转Bt基因抗虫棉叶面可培养微生物多样性的变化

在大田栽培条件下,以转Bt基因抗虫棉GK-12和常规棉泗棉3号为材料,在棉花的苗期、现蕾期、花铃期和吐絮期分别测定棉花叶面细菌、真菌和放线菌的数量变化,并在花铃期和吐絮期对叶面细菌生理群的数量和多样性进行分析.结果表明：棉花叶面可培养微生物数量与其生长发育呈正相关,叶面可培养微生物的数量一般由苗期开始增多,到花铃期达最高峰,吐絮期明显减少;花铃期转Bt基因抗虫棉叶面细菌生理群Simpson指数、Shannon-Wiener指数和均匀度比常规棉升高,吐絮期比常规棉下降.     

典型天气下植物叶面滞尘动态变化

在天气变化频繁的春季选择了几种典型天气观测了油松、女贞、珊瑚树和三叶草叶面滞尘动态变化及其与气象因子和空气中颗粒物浓度的关系。研究表明:(1)供试物种的叶面滞尘量(g/m2)由大到小依次为油松(4.57—5.45),珊瑚树(2.23—5.85),女贞(2.14—4.27)和三叶草(0.12—0.38);(2)油松和三叶草叶面滞尘量无明显变化,而天气状况对女贞和珊瑚树叶面滞尘影响明显;(3)连续2d(17.1、14.8 mm)的降雨后,女贞和珊瑚树叶面滞尘量降低了50%以上;极大风速对女贞和珊瑚树叶面滞尘量的影响均呈现先升高后降低,在极大风速为14 m/s时达到峰值;相对湿度大于80%时,女贞和珊瑚树叶面滞尘量明显降低;空气中高浓度的颗粒物可使女贞和珊瑚树叶面滞尘在4—5 d达到饱和。     

北京城区行道树国槐叶面尘分布及重金属污染特征

叶面尘分布范围广、累积时间长,能够较好地指示近地面大气颗粒物污染特征和累积状况。为揭示城市道路交通的大气颗粒物污染特征,研究了北京城区不同类型道路两侧行道树国槐(Sophora japonica)的叶面滞尘量,分析了叶面尘主要重金属的浓度和污染特征,采用相关分析和主成分分析法探讨了颗粒物重金属的主要来源。结果表明:国槐叶面滞尘量在快速路、主干路、次干路、支路上的比值为100∶84∶75∶75,受车流量影响较大。行道树国槐的平均叶面滞尘量为0.68 g/m2,庭院树国槐(远离交通)叶面滞尘量是0.51 g/m2,两者差异显著。行道树叶面尘重金属元素Cu、Zn、Pb在叶面尘中的浓度达到土壤背景值的6倍,空间分布较均匀,主要来自交通排放,庭院树叶面尘重金属污染也受到交通排放的重要影响。     

植物叶表面的润湿性及其生态学意义

植物叶表面的润湿性是各种生境中常见的一种现象,表现了叶片对水的亲和能力。叶面的润湿性可以通过测定气、固、液界面的接触角大小确定,接触角θ＜110°的为润湿,θ＞130°的为不润湿,表现出斥水性。影响叶片润湿性的主要因素有叶面蜡质含量与形态,叶面绒毛数量、质地、形态和分布方式,气孔和表皮细胞形态和大小,叶水分状况等。叶表面的化学组成和形态是影响叶润湿性的主要内在原因,但外界环境的变化通过影响表面的结构和形态来影响叶润湿性。叶面的润湿性是植物叶片截流降水的微观基础,水分在润湿性强的叶面上铺展呈膜;在不润湿的叶面上形成水珠,容易在风和重力的作用下离开叶面;铺展的水膜,又会对叶的光合作用产生重要的影响。不同润湿性的叶面,滞留、吸附、过滤各种大气污染物数量不同;这些污染物沉降在叶片表面,与叶面发生相互作用,从而改变叶面的润湿性。植物叶含水量的高低对叶感染病菌有重要的影响,在病菌感染期间如果叶表面完全润湿则有利于病菌侵染;一旦病菌侵染,又会对叶面结构造成破坏,需要考虑润湿性能对防治病虫害的农药液滴持留的影响。对于润湿性小、斥水性大的植物,其叶表面表现出一定的自清洁功能;根据这些高疏水性、具有自清洁性的植物叶面特征,可利用或借鉴生物学信息进行仿生设计或制造新的功能材料。润湿性作为固、气、液三相作用的综合结果,是认识植物界面关系的微观基础,对于植物叶面生态功能的认识具有重要的意义。     

