湿地稻-鸭复合系统的CH_4排放规律

采用小区试验。大田试验研究湿地稻—鸭复合生态系统甲烷排放规律。稻鸭复合生态系统中甲烷排放随季节变化。在早稻—晚稻耕作制度条件下,6月上旬和7月底分别有2个高峰。早稻与晚稻的排放规律也各异。早稻甲烷排放峰值出现在水稻幼穗分化期。最高值为13．693mg／(m^2．h)．晚稻峰值出现在分蘖盛期。可达23．145—105．595mg／(m^2．h)。养鸭处理与常规栽培甲烷排放差异达极显著水平。稻田养鸭的早稻生育期间甲烷排放总量为5．517g／m^2。传统栽培为9．89g/m^2。稻田养鸭的晚稻生育期间排放总量为10．113g／m^2。传统栽培为17．054g／m^2。稻田养鸭与传统栽培比较．土壤氧化还原电位增加15．3mV．还原物质总量、活性还原物质总量、活性有机还原物质总量分别降低0．365cmo1／kg、0．242cmo1／kg和0．180cmo1／kg。土壤氧化还原特性影响甲烷排放通量．土壤还原物质总量、活性还原物质及活性有机还原物质数量与甲烷排放通量的相关系数分别为0．805、0．791、0．769。湿地稻鸭复合生态系统土壤氧化还原状况改善是甲烷排放减少原因之一。     

猪粪与沼气渣对双季稻田甲烷排放的影响

随着环境温度的升高,稻田甲烷排放通量增加。早稻期间甲烷排放通量随着水稻生育期的增加而逐步加快,而晚稻甲烷排放主要集中在水稻生长的前中期,而且排放量很高。一天中甲烷排放具有很强的周期性,在6：00～8：00时,甲烷排放通量进入谷底,14：00时甲烷排放通量达到峰值。稻田甲烷排放通量与土壤5cm处的温度及土壤水溶解甲烷含量具有较高的相关性。猪粪和沼气渣的施用分别提高稻田甲烷排放量22．14％和4．40％。在早稻期间,施用猪粪和沼气渣分别提高土壤水溶解甲烷含量40．3％和11．9％,而晚稻期间仅分别提高23．9％和5．04％。     

高产水稻品种及种植方式对稻田甲烷排放的影响

采用大田试验研究了不同水稻品种（早稻：超级稻“陆两优996”和常规稻“创丰1号”;晚稻：T优259）及不同种植方式（直播和移栽）对稻田甲烷排放通量的影响.结果表明：早稻晒田前甲烷排放量占排放总量的52%～73%,排水晒田减少了甲烷排放通量;晚稻生育前期甲烷排放量占生长期间甲烷排放总量的70%.早稻直播方式的甲烷排放通量均值低于移栽种植方式,但甲烷排放总量大于移栽种植方式;晚稻直播方式的甲烷排放通量均值与排放总量都大于移栽种植方式.早、晚稻直播方式的单位稻谷甲烷排放量与移栽种植方式间均存在显著差异,早稻中超级稻和常规稻直播方式的单位稻谷甲烷排放量分别比移栽方式高4.84和3.48 g·kg^-1稻谷,常规稻的甲烷排放量高于超级稻;晚稻直播方式的单位稻谷甲烷排放量比移栽方式高6.67 g·kg^-1稻谷.相同面积、相同时间不同种植方式的稻田甲烷排放量、单位经济产量甲烷排放量表现为：早稻：常规稻直播＞常规稻移栽＞超级稻直播＞超级稻移栽;晚稻：直播＞移栽.     

