The effect of phenyl phosphorodiamidate on urease activity and ammonia volatilization in flooded rice

Summary The behaviour of urease activity, ammoniacal N concentrations and pH in flood water and that of ammonia flux was investigated in a water-logged soil either in the presence or in the absence of rice and with three different treatments (control, urea and urea + phenyl phosphorodiamidate). In the presence of the phenyl phosphorodiamidate (PPD), that is a urease inhibitor, increases in ammoniacal N concentrations and in ammonia evolution were delayed but not eliminated. The degradation and/or the inactivation of PPD might have occurred, thus removing the inhibition of the enzyme activity.     

基于不同方法测定土壤酸性磷酸酶活性的比较

土壤酸性磷酸酶与有机磷的矿化及植物的磷素营养关系最为密切。目前国内学者在测定酸性磷酸酶活性时主要参照关松荫《土壤酶及其研究法》中以磷酸苯二钠为基质的测定方法,而国外学者主要参照Dick《Methods of Soil Enzymology》中以对硝基苯磷酸二钠为基质的测定方法(PNPP)。但是,在以磷酸苯二钠为基质测定生成物的过程中,常出现显色程度不明显的问题;另外,采用不同基质测定酸性磷酸酶活性也造成了测定方法选择的困难。为合理选择土壤酸性磷酸酶活性的测定方法,本研究选用酸性、中性和碱性土壤各10个土样,分别采用以磷酸苯二钠为基质,且在显色阶段分别加入pH5.0醋酸盐缓冲液(DPP 1)和pH9.4硼酸盐缓冲液(DPP 2)的方法,以及PNPP方法测定土壤酸性磷酸酶活性。同时也研究了不同pH缓冲液和苯酚浓度对生成物显色反应的影响。结果表明:以磷酸苯二钠为基质、在显色反应阶段加入pH≤6的缓冲液时,苯酚和2,6-二溴苯醌氯亚胺不显色;当加入pH≥8的缓冲液时,两者之间显色且苯酚浓度和吸光值的Pearson相关系数极显著。这说明pH低是导致高苯酚浓度和2,6-二溴苯醌氯亚胺显色效果差的一个主要原因。此外,采用PNPP方法测定时,在酸性、中性和碱性土壤中,10个样本酸性磷酸酶活性的变异系数分别较DPP 2增加了70.04%、42.44%和21.17%;极差分别是DPP 2的27.18倍、26.85倍和39.43倍。总之,如果选用磷酸苯二钠为基质测定土壤酸性磷酸酶活性,应在显色阶段加入碱性硼酸盐缓冲液;选用对硝基苯磷酸二钠为基质,是更为简单和灵敏的方法。     

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

Summary A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with ¹⁵N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH₃ volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.     

苯乙醇相关化合物嗅香相似性的评定

建立了一种用于单体化合物嗅香相似性评价的方法，并借助该方法对苯乙醇相关化合物与苯乙醇嗅香的相似性进行了定性定量评价，所获得的评价结果与化合物结构的特征存在明显的相关性。该方法可作为香味物质定量构一香关系研究中香味物质定量评价的方法，用于化合物嗅香定量数据的获取。     

靶标酶在研究杀虫活性构效关系中的应用

运用已建立的乙酰胆碱酯酶(AChE) 活力分析规范化筛选模型, 研究N-甲基取代苯基氨基甲酸酯类化合物和含硅氨基甲酸酯类新系列化合物与AChE 酶抑制中量( I50)构效关系的规律, 并以CA SAR 软件进行Q SAR 分析, 所得结果迅速反馈给化学合成, 为高效低毒新杀虫剂的创制提供有益的信息和科学依据。     

Comparative effects of pesticides,fenitrothion and fipronil,applied as ultra-low volume formulations for locust control,on non-target invertebrate assemblages in Mitchell grass plains of south-west Queensland,Australia

The effect of an aerial application of two broad-spectrum insecticides, the organophosphorus compound, fenitrothion, and the phenyl pyrazole pesticide, fipronil, on non-target invertebrates was investigated during Australian plague locust (Chortoicetes terminifera, (Walker, 1870)) control operations on a Mitchell grass (Astrebla spp.) plain in south-western Queensland, Australia, between 2002 and 2004. The invertebrate assemblages were monitored using yellow pan and Malaise traps to target flying invertebrates and pitfall traps to target ground-dwelling invertebrates, sampled immediately before spraying and then at 3, 7, 39, 79, 189 and 414 days after spraying. Both pesticides caused significant changes to invertebrate community composition immediately after spraying, largely due to changes in the abundance of Orthoptera, Collembola and Formicidae. The richness and abundance of invertebrates in Malaise and yellow pan traps did not differ significantly with pesticide application although significant changes in assemblage composition persisted for up to 79 days. Although not statistically significant, the richness and abundance of invertebrates in pitfall traps declined at sprayed sites after treatment, relative to controls. Assemblage composition in pitfall traps at sprayed sites was significantly different from that in the control sites and these differences persisted for up to 189 days post-spray. Prolonged drought across the study site is likely to have affected the recovery of invertebrate populations and a return to pre-spray abundances did not occur until after heavy rain fell approximately one year after the commencement of the study. The controlling influence of climatic conditions on recovery of non-target arthropod populations after exposure to pesticides therefore has implications for risk assessments for the use of pesticides in arid environments.     

肉桂醛选择性氢化反应研究

以ＲａｎｅｙＮｉ为催化剂,在不同条件下实现肉桂醛的选择性氢化反应,制备３－苯丙醛、γ－苯丙醇和３－环己基－１丙醇,研究了影响氢化反应选择性的不同因素。