高压静电场胁迫对苦瓜生理代谢及主要害虫与天敌种群的影响

[目的]通过研究不同高压静电场对苦瓜生理指标、田间害虫和天敌种群数量的影响,为国家电网对输变电工程电磁辐射的预防及管理提供实践指导.[方法]在田间试验中,苦瓜持续曝露在强度为0、2和10 kV/m的极低频电磁场下,测定其农艺性状和酶的活性变化,并调查苦瓜田间害虫和天敌的种群数量.[结果]在10 kV/m电磁场处理下,苦...     

辣椒对镉胁迫的生理响应

以福湘5号、兴蔬215和川腾1号这3个辣椒品种为材料,用含有0mg/L、100mg/L、200mg/L、300mg/L重金属镉的1/2霍格兰培养液对具10片真叶的辣椒苗进行处理,7d后测定各项生理指标。结果表明,镉对辣椒的生长有很强的毒害作用,随着镉胁迫浓度的升高,3个辣椒品种的生物量、叶片叶绿素含量、电导率、丙二醛含量和活性氧清除系统酶活性都受到了不同程度的影响。在镉胁迫下,辣椒植株的株高、根长、鲜重受到明显抑制,根系发育畸形,叶片黄化。镉胁迫的毒害作用在3个辣椒品种间有差异。其中川腾1号耐镉胁迫能力较强,福湘5号次之,兴蔬215最差。     

辣椒拟种群对模拟昆虫捕食行为的反应

基于拟种群理论,动用方差分析法、主分量分析法及植物生长分析法,研究７月高温期辣椒拟种群不同程度的剪叶对模拟短期虫害的反应。结果表明,辣椒具有较强的补偿能力;老叶的数量、干重和叶面积随剪叶程度的增加而下降,新叶则相反,但总叶数量相近;总叶面积和干重受老叶影响大,差异显著;枝的数量、干重、长度差异不显著;果、花、花蕾的数量差异也不显著,但干重差异显著;用数量指标代替干重、叶面积和长度等指标来进行植物的     

水盆式性诱剂诱捕器对苹果园昆虫种群的影响

通过对有机苹果园和常规苹果园的系统调查,调查分析了果园释放性诱剂对园内目标害虫、天敌及中性昆虫的诱集作用.结果表明:无论在有机苹果园还是常规苹果园,性诱剂均对天敌昆虫和中性昆虫具有一定的诱杀作用,且益害比在有机园中为2∶1和2∶3之间,在常规园中则在3∶1和1∶10范围内.水盆式性诱剂诱捕器的使用对自然天敌在果园中的控...     

边缘效应对棉田害虫和天敌种群的影响

比较了棉田中间棉株与边缘棉株上害虫、天敌的种群动态,分析了边缘效应对棉株-害虫-天敌能量动态的影响。结果表明,棉田边缘棉株上第2代棉铃虫幼虫发生量比其中间棉株高出1．94倍;第3代棉铃虫发生量比棉田中间要低62．12％;第4代棉铃虫比中间棉株高12．5％。棉田边缘棉株上苗蚜发生量比棉田中间要高出1．09倍,伏蚜和秋蚜的数量比棉田中间分别低97．73％和37．70％。棉田边缘棉株上捕食性瓢虫、蝽类、蜘蛛和寄生性天敌的种群数量低于棉田中间的数量,分别为棉田中间的73．81％、35．79％、52．90％和39．11％;棉田边缘棉株上害虫群落多样性高于棉田中间,而天敌群落的多样性低于棉田中间;棉田边缘的光能利用率和生产力比棉田中间的值要高。     

辣椒拟种群对模拟昆虫捕食行为的反应

基于拟种群理论,运用方差分析法、主分量分析法及植物生长分析法,研究7月高温期辣椒拟种群不同程度的剪叶对模拟短期虫害的反应.结果表明,辣椒具有较强的补偿能力;老叶的数量、干重和叶面积随剪叶程度的增加而下降,新叶则相反,但总叶数量相近;总叶面积和干重受老叶影响大,差异显著;枝的数量、干重、长度差异不显著;果、花、花蕾的数量差异也不显著,但干重差异显著;用数量指标代替干重、叶面积和长度等指标来进行植物的生长分析,仅对组元个体间干重极差小的拟种群适用;高温期一定程度的虫害对辣椒生长和果实产量的提高有益.     

