米槠与杉木细根凋落物是否在自身群落中分解得更快？

本研究应用网袋法对福建省万木林自然保护区米槠(Castanopsis carlesii)、杉木(Cunninghamia lanceolata) 细根在米槠林群落和杉木林群落交叉分解进行了为期2年的研究。结果表明, 0~1 mm、1~2 mm米槠细根在米槠群落比在杉木群落分解速率快, 而相同径级杉木细根在两群落分解差异较大。0~1 mm杉木细根在杉木群落的分解速率高于米槠群落, 而1~2 mm杉木细根在杉木群落的分解速率只及米槠群落的48％。米槠、杉木细根在两群落分解的差异表明, 群落立地条件对细根分解存在较大的影响。     

亚热带不同树种凋落叶分解对氮添加的响应

为探究不同质量凋落物对氮(N)沉降的响应,该研究采用尼龙网袋分解法,在亚热带福建三明格氏栲(Castanopsis kawakamii)自然保护区的米槠(Castanopsiscarlesii)天然林,选取4种本区常见的具有不同初始化学性质的树种凋落叶进行模拟N沉降(N添加)分解实验(施N水平为对照0和50 kg·hm~(–2)·a~(–1))。研究结果表明:在2年的分解期内,对照处理的各树种凋落叶的分解速率依次为观光木(Michelia odora, 0.557 a~(–1))、米槠(0.440 a~(–1))、台湾相思(Acacia confusa, 0.357 a~(–1))、杉木(Cunninghamia lanceolata, 0.354 a~(–1)); N添加处理凋落叶分解速率依次为观光木(0.447 a~(–1))、米槠(0.354 a~(–1))、杉木(0.291 a~(–1))、台湾相思(0.230a~(–1)),除杉木凋落叶外, N添加显著降低了其他3种凋落叶分解速率。N添加不仅使4种树木凋落叶分解过程中的N释放减慢,同时还抑制凋落叶化学组成中木质素和纤维素的降解;N添加在凋落叶分解过程中总体上提高β-葡萄糖苷酶(βG)和酸性磷酸酶活性,对纤维素水解酶的活性影响不一致,而降低β-N-乙酰氨基葡萄糖苷酶活性和酚氧化酶活性。凋落叶分解速率与凋落叶中的碳获取酶(βG)活性以及其化学组分中的可萃取物含量极显著正相关,与初始碳浓度、纤维素和木质素含量极显著负相关,与初始N含量没有显著相关性。凋落物类型和N添加的交互作用虽未影响干质量损失速率,但对木质素和纤维素的降解具有显著效应。综上所述,化学组分比初始N含量能更好地预测凋落叶分解速率,而N添加主要通过抑制分解木质素的氧化酶(如PHO)来降低凋落叶分解速率。     

米槠与杉木细根凋落物是否在自身群落中分解得更快?

本研究应用网袋法对福建省万木林自然保护区米槠（Castanopsis carlesii）、杉木（Cunninghamia lanceolata）细根在米槠林群落和杉木林群落交叉分解进行了为期2年的研究。结果表明,0-1mm、1-2mm米槠细根在米槠群落比在杉木群落分解速率快,而相同径级杉木细根在两群落分解差异较大。0—1mm杉木细根在杉木群落的分解速率高于米槠群落,而1—2mm杉木细根在杉木群落的分解速率只及米槠群落的48％。米槠、杉木细根在两群落分解的差异表明,群落立地条件对细根分解存在较大的影响。     

氮沉降对中亚热带米槠天然林微生物生物量及酶活性的影响

氮沉降对土壤微生物的扰动可能会影响土壤的养分循环,然而关于中亚热带天然林土壤微生物及酶活性对氮沉降的响应鲜有报道。通过3 a的氮沉降模拟实验,研究中亚热带米槠天然林土壤的理化性质、土壤微生物量及土壤酶活性的响应。结果表明:氮沉降并未引起土壤的有机碳和总氮显著性变化;高氮(80 kg N hm~(-2)a~(-1))处理下,土壤p H下降,出现酸化现象;低氮(40 kg N hm~(-2)a~(-1))处理促进淋溶层(A层)中土壤纤维素分解酶(β-葡萄糖苷酶和纤维素水解酶)和木质素分解酶(多酚氧化酶和过氧化物酶)活性升高,同时促进土壤微生物生物量碳、氮的积累。冗余分析(RDA)表示,可溶性有机碳(DOC)是驱动A层土壤酶活性的重要环境因子;而在淀积层(B层),这4种酶活性并未发生显著性差异。施氮处理后,A、B层中土壤的酸性磷酸酶活性增加(P0.05)。研究表明:低水平氮沉降增加了土壤微生物生物量碳氮含量以及土壤有机碳分解相关酶活性,从而加速了土壤碳周转;这为未来氮沉降增长背景下,探索中亚热带天然林土壤碳源汇问题提供了依据。     

