滴灌系统网式和叠片式过滤器水力性能试验研究

滴灌系统过滤器的性能直接影响系统正常运行及使用寿命,以网式和叠片式过滤器为研究对象,进行了不同流量下清水和3种质量浓度浑水工况下,不同目数的2种过滤器水头损失和过滤性能试验,分析了过滤器水力性能的影响因素及其相互关系。结果表明,在清水条件下,过滤器的局部水头损失hj与流量Q成正比,随着系统过流量的增加而增加;相同流量下,高目数过滤器产生的水头损失大于低目数;浑水条件下,过滤器的水头损失与系统过流量、含沙量有关。随流量、含沙量的增大,过滤器初始水头损失增大,过滤周期变短。相同条件下,叠片式过滤器的水头损失明显大于网式过滤器,除沙率高于网式过滤器,即网式过滤器水力性能优于叠网式片过滤器,叠片过滤器的过滤效果优于网式过滤器。     

中棉所70分离群体农艺性状相关QTL定位

【目的】定位棉花产量相关性状的数量性状基因座(Quantitative trait locus,QTL)。【方法】以中棉所70的F_2分离群体为遗传作图群体,利用从14 820对简单序列重复(Simple sequence repeat,SSR)引物中筛选出的267对两亲本间的多态性引物检测F_2群体250个单株的标记基因型,利用Joinmap 4.0进行连锁分析,并通过WinQTLCart 2.5复合区间作图法对F_(2:3)群体的株高、单株结铃数和单株果枝数性状进行QTL定位。【结果】在F_2群体中共获得342个SSR标记位点,并构建了包括312个标记、35个连锁群,总长1 929.9 cM的遗传连锁图谱(标记间平均距离为9.2 cM,覆盖棉花基因组的43.4%)。经QTL定位,共检测到19个QTL,其中涉及株高的7个、单株果枝数4个、单株结铃数8个,这些QTL分布在8条染色体上,解释0.25%~11.28%的表型变异。【结论】这些与农艺性状相关的QTL有助于棉花产量分子标记辅助选择。     

Habitat alteration and habitat fragmentation differentially affect beta diversity of stream fish communities

Context

The cumulative impact of broad scale environmental change includes altered land-cover and fragmentation. Both altered land-cover and fragmentation have a negative effect on species diversity, but the scale they act on may differ because land-cover alters environmental characteristics, whereas fragmentation alters movement among sites.

Objectives

We evaluated the scale specific effects of land-cover, fragmentation, and habitat size on alpha and beta diversity (total, turnover, and nestedness).

Methods

Stream fish communities were sampled across five urbanizing watersheds. Generalized mixed linear models were used to test how diversity (alpha and beta) is affected by land-cover, connectivity, and habitat size. Indices of land-cover were calculated from correspondence analyses on land-cover data, fragmentation was estimated with the dendritic connectivity index, and habitat size was calculated as the length of the stream segment (alpha diversity) or the length of the stream network (beta diversity).

Results

Alpha diversity was most strongly related to land-cover variables associated with urban development and agriculture (negative relationship with urbanization). Whereas, beta diversity was most strongly influenced by habitat size (positive relationship) and fragmentation (positive relationship). Turnover was positively correlated with fragmentation and habitat size, whereas species loss was negatively correlated with habitat size.

Conclusions

Land-cover has a larger effect on alpha diversity because it alters the environmental conditions at a site, whereas fragmentation has a larger effect on beta diversity because it affects the movement of individuals among sites. Assessing the cumulative impact of environmental change requires a multiscale approach that simultaneously considers alpha and beta diversity.

