说明杓兰属植物是具备特化传粉系统的种类。以离萼杓兰为例进行的花色、花香及花结构的分析表明,杓兰拥有特化的传粉者几乎完全是由于受到花结构的限制,特别是雄蕊到唇瓣底高度(AL)、柱头到唇瓣底高度(SL)、唇瓣入口直径(DL)与唇瓣出口宽度(EL)的大小。这些因素决定了昆虫是否能进入唇瓣,是否能碰触到柱头和花粉,是否能从出口挤出来。因此,杓兰的唇瓣的主要功能不仅是象原来所认为的作为“陷阱”来诱捕昆虫,而且同样作为一种促进产生“特化传粉”的机制而存在。 4. 杓兰属植物吸引昆虫的机制 杓兰属植物具有复杂的吸引昆虫的机制。离萼杓兰、黄花杓兰主要以泛化的食源性欺骗机制来吸引昆虫,绿花杓兰能通过其唇瓣和退化雄蕊的光滑特性诱使其传粉昆虫被动进入唇瓣中,西藏杓兰可以通过“筑巢式欺骗”来吸引昆虫,无苞杓兰则可通过模拟成熟果实来吸引其特化的传粉者—果蝇Drosophila spp.。 5. 杓兰属植物的花部特征与传粉系统的适应 在整个杓兰属内,不同种类植物的花色与花香和传粉者种类间没有统一的规律。但是,杓兰属植物的唇瓣大小与其传粉者大小之间存在比较明显的适应关系。体积最大的西藏杓兰、褐花杓兰与黄花杓兰由体型最大的熊蜂Bombus spp.传粉,体积中等的离萼杓兰、绿花杓兰、四川杓兰由中等大小的蜂或蝇传粉,而体积最小的无苞杓兰与小花杓兰由体型很小的果蝇传粉。 在杓兰属中,大部分种类的花粉只是粘性的团状,只有一部分能在一次访问中被昆虫带出,如黄花杓兰、西藏杓兰、离萼杓兰及绿花杓兰的花粉团。与此不同,在2个“无苞组”的杓兰,即无苞杓兰、小花杓兰中,它们的花粉凝聚成块状,而且它们的传粉昆虫(果蝇)的一次访问可带出一侧雄蕊的全部花粉。它们的花粉成块可能是对果蝇这类小昆虫传粉的一种适应。 6. 杓兰属植物的生殖隔离机制 本文的研究表明,杓兰属植物之间人工杂交授粉可以成功结实,它们主要是通过受精前隔离机制保持物种界限的。它们的受精前隔离机制多种多样。具有相同传粉者—果蝇的无苞杓兰与小花杓兰通过地理隔离机制保持物种界限; 同域的西藏杓兰与黄花杓兰通过利用不同大小的熊蜂作为传粉者来保持生殖隔离;同域的离萼杓兰与绿花杓兰可能通过花香成分的不同特化吸引同一属中不同种的传粉昆虫;而同域的西藏杓兰与褐花杓兰之间并不具备完善的生殖隔离机制。
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植物与传粉者的关系并非一门独立的学科,它包含很多进化生物学的内容。传粉生物学研究为我们理解植物进化的一些关键问题,如生殖隔离、物种形成、适应进化等提供重要证据。兰科植物由于其精巧的花部结构及其独特的传粉机制,备受传粉生物学家的关注。从达尔文时代以来,有大量的文献记载了欧洲兰族植物的传粉生物学的各个方面,其中,共涉及4种欺骗性传粉方式,它们几乎代表了兰科植物中近1/3没有报偿兰花所有的欺骗类型。然而,到目前为止,尽管在中国有丰富的兰族植物资源,中国兰科植物的传粉生物学研究仍然很缺乏。 在本研究中,作者以黄龙自然保护区内兰族的2种根茎兰属植物和1种小蝶兰属植物为材料,研究它们的传粉生物学,并探讨他们之间的生殖隔离机制。 1. 根茎兰属Galearis 及小蝶兰属Ponerorchis植物的交配系统 所研究的2种根茎兰属植物和1种小蝶兰属植物人工自交授粉均可以成功结实。在自然条件下,广布小蝶兰和二叶根茎兰都必须依赖于昆虫才能结实成功,而黄龙根茎兰则是以自花授粉为主。 2. 广布小蝶兰Ponerorchis chusua的传粉系统 在黄龙自然保护区进行了连续2 年的野外观测和实验,结果表明,广布小蝶兰是一种自交亲和,但需要昆虫传粉的欺骗性植物。广布小蝶兰的主要传粉者为雌性Bombus rufofasciatus,雌性B. consobrinus wittenburg,B. cucorun的蜂王和雄性B. pyrosona。熊蜂对广布小蝶兰具有典型的欺骗性兰花传粉的特征,即访问十分迅速,并且一般一个植株只访问一朵花,避免了同株异花授粉。 3. 二叶根茎兰Galearis diantha的传粉系统 野外观察表明,二叶根茎兰只有一种有效的传粉者,其访问频率不高,访 问时间短,并且会一次访问一个植株的两朵花,不可避免的产生同株异花授粉。自然结实率为23.0-26.8%,人工授粉实验证明传粉者限制是结实率较低的主要原因。 4. 黄龙根茎兰Galearis huanglongensis的传粉系统 研究结果表明,黄龙根茎兰为自动自花授粉的植物,黄龙根茎兰的花粉约在花开放4天后,花粉块从花粉囊中掉出,由于重力作用,花粉块柄弯曲使花粉接触到柱头,完成传粉。 5. 根茎兰属Galearis及小蝶兰属Ponerorchis植物的生殖隔离机制 本文的研究表明,根茎兰属内的杂交及与小蝶兰属间植物之间人工杂交授粉均可以成功结实,它们物种之间的生殖隔离主要是通过受精前隔离机制。具有相同传粉者(B. rufofasciatus)的广布小蝶兰与二叶根茎兰通过机械隔离机制保持物种界限。