杉木和米槠细根混合分解及其养分释放

在福建省建瓯万木林自然保护区,选取针叶树种杉木(Cunninghamia lanceolata,CUL)细根和常绿阔叶树种米槠(Castanopsis carlesii,CAC)细根,采用网袋法进行了为期720d细根(分0-1mm、1-2mm两个径级)单独分解(在各自细根的起源林分)和混合分解(分别在杉木林和米槠林)干重损失及其养分释放动态的研究。结果表明:杉木和米槠细根混合分解前期(0-270d)曾对干重损失起促进作用,而之后(270-720d),细根混合起了抑制作用。分解过程中的养分释放与干重损失有所不同,混合分解前期(0-360d)出现过促进作用,分解后期(360-720d),除1-2mm径级混合细根P的释放既没有促进也没有抑制作用外,均表现为养分释放的抑制作用。细根混合分解过程中干重损失和养分释放速率变化与分解者生物群落有很大关系。     

施肥对杉木林土壤酶和活性有机碳的影响

以中亚热带地区的5年生杉木(Cunninghamia lanceolata)人工林为研究对象,探讨施肥对土壤酶活性和活性有机碳含量的影响,实验包括对照(CK)、施氮肥(200 kg N·hm~(-2)·a~(-1))、施磷肥(50 kg P·hm~(-2)·a~(-1))、施氮磷肥(200 kg N·hm~(-2)·a~(-1)和50 kg P·hm~(-2)·a~(-1))等4个处理。结果表明:在表层(0~10 cm)土壤中,施NP肥处理的土壤蔗糖酶和过氧化氢酶活性分别比CK降低了40.2%和36.5%,β-葡萄糖苷酶活性比施P肥处理降低了31.1%;亚表层(10~20 cm)土壤中,施N肥处理的脲酶活性显著低于CK;施N肥、P肥和NP肥处理的蔗糖酶活性分别比CK降低了46.9%、37.8%和42.4%;施NP肥处理的过氧化氢酶活性比施P肥处理降低了22.6%;在表层土壤中,施N肥、P肥处理的土壤水溶性有机碳含量分别比CK降低24.1%和29.4%;施NP肥处理的微生物生物量碳显著低于CK;土壤活性有机碳组分在不同土层之间差异显著,均表现为表层土壤活性有机碳含量高于亚表层土壤。相关性分析结果显示:蔗糖酶活性与硝态氮含量呈极显著负相关,表明施NP肥增加了硝态氮含量,一定程度上抑制了蔗糖酶的活性;水溶性有机碳与脲酶活性呈显著正相关,土壤微生物生物量碳与脲酶、过氧化氢酶和β-葡萄糖苷酶活性呈显著正相关。研究表明,水溶性有机碳、微生物生物量碳和土壤酶活性的降低可能会抑制土壤碳的释放,从而增加土壤碳的固定。     

模拟氮沉降对杉木幼苗细根化学计量学特征的影响

为了揭示全球氮(N)沉降对杉木人工林细根碳(C)、N、磷(P)元素组成的影响,在福建三明陈大国有林场开展杉木(Cunninghamia lanceolata)幼苗模拟N沉降试验,设置了对照(CK)、低N(LN,40 kg N hm~(-2)a~(-1))、高N(HN,80 kg N hm~(-2)a~(-1))3个处理,每个处理5个重复。采用内生长环法通过2年4次取样探讨N沉降对细根C、N、P化学计量学的影响。结果显示:(1) N添加在2015年降低细根C浓度,此后低N处理无影响,高N添加在2016年增加了细根C浓度;高N添加提高了细根(特别是0—1 mm细根) N浓度,但低N添加则无显著影响,甚至在2016年7月显著降低细根N浓度; N添加在2015年对细根P浓度无显著影响,但在2016年导致细根(特别是0—1 mm细根) P浓度降低。(2)低N添加在2016年显著提高细根的C∶N比,而高N添加则在2015年1月显著降低细根的C∶N比;低N添加对细根N∶P比没有显著影响,而高N添加则在大部分取样时间里显著增加了细根N∶P比。(3)不同处理细根C浓度、C∶N比均随着时间的增加呈增加趋势,而细根N浓度和N∶P比呈降低趋势。本研究表明,N添加对杉木细根化学计量学特征的影响因不同N添加水平而异,并受苗木生长的稀释效应所调节。     

