Reproductive polyphenism and its advantages in aphids: Switching between sexual and asexual reproduction

Reproductive polyphenism, which allows one genotype to produce sexual and asexual morphs, is an extreme case of phenotypic plasticity and is commonly observed in aphids. Aphids are typical species that switch these reproductive modes, and the pathway orientation is triggered by the environmental conditions(mainly photoperiod and temperature). The typical annual life of aphids includes a succession of parthenogenetic generations during the spring and summer and a single sexual generation in autumn. In this review, we describe how the environmental cues orientate the reproductive mode of aphids from photoperiodic perception to endocrine regulation, and how juvenile hormones may act on the target cells(oocytes) to initiate the gametogenesis and embryogenesis in sexual and asexual reproduction. We also discuss the paradox of sex, especially the advantages of sexual reproduction in aphids. With the recent development of genomic resources in aphids, many potential genes involved in the reproductive polyphenism will enter the public's awareness. In particular, we describe a novel RNAi method in aphids, which may provide a molecular technique for determining the developmental fate and multiple reproductive strategies.     

麦/油-稻轮作下秸秆还田与氮肥管理对直播杂交稻氮素利用特征的影响

【目的】探明秸秆还田和氮肥管理对麦/油后直播杂交稻氮素积累、转运、氮肥利用效率及籽粒产量的影响。【方法】选用优质三系杂交稻宜香优2115,采用二因素裂区设计,麦、油茬田同步开展试验,处理完全一致。主区为麦/油秸秆全量翻埋还田(M₁)和秸秆不还田(对照,M₀),副区设4个氮肥管理,即不施氮对照(N₀)、m_基肥∶m_分蘖肥∶m_促花肥∶m_保花肥比例分别为1∶0∶0∶0(N₁)、3∶3∶2∶2(N₂)、2∶2∶3∶3(N₃),测定了直播杂交稻主要生育时期各器官的氮素积累量及籽粒产量。【结果】结果表明,两种轮作方式下,氮肥管理对直播杂交稻主要生育时期的氮素积累、齐穗后茎鞘、叶片的氮素转运及稻株氮素利用效率均存在显著或极显著的调控效应。秸秆还田显著提高麦/油茬杂交稻中后期的氮素积累量、茎鞘和叶片的氮素转运量以及氮肥利用效率,其中,氮肥农学利用率、氮肥偏生产力和氮肥表观利用率较秸秆不还田分别提高了34.96%/28.76%、2.52%/2.61%和31.91%/22.30%。同时,油菜秸秆还田下直播杂交稻各生育时期氮素积累和产量较麦秆还田表现更好,籽粒产量提高481 kg/hm²(5.22%)。M₁N₂处理、M₀N₃处理下,直播杂交稻各阶段的氮素积累速率明显加大,促进结实期茎鞘和叶片的氮素向穗部转运,成熟期稻株氮素积累量优势明显且有较高的氮素利用效率(麦/油茬稻氮肥农学利用率、偏生产力和表观利用率分别达17.87 kg∙kg^-1/17.85 kg∙kg^-1、67.27 kg∙kg^-1/71.28 kg∙kg^-1、74.93%/75.05%),最终实现高产。【结论】在麦/油-稻轮作下秸秆全量还田,配合N₂氮肥管理,可有效提高直播杂交稻氮素吸收、利用效率,增加籽粒产量,尤以油菜秸杆还田的效果更好。     

不同追肥次数和用量对番茄产量及品质的影响

为推行减量施肥,提高肥料利用率,研究了不同施肥措施对连续种植的番茄产量及品质的影响。结果表明:优化施肥处理在保证不减产的情况下,节肥效果显著,与传统施肥处理(T1)相比,优化施肥各处理(T2—T5)每667 m~2施用化肥纯养分总量分别减少44.8、44.8、65.6、3.2 kg,节肥47.0%、47.0%、68.8%、3.4%,T4处理节肥效果最佳;在高肥力地力水平下,追肥用量减半完全可以保证作物所需养分,其中T3产量最高,表明在优化施肥的基础上增加追肥次数,少量多次追肥更利于作物生长;T3提高了番茄维生素C含量,降低了番茄的硝酸盐含量。综上,化肥减量对连续种植的番茄产量没有明显影响,但显著提高了番茄的品质,以T3即化肥底施减量50%配施40%有机肥且适当增加追肥次数处理的效果最好。     

郴州市辣木引种表现及矮化栽培技术

作为当代一种新资源树种辣木,在营养、保健和医药领域有很高的应用价值,开发前景广阔。本文对郴州地区辣木的引种表现进行了总结,将育苗、定植、矮化栽培管理、采收利用等技术要点进行归纳,为辣木的进一步开发利用提供技术支撑。     