长期施肥对双季稻田甲烷排放和关键功能微生物的影响

研究不同施肥措施对双季稻田甲烷(CH_4)排放特征的影响及其微生物学机理,对合理利用及评价不同施肥模式对水稻生长的影响具有重要意义。以长期施肥定位试验田为平台,采用静态箱-气相色谱法对施用化肥(MF:mineral fertilizer alone)、秸秆还田配施化肥(RF:rice residues plus mineral fertilizer)、30%有机肥配施70%化肥(LOM:30%organic matter plus 70%mineral fertilizer)、60%有机肥配施40%化肥(HOM:60%organic matter plus 40%mineral fertilizer)和无肥(CK:without fertilizer)条件下双季稻田CH_4排放及其微生物学机理进行了分析。结果表明,早稻和晚稻生长期,不同施肥处理稻田CH_4排放通量均显著高于CK,表现为HOMLOMRFMFCK。各处理间CH_4总排放量差异达显著水平,其大小顺序与排放通量趋势一致,以HOM处理为最高,比CK处理增加105.56%,其次是LOM和RF处理,分别比CK处理增加72.97%和54.17%。关键功能土壤微生物测定结果表明,早稻和晚稻各个主要生育时期,各处理稻田土壤产甲烷古菌的数量变化范围为(3.18—81.07)×10~3cfu/g,土壤甲烷氧化细菌的数量变化范围为(24.82—379.72)×10~3cfu/g。稻田土壤产甲烷古菌和甲烷氧化细菌数量大小顺序为HOMLOMRFMFCK,各施肥处理均显著高于CK;HOM、LOM、RF处理显著高于MF、CK处理。双季稻田CH_4排放与稻田土壤产甲烷古菌、甲烷氧化细菌数量变化关系密切。采用有机无机肥配施促进了双季稻田生态系统CH_4的排放和关键功能微生物的数量。     

稻-鸭复合生态系统产甲烷细菌数量

采用厌氧培养箱技术 ,用最大或然数计数法 (MPN法 )和滚管法同时测定稻 -鸭复合系统和常规稻作系统早稻不同生育期土壤中的产甲烷细菌数量。结果表明 :(1)两系统产甲烷菌数量具有明显的季节变化规律。水稻返青期前 ,两系统的产甲烷菌数量相差不大 ,随着水稻生育期的推进 ,两处理的产甲烷菌数量逐渐增加 ,均在分蘖盛期明显增高 ,孕穗期达到最高 ,乳熟期又显著减少 ,生长后期又有所回升。(2 )稻田围栏养鸭能减少稻田中的产甲烷菌数量 ,特别是减少了稻田甲烷排放高峰期的产甲烷菌数量。在水稻分蘖盛期和孕穗期 ,MPN计数法中 ,稻 -鸭复合生态系统低于常规稻作系统 2 0 .0 %～ 96 .9% ;滚管法计数中 ,前者比后者降低 33.3%～ 98.1% ,两系统的产甲烷菌数量之间的差异均达极显著水平。 (3)产甲烷细菌对甲醇、异丙醇、CO2 / H2 、乙酸钠有嗜好表现 ,对甲胺、甲酸、甲胺 甲醇 甲酸 异丙醇 乙酸钠 (混合基质 1)、甲酸 甲醇 异丙醇 乙酸钠 (混合基质2 )、甲醇 异丙醇 乙酸钠 (混合基质 3)有不适应的表现     

长期不同施肥制度下湖南红壤晚稻田CH4的排放

选取湖南双季稻田长期不同施肥制度为研究对象,采用静态箱-气相色谱法对晚稻稻田甲烷排放进行观测.研究结果表明,不同施肥制度下的晚稻稻田甲烷排放的季节变化具有一定的规律,晚稻生育期内CH4的排放速率呈先升高后降低的变化趋势.施入秸秆的处理CH4平均排放通量和累积排放通量大于单施化肥的处理;单施化肥的各处理中由于养分缺失情况的不同,CH4平均排放通量和累积排放量具有一定的差异.秸秆区CH4平均排放通量和累积排放量都较大,全量化肥养分施肥区次之,偏施养分和无肥区较小.同时还研究了长期不同施肥制度条件下各环境因素包括土壤温度、灌溉水层深度和土壤Eh,对CH4排放的影响.结果表明,不同的施肥处理,晚稻田CH4排放的季节变化和土壤Eh呈显著负相关,与土壤温度呈显著正相关,与水层深度相关不明显.     

互花米草入侵对滩涂湿地甲烷排放的影响

在浙江省台州市附近滩涂湿地设置3个不同互花米草入侵密度梯度,即仅有本土植物样地、互花米草与本土植物混生样地和互花米草单优群落样地,研究互花米草入侵对滩涂湿地CH₄排放的影响.结果表明: 3个样地CH₄排放通量为0.68～5.88 mg·m^-2·h^-1,CH₄排放通量随着互花米草入侵梯度的增加而显著升高,互花米草单优群落样地CH₄排放通量分别为本土植物样地和混生样地的8.7和2.3倍.互花米草入侵显著提高了产甲烷菌数量、产甲烷潜力、甲烷氧化菌数量、甲烷氧化潜力、植物生物量、土壤有机碳含量和土壤pH,降低了土壤全氮含量.CH₄排放通量与土壤全氮呈显著负相关,与产甲烷菌数量、产甲烷潜力、甲烷氧化菌数量、甲烷氧化潜力、植物生物量和土壤pH呈显著正相关.互花米草的入侵提高了滩涂湿地植物群落生物量和土壤pH,促进了产甲烷菌数量和产甲烷潜力,从而提高了滩涂湿地的CH₄排放.     

