5种沉水植物无性繁殖和定居能力的比较研究

 竹叶眼子菜(Potamogeton malaianus)、微齿眼子菜(Potamogeton maackianus)、苦草(Vallisneria spiralis)、穗花狐尾藻(Myriophyllum spicatum)、黑藻(Hydrilla verticillata)是长江中下游湖泊主要的沉水植物。在栽培条件下,它们的无性繁殖速率(单位时间内新增个体数)大小顺序为黑藻>微齿眼子菜>竹叶眼子菜>苦草>穗花狐尾藻。同时采用抛掷实验的方法观察研究了这5种沉水植物及其无性繁殖体的存活和生根情况;完整植株存活率为黑藻>穗花狐尾藻>微齿眼子菜>竹叶眼子菜>苦草,无性繁殖体部分存活率为黑藻>苦草>穗花狐尾藻>微齿眼子菜>竹叶眼子菜。生根能力和其存活时间长短相关,而且生根能力与存活率大小基本一致。在实验中,只有穗花狐尾藻的断枝存活率和生根能力存在差异,故无性繁殖体生根能力为黑藻>苦草>微齿眼子菜>竹叶眼子菜>穗花狐尾藻。     

五种沉水植物对富营养化水体的净化效果

为达到净化水质的目的,采用移栽沉水植物控制富营养化水体中营养盐含量和浮游藻类生物量。本研究在夏季藻类密度较高的富营养化水体中移栽5种长江中下游流域常见沉水植物,比较不同沉水植物去除营养盐和控制藻类总量的能力。研究结果:5种沉水植物对水体总氮含量去除率的大小顺序为:竹叶眼子菜>黑藻>苦草>微齿眼子菜>菹草,对总磷去除率大小顺序为:竹叶眼子菜>黑藻>微齿眼子菜>苦草>菹草;竹叶眼子菜控制水体中藻类总量的效果最佳,苦草、微齿眼子菜及菹草次之,黑藻对水体总磷和浮游植物的去除效果均极显著(p≤0.01),而对总氮含量的作用影响不明显(p=0.209)。综合营养盐吸收作用和藻类控制效果来看,竹叶眼子菜在整个实验过程中生长状态良好并达到较为稳定的净化作用,是夏季治理浅型富营养化静水水体的理想物种之一。     

温度对五种沉水植物生长和营养去除效果的影响

研究温度对黑藻(Hydrilla verticillata)、伊乐藻(Elodea canadensis)、狐尾藻(Myriophyllum spicatum)、苦草(Vallisneria spiralis)和竹叶眼子菜(Potamogeton malaianus)在霍格兰氏水培条件下的生长和营养去除效果的影响。结果表明 : 温度对五种沉水植物的生长有显著影响。除苦草的最适生长温度为 30 ℃外, 其余四种植物的最适生长温度为 20 ℃。五种植物的生长速度有显著性差异, 以伊乐藻、竹叶眼子菜、黑藻生长较快。对 TP 和 CODCr 的去除率随温度的升高而升高, 对 NH4-N的去除率除竹叶眼子菜外, 呈单峰曲线, 去除率最适温度为 25 ℃。五种沉水植物对 TP 的去除率通常差异不显著; 竹叶眼子菜对 NH4-N 去除率显著低于其他植物(p<0.05), 而对 CODCr 的去除率显著高于其他植物(p<0.05)。     

硅和稻瘟病菌接种对水稻植株有机酸含量的影响

以抗病性不同的一对水稻近等基因系——感病CO39和抗病C101LAC(Pi-1)为实验材料,在水培条件下研究了施硅和稻瘟病接菌对水稻根系和叶片抗性物质有机酸含量的影响,揭示硅提高水稻对稻瘟病抗性的机理。结果表明:接菌条件下硅处理显著降低了2个基因型材料的叶片反丁烯二酸、柠檬酸的含量,而增加了叶片中草酸、顺丁烯二酸的含量;加硅显著降低接菌后第3天的CO39叶片酒石酸含量,但增加了C101LAC(Pi-1)接菌后第7天的叶片酒石酸含量;硅处理还显著增加了根系中苹果酸和草酸的含量;各种有机酸在水稻植株体内的分布也不尽相同,如柠檬酸主要分布在叶片中,苹果酸主要分布在根系中,顺丁烯二酸、反丁烯二酸、酒石酸和草酸在叶片和根系中都有分布。研究表明,硅可能通过影响植株体内的有机酸代谢而增强稻瘟病的抗性。     