肠道微生物群对肺部免疫微环境稳态影响的研究进展

肠道微生物群是与宿主共生的最大的微生态系统的重要组成部分,它们通过调节宿主的内分泌、代谢、神经和免疫微环境影响人体的多种基本功能。近年来,肠道微生物群对机体局部和远端免疫器官的影响引起了科学家们的广泛关注。肠道微生物和肺之间的相互作用被称为“肠-肺轴”,对肺部免疫微环境稳态的维持至关重要。研究表明,肠道微生物群失调与哮喘、肺炎和囊性纤维化等多种肺部疾病密切相关。本文将对肠道微生物群对肺部免疫微环境稳态的影响及在多种肺部疾病中的作用进行阐述,为临床通过调整肠道微生物群来治疗肺部疾病和维持肺部免疫微环境稳态提供理论依据。     

叶面喷施硅肥对水稻农艺性状和抗性的影响

硅是地壳中重要的元素,且在水稻生长中发挥重要作用,但叶面喷施硅肥对水稻增产和抗病虫的影响研究甚少.为探讨叶面硅肥的作用,本文通过大田试验研究了叶面喷施硅肥对水稻的农艺性状、抗病和抗虫性的影响.田间试验结果表明,与对照相比,叶面喷施硅肥的水稻植株颜色更绿、茎秆更粗壮且抗倒伏,分蘖数、穗数、每穗的实粒数、千粒重及产量均提高...     

肿瘤微环境中微生物影响肿瘤发生发展的分子机制

肿瘤微环境呈现出一个错综复杂的生态系统,包括肿瘤细胞、非癌细胞、细胞外基质以及微生物群落等多种要素。微生物在肿瘤内广泛分布,其在空间分布上呈现出显著的特异性。这些微生物的组成成分与功能状态在肿瘤的发生和进展中发挥着至关重要的作用。本文深入阐明了肿瘤微环境内微生物菌群的特征,并探索其对肿瘤发生发展的影响机制,以期为肿瘤的诊断和治疗提供全新的策略和视角。     

应用参数和辅助剂对昆虫病原线虫Steinernema carpocapsae All品系于小白菜叶面存活和黏附数量的影响

测定了叶面应用参数(喷雾压力、高度、线虫悬浮液浓度、线虫悬液量、温度和湿度)以及辅助剂对昆虫病原线虫S．carpocapsaeAll于小白菜叶面的存活率和叶面黏附数量的影响。结果显示：(1)喷雾压力对线虫于叶面的黏附数量有负影响;(2)线虫悬浮液浓度高于2000IJs／mL时,随着线虫浓度的增加,叶面上黏附的线虫数量也明显提高;(3)喷洒的线虫悬液量越多(从3．3mL到19．8mL),叶面上黏附的线虫数量也就越多(从10．1IJs／cm^2到45．5IJs／cm^2),但是当线虫悬液量超出19．8mL时,叶面上黏附的线虫数量不再提高;(4)感染期线虫在叶面存活率随着暴露时间的增长而下降;(6)加入黄原胶和表面活性剂可以提高线虫在叶面的存活率和黏附数量,其中加入0．3％黄原胶的线虫悬浮液在叶面存活的线虫数量是清水对照的150倍。线虫喷洒叶面停留24小时后,2％甘油的线虫悬浮液的线虫在叶面上的存活率大约是清水对照液的62倍,叶面上存活线虫数量也是清水对照液的53倍。     