森林转换后土壤因素影响中亚热带土壤磷的积累

磷是植物生长的必需元素之一,是维持亚热带森林生态系统生产力的关键因子。研究森林转换后土壤因素对磷素的影响,对生态系统的稳定和森林经营具有重要意义。本文选取由亚热带常绿阔叶林转换而成的米槠次生林(SF)、米槠人促林(AR)和杉木人工林(CF)为研究对象,测定了土壤理化性质、铁铝氧化物、各形态磷含量以及酸性磷酸酶活性,旨在探究土壤磷对森林转换的响应和驱动土壤磷变化的影响因子。结果显示:米槠人促林土壤的全磷、有机磷和微生物生物量磷显著高于米槠次生林和杉木人工林;冗余分析(RDA)发现,土壤含水量、总氮和无定型铁是影响A层土壤磷的主要因子,而在B层,则是酸性磷酸酶、游离型铁和总氮起主要作用;土壤生物化学属性和微生物特性都会影响着不同形态土壤P的积累,其中土壤中的水分和酸性磷酸酶活性是调控土壤磷的关键因子。研究表明,中亚热带地区天然林转换为人促更新林更有利于森林土壤磷的储存和供应,有助于维持本区域森林生态系统的稳定。本文的研究结果可为中亚热带森林经营提供科学依据。     

中亚热带森林转换对土壤磷积累的影响

磷是植物生长的必需元素之一,是维持亚热带森林生态系统生产力的关键因子。研究森林转换后土壤因素对磷素的影响,对生态系统的稳定和森林经营具有重要意义。选取由亚热带常绿阔叶林转换而成的米槠次生林(SF)、米槠人促林(AR)和杉木人工林(CF)为研究对象,测定了土壤理化性质、铁铝氧化物、各形态磷含量以及酸性磷酸酶活性,旨在探究土壤磷对森林转换的响应和驱动土壤磷变化的影响因子。结果显示:米槠人促林土壤的全磷、有机磷和微生物生物量磷显著高于米槠次生林和杉木人工林;冗余分析(RDA)发现,土壤含水量、总氮和无定型铁是影响淋溶层土壤磷的主要因子,而在淀积层,则是酸性磷酸酶、游离型铁和总氮起主要作用;土壤生物化学属性和微生物特性都会影响着不同形态土壤P的积累,其中土壤中的水分和酸性磷酸酶活性是调控土壤磷的关键因子。研究表明,中亚热带地区天然林转换为人促更新林更有利于森林土壤磷的储存和供应,有助于维持本区域森林生态系统的稳定。     

施氮磷肥对杉木人工林土壤活性有机碳的影响

为确定施氮、磷肥对中亚热带人工林土壤不同活性组分有机碳的影响,本研究在5年生杉木(Cunninghamia lanceolata)人工林中设置氮、磷施肥试验,包括对照(CK)、施氮肥(200 kg N·hm~(-2)·a~(-1))、施磷肥(50 kg P·hm~(-2)·a~(-1))、施氮磷肥(200 kg N·hm~(-2)·a~(-1)+50kg P·hm~(-2)·a~(-1)) 4个处理。连续施肥5年后,采取(0~10 cm)表层土壤,测定了活性有机碳不同组分的变化。结果表明:施肥对土壤有机碳(SOC)影响不显著,施氮肥和氮磷配施使土壤微生物量碳(MBC)分别降低34.6%和45.8%,施氮肥降低了常温浸提水溶性有机碳(WSOC)含量,且施氮磷肥对WSOC有交互作用,施氮磷肥使热水浸提有机碳(HWC)含量显著提高了31.5%,施肥对易氧化有机碳(LOC)、颗粒有机碳(POC)、热水浸提碳水化合物(HWc C)的影响不显著;在施肥处理下,MBC/SOC对单施磷肥和氮肥不敏感,氮磷配施使MBC/SOC下降了48.4%,与CK相比,施氮磷肥对POC/SOC没有影响,但与氮肥处理相比,施氮磷肥使POC/SOC显著增加了24.3%;经相关性分析,HWC与硝态氮、有效磷呈显著或极显著正相关。     

Flavonoids of Astilbe and Rodgersia compared to Aruncus

The flavonoid profiles of Astilbe (four taxa studied) and Rodgersia (two taxa studied) are based on simple flavonol glycosides. Astilbe has 3-O-mono-, 3-O-di-, and 3-O-triglycosides of kaempferol, quercetin, and myricetin, while Rodgersia has only mono- and diglycosides of kaempferol and quercetin. Astilbe×arendsii was also shown to accumulate dihydrochalcone glycosides. The flavonoid profile of Rodgersia is the simplest recorded so far in the herbaceous Saxifragaceae. The flavonoids of two species of Aruncus were shown to be based upon kaempferol and quercetin 3-O-mono- and 3-O-diglycosides. One of the species also exhibited an eriodictyol glycoside. The triglycoside differences were not considered important, but the differences in myricetin occurrences were taken as evidence against derivation of Saxifragaceae from an Aruncus-like ancestor. Should such an event be proposed, however, serious consideration would have to be given to the current pattern of myricetin occurrence in the two families.     

