A homonuclear molecule with a permanent electric dipole moment

Permanent electric dipole moments in molecules require a breaking of parity symmetry. Conventionally, this symmetry breaking relies on the presence of heteronuclear constituents. We report the observation of a permanent electric dipole moment in a homonuclear molecule in which the binding is based on asymmetric electronic excitation between the atoms. These exotic molecules consist of a ground-state rubidium (Rb) atom bound inside a second Rb atom electronically excited to a high-lying Rydberg state. Detailed calculations predict appreciable dipole moments on the order of 1 Debye, in excellent agreement with the observations.     

裂叶牵牛花色变异株后代的表型分析

以花色变异的裂叶牵牛的15株自交后代为材料,对其植物学性状、花冠性状、花粉育性、花粉纹饰及结实性进行了表型分析。结果表明：15株后代植株生长较慢,藤蔓右旋、节间变短、攀缘能力差;每叶腋间着生1个花蕾,偶有2个同时着生。15株观察后代都开有蓝色和蓝白相间的花冠,在400多朵蓝白相间的牵牛花中,没有完全相同的花纹。在蓝自相间的花朵中有部分雄蕊出现瓣化现象,花粉观察表明雄蕊瓣化的花粉育性严重下降。蒴果和种子调查表明,雌蕊的育性并未降低,但电镜扫描观察发现,两者的表面性状(如纹饰)无差异,这种现象有待进一步研究。     

Ameliorating Nickel Stress by Jasmonic Acid Treatment in <Emphasis Type="Italic">Zea mays</Emphasis> L.

Plants need various micro and macronutrients for their growth and metabolism. Of these nickel (Ni) plays a role of micronutrient but causes adverse effects when present above optimum level. To combat such situations plants possess different growth regulators. Jasmonates are a class of plant growth regulators modulating various growth and physiological responses in plants. Aiming to evaluate the effect of nickel and jasmonic acid on growth and antioxidant enzymes Superoxide distmutase (SOD), Catalse (CAT), Ascorbate peroxidase (APX), Guaiacol peroxidase (GPX) and glutathione reductase (GR), seeds of Zea mays L. were sown in field after giving presowing treatment of NiSO₄ · 6H₂O (8 mM), jasmonic acid JA (10^–6, 10^–8 and 10^–10 M) alone and JA (10^–6, 10^–8 and 10^–10 M) in 1: 1 combination with NiSO₄ · 6H₂O (8 mM) in plant conservatory, Punjabi University, Patiala, Punjab, India. Plants of each treatment group were then subjected to spraying treatment with the respective treatment solutions at regular intervals of 22 days up to 66 days after sowing (DAS). The present findings signified reduced growth with Ni treatment but co-application of JA alleviated the effect of nickel through activity of antioxidant enzymes.     

Biomolecular relationships among isolates of<Emphasis Type="Italic">Tomato Yellow Leaf Curl Tanzania Virus</Emphasis>

An investigation of the biological properties of the virus causing tomato yellow leaf curl disease in Tanzania was initiated to compare it with other known tomato yellow leaf curl viruses. Properties relating to acquisition and inoculation feeding time, persistence, mechanical inoculation, seed transmission and host range were studied. Results obtained indicate that the virus was transmitted persistently byBemisia tabaci Genn., but it was not mechanically, sap- or seed-transmissible. Minimum acquisition and inoculation feeding time was 30 min.Capsicum annuum, Datura stramonium, Nicotiana glutinosa, N. tabacum andLycopersicon esculentum were found to be hosts of the virus among the plant species tested, whereasPhaseolus vulgaris was not. It is concluded that the properties of the agent causing yellow leaf curl symptoms in tomato plants from different regions in Tanzania are similar to those ofTomato yellow leaf curl Sardinia virus species studied elsewhere. http://www.phytoparasitica.org posting Feb. 20, 2003.     

<Emphasis Type="Italic">p</Emphasis>-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.     

Assessment of Genetic Diversity in Upland Cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L.) Breeding Lines by using Amplified Fragment Length Polymorphism (AFLP) Markers and Morphological Characteristics

Genetic diversity in 24 advanced breeding lines of cotton was studied by using six amplified fragment length polymorphism (AFLP) primer-pairs and 14 morphological characters. The six selected AFLP primer-pairs generated a total of 535 amplification products, of which 460 were found to be polymorphic resulting in 85.9% polymorphism. The observed genetic distances using AFLP markers ranged from 30% to 87% with an average of 34%. A wide range of variability was observed for all the morphological traits studied. The range in taxonomic distance was from 0.60 to 2.77. Most of the lines could be clustered in two major clusters in both the analyses. But the correlation coefficient between the pair-wise distances estimated from AFLPs and the average taxonomic distances estimated from morphological characters was found to be 0.04. UPGMA cluster analysis revealed inconsistencies in the clustering patterns, as the co-phenetic correlation coefficient between the dendrograms for morphological and AFLP data indicated a poor fit for the two data types. From combined information, genotypes ‘RST-12’, ‘H 1226’, ‘P 348’, ‘KDCAKD’, ‘CISV 24’ and ‘H1222’ were found to be distinct from rest of the material.     

