干旱胁迫对不同根型苜蓿根系生长及根际土壤细菌的影响

为明确干旱胁迫对根茎型清水紫花苜蓿、直根型陇东紫花苜蓿、根蘖型公农4号杂花苜蓿根系生长及根际土壤细菌群落的影响,采用盆栽试验,运用16S rRNA基因测序技术,研究了幼苗期干旱胁迫下各根型苜蓿根系生长及根际土壤细菌群落结构的变化。结果表明：干旱胁迫下各根型苜蓿的Chao1和ACE丰富度指数均在中度胁迫下最大,Simpson和Shannon-wiener多样性指数各处理间差异不显著;根际土壤细菌群落均以变形菌门、绿弯菌门、类杆菌门、放线菌门和厚壁菌门为主,干旱胁迫均显著增加了变形菌门和厚壁菌门的相对丰度,显著降低了绿弯菌门的相对丰度,但类杆菌门和放线菌门先提高后下降。统计学分析显示,幼苗期干旱胁迫显著影响各根型苜蓿生长发育,随胁迫程度增加,其株高、地上生物量、地下生物量、根系活力、根体积、根系总长均显著降低,根冠比先增加后下降且在中度胁迫时达到最大值。重度胁迫下,清水苜蓿的株高、根系活力显著大于其他品种,而根冠比、根系干重显著小于其他品种;陇东苜蓿的根长、根尖数均显著大于其他品种;根系平均直径、根系总表面积各根型苜蓿间差异不显著。研究结果为植物的抗干旱胁迫以及提高各根型苜蓿在干旱胁迫下的水分利用提供参考。     

嫁接对铜胁迫下黄瓜根际土壤微生物特性和酶活性的影响

采用盆栽试验方法,研究了嫁接（以黑籽南瓜为砧木）对铜胁迫下黄瓜根际土壤微生物生物量、微生物种群数量和土壤酶活性的影响.结果表明： 铜胁迫下黄瓜根际土壤微生物生物量碳（MBC）和微生物生物量氮（MBN）含量显著下降,基础呼吸和代谢熵显著上升,但嫁接黄瓜根际土壤MBC和MBN含量显著高于自根黄瓜,而基础呼吸和代谢熵则显著低于自根黄瓜.铜胁迫下,根际土壤放线菌和自生固氮菌的数量显著下降,真菌数量显著上升,而细菌数量变化不显著;嫁接黄瓜根系土壤细菌、放线菌、自生固氮菌的数量显著高于自根黄瓜,而真菌数量显著低于自根黄瓜.嫁接黄瓜根际土壤脲酶、磷酸酶、蔗糖酶、过氧化氢酶活性在铜胁迫下显著高于自根黄瓜.试验结果证明嫁接使铜胁迫下黄瓜根际土壤微生物环境和酶活性得到了改善和提高,从而提高了黄瓜植株对铜胁迫的抵抗力.     

CO2倍增及UV-B增强对大豆植株生长和根际微生物的影响

以大豆'齐黄27'为研究材料,采用人工气候室模拟大气CO2浓度倍增(350～700 μmol*mol-1)及紫外线B(UV-B,280～320 nm)辐射增强(4～15 μW*cm-2)的环境条件,研究了CO2浓度增加及UV-B辐射增强对大豆生育前期的生长及根瘤、根际微生物数量的影响.结果表明:(1)增强UV-B能显著减少大豆植株地上部生物量,而对株高的抑制作用不显著;CO2浓度倍增促使大豆株高和地上生物量显著增加,对根系生物量的促进作用不显著,但能够减轻UV-B辐射增强对地上及根系生物量的抑制作用;CO2浓度增加、UV-B辐射增强及其复合胁迫均导致大豆植株根冠比下降,且复合胁迫对根冠比的抑制作用更明显.(2)CO2浓度倍增降低了大豆叶片叶绿素、类胡萝卜素及花青素含量,提高了净光合速率;UV-B辐射增强导致叶绿素含量减少,光合速率下降,却增加了类胡萝卜素及花青素含量;CO2浓度增加、UV-B辐射增强复合处理对叶片色素含量及光合速率的影响具有复合效应.(3)CO2浓度倍增能够促进根瘤数量及根际真菌数量的增加,而UV-B增强处理则显著降低细菌和放线菌的数量;CO2浓度倍增能够缓解UV-B增强处理对放线菌的抑制作用,却导致根际细菌数量进一步减少.研究发现,CO2浓度增加及UV-B辐射增强对大豆生育前期植株生长、叶片色素含量及根际微生物数量存在抑制或促进效应,而且在某些性状上存在复合效应,它们可能主要是通过调节大豆植株的干物质分配及根系的代谢间接影响根瘤数量及根际微生物数量.     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