播种时间对棉田害虫和天敌种群的影响

通过对3种不同时间播种的棉田内害虫、天敌系统调查,分析和比较了播种时间对棉田害虫、天敌种群和群落的影响。结果表明,播种期推后,可减轻或避免第二代棉铃虫的为害,加重第三代和第四代棉铃虫的为害;但不同播种日期对不同时期的棉蚜影响不同,苗蚜以迟播棉田内种群数量最高,伏蚜则以夏播棉田内种群数量最高。播种期的推后,不利于棉田捕食性瓢虫、蝽类、蜘蛛和寄生性天敌种群增长。棉田害虫和天敌群落多样性指数也随播种期的推后而下降．因此．应针对不同时间播种的棉田开展相应的害虫生态管理。     

落叶松人工混交林内害虫—天敌种群动态及其相关的初步研究

在落叶松(Larix olgensis Henry)人工林内,昆虫及其他节肢动物种群,由于其各种群本身的生物、生态学特性,相互作用及环境因子对它们的影响,造成种群的数量波动是经常性的,无论这种波动是否带有明显的规律性,都会对落叶松林这一生态系统带来影响。     

桃园主要害虫、天敌种群动态及其群落结构的研究

系统研究了3月中旬～10月上旬桃园主要害虫、天敌的种群动态和昆虫群落的相对多度、丰富度、生态优势度、多样性指数、均匀度等群落特征指数的变动,分析了影响昆虫群落多样性的主要因素．     

抗虫辣椒叶片对斜纹夜蛾幼虫相关生理生化指标的影响

为明确朝天椒(品种：BLTY2)叶片饲喂的斜纹夜蛾Spodoptera litura幼虫生长发育受到抑制的关键原因,本研究以人工饲料及牛角椒（品种：FXBX）叶片饲喂的斜纹夜蛾幼虫为对照,通过比较3种食料饲喂后斜纹夜蛾幼虫相关生理生化指标的变化,分析BLTY 2辣椒叶片饲喂所致的斜纹夜蛾幼虫生长发育异常的原因。结果表明,朝天椒辣椒叶片饲喂的斜纹夜蛾幼虫生长发育速率滞后于牛角椒辣椒叶片及人工饲料饲喂的斜纹夜蛾幼虫,且每头幼虫的发育时长均显著延长（P<0.05）。饲喂后第1天、第3天、第4天、第5天、第6天和第7天,饲喂BLTY 2辣椒叶片的斜纹夜蛾幼虫体内保幼激素（JH）含量均显著高于其他2种食料饲喂的斜纹夜蛾幼虫（P<0.05）。饲喂后第3天、第4天、第5天和第7天,饲喂BLTY 2辣椒叶片的斜纹夜蛾幼虫体内蜕皮激素（Ecd）含量均显著高于其他2种食料饲喂的斜纹夜蛾幼虫（P<0.05）。3种食料饲喂后斜纹夜蛾幼虫体内的几丁质酶（CHT）活性变化差异较大,而2种辣椒叶片饲喂后斜纹夜蛾幼虫体内的组织蛋白酶（CTS）活性变化趋势相似,且不同于人工饲料饲喂的斜纹夜蛾幼虫体内的CTS活性变化趋势。由此可见,BLTY 2辣椒主要干扰斜纹夜蛾幼虫体内JH与Ecd的含量抑制其生长发育。本研究结果可为筛选具有抗虫活性的植物次生代谢物质奠定基础。     

Specific herbivore-induced volatiles defend plants and determine insect community composition in the field