中国叶围煤污菌初探II．毛白杨叶围煤污菌的研究

对毛白杨(Populus tomentosa Carr.)叶围煤污菌(sooty moulds)群落组成及演替进行了探罚,分析了叶面营养物及其变化。 结果表明,叶面真菌的分离物密度随叶片的衰老而增加。对毛白杨叶面真菌分离鉴定,属于煤污菌有8种真菌：链格孢(Alternaria alternata),芽枝状枝孢(Cladosporium cladosporioides),球孢枝孢(Coladosporium sphaerospermum),尖孢枝孢(Cladosporium oxysporum),出芽短梗霉(Aurecobasidium pullulans),棕黑腐质霉(Humtco'a tuscoatra),伏克盾壳霉(Coniothyrixm fuckelii)和直立枝顶孢(Acremoniumstrictum)。不同生长期叶面真菌群落组成及优势种不同,叶面出现黑霉层后,以3种煤污菌为优势种即出芽短梗霉、链格孢和芽枝状枝孢。不同的菌表现一定的演替模式,定殖及达到峰值的时间不同。毛白杨叶面含有多种营养物,其含量及组分随生长期不同而异．与叶面真菌分离物密度呈显著性相关。此外,对蚜虫的发生、叶面营养物含量、煤污菌三者的关系进行了讨论。     

中国西北干旱区树木蒸腾对气象因子的响应

应用数值方法 ,对中国西北干旱区 5个主要树种 (樟子松、榆树、二白杨、胡杨和沙枣 )的叶面蒸腾及气孔导度对气象因子的响应进行了探讨 ,时间尺度为日。两套综合环境观测系统分别安置在黑河中游的临泽和下游的额济纳旗 ,每半小时自动记录微气象因子、土壤水分和树汁流量。应用日平均树汁流量、饱和差、总辐射、平均气温和土壤含水量拟合树木叶面蒸腾及气孔导度的经验公式。气孔导度和单个气象因子之间具有很高的相关性。应用多个气象因子所建立的经验公式能够很好的模拟气孔导度 ,模拟效果比气孔导度与单一因子的相关性高。气孔导度总体上和饱和差和气温呈指数关系 ,与总辐射的关系多种多样 ,与土壤含水量的关系较复杂。在中游地区 ,二白杨气孔导度、叶面蒸腾量和单株树木树汁流量最大。试验期间下游试验点土壤水分充足 ,耐旱树种胡杨及沙枣树汁流量较大 ,但其气孔导度及叶面蒸腾量均较小。本次研究没有发现树木叶面蒸腾量和单一环境因子之间具有明显的相关性。叶面蒸腾模拟效果没有气孔导度模拟效果好 ,原因是叶面蒸腾是气孔导度和饱和差的函数。     

Phyllosphere fungi on living and decomposing leaves of giant dogwood

Phyllosphere fungi on living leaves and their succession on decomposing leaves were studied on giant dogwood (Swida controversa). A total of 12 and 34 fungal species were isolated from the interior and surface, respectively, of living leaves, and 15 frequent species were considered as phyllosphere fungi. Six of these 15 species were also frequent on decomposing litter. Characteristic successional trends were observed in the 6 phyllosphere fungi during decomposition. The sum of frequencies of endophytes decreased as decomposition progressed, and no endophytes were isolated from the litter at the 11th month of decomposition. The sum of frequencies of epiphytes increased as decomposition progressed. Endophytes and epiphytes showed different responses to litter mass loss and concentrations of nitrogen, lignin, and total carbohydrates during the decomposition process. These results suggested that epiphytes may survive on decomposing leaves as primary decomposers on the ground, thereby excluding endophytes by competition for available energy sources, and that epiphytes may have a greater contribution to decomposition than endophytes in dogwood leaves.     

