北京夏植黄瓜内生真菌区系研究

为了解黄瓜植株内生真菌的区系组成及其变化,从而为进一步研究黄瓜内生真菌的生态和功能奠定基础,对采自北京延庆的不同品种和不同生育期的40株黄瓜进行了内生真菌的分离培养。经形态学鉴定和18S rDNA序列分析,分离到的1,024株内生真菌属于18属,其中Exserohilum和Neocosmospora尚未见内生真菌的报道。Alternaria、Aspergillus、Chaetomium、Cladosporium和Fusarium在各生育期和各器官普遍存在。其中,Alternaria在叶中的定殖率达47.0%,远高于在其他器官中的定殖率;Fusarium在根中的定殖率达32.5%,远高于在其他器官中的定殖率。多数真菌类群表现出不同程度的器官偏好性,有些真菌类群则只出现在特定器官中。叶和根的内生真菌类群数量和总定殖率均高于茎和果实。随着黄瓜的生长,各器官内生真菌的类群数在增加,部分真菌的定殖率也呈上升趋势,但Neocosmospora和Chaetomium在各器官中的定殖率则随植株生长呈下降趋势。     

L-FABP is a critical host factor for successful malaria liver stage development

The malaria parasite liver stage produces tens of thousands of red cell-infectious forms within its host hepatocyte. It is thought that the vacuole-enclosed parasite completely depends on the host cell for successful development but the molecular parasite-host cell interactions underlying this remarkable growth have remained elusive. Using a yeast two-hybrid screen and a yeast overexpression system we show that UIS3, a parasite protein essential for liver stage development, interacts directly with liver-fatty acid binding protein, L-FABP. Down-regulation of L-FABP expression in hepatocytes severely impairs parasite growth and overexpression of L-FABP promotes growth. This is the first identified direct liver stage-host cell protein interaction, providing a possible explanation for the importance of UIS3 in liver infection.     

Human disturbance and environmental factors as drivers of long‐term post‐fire regeneration patterns in Mediterranean forests

Question: What are the main forces driving natural regeneration in burned mature Mediterranean forests in the medium‐long term and what are the likely successional trajectories of unmanaged vegetation? Location: Valencia Region, eastern Spain. Methods: A wildfire burned 33 000 ha of Pinus halepensis and P. pinaster forest in 1979, and subsequent smaller wildfires took place between 1984 and 1996. The study was designed to sample the range of environmental and disturbance (fire recurrence and land use) conditions. The territory was classified into 17 different geomorphological and fire‐recurrence units. Vegetation cover and floristic composition were measured on a total of 113 plots (1000 m² each) randomly selected within these units. Results: The results show that 23 years after the fire the regenerated vegetation consists of successional shrublands, and that forest ecosystem resilience can be very low. The vegetation presents a strong correlation with most of the environmental variables, but fire (one or two fires), soil type and land use (in that order) are the main drivers of vegetation composition. Quercus coccifera shrublands persist on limestone soils while diverse types of other shrublands (dominated by seeder species) are found on marl soils. Conclusions: The results of this study indicate that disturbance factors strongly coupled to human activities, such as land use and fire, play a critical role in the current state of vegetation. Fire creates vegetation patches in different successional states while land use and soil type define the different types of shrubland in terms of their specific composition.     

Sources of Nitrogen in Combination with Systems of Irrigation Influence the Productivity of Modern Rice (<i>Oryza sativa</i> L.) Cultivars during Dry Season in Sub-Tropical Environment

In irrigated agricultural systems, nitrogen (N) and water are the vital resources for sustainability of the crop production in the modern era of climate change. The current study aimed to assess the impact of water and N management on the productivity of irrigated rice cultivars. In the context, a field observation was done at the research farm of Bangladesh Agricultural University, Mymensingh, during dry seasons in consecutive two years (2018–2019 and 2019–2020). The experiments were set up following split-plot design assigning water management in the main plots, nitrogen management in the sub-plots, and the cultivars were approved in the split-split plot with three replications. After two years observation, it was revealed that rice cultivar Binadhan-8 gave the maximum value of leaf area index, number effective tillers hill^-1 and grains panicle^-1 which lead to the higher grain yield (GY). Substantial relationships were observed among the concentration of N, growth, total dry matter (TDM) and N content, N uptake, N utilization effectiveness, and GY. However, with little exception, the Combined effect of water and N, cultivars and water management were varied significantly for all parameters. Finally, the results of the current study concluded that application of irrigation at 8 days after the disappearance of ponded water and source of 105 kg N ha^-1 from PU + Poultry manure are the best management approach for the excellent performance of rice cultivar Binadhan-8.     