In response to insect attack, plants release complex blends of volatile compounds. These volatiles serve as foraging cues for herbivores, predators and parasitoids, leading to plant-mediated interactions within and between trophic levels. Hence, plant volatiles may be important determinants of insect community composition. To test this, we created rice lines that are impaired in the emission of two major signals, S-linalool and (E)-β-caryophyllene. We found that inducible S-linalool attracted predators and parasitoids as well as chewing herbivores, but repelled the rice brown planthopper Nilaparvata lugens, a major pest. The constitutively produced (E)-β-caryophyllene on the other hand attracted both parasitoids and planthoppers, resulting in an increased herbivore load. Thus, silencing either signal resulted in specific insect assemblages in the field, highlighting the importance of plant volatiles in determining insect community structures. Moreover, the results imply that the manipulation of volatile emissions in crops has great potential for the control of pest populations.     

Effect of sanitized and non-sanitized sewage sludge on soil microbial community and the physiology of pepper plants

A greenhouse experiment was conducted to investigate the impact of sanitized (Autothermal Thermophilic Aerobic Digested, ATAD) and non-sanitized (Anaerobic Mesophile Digested) sewage sludge on the activity and functional diversity of soil microbial community and the physiology of pepper plants (Capsicum annuum L. cv. Piquillo). ATAD and anaerobic mesophile sludges were applied to soils at three rates (3, 6 and 12 g (dry matter) per pot) and unamended soil was included as a control. Results showed that ATAD and mesophile sludge application increased the growth and yield of plants, and accelerated their phenological development as the sludge rate increased. The increased growth was a result of the enhanced capacity of plants to produce more leaves and the greater photosynthetic activity per unit leaf area. Besides nutrient supply, the increased soil microbial activity and biomass in amended soils might have indirectly contributed to the enhanced growth and yield of plants. Sludge application decreased soil functional diversity and caused a shift in the community-level physiological profile. Although ATAD and anaerobic mesophile sludges exerted similar effects on plant development, the type of sludge influenced the activity and functional diversity of soil microbial community. Results are discussed in relation to the environmental benefits associated with the ATAD process for sludge treatment.     

Effects of non-native plants on the native insect community of Delaware

Due to the lack of a co-evolutionary history, the novel defenses presented by introduced plants may be insurmountable to many native insects. Accordingly, non-native plants are expected to support less insect biomass than native plants. Further, native insect specialists may be more affected by introduced plants than native generalist herbivores, resulting in decreased insect diversity on non-native plants due to the loss of specialists. To test these hypotheses, we used a common garden experiment to compare native insect biomass, species richness, and the proportion of native specialist to native generalist insects supported by 45 species of woody plants. Plants were classified into three groupings, with 10 replicates of each species: 15 species native to Delaware (Natives), 15 non-native species that were congeneric with a member of the Native group (Non-native Congeners), and 15 non-native species that did not have a congener present in the United States (Aliens). Native herbivorous insects were sampled in May, June, and July of 2004 and 2005. Overall, insect biomass was greater on Natives than Non-native Congeners and Aliens, but insect biomass varied unpredictably between congeneric pair members. Counter to expectations, Aliens held more insect biomass than did Non-native Congeners. There was no difference in species richness or the number of specialist and generalist species collected among the three plant groupings in either year, although our protocol was biased against sampling specialists. If these results generalize to other studies, loss of native insect biomass due to introduced plants may negatively affect higher trophic levels of the ecosystem.     

Influence of relative humidity on analyzing electric field exposure using ELF electric field measurements

The objective of the study was to investigate the influence of humidity on analyzing electric field exposure using extremely low frequency (ELF) electric field measurements. The study included 322 measurements in a climate room. We used two commercial three‐axis meters, EFA‐3 and EFA‐300, and employed two measurement techniques in the climate room where we varied the temperature from 15 to 25 °C, the relative humidity from 55% to 95%, and the electric field from 1 to 25 kV/m. We calculated Pearson correlations between humidity and percentage errors for all data and for data at different levels of humidity. When the relative humidity was below 70%, the results obtained by the different measurement methods in terms of percentage errors were of the same order of magnitude for the considered temperatures and field strength, but the results were less reliable when the relative humidity was higher than 80%. In the future, it is important to take humidity into account when electric field measurement results will be compared to the values given in different exposure guidelines. Bioelectromagnetics 34:414–418, 2013. © 2012 Wiley Periodicals, Inc.     