Chemical composition, in situ ruminal degradability and post-ruminal disappearance of dry matter and crude protein from the halophytic plants Kochia scoparia, Atriplex dimorphostegia, Suaeda arcuata and Gamanthus gamacarpus

Samples of Kochia (K. scoparia), Atriplex (A. dimorphostegia), Suaeda (S. arcuata) and Gamanthus (G. gamacarpus) were collected and analyzed for chemical composition including crude protein (CP), ether extract (EE), ash, neutral detergent fiber (NDFom), acid detergent fiber (ADFom), non-protein N (NPN), Ca, P, Na, K, Cl, Mg, Fe, Cu and Se. In addition, in situ ruminal degradability and post-ruminal disappearance of dry matter (DM) and CP of the samples using a mobile bag technique were determined. Results indicate that the chemical composition of Kochia and Atriplex was notably different from those of Suaeda and Gamanthus. All of these halophytic plants had high concentrations of Na, K, Cl, Cu and Se, and low levels of Ca, P and Mg. The rapidly degradable fractions of DM and CP (g/g) of Kochia (0.31 and 0.35, respectively) and Atriplex (0.39 and 0.50, respectively) were lower than for Suaeda (0.53 and 0.55, respectively) and Gamanthus (0.56 and 0.66, respectively). Ruminal DM and CP disappearance of Kochia (444 and 517 g/kg, respectively) and Atriplex (472 and 529 g/kg, respectively) were lower (P<0.05) than those of Suaeda (553 and 577 g/kg, respectively) and Gamanthus (663 and 677 g/kg, respectively) (P<0.05) using the mobile bag technique. Suaeda had the lowest (P<0.05) NDFom and ADFom disappearance (214 and 232 g/kg, respectively) in the rumen. Kochia scoparia and Atriplex dimorphostegia have more beneficial chemical nutritive components and digestible values versus Suaeda arcuata and Gamanthus gamacarpus.     

Cloning and characterization of femA and femB from Staphylococcus epidermidis

A DNA fragment was identified and cloned from Staphylococcus epidermidis (Se) using femA from S. aureus (Sa) as a heterologous hybridization probe. DNA sequence analysis of a portion of this clone revealed two complete ORFs highly related to femA and femB of Sa. The genomic arrangement of the Se femA/B complex was nearly identical to that observed in Sa. Intra- and interspecies relatedness of these genes and conservation of genomic organization were consistent with gene duplication of one of these genes in an ancestral organism. Recombinant FEMA, produced in Escherichia coli (Ec), was purified to near homogeneity. Identity of the purified protein was verified by N-terminal amino acid (aa) sequence analysis.     

Multiple invasions of Gypsy and Micropia retroelements in genus Zaprionus and melanogaster subgroup of the genus Drosophila

Background  

The Zaprionus genus shares evolutionary features with the melanogaster subgroup, such as space and time of origin. Although little information about the transposable element content in the Zaprionus genus had been accumulated, some of their elements appear to be more closely related with those of the melanogaster subgroup, indicating that these two groups of species were involved in horizontal transfer events during their evolution. Among these elements, the Gypsy and the Micropia retroelements were chosen for screening in seven species of the two Zaprionus subgenera, Anaprionus and Zaprionus.     

百合LbCAT和LbGPX基因的克隆与表达分析

以切花百合(Lilium brownii var. viridulum)‘卡瓦纳’cDNA为模板,克隆了过氧化氢酶(LbCAT)和谷胱甘肽过氧化物酶(LbGPX)基因。序列分析表明,这2个基因分别包含1 479 bp和519 bp的开放阅读框(ORF),编码492个和172个氨基酸。进化分析结果表明,LbCAT蛋白与岷江百合CAT蛋白的氨基酸序列相似性最高(99.19%),且亲缘关系最近;LbGPX蛋白与油棕GPX蛋白的氨基酸序列相似性最高(78.61%),亲缘关系最近。qRT PCR结果显示,LbCAT和LbGPX在百合根、鳞茎、叶和花中都有表达。LbCAT在叶中表达量最高,LbGPX在花中表达量最高。这2个基因在百合花蕾的生长发育过程中均有表达,且表达量逐渐增加;在PEG处理后2个基因的转录水平升高,但独角金内酯(SLs)处理却显著降低了这2个基因的转录水平;该结果为百合抗逆性机理研究以及抗逆育种奠定了基础。     

