Acquisition and assimilation of gaseous ammonia as revealed by intracellular pH changes in leaves of higher plants

Atmospheric ammonia (NH₃) from various anthropogenic sources has become a serious problem for natural vegetation. Ammonia not only causes changes in plant nitrogen metabolism, but also affects the acid-base balance of plants. Using the pH-sensitive fluorescent dyes pyranine and esculin, cytosolic and vacuolar pH changes were measured in leaves of C₃ and C₄ plants exposed for brief periods to concentrations of NH₃ in air ranging from 1.33 to 8.29 mol NH₃ · mol^-1 gas (0.94–5.86 mg · m^-3). After a lag phase, uptake of NH₃ from air at a rate of 200 nmol NH₃ · m ^{- 2} leaf area · s^{- 1} into leaves of Zea mays L. increased pyranine fluorescence indicating cytosolic alkalinisation. The increase was much larger in the dark than in the light. In illuminated leaves of the C₃ plant Pelargonium zonale L. and the C₄ plants Z. mays and Amaranthus caudatus L., NH₃-dependent cytosolic alkalinisation was particularly pronounced when CO₂ was supplied at very low levels (16 or 20 mol CO₂ · mol^{- 1} gas, containing 210 mmol O₂ · mol^{- 1} gas). An increase in esculin fluorescence, which was smaller than that of pyranine, was indicative of trapping of some of the NH₃ in the vacuoles of leaves of Spinacia oleracea L. and Z. mays. Photosynthesis and transpiration remained unchanged during exposure of illuminated leaves to NH₃, yielding an influx of 200 nmol NH₃ · m^-2 leaf area · s^-1 for up to 30 min, the longest exposure time used. Both CO₂ and O₂ influenced the extent of cytosolic alkalinisation. At 500 mol CO₂ · mol^-1 gas the cytosolic alkalinisation was suppressed more than at 16 or 20 mol CO₂ · mol^-1 gas. The suppressing effect of CO₂ on the NH₃induced alkalinisation was larger in illuminated leaves of the C₄ plants Z. mays and A. caudatus than in leaves of the C₃ plant P. zonale. A reduction of the O₂ concentration from 210 to 10 mmol O₂ · mol ^-1 gas, which inhibits photorespiration, increased the NH₃induced cytosolic alkalinisation in C₃ plants. Suppression by CO₂ or O₂ of the alkaline pH shift caused by the dissolution and protonation of NH₃ in queous leaf compartments, and possibly by the production of organic compounds synthesised from atmospheric NH₃, indicates that NH₃ which enters leaves is rapidly assimilated if photosynthesis or photorespiration provide nitrogen acceptor molecules.This work was supported by the Biotechnology and Biological Sciences Research Council and the Deutsche Forschungsgemein-schaft within the framework of the research of Sonderforschun-gsbreich 251 of the University of Würzburg. We are grateful to Dr. B. Wollenweber (The Royal Veterinary and Agricultural University, Denmark) for discussions.     

The structure of d(TpA), the major photoproduct of thymidylyl-(3'5')-deoxyadenosine.

Irradiation of the dinucleotide TpdA and TA-containing oligonucleotides and DNA produces the TA* photoproduct which was proposed to be the [2+2] cyclo-addition adduct between the C5-C6 double bonds of the T and the A [Bose,S.N., Kumar,S., Davies,R.J.H., Sethi,S.K. and McCloskey,J.A. (1984) Nucleic Acids Res. 12, 7929-7947]. The proposed structure was based on a variety of spectroscopic and chemical degradation studies, and the assignment of a trans-syn-I stereochemistry was based on an extensive 1H-NMR and molecular modeling study of the dinucleotide adduct [Koning,T.M.G., Davies,R.J.H. and Kaptein,R. (1990) Nucleic Acids Res. 18, 277-284]. However, a number of properties of TA* are not in accord with the originally proposed structure, and prompted a re-evaluation of the structure. To assign the 13C spectrum and establish the bond connectivities of the TA* photoproduct of TpdA [d(TpA)*], 1H-13C heteronuclear multiple-quantum coherence (HMQC) and heteronuclear multiple bond correlation (HMBC) spectra were obtained. The 13C shifts and connectivities were found to be inconsistent with the originally proposed cyclobutane ring fusion between the thymine and adenine, but could be explained by a subsequent ring-expansion reaction to give an eight-membered ring valence isomer. The new structure for the d(TpA)* resolves the inconsistencies with the originally proposed structure, and could have a stereochemistry that arises from the anti, anti glycosyl conformation found in B form DNA.     

自养黄杆菌合成羟基丁酸和羟基戊酸共聚体的发酵研究

采用本实验室从土壤中分离到的一株自养黄杆菌进行了羟基丁酸和羟基戊酸共聚体〔P(HB-co-HV)〕的发酵试验。实验结果表明,该菌株是自养黄杆菌葡萄糖运输突变株,可以葡萄糖、果糖、蔗糖、麦芽糖、乙酸盐、乳酸盐和苹果酸盐作为唯一碳源,尤以葡萄糖和果糖效果最佳。硫酸铵、氯化铵和蛋白胨等不同氮源不影响其生长,却影响细胞中P(HB-co-HV)的含量和P(HB-co-HV)中HV/HB的比例。应用两阶段控制方式,经42h的补料分批发酵,细胞浓度达34.9g·L~(-1),P(HB-co-HV)浓度达25.28g·L~(-1)。细胞和P(HB-co-HV)生产速率系数分别为0.83g·L~(-1)”·h~(-1)和0.61g·L~(-1)·h~(-1)。以基质为基准的细胞得率系数(Yx/s)、产物得率系数(Yp/s)和以干细胞为基准的产物得率系数(Yp/x)分别为0.283(g/g)、0.174(g/g)和0.73(g/g)。改变培养基中碳氮源组分可将P(HB-co-HV)中HB的含量调节在24％～78％之间。     