Na2CO3胁迫下甜菜幼苗根际土壤环境因子的变化及其相关性

以两个甜菜品种‘KWS0143’(耐盐碱性强)和‘Beta464’(耐盐碱性较弱)为对象,设置4个Na₂CO₃浓度处理[占土壤质量的0%(CK)、0.4%、0.8%和1.2%],采用盆栽方法研究甜菜幼苗时期植株干质量、根际土壤酶活性和微生物数量的变化.结果表明: 与对照相比,0.4%处理的植株干质量明显增加,而0.8%和1.2%处理显著受到抑制,且处理间差异显著. 不同处理下甜菜幼苗根际土壤脲酶、过氧化氢酶和碱性磷酸酶活性表现出相似的变化规律,0.4%处理酶活性较对照有所增加但不显著;0.8%和1.2%处理则显著降低了酶活性,同时‘KWS0143’的土壤酶活性均高于‘Beta464’.与对照相比,0.4%处理土壤微生物群落没有显著变化;0.8%和1.2%处理的根际土壤细菌、真菌和放线菌数量显著减少,且‘KWS0143’的根际微生物数量高于‘Beta464’.两品种植株干质量、土壤酶和土壤微生物之间呈显著正相关;通径分析表明,‘KWS0143’植株干质量决定系数表现为:放线菌>细菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶,‘Beta464’表现为:放线菌>过氧化氢酶>脲酶>真菌>碱性磷酸酶>细菌.     

嫁接辣椒根系特征及根际土壤酶活性与青枯病抗性的关系

以‘卫士’辣椒为砧木,‘新丰2号’为接穂嫁接,通过人工接种青枯病菌研究嫁接和自根辣椒根系特征、根际土壤微生物及酶活性的变化,探讨嫁接辣椒的抗病机理.结果显示:接种青枯病菌前,嫁接辣椒的根系重量、总长度、总体积、表面积、根尖数和分叉数均显著高于自根苗,根系活力、根际土壤放线菌数量和比例,以及根际土壤酶(多酚氧化酶、过氧化物酶和脱氢酶)活性也明显高于自根苗.接种青枯病菌后,嫁接辣椒的根系受伤程度较自根苗轻,根系重量、总长度、总体积、表面积、根尖数和分叉数的降低幅度均显著小于自根苗,根系活力、根际土壤微生物数量、放线菌比例及土壤酶活性明显大于自根苗.研究表明,嫁接辣椒根系发达,根系活力增强,根际土壤放线菌比例增加及酶活性提高是其青枯病抗性增强的重要原因.     

PEG胁迫及复水对不同抗旱性小麦幼苗脯氨酸代谢关键酶活性的影响

以两种不同抗旱性小麦品种幼苗为试验材料,采用PEG模拟干旱胁迫处理,探究干旱胁迫及复水对小麦幼苗叶片与根系脯氨酸累积及关键酶活性的影响。结果显示:(1)PEG胁迫下抗旱品种‘普冰143’根长和根干重下降不大,而水敏感品种‘郑引1号’根长和根干重下降显著;且于胁迫处理36h时‘普冰143’根系脯氨酸含量增加(75.0%)显著大于‘郑引1号’(37.7%),复水24h后均恢复至对照水平。(2)PEG胁迫下‘普冰143’叶片中谷氨酸合成途径关键酶P5CS和鸟氨酸合成途径关键酶δ-OAT活性均显著增加,且‘普冰143’叶片脯氨酸两条合成途径关键酶活性均得以加强;PEG胁迫处理36h时,‘郑引1号’叶片中P5CS活性增加显著,δ-OAT活性变化较小,且‘郑引1号’叶片脯氨酸合成可能以谷氨酸途径为主;但在PEG胁迫下两个不同抗旱性品种的根中P5CS、δ-OAT活性均变化较小。(3)PEG胁迫处理36h时‘普冰143’叶片脯氨酸降解酶PDH活性显著下降,而‘郑引1号’叶片PDH活性显著增加,复水后抗旱品种叶片该酶活性显著增加,水敏感品种恢复至对照水平;但PEG胁迫处理下两个不同抗旱性品种的根中PDH活性均显著下降。研究表明,PEG胁迫下小麦叶片是合成脯氨酸的主要部位,抗旱品种‘普冰143’根系脯氨酸持续积累与叶片中高的脯氨酸合成关键酶活性及脯氨酸转运有关。     