     

桑寄生种子质量分级标准研究

以桑寄生种子为试材,采用相关指标测定和外观形态观测的方法,研究了桑寄生种子的百粒质量、含水量、发芽率、发芽势等指标,通过进一步的数据分析制定桑寄生种子的质量分级标准。结果表明:可将桑寄生种子的质量分为3级,一级品种纯度和净度为100%,发芽率不低于75.0%,水分不低于50.0%,百粒质量不低于60.0g;二级品种纯度和净度为100%,发芽率不低于70.0%,水分不低于40%,百粒质量不低于50.0g;三级品种纯度和净度为100%,发芽率不低于60.0%,水分小于40.0%,百粒质量小于50.0g。该方法制定出的桑寄生种子质量分级标准适用于桑寄生种子生产的质量控制。     

Physical,Predictive Glycaemic Response and Antioxidative Properties of Black Ear Mushroom (<Emphasis Type="Italic">Auricularia auricula</Emphasis>) Extrudates

Black ear mushroom (<em class="EmphasisTypeItalic ">Auricularia auriculaem>) is an important genus of cultivated mushroom, which contains health benefits. Incorporating black ear (BE) mushroom into brown rice by extrusion changed the physicochemical, and more importantly, the nutritional characteristics of the extrudates. With increased incorporation of BE mushroom in the extrudates <em class="EmphasisTypeItalic ">in vitroem> starch digestion of the different extrudates revealed significantly reduced starch digestion, suggesting a lower glycaemic index. In addition, incorporation of BE in brown rice extrudates increased the total phenolic concentration of the samples, which led to higher % scavenging effect against free-radicals in DPPH assay. In the ORAC assay for anti-oxidant activity, BE powder exhibited the highest anti-oxidant activity, followed by 10% BE and 15% BE, and 5% BE extruded products. The extruded brown rice control exhibited the lowest antioxidant activity. Inclusion of black ear mushroom was shown to improve the nutritional qualities of the food product illustrating the connection between plant bioactive ingredients and human health.     

The control of floating macrophytes by grass carp in net cages: experiments in two tropical hydroelectric reservoirs

The efficiency of grass carp (Ctenopharyngodon idella Val.) for biological control of floating aquatic macrophytes in net cages was assessed in two eutrophic tropical hydroelectric reservoirs through experiments using three macrophyte species (Eichhornia crassipes, Pistia stratiotes and Salvinia auriculata). A total of twenty experiments were performed in these reservoirs with a duration period between 21 and 30 days, during distinct seasons of the year. Sets of experiments were conducted using the three macrophyte species simultaneously in both reservoirs, and additional experiments were performed in one reservoir involving the separate use of each species. All macrophytes demonstrated significant growth in the absence of fish with total per day biomass increase rate ranging from 0.06 to 17.00%. The presence of grass carp significantly reduced macrophyte biomass in both reservoirs independent of fish size, stocking rate and available cage space. In all seasons, grass carp grazing pressure was higher for S. auriculata and lower for P. stratiotes. The results show that grass carp in net cages was able to use aquatic macrophytes as the only food source, controlling massive plant growth (especially S. auriculata and E. crassipes). Fish cages, already implemented in several reservoirs in Brazil, are easily manageable units at relatively low cost. Thus, biocontrol of macrophytes using caged grass carp is proposed as an effective low‐budget ecotechnological tool to control consumable plants while avoiding the removal of desirable aquatic vegetation and the resultant impact on local fauna.     

Variability in the solubility of agricultural limestone from different sources and its pertinence for aquaculture

Samples of agricultural limestone were obtained from quarries in the USA as follows: Talking Rock, GA; Whitestone, GA; Austinville, VA; Bonham, TX; and Thomasville, PA, referred as GA‐1, GA‐2, VA, TX and PA respectively. The limestone products were tested initially for non‐equilibrium pH, concentrations of calcium and magnesium, neutralizing value (NV) and fineness rate. Laboratory solubility test of the products was conducted in which pH, specific conductance (SC), total alkalinity (TA), total and calcium hardness were measured weekly for 9 weeks. It was found that the agricultural limestone samples had comparable chemical compositions, that is NV (97–108%), Ca (19.8–32.1%), Mg (3.2–12.2%), pH of slurry (8.1–9.7), but somewhat different solubilities in water. Total alkalinity concentrations at equilibrium ranged from 30 to 60 mg L^?1. It was possible to quickly estimate the relative solubility of different agricultural limestone samples by comparing their specific conductance under standardized conditions (2.0 g samples w/0.15–0.25 mm fineness; 3.5 L distilled water; 24 h). This procedure might be helpful in achieving better results when liming aquaculture ponds, that is choosing the agricultural limestones with the highest solubilities in water.     