Genomic Analysis of a New Mammalian Distal-less Gene: Dlx7

We have cloned a new Dlx gene (Dlx7) from human and mouse that may represent the mammalian orthologue of the newt geneNvHBox-5.The homeodomains of these genes are highly similar to all other vertebrate Dlx genes, and regions of similarity also exist between mammalian Dlx7 and a subset of vertebrate Dlx genes downstream of the homeodomain. The sequence divergence between human and mouse Dlx7 in these regions is greater than that predicted from comparisons of other vertebrate Dlx genes, however, and there is little sequence similarity upstream of the homeodomain both between these two genes and with other Dlx genes. We present evidence for alternative splicing of mouseDlx7upstream of the homeodomain that may account for some of this divergence. We have mapped humanDLX7distal to the 5′ end of the HOXB cluster at an estimated distance of between 1 and 2 Mb by FISH. Both the human and the mouse Dlx7 are shown to be closely linked to Dlx3 in a convergently transcribed orientation. These mapping results support the possibility that vertebrate distal-less genes have been duplicated in concert with the Hox clusters.     

鹅掌楸属植物的多糖壁前体和花粉管的生长

本文观察描述了中国鹅掌楸（Ｌｉｒｉｏｄｅｎｄｒｏｎｃｈｉｎｅｎｓｅ）和北美鹅掌楸（Ｌ．ｔｕｌｉｐｉｆｅｒａ）花粉在异已柱头萌发和花粉管生长期间多糖壁前体的发生、形态结构和生理功能．１、多糖壁前体在形态上有Ｐ－粒子（Ｐｏｌｙｓａｃｃｈａｒｉｄｅｐａｒｔｉｃｌｅｓ）,被膜小泡（ｃｏａｔｅｄｖｅｓｉｃｌｅ）和小泡（ｖｅｓｉｃｌｅ）三种。２、Ｐ－粒子于单核花粉期已经发生,至花粉管延伸期为发生高峰。多糖壁前体是在高尔基体,内质网和线粒体的相继、连续作用下,由淀粉质体、蛋白体和脂滴降解形成．３、Ｐ－粒子的形态随不同发育时期而变化,早期为成群的电子透明小泡,或为蛋白质束缚的挤压成多面体形,后期为内含颗粒或微纤丝的无被膜粒子或具刺被膜粒子。４、Ｐ－粒子移至管端．或融合或单个通过周质内质网（ＣＥＲ）,释放内容物参与管端壁的形成,被膜小池和小泡移至花粉管次顶端区向质膜外分泌,参与花粉管壁内层的形成,或移至管端,提供膜片。最后讨论了亲和性与超微结构特征的关系．     

不同施肥杨树主要营养元素内外循环比较研究 Ⅱ．施肥对落叶前后杨树叶片营养元素浓度及贮量的影响

杨树叶片在凋落前将大量有机质输入干、枝、根中,在不同处理中,不施肥输出的比例大于施肥．施Ｐ并不导致杨树对Ｐ的奢侈吸收．施肥可使杨树主要营养元素的外循环通量高于不施肥．不施肥杨树叶片在凋落前Ｐ、Ｋ的输出率比施肥高约１０％．     

地膜条件下土壤生态因子与玉米产量的关系

研究干旱地区地膜条件下,土壤生态因子对玉米产量的影响．结果表明,最佳种植模式为作物距地膜中心线２１．３—３３．２Ｃｍ,施纯Ｎ＋Ｐ为５９８—７４３ｋｇ·ｈａ－１,玉米产量为１４４９２≤Ｙ佳≤１６５９ｋｇ·ｈ－１．该种植模式有利于提高作物产量及残膜回收．     

长白山劲松林场植物群落的分类和排序

将长白山白河林业局劲松林场的５４块样地用聚类分析法划分成６个植被类群,再用ＰＣ－ＶＴＡＢ程序中经过改进的Ｂｒａｕｎ－Ｂｌａｎｑｕｅｔ学派的植被排表分析法进行综合,产生了鉴别概要表,为各个等级的植被类群筛选出诊断种。此外,还用鉴别种地样地记录进行主成分分析,以验证诊断种的有效性,结果表明,ＰＣ－ＶＴＡＢ中的植被排表分析法是筛选鉴别种的有效方法,而鉴别种以显著地提高植被分析和排序的质量。     

复方克痛宁临床应用镇痛效果

应用复方克痛宁注射液,治疗各种痛证８２例,显效５０％,有效４３．９％,总有效率９３．９％。其中大多数病例都是经用其它药或疗法无效或效差而用本药获效的。对关节痛、神经血管性头痛等顽固性疼痛显著独特。用药次数最少１次,最多３５例,仅极个别有轻微短暂口干、头晕副作用,各项常规化验检查均无异常,效果显著高于克痛宁或盐酸平痛新单用。临床应用的结果与动物试验观察到的协同增效结果一致。     

草鱼出血病病毒多肽的免疫原性

采用中和试验比较了草鱼出血病病毒ＧＣＨＶ８７３的１１个多肽的免疫原性,确定了主要中和抗原。纯化的单个病毒多肽免疫家兔获得抗血清,多太ＶＰ１、ＶＰ５、ＶＰ６和ＶＰ９的抗血清具有中和效价,而ＶＰ２、ＶＰ３、ＶＰ４、ＶＰ８、ＶＰ１０和ＶＰ１１则不能诱生中和抗体。其中ＶＰ５的抗血清中和效价最高,因此,ＶＰ６极可能是病毒多肽中的主要中和抗原。