不同饵料对匙吻鲟仔鱼生长发育和消化酶活性的影响

本文研究了不同强化饵料对匙吻鲟(Polyodon spathala)仔鱼生长和发育的影响,实验采用蛋黄或鱼油强化卤虫无节幼体或桡足幼体为饵料的共6个实验组,即未强化卤虫组、蛋黄强化卤虫组、鱼油强化卤虫组和未强化桡足幼体组、蛋黄强化桡足幼体组、鱼油强化桡足幼体组,对匙吻鲟仔鱼开口驯化14 d,动态监测和统计不同饵料组匙吻鲟仔鱼的生长和存活情况,并对消化酶活性进行相关性分析。体重、体长、日增重和存活率4个指标,均为桡足幼体组显著高于卤虫组(P0.05),尤其在存活率方面,鱼油强化卤虫组不足50%,而未强化桡足幼体组最高可达86.59%;不同饵料组生长模式方程都获得较好的拟合,从体重和体长生长曲线看,桡足幼体组从饲喂8天起体长和体重进入快速生长期,而卤虫组生长一直相对缓慢;胃蛋白酶活性在未强化桡足幼体组显著高于其他组(P0.05),不同饵料组对仔鱼的淀粉酶活性无显著性影响。结果表明,在匙吻鲟仔鱼开口期以桡足幼体开口饵料驯化效果较好,特别是未强化桡足幼体组仔鱼的存活率高,鱼油强化桡足幼体组仔鱼生长速度较快,而以卤虫饲喂效果相对较差。     

冷藏对美洲斑潜蝇蛹期发育和生存的影响

【目的】美洲斑潜蝇Liriomyza sativae Blanchard自20世纪90年代入侵我国后已经成为蔬菜和观赏植物的重要害虫。然而,近些年该昆虫已经逐渐成为研究植物和昆虫、昆虫抗寒性和寄主适应性等热点课题的模式种类。因此,为了实验室条件下更好保藏该虫的种群,本文研究了冷藏(世代发育起点温度8℃)对该斑潜蝇蛹发育和生存的影响。【方法】以化蛹后第3天的蛹为实验对象,8℃低温冷藏,并以冷藏时间(0、7、14、21、28和35 d)为参试因子研究了冷藏时间对美洲斑潜蝇蛹羽化率的影响;化蛹后每24 h解剖观察一次蛹并对蛹期发育阶段进行划分;根据划分的蛹期阶段,对处理中未羽化的蛹进行解剖比对,得到对低温最敏感的蛹期。【结果】随着冷藏时间的增长,美洲斑潜蝇的蛹羽化率逐渐降低。超过14 d后,羽化率明显下降。冷藏至35 d时羽化率为零。解剖正常发育的美洲斑潜蝇的蛹,将蛹期分为预蛹期、隐头蛹期、显头蛹初期、半透明眼期、浅黄色到琥珀色眼期、红褐色眼期、鬃毛蛹期。不同冷藏时间条件下,未羽化的蛹死亡时间主要为鬃毛蛹期,且鬃毛蛹期死亡的蛹的数量与贮藏时间呈正比例关系。【结论】在室内冷藏美洲斑潜蝇时,3日龄蛹8℃贮藏少于14 d为宜;鬃毛蛹期(10~11日龄蛹)对低温比较敏感,冷藏过程中,应避免鬃毛蛹期的蛹。     

季风常绿阔叶林不同恢复阶段群落优势物种的空间分布格局

运用相邻格子法及聚集度指标测定法,在植被调查的基础上,对云南普洱不同恢复阶段(恢复15a、30a和老龄林)季风常绿阔叶林的刺栲(Castanopsis hystrix)、短刺栲(Castanopsis echidnocarpa)和红木荷(Schima wallichii)3个优势物种进行种群空间分布格局研究,以阐明种群分布格局与生境条件、种群年龄结构的动态关系,揭示种群发育过程中空间动态与生物学机理。结果发现:在所有恢复阶段内,刺栲、短刺栲、红木荷均为聚集分布。在不同尺度下,刺栲在原始林中10m×10m尺度下为均匀分布,而在恢复15年中20m×20m尺度为随机分布;红木荷在10m×20m尺度下为均匀分布,在其它所有恢复阶段和尺度下3个物种均为聚集分布。研究结果表明,不同恢复阶段和不同尺度下刺栲、短刺栲和红木荷3个优势物种绝大多数为聚集分布,说明聚集分布为3个优势种的基本属性。     

Decimal growth stages for precision wheat production in changing environments?

The utility of the decimal growth stage (DGS) scoring system for cereals is reviewed. The DGS is the most widely used scale in academic and commercial applications because of its comprehensive coverage of cereal developmental stages, the ease of use and definition provided and adoption by official agencies. The DGS has demonstrable and established value in helping to optimise the timing of agronomic inputs, particularly with regard to plant growth regulators, herbicides, fungicides and soluble nitrogen fertilisers. In addition, the DGS is used to help parameterise crop models, and also in understanding the response and adaptation of crops to the environment. The value of the DGS for increasing precision relies on it indicating, to some degree, the various stages in the development of the stem apex and spike. Coincidence of specific growth stage scores with the transition of the apical meristem from a vegetative to a reproductive state, and also with the period of meiosis, is unreliable. Nonetheless, in pot experiments it is shown that the broad period of booting (DGS 41–49) appears adequate for covering the duration when the vulnerability of meiosis to drought and heat stress is exposed. Similarly, the duration of anthesis (61–69) is particularly susceptible to abiotic stresses: initially from a fertility perspective, but increasingly from a mean grain weight perspective as flowering progresses to DGS 69 and then milk development. These associations with DGS can have value at the crop level of organisation: for interpreting environmental effects, and in crop modelling. However, genetic, biochemical and physiological analysis to develop greater understanding of stress acclimation during the vegetative state, and tolerance at meiosis, does require more precision than DGS can provide. Similarly, individual floret analysis is needed to further understand the genetic basis of stress tolerance during anthesis.