咯菌腈与戊唑醇复配对小麦赤霉病菌的增效作用研究

研究旨在明确咯菌腈和戊唑醇复配剂抑制小麦赤霉病菌菌丝生长的最佳药剂配比.采用菌丝生长速率法测定了咯菌腈、戊唑醇及其复配剂对小麦赤霉病菌的有效抑制中浓度(EC50).采用wadley的增效比率法,评价了复配剂的增效作用.结果 显示,咯菌腈和戊唑醇对小麦赤霉病菌的EC50值分别为0.0205 μg/mL和0.1704 μg...     

Effect of sucrose on the thermomechanical behavior of concentrated wheat and waxy corn starch-water preparations

The rheological behavior of concentrated starch preparations from two different origins (wheat and waxy corn) was studied in the presence of sucrose by dynamic mechanical thermal analysis (DMTA). Moisture contents ranged from 30 to 60% (w/w wsb), and samples contained 0, 10, or 20 g of sucrose for 100 g of the starch-water mixture. The storage modulus (G') changes during heating depended strongly on water content (in the moisture range studied), and the importance of these variations was dependent upon the starch type. Sucrose addition resulted in a shift to higher temperatures of the increase in G' during heating. Differential scanning calorimetry (DSC) and electron-spin resonance (ESR) analyses were performed in parallel in order to relate the viscoelastic changes to water migrations and to structural disorganization of starch. Sucrose was found to increase the gelatinization temperature and enthalpy of both starches, implying a stabilization of the granular structure during heating. The sugar-water interactions do not appear to be the only way by which sucrose delays starch gelatinization. The obtained results suggest that sugar-starch interactions in the amorphous and/or the crystalline regions of the starch granules should be envisaged.     

A comparison between seasonal changes in soil water storage and penetration resistance under conventional and conservation tillage systems in Aragón

Low and extremely variable precipitations limit dryland crop production in the semi-arid areas of Aragón (NE Spain). These areas are also affected by high annual rates of topsoil losses by both wind and water erosion. A long-term experiment to determine the feasibility of conservation tillage in the main winter barley production areas of Aragón was initiated in 1989 at four locations, three on loam to silt loam soils (Xerollic Calciorthid) and one on a silty clay loam (Fluventic Ustochrept), receiving between 300 and 600 mm of average annual rainfall. In this study, we compared, under both continuous cropping and cereal-fallow rotation, the effects of conventional tillage (mouldboard plough) and two conservation tillage systems, reduced tillage (chisel plough) and no-tillage, on soil water content and penetration resistance during the first two growing seasons. Whereas reduced and conventionally tilled treatments generally had similar soil water content during the experimental period, the effects of no-tillage were inconsistent. No-tilled plots had from 26% less to 17% more stored soil water (0–80 cm) than conventional tilled plots at the beginning of the growing season. In contrast to the conventional and reduced tillage treatments, penetration resistances were between 2 and 4 MPa after sowing in most of the plough layer (0–40 cm) under no-tillage at all sites. Fallow efficiencies in moisture storage in the cereal-fallow rotation, when compared with the continuous cropping system, ranged from −8.7 to 12%. The highest efficiencies were recorded when the rainfall in the months close to primary tillage exceeded 100 mm. Since this event is very unlikely, long fallowing (9–10 months) appears to be an inefficient practice for water conservation under both conventional and conservation management. Our results suggest that, up to now, only reduced tillage could replace conventional tillage without adverse effects on soil water content and penetration resistance in the dryland cereal-growing areas of Aragón.