淹水条件对土壤砷形态转化的影响

通过淹水条件下的培养试验, 探讨了外源二甲基砷酸（DMA）、一甲基砷酸（MMA）、砷酸盐［As(V)］在土壤中的动态转化规律. 结果表明: 随着培养时间的推移, 加入土壤中的DMA和MMA均主要转化为As(V), 且土壤中As(V)含量均呈增加趋势, 培养到150 d时土壤中As(V)含量均显著高于1 d时的含量(P<0.01). 外源DMA通过脱甲基化作用, 在30 d内即基本转化为As(V), 且有少量的亚砷酸盐［As(Ⅲ)］生成; 而外源MMA的转化速度相对较慢, 培养60 d后才基本完成向As(V)的转化, 同时伴随少量DMA和As(Ⅲ)的生成; 在淹水条件下外源As(V)含量随培养时间的增加而逐渐降低,该过程中除有少量As(Ⅲ)生成外,其形态基本未发生改变.     

外源二甲基砷对油菜生长及土壤中砷生物有效性的影响

通过盆栽试验研究了土壤中添加外源二甲基砷(DMA)对油菜(Brassica campestris)生长及土壤中砷生物有效性的影响.结果表明:随着外源DMA添加量的增加,油菜的出苗率和生物量均在一定程度上表现出了低浓度促进而高浓度抑制的现象.当外源DMA添加量达到90 mg·kg-1时,第2季盆栽油菜的出苗率和生物量与对照相比分别下降了9.5%和57.0%,表明DMA对油菜生长的影响具有长期性;随着外源DMA浓度的增加,土壤中有效态砷及油菜体内的砷含量均表现出增加的趋势,相关性分析表明,该三者间具有极显著相关关系;添加入土壤中的DMA主要发生去甲基化作用,产物主要为As(V)及少量的As(Ⅲ),且随着外源DMA添加量的增加,As(V)和As(Ⅲ)的浓度均表现出增加的趋势.     

外源有机酸对玉米磷吸收及其生长发育的影响

以玉米品种郑单958为材料,通过施加外源有机酸的盆栽试验方法,设置了土壤中不施磷肥和有机酸(CKo)、仅施磷肥(CKP)、施柠檬酸(Tca)、施苹果酸(Tma)和施草酸(Toa)处理,研究外源有机酸对玉米生长过程中的磷素吸收及其生长发育的影响.结果显示:(1)3种外源有机酸均可显著提高土壤中速效磷含量和磷素利用效率,Tca、Tma和Toa处理玉米根际土壤的速效磷含量分别为CKo的2.25、1.96和2.04倍,且各处理间的磷素利用效率依次为:CKp>Tca>Tma>Toa>CKo.(2)在拔节期、抽雄期和成熟期,Tca处理玉米的磷素利用效率依次为CKo的1.16、1.05和1.04倍.(3)3种外源有机酸均可显著提高玉米根系体积和根系活力、单株玉米的氮磷钾的累积量、玉米的生物量及相对籽粒产量.研究表明,外源柠檬酸、苹果酸和草酸均可显著提高玉米根际土壤中固态磷的溶解,促进植株体内营养元素的累积,保证植物生长发育的需要,从而提高玉米的生物量和产量;并以外源柠檬酸处理对玉米磷吸收及其生长发育效果最好.     