Colonization of Japanese beech leaves by phyllosphere fungi

To examine the colonization of living leaves from buds and twigs by phyllosphere fungi of Japanese beech, the mycobiota were investigated on buds and twigs and on leaves covered with well-ventilated bags before budbreak. Ten phyllosphere fungi were isolated from rolled-up leaves within buds, bud scales, and twigs. However, frequencies of phyllosphere fungi on expanded leaves were reduced markedly when the buds were covered with well-ventilated bags before budbreak compared to the leaves that were not covered. This observation suggests that invasion of the fungi to the leaves from buds and twigs may be possible but is not the main route. Horizontal transmission may be common in endophytes and epiphytes of beech leaves. Phyllosphere mycobiota were then compared between sun and shade leaves. Of 13 species recorded as phyllosphere fungi, the frequencies of 2 species were lower and those of 3 species were higher in sun leaves than in shade leaves. Frequencies of the other 8 phyllosphere species were not different between sun and shade leaves. This result indicates that the colonization of leaves by some phyllosphere fungi was affected by the microenvironmental conditions on leaf surfaces.     

Endophytic and epiphytic phyllosphere fungi of Camellia japonica: seasonal and leaf age-dependent variations

Seasonal and leaf age-dependent variations in the endophytic and epiphytic phyllosphere fungal assemblages of Camellia japonica were examined and compared. Live leaves of C. japonica were collected in four seasons (May, Aug, Nov, Feb), and fungi were isolated from healthy-looking leaves of 0, 1, 2 and 3 y old. The infection rate and total number of endophytic fungi increased May-Feb, and species richness of endophytes increased as leaves aged. In contrast the infection rate of epiphytic fungi was 100% for all leaf ages at every sampling date. The total number of epiphytic fungi isolated was greatest in May and lowest in Aug. The species richness of epiphytes did not differ significantly by season or leaf age. Eight fungal species were recorded as major phyllosphere fungi of C. japonica. Seasonal variations were detected for the frequencies of Colletotrichum gloeosporioides, C. acutatum, and epiphytes Pestalotiopsis sp.1, Aureobasidium pullulans, Phoma sp.1 and Ramichloridium sp., whereas the frequency of the endophyte Geniculosporium sp.1 varied with leaf age. The frequency of the epiphyte Cladosporium cladosporioides varied with both season and leaf age.     

Coexistence among Epiphytic Bacterial Populations Mediated through Nutritional Resource Partitioning

The levels of coexistence between Pseudomonas syringae and various nonpathogenic epiphytic species in the phyllosphere of beans (Phaseolus vulgaris) were assessed by using replacement series. The epiphytic species Pseudomonas fluorescens, Pantoea agglomerans, Stenotrophomonas maltophilia, and Methylobacterium organophilum were all capable of exhibiting higher levels of coexistence with P. syringae than was observed with a near-isogenic P. syringae strain pair. The ecological similarity of the epiphytes was estimated with niche overlap indices derived from in vitro carbon source utilization profiles. The level of coexistence of the epiphytes was inversely correlated with the ecological similarity of the strains. Hence, the level of coexistence between the epiphytes was proportional to the degree of niche differentiation, defined as the ability to utilize carbon sources not utilized by a competing strain. Comparisons of utilization profiles for groups of carbon sources (amino acids, organic acids, and carbohydrates) indicated the types of carbon sources for which the strains likely competed in the bean phyllosphere. P. fluorescens and P. syringae strains probably competed for most carbon sources. S. maltophilia and M. organophilum strains probably competed with P. syringae for most organic acids but few amino acids or carbohydrates. P. agglomerans strains probably competed with P. syringae for most amino acids and organic acids but few carbohydrates. A variable level of coexistence observed between P. agglomerans and P. syringae probably reflected the variability in abundance in the bean phyllosphere of the carbohydrates that P. agglomerans utilized exclusively.     