基于模型和GIS技术的中国稻田甲烷排放估计

将一个比较成熟的稻田甲烷排放模型CH4MOD和GIS空间化数据库结合,模拟估计了中国大陆2000年水稻生长季稻田甲烷的排放。模型的空间输入参数包括:逐日气温、耕层土壤砂粒含量、外源有机质施用量、稻田水分管理模式、水稻移栽期与收获期、水稻种植面积与单产,空间分辨率为10km×10km。模拟结果表明:2000年稻田甲烷排放量为6.02Tg,其中:早稻生长季排放1.63Tg、晚稻1.46Tg、单季稻2.93Tg。提高区域稻田甲烷排放估计精度的进一步目标应放在减小输入参数误差和提高空间数据精度上,在现有数据库基础和模型———GIS技术下探讨我国稻田甲烷排放估计的不确定性范围是必要的。     

免耕稻-鸭生态种养技术的环境经济学分析

采用田间试验及环境经济学方法研究免耕稻-鸭生态种养技术的生态、经济效益。试验结果表明:农户采用免耕稻-鸭生态种养技术对稻田杂草的控制效果显著;在晚稻分蘖盛期和孕穗期,采用免耕稻-鸭生态种养技术对稻二化螟防效达100%,稻纵卷叶螟发生率分别比免耕抛秧不养鸭的稻田低48.05%、93.55%,免耕抛秧养鸭稻田中水稻纹枯病的病株率比免耕抛秧不养鸭的稻田分别低48.15%、38.21%;在稻田甲烷排放高峰期(晚稻分蘖始期-分蘖盛期),免耕抛秧养鸭对甲烷排放的控制效果明显,分别比翻耕抛秧不养鸭稻田、免耕抛秧不养鸭稻田的甲烷排放量减少4.723g/m2、2.333g/m2,晚稻整个生育期间,免耕抛秧养鸭稻田甲烷排放量比免耕抛秧不养鸭稻田减少3.37g/m2,比翻耕抛秧不养鸭稻田减少5.59g/m2;免耕可节约灌溉用水1300m3/hm2。环境经济学分析结果表明:采用免耕稻-鸭生态种养技术的农户比采用免耕抛秧不养鸭技术或采用翻耕抛秧不养鸭技术的农户分别增加财务净收益2166yuan/hm2、4207yuan/hm2;免耕抛秧养鸭获得的经济净效益为4062yuan/hm2,而免耕抛秧不养鸭、翻耕抛秧不养鸭的经济净效益分别为1592yuan/hm2、-997yuan/hm2。免耕稻-鸭生态种养技术既能充分发挥稻-鸭复合生态系统的生态和经济效益,又能较好地克服免耕给生态环境带来的不利影响,是一种很有发展潜力的可持续农业生产模式,具有良好的推广和发展前景。     

炉渣与生物炭施加对稻田土壤产甲烷菌群落结构的影响

为了了解废弃物施加处理影响稻田甲烷排放通量的微生物学机制,对稻田分别进行炉渣、生物炭单一施加和混合施加处理,分析施加处理条件下早、晚稻拔节期稻田土壤的理化性质,并采用PCR-RFLP技术及克隆测序对稻田土壤中的产甲烷菌群落组成多样性及其结构进行分析。研究结果表明:早稻拔节期,混施处理显著提高土壤盐度和pH;晚稻拔节期,混施处理显著提高土壤盐度,炉渣和混施处理显著提高pH。香农-威纳指数(H')和辛普森指数(D)显示:炉渣、生物炭和混施处理提高了稻田土壤产甲烷菌的多样性。群落组成分析结果表明:稻田土壤产甲烷菌主要含有甲烷微菌目(Methanomicrobiales)、甲烷杆菌目(Methanobacteriales)、甲烷八叠球菌目(Methanosarcinales)、甲烷球菌目(Methanococcales)、甲烷胞菌目(Methanocellales)和Methanomassiliicoccales等6大类群,其中甲烷微菌目(Methanomicrobiales)为优势类群。从属水平的群落结构来看,与对照相比,3种施加处理均降低了早稻土壤Methanomassiliicoccus相对丰度;生物炭处理还降低了Methanosarcina相对丰度。初步认为Methanomassiliicoccus和Methanosarcina这2个菌属与CH_4排放量减少密切相关。     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.