不同梨品种果实有机酸含量变化与相关酶活性的研究

以梨品种‘鸭梨’、‘茌梨’和‘八里香’为试材,对不同品种果实有机酸积累及相关酶活性随发育的动态变化特征进行分析比较,探讨果实有机酸含量与相关酶活性的关系。结果表明:(1)梨果实发育过程中有机酸含量呈逐渐下降趋势,果实成熟时的总有机酸含量以‘茌梨’最高,‘鸭梨’次之,‘八里香’最低,且3品种间总酸含量差异显著。(2)果实发育后期,‘鸭梨’、‘茌梨’和‘八里香’的柠檬酸含量几乎相同,而苹果酸的含量差异显著,说明苹果酸是引起品种间总酸含量差异的主要因素。(3)在苹果酸代谢中,不同品种间NADP-ME酶活性在果实发育后期差异显著,而NAD-MDH和PEPC酶活性无显著差异,表明NADP-ME酶是引起‘鸭梨’、‘茌梨’和‘八里香’成熟果实苹果酸含量差异的主要原因。(4)不同品种的柠檬酸代谢酶CS、Cyt-ACO、Mit-ACO和NAD-IDH的活性变化趋势一致,且成熟时无显著差异,表明它们不是引起梨果实酸含量差异的主要原因。(5)梨果实发育过程中有机酸含量与相关代谢酶活性的相关性分析表明,苹果酸和柠檬酸代谢酶共同影响梨果实的酸含量水平。     

有机酸对土壤无机态磷转化和速效磷的影响

土壤有效磷含量低是影响作物生产的重要限制因素之一.作物根分泌活化难溶性磷的有机酸对改善其磷素营养具有重要意义.采用张守敬和Jackson无机磷分级方法,以湖北省3种pH值土壤为材料,加入不同磷源和有机酸,经过室温培养后,测定速效磷含量和无机磷组分的变化.结果表明:施磷显著提高了土壤中速效磷含量,中性土、酸性土Fe-P和Al-P含量大幅上升, Fe-P占增加量的50%以上,而碱性土Ca-P含量显著增加.加施有机酸使中性土速效磷含量增多,除苹果酸处理的变幅较小外,草酸和柠檬酸的加入速效磷显著增加.由于有机酸的作用,中性土Al-P含量下降,Ca-P含量上升,变幅大小依次为草酸＞柠檬酸＞苹果酸;酸性土中Al-P含量呈下降趋势,碱性土中Ca-P含量有不同程度的减少,3种土壤中O-P含量均有所增加.说明有机酸活化的磷主要来源于中性土和酸性土Al-P、Fe-P及碱性土Ca-P中的磷,同时有机酸能够促进土壤中闭蓄态磷(O-P)的形成与积累.     

4种植物幼苗根茎叶及根系分泌物中低分子量有机酸的特征

该研究建立了植物根茎叶及根系分泌物中有机酸的离子色谱分析测定方法,并测定了4种不同植物幼苗根茎叶及根系分泌物中低分子量有机酸的组成,为揭示逆境胁迫下植物体内有机酸的作用提供依据。结果表明:离子色谱分析法对植物有机酸的加标回收率为91.10%~105.42%,检测限为0.12~0.36mg/L,方法线性关系良好(R2=0.965 3~0.998 8);4种植物根茎叶及根系分泌物中都可以检测出草酸、柠檬酸、苹果酸、丁二酸和酒石酸,其中草酸、柠檬酸和苹果酸为优势酸;有机酸的组成和含量具有物种以及器官的差异性;根系分泌物中的有机酸与根茎叶中有机酸的相关性也因种属差异而不同。这为研究逆境胁迫下植物器官及根系分泌物提供了可靠方法。     

Leishmania (Viannia) panamensis: An in vitro assay using the expression of GFP for screening of antileishmanial drug

Promastigotes of Leishmania (Viannia) panamensis were successfully transfected with p6.5-egfp to express green fluorescent protein. The transfectants remained infective to macrophages, providing an in vitro model for screening antileishmanial drugs. This was demonstrated by flow cytometry of macrophage-associated GFP after exposure of infected cultures to known antileishmanial drugs, i.e. amphotericin B and glucantime^®. Fluorescence of GFP diminished progressively from infected cells with increasing drug concentrations used in both cases. The availability of this fluorescent assay for infection of macrophages by L. (V.) panamensis facilitates drug discovery program for the Viannia species, which differ significantly from those of the Leishmania subgenus.     