新疆杨树/紫花苜蓿林草复合系统中根系分布特征及生产力

为了解杨树（Populus L.）/紫花苜蓿（Medicago sativa L.）林草复合系统中两种植物根系的分布及相互关系,利用WinRHIZOTM对3 a生紫花苜蓿和7 a生杨树在单作和间作条件下0~60 cm土层中的根长密度（RLD）、平均根直径（ARD）和比根长（SRL）的分布进行测定分析。结果表明：间作紫花苜蓿RLD降低了10.01%~54.29%,20~60 cm土壤中紫花苜蓿ARD降低了11.15%~37.30%, 间作苜蓿的SRL比单作苜蓿高10.52%~28.78%;间作增加了 0~40 cm土层中杨树ARD的20.36%~28.08%,增加了苜蓿种植区域0~20 cm土层中杨树RLD的15.51%~34.23%。杨树SRL受到的影响较小,仅在8月5日的0~20 cm 土层中测得单作和间作SRL存在差异,单作杨树SRL比间作杨树高14.46%。单作和间作苜蓿的最高产量均在第一次收获时期,间作降低了苜蓿的产量,在第一次、第二次和第三次收获中产量分别降低了24.7%、30.9% 和 43.7%,与单作苜蓿相比,杨树/紫花苜蓿林草复合系统中苜蓿的总产量减少了31.2%。通过计算土地当量比,发现杨树与紫花苜蓿复合经营为杨树林带增加了额外来自紫花苜蓿的收入,能够提高系统41%的生产力。综上所述,林草复合系统中紫花苜蓿根系分布及生长受到了不利影响,而杨树根系受到了有利的影响。相比单作种植,林草复合系统有较高的生产力和资源利用效率,具有提高新疆地区防护林带生态和经济回报率的潜能。     

我国饲草重大病虫鼠害研究进展

为全面了解我国饲草重大病虫鼠害分布和危害,充分掌握其传播扩散规律及其造成的重大经济损失,我们系统分析了我国饲草病害、虫害、鼠害等生物灾害危害情况,总结了国内外饲草病虫鼠害防控现状与研究进展,提出了饲草重大生物灾害的防控对策,为保障饲草产业和草牧业健康发展提供理论支撑。此外,本文还总结了我国饲草病虫鼠害的防控难题,为今后饲草病虫鼠害的研究提供了方向。     

燕麦β-葡聚糖降血糖性能研究进展

本文从三个方面综述了燕麦β-葡聚糖降血糖性能研究进展。首先从食品血糖生成指数(glycemic index,GI)、餐后血糖、空腹血糖和α-淀粉酶活性等方面阐述了燕麦β-葡聚糖降血糖的功效,进而介绍了燕麦β-葡聚糖的结构因素——分子量和含量,以及食品加工过程对其降血糖功效的影响,最后综述了燕麦β-葡聚糖几种可能的降血糖机制,以期对后续研究提供参考。     

Spatio-temporal dynamics of technical efficiency in China’s specialized markets: A stochastic frontier analysis approach

China’s specialized markets as a special form of bottom-up capital agglomeration have played a key role in fostering regional development. It once exhibited positive externalities with high efficiencies. However, given the rapid proliferation of specialized markets and the penetration of E-commerce, their advantages may have shifted and the understanding of this shift is limited. The paper explores the spatio-temporal dynamics of China’s specialized markets in terms of technical efficiency. Based on turnover data from Statistical Yearbooks of China Commodity Exchange Market from 2000 to 2016, technical efficiencies in specialized markets are measured by a Stochastic Frontier Analysis (SFA) approach using panel data. The results show that (a) the technical efficiencies in China’s specialized markets are significantly divergent in space over time; (b) labor input has notable effect on efficiency increase, while capital input has no significant effect; (c) informatization level, cluster size, and degree of market openness are identified to have a positive effect on specialized market’s technical efficiency. This paper argues that specialized markets should be taken seriously in the cluster evolution research. The role of proximity and the bounded links between specialized markets and their local clusters is the key to understanding their changing forms, performances, and trajectories.     

大白菜小植株突变体s1光合能力及光反应相关基因的转录组分析

植株的大小与光合能力密切相关。本研究以大白菜小植株突变体s1和其野生型WT为材料,通过测定叶绿素含量、净光合速率、叶绿素荧光参数以及对光反应相关基因的转录水平分析,解析大白菜植株大小与光合能力的相关性。结果表明:与野生型相比,大白菜小植株突变体s1的叶绿素含量无显著差异,但光合速率显著降低29%;Fv/Fm和Y(II)值在二者之间无显著差异(P>0.05),而s1的外叶和新叶ETR值都显著低于WT;进一步的转录组分析表明光合电子传递链上的PSII、PC、FNR、ATP合酶相关基因表达下调0.94～1.69倍。由此证实,大白菜小植株突变体s1光合速率低与光合电子传递链中的基因表达下降及光合电子传递速率下降有关。该研究为进一步挖掘大白菜植株大小相关的优异基因资源提供了良好的试验材料,也为大白菜分子设计育种提供了理论依据。     

高炭基肥配施氮肥对牡丹江烤烟生长及产量和质量的影响

采用田间试验,设置4个处理[CK(常规施氮量,不施高炭基肥)、T1(常规施氮量,900 kg·hm~(-2)高炭基肥)、T2(85%常规施氮量,900 kg·hm~(-2)高炭基肥)、T3(70%常规施氮量,900 kg·hm~(-2)高炭基肥)],研究了减氮配施高炭基肥对牡丹江烤烟生长和产量、质量的影响。结果表明,T1处理烤烟各生育时期的农艺性状均有所提高,T3处理对烤烟的生长产生了负面效应;T1处理显著提高了中上部叶总氮含量(1.59%,1.65%)、烟碱含量(1.71%,1.99%),T1和T2处理显著提高了中部叶钾含量(1.68%,1.69%);与CK相比,T1处理中上部叶感官评吸总得分均有显著提高,增幅分别为4.06%和5.92%,其烟叶产量、产值及中上等烟比例均有所提高。在牡丹江烟区白浆土条件下,控制总施氮量为45 kg·hm~(-2)、高炭基肥料施用量为900 kg·hm~(-2)时,有利于促进烤烟生长、提高经济效益、改善烟叶品质。