蕹菜镉积累典型品种根际微生物群落特征研究

通过根箱试验研究蕹菜(Ipomoea aquatica Forsk)镉低量积累(QLQ)和高量积累(T308)典型品种根际微生物群落特征。结果表明两个品种根际微生物数量、微生物生物量碳均显著高于非根际(p<0.05)。污染土壤和无污染土壤上T308根际可培养微生物总数、细菌和放线菌数量均显著高于QLQ(p<0.05); 而污染土壤上T308 根际真菌数量显著低于QLQ(p<0.05)。无污染土壤上QLQ 根际微生物生物量碳显著高于T308(p<0.05)。两种土壤上平均颜色变化率(AWCD)均为QLQ 高于T308。污染土壤上QLQ 根际微生物对BIOLOG Eco 板各类碳源的利用程度均高于T308, 两个品种根际微生物对不同碳源的利用模式亦不同。表明两个蕹菜典型品种根际微生物群落结构和功能存在显著差异, 代谢活性较高可能是QLQ 区别于T308 的重要根际微生物群落特征。     

根际低氧逆境对网纹甜瓜幼苗生长及根系呼吸代谢途径的影响

以耐低氧性具有明显差异的两个网纹甜瓜(Cucumis melo var. raticulalus)品种为试材,研究了根际低氧胁迫下幼苗生长、根系活力及根系呼吸关键酶活性的变化。结果表明,根际低氧胁迫下,两品种幼苗生长均受到明显抑制,而根系活力升高;根系PDC活性两品种均显著提高,品种间无显著差异; MDH活性两品种均显著降低,且耐低氧性弱的‘西域一号’下降幅度较大;根系ADH和LDH活性两品种均显著提高,耐低氧性强的‘东方星光’ADH活性增加的幅度显著高于耐低氧性弱的‘西域一号’,而‘西域一号’LDH活性增加幅度显著高于‘东方星光’。说明‘东方星光’在低氧胁迫下能保持较高的有氧呼吸水平,无氧呼吸的主要途径为乙醇发酵,而‘西域一号’在低氧胁迫下无氧呼吸的主要途径为乳酸发酵。     

施磷对干旱胁迫下箭竹根际土壤养分及微生物群落的影响

以箭竹及其根际土壤作为研究对象,采用两因素随机区组实验,设置2种水分处理（正常浇水和干旱胁迫）和2种施磷量处理（施磷和不施磷）,探究施磷对干旱胁迫下箭竹根际土壤养分及微生物群落结构和多样性的影响。结果表明：（1）干旱胁迫显著降低了箭竹根际土壤中微生物量碳、可溶性有机氮和有效磷的含量,虽对箭竹根际土壤微生物群落的多样性无显著影响,但显著降低了箭竹根际土壤中总PLFA（phospholipid fatty acid contents）的含量和真菌、细菌、革兰氏阳性菌与革兰氏阴性菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌的PLFA比值,显著改变了箭竹根际土壤微生物群落结构,结果显著降低了箭竹的生物量。（2）施磷显著增加了受旱箭竹根际土壤中微生物量碳和有效磷的含量,虽大体上对受旱箭竹根际土壤微生物群落的多样性无显著影响,但显著增加了受旱箭竹根际土壤中总PLFA和真菌PLFA的含量,并在一定程度上增加了细菌、革兰氏阳性菌、革兰氏阴性菌和放线菌的PLFA含量以及革兰氏阳性菌/革兰氏阴性菌和真菌/细菌的PLFA比值,也在一定程度上改善了受旱箭竹根际土壤微生物群落结构,从而改善受旱箭竹的生长。（3）主成分分析表明,干旱对箭竹根际土壤微生物群落结构的影响显著,而施磷的影响不明显。（4）相关分析发现,箭竹根际土壤微生物群落结构与箭竹根际土壤微生物量碳、可溶性有机氮及箭竹生物量呈显著正相关。综上,干旱降低了箭竹根际土壤养分含量和微生物生物量,改变了箭竹根际土壤微生物群落结构,抑制了箭竹的生长;施磷能增加受旱箭竹根际土壤养分含量和微生物生物量,改善受旱箭竹根际土壤微生物群落结构,进而改善受旱箭竹的生长。     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Biological control of three floating water weeds,<Emphasis Type="Italic">Eichhornia crassipes,Pistia stratiotes</Emphasis>, and <Emphasis Type="Italic">Salviniamolesta</Emphasis> in the Republic of Congo

Since 1999, four specific weevils (Coleoptera, Curculionidae) were released in the Republic of Congo against three exotic floating water weeds: Neochetina eichhorniae Warner and N. bruchi Hustache against water hyacinth, Neohydronomus affinis Hustache against water lettuce, and Cyrtobagous salviniae Calder and Sands against water fern. Recoveries of exotic weevils were made from all 24 release sites except one, and all four species have established and spread (up to 800 km for water hyacinth weevils). Within a few years of releases, control of water fern and water lettuce was such that fishing and navigation could be resumed, while reductions of water hyacinth populations were only beginning.     