Destabilization of the cardiac function of an insect by a low-frequency electric field

The effect of high-intensity low-frequency electric field on the functioning of the heart of an insect was estimated from electrocardiogram. It was found that electric field causes a disturbance of the cardiac function. Its stressing activity is mainly related to the excitation of the insect by induced currents whose exciting action is enhanced by vibration in trichoid sensillas and antennas.     

Addition of magnetic field capability to existing extremely-low-frequency electric field exposure systems

Magnetic field systems were added to existing electric field exposure apparatuses for exposing cell suspensions in vitro and small animals in vivo. Two horizontally oriented, rectangular coils, stacked one directly above the other, have opposite electric currents. This configuration minimizes leakage fields and allows sham- and field-exposure systems to be placed in the same room or incubator. For the in vitro system, copper plates formed the loop-pair, with up to 900 A supplied by a 180:1 transformer. Electric fields were supplied via electrodes at the ends of cell-culture tubes, eight of which can be accommodated by each exposure system. Two complete systems are situated in an incubator to allow simultaneous sham and field exposure up to 1 mT. For the in vivo system, four pairs of 0.8 x 2.7-m coils made of copper bus bar are employed. This arrangement is energized from the power grid via a 30:1 transformer; horizontal magnetic flux densities up to 1 mT can be generated. Pairs of electrode plates spaced 30.5 cm apart provide electric field exposure of up to 130 kV/m. Four systems with a capacity of 48 rats each are located in one room. For both the in vitro and in vivo systems, magnetic exposure fields are uniform to within +/- 2.5%, and sham levels are at least 2,500-fold lower than exposure levels. Potential confounding factors, such as heating and vibration, were examined and found to be minimal.     

Destabilization of the insect heart function by low-frequency electric field

The effect of an intense low-frequency field on the insect heart function has been estimated with the use of electrocardiograms. An electric field has been found to upset heart function. The resultant stress is mainly determined by induced currents whose excitatory effect is enhanced by the vibration of trichoid sensillas and antennae in the electric field.     

Impact of biochar application to soil on the root-associated bacterial community structure of fully developed greenhouse pepper plants

Adding biochar to soil has environmental and agricultural potential due to its long-term carbon sequestration capacity and its ability to improve crop productivity. Recent studies have demonstrated that soil-applied biochar promotes the systemic resistance of plants to several prominent foliar pathogens. One potential mechanism for this phenomenon is root-associated microbial elicitors whose presence is somehow augmented in the biochar-amended soils. The objective of this study was to assess the effect of biochar amendment on the root-associated bacterial community composition of mature sweet pepper (Capsicum annuum L.) plants. Molecular fingerprinting (denaturing gradient gel electrophoresis and terminal restriction fragment length polymorphism) of 16S rRNA gene fragments showed a clear differentiation between the root-associated bacterial community structures of biochar-amended and control plants. The pyrosequencing of 16S rRNA amplicons from the rhizoplane of both treatments generated a total of 20,142 sequences, 92 to 95% of which were affiliated with the Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes phyla. The relative abundance of members of the Bacteroidetes phylum increased from 12 to 30% as a result of biochar amendment, while that of the Proteobacteria decreased from 71 to 47%. The Bacteroidetes-affiliated Flavobacterium was the strongest biochar-induced genus. The relative abundance of this group increased from 4.2% of total root-associated operational taxonomic units (OTUs) in control samples to 19.6% in biochar-amended samples. Additional biochar-induced genera included chitin and cellulose degraders (Chitinophaga and Cellvibrio, respectively) and aromatic compound degraders (Hydrogenophaga and Dechloromonas). We hypothesize that these biochar-augmented genera may be at least partially responsible for the beneficial effect of biochar amendment on plant growth and viability.