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本文通过根农杆菌(Agrobacterium tumfaciens)介导法分别将Signal和KDEL修饰的豇豆胰蛋白酶抑制剂(Cowpea trypsin inhibitor, CpTI)基因、豌豆外源凝集素(Pea lectin, P-Lec)和大豆Kunitz型胰蛋白酶抑制剂(Soybean Kunitz typsin inhibitor, SKTI)双价抗虫基因、雪花莲外源凝集素(Galanthus nivals agglutinin, GNA)基因以及高效复合启动子OM控制的苏云金杆菌(Bacillus thuringiensis, B.t.)杀虫毒蛋白基因导入了陆地棉(Gossypium hirsutum L.)栽培品种新陆早1号、新陆中2号、晋棉7号、冀合321、辽9和晋棉12号,并获得了大批转基因再生植株。 实验中对影响棉花转化和再生的一些条件进行了研究,从根农杆菌培养、棉花无菌苗的制备、转化操作和共培养等方面对转化条件进行了探讨;从激素配化、植物表达载体、外植体类型、基因型等方面对抗性愈伤组织的诱导进行了摸索;从激素、从碳源、培养容器、pH值、抗褐化剂及固化剂的选择等方面对影响植株再生的条件进行了优化。 本文开创性地采用嫁接代替移栽,从而极大地提高了转化植株定植成活率,缩短了缓苗时间并增加了转化植株当代的繁殖系数。 在建立了一套较为高效的陆地棉转化及再生系统基础上,本文还进行了其它转化方式和转化体系的初步探讨。利用棉花幼嫩种子无菌苗下胚轴作为外植体,通过改变愈伤组织诱导培养基配方面提高胚性愈伤组织的诱导频率,进而得到更多的体细胞胚状和再生植株,缩短再生周期;尝试用胚性愈伤组织作为外植体的根农杆菌介导法转化,确定了一些与转化有关的条件;建立了一套棉花茎尖培养程序,为运用基因枪法轰击棉花茎尖分生组织或用根农杆菌直接转化茎尖分生组织,以克服根农杆菌转化棉花时体胚发生的基因型局限开辟了一条新途径。 本文还建立了一种快速鉴定转化植株后代的方法。这一简便方法还有助于进行转基因棉纯合系的筛选以及外源基因的遗传稳定性研究。 转基因植株经Npt-II ELISA、PCR、PCR Southern 检测证明外源抗虫基因CpTI、SKTI、P-lec、GNA以及B.t.基因已存在于转化植株基因组内。修饰的CpTI转基因植株抗棉铃虫(Heliothis armigera Hubner)试验结果表明,其杀虫效果显著优于前期未修饰的CpTI转化植株。P-lec和SKTI双价转基因植株抗棉铃虫试验结果表明,转基因植株对棉铃虫幼虫具有较强的杀虫活力。 目前,已获得转以上抗虫基因棉花T1代植株。为今后进一步将植物基因工程技术应用于棉花遗传改良打下了基础。
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以陆地棉(Gossypium hirsutum L.)栽培品种新陆早4号、系550、冀资492、衡无89-30、邯93-2、冀资123等为材料,进行了组织培养及植株再生研究,建立了一套陆地棉体细胞植株再生速成体系。通过调整激素种类与比例以及改善培养条件,降低了畸形胚发生频率(从80%降为41%),并可将畸形苗转化为正常苗(转化率约为78%);通过水培和嫁接,结合试管扦插、扩繁技术,解决了棉花生根及移栽难题,为农杆菌介导法转化棉花奠定了基础。 用绿色荧光蛋白基因(gfp)作为报告基因,构建了pBGb1m(含Bt和gfp二价基因)、pBGbf(含Bt-gfp融合基因)和pBGbfg(含Bt-gfp融合基因和gna基因)等三种植物表达载体。通过农杆菌介导法转化烟草,转基因再生植株经过荧光、虫试、PCR、Southern blot和Western blot等检测,表明三种植物表达载体能够在转基因植物中有效表达,同时,绿色荧光蛋白(GFP)的检测表现出了简便、经济、快速、可靠等优点,为大量棉花转基因苗的检测提供了一种有效方法。 采用花粉管通道法将携带细胞间隙定位信号肽的Bt基因的pBin438-S1m质粒导入棉花品种冀资492,经过田间卡那霉素筛选、虫试、PCR、PCR-Southern blot和Southern blot检测,证明Bt基因已整合至棉花基因组中,而且可能是以单拷贝形式插入。 同时,通过农杆菌介导法将三种植物表达载体(pBGb1m、pBGbf和pBGbfg)转化陆地棉栽培品种新陆早4号、冀资492、衡无89-30和邯93-2等材料,获得了大量转化再生棉株。经过PCR和PCR-Southern blot检测,转基因阳性植株为转为再生植株总数的89.45%。目前,虫试、Southern blot及Western blot正在进行之中。
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EXTRACT (SEE PDF FOR FULL ABSTRACT): We argue that the most important climatically-driven terrestrial ecosystem changes are concentrated in annual- to decadal-scale episodic events. These rapid ecosystem responses to climate change are manifested as regionally synchronized disturbance events (eg, floods, fires, and insect outbreaks) and increased drought-caused plant mortality rates.