水椰八角铁甲和椰心叶甲对椰子和银海枣的寄主选择性

【目的】水椰八角铁甲和椰心叶甲均为棕榈科植物的重要入侵害虫,两者的外部形态、取食部位和危害特征相似。研究它们的寄主选择性有助于了解这2种害虫的扩散和成灾机制。【方法】在室内用椰子和银海枣2种寄主植物分别饲养水椰八角铁甲和椰心叶甲,研究在不同寄主植物上水椰八角铁甲和椰心叶甲的存活率、产卵率、发育历期等以及这2种害虫对不同寄主植物的选择性。【结果】水椰八角铁甲在2种寄主上的存活率差异显著,除了卵期和蛹期之外,幼虫期各虫态在银海枣上的存活率明显比在椰子上的存活率高;椰心叶甲在椰子上的存活率高于银海枣,各虫态平均存活率分别为95%和86%。取食银海枣的水椰八角铁甲达标准卵量概率为0.23,取食椰子不产卵,无法完成整个世代;取食椰子的椰心叶甲达标准卵量概率为0.86,取食银海枣不产卵,也无法完成整个世代;水椰八角铁甲取食银海枣完成世代的实验种群趋势指数为12.55,椰心叶甲取食椰子完成世代的实验种群趋势指数为66.55。【结论】水椰八角铁甲和椰心叶甲分别对银海枣和椰子这2种寄主植物具有明显的选择性。在海南椰子树的数量远远超过银海枣,该实验结果在一定程度上解释了椰心叶甲在海南岛广泛分布而水椰八角铁甲只是零星发生的原因。     

Ester production in E. coli and C. acetobutylicum

Genetic engineering has improved the product yield of a variety of compounds by overexpressing, inactivating, or introducing new genes in microbial systems. The production of flavor-enhancing ester compounds is an emerging area of heterologous gene expression for desired product yield in Escherichia coli. Isoamyl acetate, butyl acetate, ethyl acetate, and butyl butyrate are reported here to be produced by expressing Saccharomyces cerevisiae genes ATF1 or ATF2 and the strawberry gene SAAT in E. coli when the appropriate substrates are provided. Increasing the concentration of alcohol added to the reaction generally resulted in increased ester production. ATF1 expression was found to produce more isoamyl acetate and butyl acetate than ATF2 expression or SAAT expression in the strains and culture conditions examined. Additionally, SAAT expression resulted in greater isoamyl acetate and butyl acetate production than ATF2 expression. Butyl butyrate is produced by cell-free extracts of E. coli harboring SAAT but not ATF1 or ATF2.     

Characterisation of cell wall polysaccharides, arabinogalactans-proteins (AGPs) and phenolics of Cola nitida, Cola acuminata and Garcinia kola seeds

Many Cola plant species are endemic to West and Central Africa. Cola acuminata and Cola nitida are used as masticatory when fresh, while the dried nuts are used for beverages and pharmaceutical purposes in Europe and North America. Garcinia kola seeds, that serve as a substitute for the true kola nuts, are used in African traditional medicine for the treatment of various diseases, including colic, headache and liver cirrhosis. Seeds extracts of G. kola are also known for their anti-inflammatory, antimicrobial and antiviral properties. To gain information on the chemical properties of the kolas, we have isolated and analyzed cell wall polysaccharides, arabinogalactan-proteins and phenolic substances from the seeds of the three kola species. The sugar composition of cell wall material of C. acuminata, C. nitida and G. kola revealed that Gal (up to 30%), Ara, GalA and Glc as the predominant monosaccharides, representing approximately 90% by mol of the total hydrolysable sugar present in this material. In Ammonium oxalate cell wall fraction, GalA was found to be the major sugar present in all kola species. In the alkali-soluble fraction, there were significant differences in the level of Glc and Gal. The level of Glc was high in C. acuminata and C. nitida while the level of Gal and Xyl were high in C. nitida and G. cola. Isolation and quantification of arabinogalactan-proteins demonstrate that G. kola seeds contained four to eight times more of these proteoglycans than the seeds of the other two species. Finally, analysis of soluble phenolic substances shows that caffeine and catechin were largely represented in C. acumina and C. nitida seeds, with caffeine accounting for 50% of all soluble phenolics. These findings indicate that the three Kola seeds are highly enriched in pectins and proteoglycans and that C. acuminata and C. nitida can be used as a possible source of caffeine and catechin.