Mycobiota associated with the ambrosia beetle Scolytodes unipunctatus (Coleoptera: Curculionidae, Scolytinae)

Ambrosia beetles (Coleoptera: Scolytinae) are associated with strictly entomochoric and mutualistic fungi. We studied the mycobiota associated with Scolytodes unipunctatus, ambrosia beetles that infest Cecropia trees in Central America. Isolates were characterized using morphology and rDNA sequences (ITS region, LSU, and SSU rDNA). Four species are described here: Raffaelea scolytodis sp. nov. (Ophiostomatales), Gondwanamyces scolytodis sp. nov., Custingophora cecropiae sp. nov., and Graphium sp. (Microascales). The genus Custingophora is emended to include Knoxdaviesia anamorphs of Gondwanamyces based on uniformity of DNA sequences and phenotype.     

Septal pore complex morphology in the Agaricomycotina (Basidiomycota) with emphasis on the Cantharellales and Hymenochaetales

The ultrastructure of septa and septum-associated septal pore caps are important taxonomic markers in the Agaricomycotina (Basidiomycota, Fungi). The septal pore caps covering the typical basidiomycetous dolipore septum are divided into three main phenotypically recognized morphotypes: vesicular-tubular (including the vesicular, sacculate, tubular, ampulliform, and globular morphotypes), imperforate, and perforate. Until recently, the septal pore cap-type reflected the higher-order relationships within the Agaricomycotina. However, the new classification of Fungi resulted in many changes including revision of existing and addition of new orders. Therefore, the septal pore cap ultrastructure of more than 325 species as reported in literature was related to this new classification. In addition, the septal pore cap ultrastructures of Rickenella fibula and Cantharellus formosus were examined by transmission electron microscopy. Both fungi have dolipore septa associated with perforate septal pore caps. These results combined with data from the literature show that the septal pore cap-type within orders of the Agaricomycotina is generally monomorphic, except for the Cantharellales and Hymenochaetales.It appears from the fungal phylogeny combined with the septal pore cap ultrastructure that the vesicular-tubular and the imperforate type both may have arisen from endoplasmic reticulum. Thereafter, the imperforate type eventually gave rise to the perforate septal pore cap-type.     

Systematics and evolution of the genus Torrubiella (Hypocreales, Ascomycota)

Torrubiella is a genus of arthropod-pathogenic fungi that primarily attacks spiders and scale insects. Based on the morphology of the perithecia, asci, and ascospores, it is classified in Clavicipitaceae s. lat. (Hypocreales), and is considered a close relative of Cordyceps s. 1., which was recently reclassified into three families (Clavicipitaceae s. str., Cordycipitaceae, Ophiocordycipitaceae) and four genera (Cordyceps s. str, Elaphocordyceps, Metacordyceps, and Ophiocordyceps). Torrubiella is distinguished morphologically from Cordyceps s. lat. mainly by the production of superficial perithecia and the absence of a well-developed stipitate stroma. To test and refine evolutionary hypotheses regarding the placement of Torrubiella and its relationship to Cordyceps s. lat., a multi-gene phylogeny was constructed by conducting ML and Bayesian analyses. The monophyly of Torrubiella was rejected by these analyses with species of the genus present in Clavicipitaceae, Cordycipitaceae, and Ophiocordycipitaceae, and often intermixed among species of Cordyceps s. lat. The morphological characters traditionally used to define the genus are, therefore, not phylogenetically informative, with the stipitate stromata being gained and/or lost several times among clavicipitaceous fungi. Two new genera (Conoideocrella, Orbiocrella) are proposed to accommodate two separate lineages of torrubielloid fungi in the Clavicipitaceae s. str. In addition, one species is reclassified in Cordyceps s. str. and three are reclassified in Ophiocordyceps. The phylogenetic importance of anamorphic genera, host affiliation, and stipitate stromata is discussed.