普通小麦和华山新麦草及其属间杂种F_1同工酶分析

用聚丙烯酰胺凝胶电泳法对普通小麦和华山新麦草及其属间杂种 F_1的三叶期叶片、拔节期叶片、剑叶、幼穗和幼根进行了酯酶同工酶分析。结果表明,不同器官及同一器官的不同发育时期酯酶同工酶酶谱表型有明显差异。普通小麦和华山新麦草就同一器官、同一发育时期相比,酶谱差异较大,佐证了普通小麦和华山新麦草间亲缘关系较远。     

驱动圆盘刀切断玉米秸秆和根茬的土槽试验

通过动力驱动的平圆盘和缺口圆盘切断玉米秸秆和根茬的土槽试验研究表明，随着刀轴转速和机器前进速度增加驱动圆盘刀功率消耗随之增加。当刀轴转速为350r／min、机器前进速度为0．65m／s时，在有秸秆和根茬土壤地表上缺口圆盘刀消耗的功率是平圆盘刀的45％。当刀轴转速大于350r／min即圆盘圆周速度大于7．4m／s时，缺口圆盘刀秸秆切断率和根茬切断率达到97％以上。     

Soil compaction and forest floor removal reduced microbial biomass and enzyme activities in a boreal aspen forest soil

Soil enzymes are linked to microbial functions and nutrient cycling in forest ecosystems and are considered sensitive to soil disturbances. We investigated the effects of severe soil compaction and whole-tree harvesting plus forest floor removal (referred to as FFR below, compared with stem-only harvesting) on available N, microbial biomass C (MBC), microbial biomass N (MBN), and microbial biomass P (MBP), and dehydrogenase, protease, and phosphatase activities in the forest floor and 0–10 cm mineral soil in a boreal aspen (Populus tremuloides Michx.) forest soil near Dawson Creek, British Columbia, Canada. In the forest floor, no soil compaction effects were observed for any of the soil microbial or enzyme activity parameters measured. In the mineral soil, compaction reduced available N, MBP, and acid phosphatase by 53, 47, and 48%, respectively, when forest floor was intact, and protease and alkaline phosphatase activities by 28 and 27%, respectively, regardless of FFR. Forest floor removal reduced available P, MBC, MBN, and protease and alkaline phosphatase activities by 38, 46, 49, 25, and 45%, respectively, regardless of soil compaction, and available N, MBP, and acid phosphatase activity by 52, 50, and 39%, respectively, in the noncompacted soil. Neither soil compaction nor FFR affected dehydrogenase activities. Reductions in microbial biomass and protease and phosphatase activities after compaction and FFR likely led to the reduced N and P availabilities in the soil. Our results indicate that microbial biomass and enzyme activities were sensitive to soil compaction and FFR and that such disturbances had negative consequences for forest soil N and P cycling and fertility.     

Influence of non-cellulose structural carbohydrate composition on plant material decomposition in soil

The C mineralisation pattern during the early stage of decomposition of plant materials is largely determined by their content of different carbohydrates. This study investigated whether detailed plant analysis could provide a better prediction of C mineralisation during decomposition than proximate analysis [neutral detergent solution (NDF)/acid detergent solution (ADF)]. The detailed analysis included sugars, fructans, starch, pectin, cellulose, lignin and organic N. To determine whether differences in decomposition rate were related to differences in hemicellulose composition, the analysis particularly emphasised the concentrations of arabinose and xylose in hemicelluloses. Carbon dioxide evolution was monitored hourly in soil amended with ten different plant materials. Principal component and regression analysis showed that C mineralisation during day 1 was closely related to free sugars, fructans and soluble organic N components (R ² = 0.83). The sum of non-cellulose structural carbohydrates (intermediate NDF/ADF fraction) was not related to C mineralisation between days 1 and 9. In contrast, a model including starch and protein in addition to the non-cellulose structural carbohydrates, with the hemicelluloses replaced by arabinose and xylose, showed a strong relationship with evolved CO₂ (R ² = 0.87). Carbon mineralisation between days 9 and 34 was better explained by xylan, cellulose and lignin (R ² = 0.72) than by lignocellulose in the ADF fraction. Our results indicated that proximate analyses were not sufficient to explain differences in decomposition. To predict C mineralisation from the range of plant materials studied, we propose a minimum set of analyses comprising total N, free sugars, starch, arabinose, xylan, cellulose and lignin.     

汇率预测的理论与方法及其最新进展

总结了众多国内外学者在汇率预测方面的理论及其研究方法。通过对传统的统计方法与非参数方法的比较分析,得出结论:大多数传统的时间序列模型是线性的,不能抓住非线性时间序列数据的内在特征。而相对于传统的预测模型而言,非参数方法能发现观察结果和输入数据的关系,不需要事先确定模型,其拟合结果能更好的捕捉汇率的动态特征与走势。     

Leaching characteristics of homologues of benzalkonium chloride from wood treated with ammoniacal copper quaternary wood preservative

In Japan, ammoniacal copper quaternary wood preservatives type-1 (ACQ-1), which contains copper and benzalkonium chloride as its active ingredients, is among the most widely used wood preservatives in the pressure treatment of wood. Benzalkonium chloride (BAC) in commercial ACQ-1 products mainly comprises C12 and C14 homologues. In the present study, the leaching characteristics of these BAC homologues were investigated using the heartwood and sapwood portions of Japanese cedar, Japanese larch, and Sakhalin fir treated with ACQ-1 and 1% monoethanolamine (MEA) solution containing equimolar amounts of homologues. Distilled water (DW) and artificial seawater (SW) were used as leaching media. Consequently, it was observed that the leaching rate of the C12 homologue tended to be higher than that of the C14 homologue in DW. The leaching of C12 homologues was accelerated by using SW, resulting in a significantly higher leaching rate than the C14 homologue using SW. It was thought that the difference in the hydrophobicities based on alkyl chain lengths resulted in these phenomena. However, when the heartwood portion of Japanese larch was treated with the homologues in MEA, the leaching rate of the C14 homologue was significantly higher than that of the C12 homologue.     

云南箭竹不同地理种源竹笋营养成分之比较

对不同地理种源的云南箭竹竹笋的营养成分进行测定、比较．结果发现：影响竹笋风味的营养物质如总糖、天冬氨酸、谷氨酸以及甘氨酸等物质的含量,白马河林场和鸡足山的云南箭竹笋均高于西山的云南箭竹笋。因此这两地比西山更适合作为云南箭竹笋用竹的种源地。而这两地当中则以白马河林场的云南箭竹笋为最。     

农业科技信息传播对农业发展的促进作用及其发展趋势

介绍了农业科技信息传播在促进农业技术推广和农业发展中的重要作用,指出了当前农业科技信息传播的主要途径和存在问题。认为农业科技信息传播有四大发展趋势：农业科技信息量大幅度增加,更加精准;各种渠道的农业科技信息传播能力将大大增强;农民素质提高将使农业科技信息刺用率提高;网络信息平台将会得到较好利用。     

Water absorption of boron-treated and heat-modified wood

Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic properties of BA and DOT.     

多指标优化提取地榆有效成分工艺研究

采用加热回流方法提取地榆中的有效成分,分别以地榆中黄酮、皂苷和鞣质提取率为指标,考察同时提取这三种成分的影响因素（乙醇浓度、溶剂倍量、提取时间、提取温度和粒径）和最佳提取条件。结果表明,以60%乙醇为溶剂,药材粉碎粒径为20～40目,溶剂倍量为60,80℃下浸提1.5h的条件下提取效果最佳,在此条件下能够最好的兼顾三种有效成分的综合提取效率。