紫杆柽柳cDNA文库构建与硫氧还蛋白基因的克隆

以NaHCO3胁迫的紫杆柽柳(Tamarixandrossowii)为材料建立了cDNA文库。经检测,文库的初始滴度为5.7×105pfu,重组率为96%,插入片段的长度在0.3~3.0kb之间,平均长度为1.2kb,扩增后文库的滴度为4.0×109pfu/ml。对文库克隆进行随机测序,获得了紫杆柽柳的硫氧还蛋白(Thioredoxin)基因序列。生物信息学分析表明获得的硫氧还蛋白基因全长683bp,其中5'非翻译区长56bp,3'非翻译区长204bp,开放读码框长423bp,编码140个氨基酸,蛋白的分子量为15.1kD,理论等电点为5.59,其氨基酸序列中具有硫氧还蛋白的保守活性位点“WCGPC”序列,Clustal分析表明该硫氧还蛋白与蓖麻(Ricinuscommunis)的硫氧还蛋白氨基酸序列同源性高,达65%。本研究构建的cDNA文库为柽柳基因克隆和系统研究柽柳抗逆分子机理奠定了基础。     

土壤有机碳动态模型的研究进展

As the largest pool of terrestrial organic carbon, soils interact strongly with atmosphere composition, climate, and land change. Soil organic carbon dynamics in ecosystem plays a great role in global carbon cycle and global change. With development of mathematical models that simulate changes in soil organic carbon, there have been considerable advances in understanding soil organic carbon dynamics. This paper mainly reviewed the composition of soil organic matter and its influenced factors, and recommended some soil organic matter models worldwide. Based on the analyses of the developed results at home and abroad, it is suggested that future soil organic matter models should be developed toward based-process models, and not always empirical ones. The models are able to reveal their interaction between soil carbon systems, climate and land cover by technique and methods of GIS (Geographical Information System) and RS (Remote Sensing). These models should be developed at a global scale, in dynamically describing the spatial and temporal changes of soil organic matter cycle. Meanwhile, the further researches on models should be strengthen for providing theory basis and foundation in making policy of green house gas emission in China.     

龙牙百合的植株再生与遗传转化

以龙牙百合鳞片叶切块为外植体,通过多种培养基的比较试验,得出MS 2,4-D 2mg／L 6-BA 0．2mg／L是诱导愈伤的最佳培养基,MS 6-BA 1mg／L NAA 0．05mg／L是不定芽诱导及伸长的适宜培养基。MS N_AA2mg／L是生根的最佳培养基。本试验已建立了适用于龙牙百合遗传转化的快速高频再生系统。用携带有几丁质酶基因和β—1、3葡聚糖酶基因的工程菌,通过农杆菌介导法和基因枪转化法转化龙牙百合,经PCR和点杂交检测证明外源基因已经整合到植物染色体中。同时对农杆菌介导法和基因枪法进行比较,发现农杆菌介导法的转化率为16．7％,基因枪法的转化率为50％,因此可能基因枪转化法更适于龙牙百合的遗传转化。     

大豆孢囊线虫4号生理小种侵染大豆根系诱导表达的cDNA分析

大豆孢囊线虫(Heterodera glycines Ichinohe;Soybean Cyst Nematode,SCN)是一种土传的专性内寄生线虫。SCN的二龄幼虫侵入到大豆幼嫩的根组织中,导致大豆根内的细胞变形并与之形成“合胞体”。合胞体在形态上和生理上的变化是SCN直接诱导大豆基因表达的结果。本研究以高抗SCN的灰布支黑豆为材料,用大豆孢囊线虫二龄幼虫直接接种大豆的根系,应用DDRT—PCR技术及RDB(Reversedot—blotting)杂交鉴定,获得6个阳性cDNA克隆,分别是SCN侵染后5天的A32克隆(GenBank登录号为B1173978);侵染后10天的B12克隆(GenBank登录号为B1173979)、B71克隆(GenBank登录号为B1173980);侵染后15天的Cll克隆(GenBank登录号为B1173981)、CPl2(GenBank登录号为B1173982)克隆和CP32克隆(GenBank登录号为B1173983)。序列的同源比较表明,6个cDNA均与Shoemaker构建的大豆基因表达库中的cDNA序列有非常高的同源性,证明这些cDNA是大豆基因表达的产物。其中A32克隆的序列与控制拟南芥下胚轴生长的MYB转录因子、营养元素缺失诱导的番茄根的表达文库中的一个cDNA及番茄抗假单胞杆菌表达文库中的一个cDNA有较高的同源性。