Microbial and Functional Diversity within the Phyllosphere of Espeletia Species in an Andean High-Mountain Ecosystem

Microbial populations residing in close contact with plants can be found in the rhizosphere, in the phyllosphere as epiphytes on the surface, or inside plants as endophytes. Here, we analyzed the microbiota associated with Espeletia plants, endemic to the Páramo environment of the Andes Mountains and a unique model for studying microbial populations and their adaptations to the adverse conditions of high-mountain neotropical ecosystems. Communities were analyzed using samples from the rhizosphere, necromass, and young and mature leaves, the last two analyzed separately as endophytes and epiphytes. The taxonomic composition determined by performing sequencing of the V5-V6 region of the 16S rRNA gene indicated differences among populations of the leaf phyllosphere, the necromass, and the rhizosphere, with predominance of some phyla but only few shared operational taxonomic units (OTUs). Functional profiles predicted on the basis of taxonomic affiliations differed from those obtained by GeoChip microarray analysis, which separated community functional capacities based on plant microenvironment. The identified metabolic pathways provided insight regarding microbial strategies for colonization and survival in these ecosystems. This study of novel plant phyllosphere microbiomes and their putative functional ecology is also the first step for future bioprospecting studies in search of enzymes, compounds, or microorganisms relevant to industry or for remediation efforts.     

Geographical location determines the population structure in phyllosphere microbial communities of a salt-excreting desert tree

The leaf surfaces of Tamarix, a salt-secreting desert tree, harbor a diverse community of microbial epiphytes. This ecosystem presents a unique combination of ecological characteristics and imposes a set of extreme stress conditions. The composition of the microbial community along ecological gradients was studied from analyses of microbial richness and diversity in the phyllosphere of three Tamarix species in the Mediterranean and Dead Sea regions in Israel and in two locations in the United States. Over 200,000 sequences of the 16S V6 and 18S V9 hypervariable regions revealed a diverse community, with 788 bacterial and 64 eukaryotic genera but only one archaeal genus. Both geographic location and tree species were determinants of microbial community structures, with the former being more dominant. Tree leaves of all three species in the Mediterranean region were dominated by Halomonas and Halobacteria, whereas trees from the Dead Sea area were dominated by Actinomycetales and Bacillales. Our findings demonstrate that microbial phyllosphere communities on different Tamarix species are highly similar in the same locale, whereas trees of the same species that grow in different climatic regions host distinct microbial communities.     

Nitrogen Fixation in the Phyllosphere of Tropical Plants: Occurrence of Phyllosphere Nitrogen-Fixing Micro-organisms in Eastern India and their Utility for the Growth and Nitrogen Nutrition of Host Plants

Of the 560 leaf samples belonging to 259 species of green plantsexamined more than 50 per cent of the Angiosperms and 25 percent of the Pteridophytes and Gymnosperms revealed the presenceof N₂-fixing micro-organisms in their phyllosphere. Plants particularlyremarkable in this respect are orchids and several other epiphytes,Scindapsus officinalis, Ficus and cucurbits. Most of the isolatesappear to be biotypes of Klebsiella pneumoniae. The more activestrains fixed more than 5 mg N g^–1 glucose utilized andreduced more than 100 nmol C₂H₂ mg^–1 cell d. w h^–1. The efficacy of the phyllosphere N₂-fixing isolates for N-nutritionof host plants was studied by spraying suspensions of the culturesgrown on N-free media on rice and wheat seedlings. In IR-26rice or Sonalika and Janak wheat grown on soil in wooden flatsor earthenware pots, 22 per cent of the 161 cultures studiedcaused increased height and about three-quarters of the culturesenhanced dry weight by more than 50 per cent; chlorophyll andN-contents were enhanced more than 50 per cent by about halfand two-thirds of the cultures respectively. In N-free sandculture 26 of the 50 promising strains doubled N-content, and30 doubled dry weight of the tested plants. In some cases dryweight, number of grains per panicle, and 1000 grain weightwere increased by 300, 70–83 and 126–158 per centrespectively; N-content of straw and seed was increased three-or fourfold. In several cases the beneficial effects were foundto match closely the performance of plants receiving ammoniumsulphate. Nitrogen-fixing micro-organisms, nitrogen nutrition, phyllosphere, rice, tropical plants, wheat     