A molecular phylogeny of Hebeloma species from Europe

In order to widen the scope of existing phylogenies of the ectomycorrhizal agaric genus Hebeloma a total of 53 new rDNA ITS sequences from that genus was generated, augmented by sequences retrieved from GenBank, and analysed using Bayesian, strict consensus and neighbour joining methods. The lignicolous Hebelomina neerlandica, Gymnopilus penetrans, and two species of Galerina served as outgroup taxa. Anamika indica, as well as representatives of the genera Hymenogaster and Naucoria, were included to test the monophyly of Hebeloma, which is confirmed by the results. Hebeloma, Naucoria, Hymenogaster and Anamika indica cluster in a strongly supported monophyletic hebelomatoid clade. All trees largely reflect the current infrageneric classification within Hebeloma, and divide the genus into mostly well-supported monophyletic groups surrounding H. crustuliniforme, H. velutipes, H. sacchariolens, H. sinapizans, and H. radicosum, with H. sarcophyllum being shown at an independent position; however this is not well supported. The section Indusiata divides with strong support into three groups, the position of the pleurocystidiate Hebeloma cistophilum suggests the possible existence of a third subsection within sect. Indusiata. Subsection Sacchariolentia is raised to the rank of section.     

Taxonomic status of the species of the green algal genusNeochloris

Komárek has recently reviewed the various species assigned to the green algal genusNeochloris Starr (Chlorococcales, Chlorococcaceae) and removed those with uninucleate vegetative cells to a new genus,Ettlia. Watanabe & Floyd, unaware ofKomárek's work, also reviewed the species ofNeochloris and distributed them among three genera—Neochloris, Chlorococcopsis gen. nov., andParietochloris gen. nov.—on the basis of details of the covering of the zoospore and the arrangement of the basal bodies of the flagellar apparatus. This paper reconciles these two treatments and makes additional recommendations at the ranks of genus, family, order, and class.     

Die GattungKarschia — Bindeglied zwischen bitunicaten Ascomyceten und lecanoralen Flechtenpilzen?

The genusKarschia, in the earlier sense, including saprophytes and parasites on lichens, has been thought to be a non-lichenized parallel genus of the lichen genusBuellia. Modern workers included it on the one hand inBuellia, on the other hand combined it with bitunicate ascomycetes. It is now proved thatKarschia is heterogeneous and contains but superficially similar members both of the genusBuellia of theLecanorales and of typical or masked bitunicateAscomycetes. Therefore, it can not be regarded as a link betweenLecanorales andDothideales. The type species ofKarschia belongs to theDothideales.

     

Demographic characteristics of an intertidal bay goby (Lepidogobius lepidus)

Synopsis In a fourteen month study (May 1976 – June 1977) I examined the following characteristics of an intertidal bay goby (Lepidogobius lepidus) in Morro Bay, California, U.S.A.: annual and seasonal patterns of abundance, age composition and growth rates, survivorship and mortality patterns, and the reproductive cycle for female gobies. Fishes were collected with the aid of quinaldine and otoliths and ovaries removed. Age and growth rates were estimated from otolith annuli using a back calculation formula and a Brody-Bertalanffy growth curve. Mortality rates were derived using the methods of Heincke (1913), Robson & Chapman (1960), mean age, and a catch curve (Ricker 1975). A gonad index was used to describe the annual reproductive cycle. Results indicated that abundance fluctuated seasonally and that these fluctuations appeared to be caused by reproductive emigrations. Bay gobies reached an age of 7+ and a standard length of 87 mm. Growth was relatively constant (6 mm yr⁻¹) until age 5, at which point it began to decline. The mean rates of survivorship, mortality, and instantaneous mortality were 0.75, 0.25, and 0.29 respectively. Mortality rates for individual age classes ranged from 0.13 to 0.51 and increased with age. This stock appears to reproduce mainly during the winter.     

Systematic significance of mature embryo of bamboos

The mature embryo of seven species belonging to five genera of Indian bamboos is described. In all these the basic pattern of embryo organisation is same: the scutellar and coleoptilar bundles are not separated by an internode, the epiblast is absent, the lower portion of the scutellum and the coleorhiza are separated by a cleft and the margins of embryonic leaves overlap. The features unique to fleshy fruited bamboos are: presence of a massive scutellum, the juxtaposition of plumule and radicle and the occurrence of a bud in the axil of the coleoptile. The fleshy fruit bearing bamboos should be classified into one group, the tribeMelocanneae. Evidence is provided to recognise additional groups in the subfamilyBambusoideae.