Two biomass preparation methods provide insights into studying microbial communities of intestinal mucosa in grass carp (Ctenopharyngodon idellus)

Animal digestive tract is habitat for a large number of autochthonous microbiota, which play central roles in multiple biological and physiological processes of the host. In this study, two different micro‐biomass preparation methods were employed to evaluate the diversity of intestinal mucosa‐associated microbiota in grass carp (Ctenopharyngodon idellus). Genomic DNAs were isolated either directly from intestinal mucosal samples (group A), or from micro‐biomass after microbial dissociation (group B). Community richness, diversity and evenness indices were all higher in group B, but differences were not statistically significant (P = 0.97, P = 0.33, P = 0.34 respectively). Furthermore, group B samples exhibited an increased ratio of bacterial DNA in comparison with group A samples, but the difference was also not statistically significant (P = 0.74). In addition, there were no statistically significant differences between the two groups (P > 0.05) at the taxonomic level. Our results support previous findings that there exists a great abundance of the intestinal mucosa‐adherent microbiota in the grass carp; among these, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Spirochaetes and Fusobacteria were the most common phyla. Within these microbiota, Paenibacillus, Bacteroides, Bacillus and Cetobacterium genera comprise the majority of the community, implicating their functional importance (e.g. as probiotics) to their host. Our results contribute towards a better understanding of the intestinal microbial profile of grass carp. Both micro‐biomass preparation techniques proved to be feasible for studying mucosa‐adherent microbiota of grass carp; however, the second method (group B) provides a protocol that is somewhat more effective than the first method (group A).     

Is N‐feedback involved in the regulation of nitrogenase activity in Medicago truncatula?

To determine whether senescing leaves provoke an active nitrogen (N) remobilization that results in the reduction of nitrogenase activity, 60% of Medicago truncatula lower leaves were either darkened or individually excised for two weeks. Although a considerable amount of N was remobilized, N₂ fixation activity was found to be increased to maintain the N source/sink balance, indicating an absence of the negative N‐feedback regulation of nitrogenase activity in the senescing M. truncatula.     

不同秸秆还田方式对北方超级稻氮素吸收利用的影响

以北方超级稻沈农265为试验材料,研究了秸秆直接还田和秸秆热解成生物炭施入对水稻氮素吸收利用的影响。结果表明:与常规生产相比,秸秆直接还田主要提高了水稻生育中期的叶、茎含氮量,但同时降低了后期穗氮素累积量,氮素回收率、生理利用率和氮肥农学利用率分别下降5.28%、11.65%和16.19%,使产量有降低趋势;少量秸秆生物炭施入有助于提高生育中后期叶、茎含氮量并促进穗氮素累积量增加,氮素回收率和氮肥农学利用率分别增加6.02%和7.71%,有增加产量的潜力;大量秸秆生物炭施入降低了叶、茎和穗含氮量,氮素回收率负向效应强度高达34.31%,但氮素生理利用率增加45.62%,不利于产量的提高。秸秆直接还田和大量秸秆生物炭施入对水稻氮素吸收有一定抑制作用且不利于产量的提升,少量秸秆生物炭施入则能提高水稻氮素利用率并增加产量。     

Preliminary assessment of large‐scale co‐culture of sandfish (Holothuria scabra) with the Babylon snail (Babylonia areolata) in earthen ponds and in raceways

Holothuria scabra (sandfish) and Babylonia areolata were trialed in two large‐scale co‐culture experiments. Experiment 1 assessed co‐culture in 4 × 400 m² earthen ponds where Babylonia were cultured in a central pen at a density of 400 individuals/m² with sandfish occupying the remaining pond space at 1.1 individuals/m². Sandfish grew from 18.20 ± 6.67 g to 119.03 ± 17.74 g in 92 days and Babylonia (fed trash fish in both experiments) grew from 0.90 ± 0.38 g to 4.93 ± 1.44 g, but Babylonia growth was not increased in co‐culture compared to monoculture. Water and sediment quality varied between co‐culture and monoculture ponds. Neither showed clear improvement due to sandfish culture. Experiment 2 compared non‐segregated sandfish‐Babylonia co‐culture with Babylonia monoculture in 20 m² concrete raceways. Sandfish were cultured at 2 individuals/m² and Babylonia at 300 individuals/m². Sandfish grew up to 1.91 g.day^?1 with 100% survival. Babylonia weight gain was significantly greater in co‐culture raceways (3.35 ± 0.64 g over 61 days), which was double that of Babylonia in monoculture. Substrate total N was reduced by 20% in co‐culture compared with monoculture (p = .032). This provisional study of commercial scale sandfish‐Babylonia co‐culture demonstrates culture compatibility, providing a basis for further system development.     