Strong leaf surface basification and CO2 limitation of seagrass induced by epiphytic biofilm microenvironments

Coastal eutrophication is a growing problem worldwide, leading to increased epiphyte overgrowth of seagrass leaves. Yet little is known about how epiphytes affect key biogeochemical conditions and processes in the seagrass phyllosphere. We used electrochemical microsensors to measure microgradients of O₂, pH, and CO₂ at the bare and epiphyte-covered leaf surface of seagrass (Zostera marina L.) to determine effects of epiphytes on the leaf chemical microenvironment. Epiphytes result in extreme daily fluctuations in pH, O₂, and inorganic carbon concentrations at the seagrass leaf surface severely hampering the plant's performance. In light, leaf epiphyte biofilms and their diffusive boundary layer lead to strong basification, markedly reducing the CO₂ and HCO₃^- availability at the leaf surface, leading to reduced photosynthetic efficiency as a result of carbon limitation and enhanced photorespiration. With epiphytes, leaf surface pH increased to >10, thereby exceeding final pH levels (~9.62) and CO₂ compensation points for active photosynthesis. In darkness, epiphyte biofilms resulted in increased CO₂ and hypoxia at the leaf surface. Epiphytes can lead to severe carbon limitation in seagrasses owing to strong phyllosphere basification leading to CO₂ depletion and costly, yet limiting, HCO₃^- utilization, increasing the risk of plant starvation.     

ROLE OF THE NITROGEN-FIXING BACTERIAL MICROFLORA IN THE EPIPHYTISM OF TILLANDSIA (BROMELIACEAE)

Nitrogen-fixing activity in the phyllosphere of 12 species of Tillandsia from different Mexican habitats was evaluated by the acetylene reduction assay, and nitrogen-fixing microorganisms were isolated and characterized. The leaves from eight of the 12 Tillandsia species examined exhibited nitrogenase activity in enrichment cultures. Among the microorganisms implicated—Agrobacterium, Bacillus, Erwinia, Pseudomonas, Rahnella, Vibrio, and Xanthomonas—only Bacillus megatherium reduced acetylene in pure culture. Our findings suggest that nitrogen fixation in the phyllosphere of the sampled epiphytes occurs under suitable conditions and that most of the bacteria involved are primarily soil and water inhabitants. The results also suggest a relationship between the composition of the nitrogen-fixing microbial communities grown on the leaf and the different development of the leaf area in Tillandsia due to the aerial components (wings) of the trichomes.     

Endophytic and epiphytic phyllosphere fungi of red-osier dogwood (<Emphasis Type="Italic">Cornus stolonifera</Emphasis>) in British Columbia

Endophytic and epiphytic phyllosphere fungi associated with red-osier dogwood (Cornus stolonifera), a deciduous shrub, were examined in coastal British Columbia, Canada. Current-year shoots were divided into four types based on the absence or presence of inflorescence and secondary elongated shoots at the apex of primary shoots. Leaves on these shoots were then classified into six categories so as to examine the effect of flowering, secondary shoot elongation, and shoot order within current-year shoots on the occurrence of phyllosphere fungi. Species composition of fungi was markedly different between the interior and surface of leaves, whereas it was relatively similar among the six leaf categories in the interior or on the surface. Frequencies of the eight major species were not different between leaves on flowering and nonflowering shoots. The frequency of Colletotrichum gloeosporioides in the leaf interior was greater on leaves on the primary shoots that elongated the secondary shoots than on those that did not, and was greater on leaves on the primary shoots than on those on the secondary shoots. On the other hand, secondary shoot elongation and shoot order had no effect on the frequencies of C. gloeosporioides and the other seven epiphytes on leaf surfaces.