互花米草生境中人工巢巢捕食研究

为了研究江苏大丰麋鹿国家级自然保护区互花米草生境中繁殖鸟巢的被捕食情况及影响捕食的因素,2014年3~6月,在保护区第三核心区鸟类繁殖生境中,使用人工巢及真实鹌鹑蛋进行巢捕食实验的方法进行巢捕食实验,分析不同巢高度、覆盖度、边缘距离、植被密度等因素对鸟巢被捕食的影响。实验共放置520个人工巢,1 040枚卵,使用红外相机对部分人工巢进行监测。结果表明:在江苏大丰麋鹿自然保护区互花米草生境内,人工巢存在较高的被捕食率,共有352巢被捕食,占67.7%,对11个变量进行逻辑斯蒂回归,巢高度、植被均高、主要植被密度、距边缘距离、水平覆盖度、上层垂直覆盖度等6个变量进人最终模型,巢高度、距边缘距离与巢被捕食显著相关。通过红外相机拍摄从102个监测巢中记录到69个捕食事件,68巢黑线姬鼠(Apodemus agrarius)和1巢黑眉锦蛇(Elaphe taeniura)捕食。我们认为互花米草生境中缺乏啮齿类动物的天敌是当地人工巢被捕食的主要原因。     

植物组织培养中的专家系统

参考各种专家系统的设计方案,将植物组织培养的有关知识与专家系统相结合,提供创立植物组织培养专家系统的一些思路。     

易县旺隆建立生态农业结构短期经济效益的评价

根据低山丘陵区的特点,因地制宜地实行农、林、果、牧等生物措施与工程措施相结合,充分发挥当地的资源优势,建立良性的生态农业结构,取得短期的经济效益,是开发低山丘陵区的有效途径。     

河北零叶蝉的研究

河北零叶蝉系一新种，是吸食柿树叶片汁液的害虫。分布河北、安徽。此虫在河北西部山区１年发生２代或３代，以卵在柿树当年生小枝皮层内越冬。在大发生地区，可用４０％氧化乐果喷冠、涂干或干基钻孔挂瓶输药进行化学防治。天敌有日本高姬蝽、红点平盲蝽、紫斑突额盲蝽、碎斑平盲蝽等。     

Seed dormancy and germination of Ficus lundellii and tropical forest restoration

We investigated seed dormancy and germination in Ficus lundellii Standl. (Moraceae), a native species of Mexico's Los Tuxtlas tropical rain forest. In an 8-h photoperiod at an alternating diurnal (16/8 h) temperature of 20/30 degrees C, germination was essentially complete (96%) within 28 days, whereas in darkness, all seeds remained dormant. Neither potassium nitrate (0.05-0.2%) applied continuously nor gibberellic acid applied either continuously (10-200 ppm) or as a 24 hour pretreatment (2000 ppm) induced germination in the dark. Germination in the light was not reduced by a 24-h hydrochloric acid (0.1-1%) pretreatment, but it was reduced both by a 24-h pretreatment with either H(2)O(2) (0.1-5 M) or 5% HCl, or by more than 5 days of storage at 40 degrees C (4.5% seed water content). In a study with a 2-dimensional temperature gradient plate, seeds germinated fully and rapidly in the light at a constant temperature of 30 degrees C, and fully but less rapidly in the light at alternating temperatures with low amplitudes (< 12 degrees C) about the optimal constant temperature. The base, optimal and ceiling temperatures for rate of germination were estimated as 13.8, 30.1 and 41.1 degrees C, respectively. In all temperature regimes, light was essential for the germination of F. lundellii seeds.