植物激素对草莓叶片不定芽形成的影响

用试管内生长的草莓幼嫩叶片作外植体,培养在MS基本培养基上附加1.5—2.5毫克/升6—BA和0.1毫克/升NAA,可直接诱导成不定芽,诱导率可达20%。如果不定芽继代培养在同样浓度的培养基上,继而可形成大量的丛生芽。能使叶外植体形成不定芽的植物激素组合而不能使其愈伤组织分化成芽。IAA与6—BA的不同浓度组合对不定芽形成效果不明显。     

稻米垩白形成的气象生态基础研究

在全国13个点、19个品种多播期试验基础上,对稻米垩自形成的气象生态基础进行了分析。结果表明,水稻齐穗后15天的日均温是影响稻米垩白大小的主要气象因子。经对稻米垩白与齐穗后15天内均温关系的动态分析可知,稻米垩白随该时段温度提高而增大的拐点温度约为29℃(品种间略有差异),接近或超过该点温度,稻米垩白会突发性地增加。     

Cell surface contact mediates neuronal recognition and synapse formation between two identified leech neurons

An early event in the formation of the serotonergic synapse by the Retzius (R) onto the pressure-sensitive (P) neurons of the leech is the elimination of an extrasynaptic response to transmitter from sites of contact on the postsynaptic cell. This event during synapse formation is cell-specific in that it is elicited in vitro by contact with the presynaptic R cell but not with other neurons. In the study reported here, we investigated the nature of this interaction between R and P neurons. The loss of the extrasynaptic response of the P cell was elicited by contact with R cells fixed in a mild paraformaldehyde solution, but not by R cells treated with the proteolytic enzyme trypsin prior to fixation. As well, a variety of lectins were assayed for their ability to interfere with synapse formation. The transmitter responses of P cells plated on lectin-coated substrates were unaffected. However, exposure of the R cell to the lectin wheat germ agglutinin (WGA), but not to other lectins, prior to pairing prevented the loss of the extrasynaptic response in contacted P cells and blocked the formation of the R? P synapse in culture. We conclude that recognition by the P cell of the R cell during synapse formation may be mediated by an R cell-specific surface protein which binds wheat germ agglutinin. 1994 John Wiley & Sons, Inc.     

Organization and possible origin of the Bari-1 cluster in the heterochromatic h39 region of Drosophila melanogaster

The molecular organization of the heterochromatic h39 region of the Drosophila melanogaster second chromosome has been investigated by studying two BAC clones identified both by Southern blotting and by FISH experiments as containing tandem arrays of Bari1, a transposable element present only in this region. Such BAC clones appear to contain different portions of the h39 region since they differ in the DNA sequences flanking the Bari1 repeats on both sides. Thus, the 80 Bari1 copies estimated to be present in the h39 region are split into at least two separated subregions. On the basis of the analysis of the flanking sequences a possible mechanism depending on an aberrant activity of the Bari1 transposase is proposed for the genesis of the heterochromatic tandem arrays of the element.     

Optimization of in vitro bud induction and plantlet formation from mature embryos of Aleppo pine (Pinus halepensis Mill.)

Summary Studies were undertaken to optimize tissue culture conditions for micropropagation of Aleppo pine (Pinus halepensis Mill.) from mature embryos and various explants of the embryo. Over 90% of the embryo explants gave rise to adventitious buds within 4 wk. Intact embryos were the most suitable explants for shoot bud induction. Both isolated cotyledons and hypocotyls produced adventitious buds, but these developed slowly and failed to elongate. N⁶-Benzyladenine (BA) alone at 5.0μM was the most effective cytokinin when added to gelled to gelled von Arnold and Eriksson’s (AE) medium containing 3% sucrose. Adventitious bud development was achieved on hormone-free AE medium, and shoot elongation was optimum on three quarter-strength Bornman’s MCM medium, with 0.1% conifer-derived activated charcoal. Shoots were multiplied on three-quarter strength MCM medium, containing 5μM BA. To induce adventitious roots on the elongated shoots, pulse treatment with 1 mM IBA for 6 h, followed by the transfer of the shoots to sterile peat:vermiculite (1:1) mixture, was beneficial. After acclimatization for 3 to 4 wk under mist, almost all the rooted shoots could be transplanted successfully to the greenhouse, where the plants exhibited normal growth habit. Histologic studies on the ontogeny of adventitious shoot formation from mature embryo explants revealed temporal structural changes in different parts of the explant. Induction of mitotic divisions on the shoot-forming medium resulted in the formation of meristemoids in the epidermal and subepidermal layers of the explant, located initially at both the tips of the cotyledons and the axils of adjacent cotyledons. Shoot buds arising in the axils of adjacent cotyledons were due to new cell division and not to any preexisting meristem.     

基于生态效率理论和TOPSIS法的工业园区循环经济发展评价

工业园区层面的生态效率评价是生态效率研究领域有待深入探索的课题。TOPSIS方法则可能是适用于生态效率评价的一种方法,它以空间统计学为基础,借助于多目标决策问题的理想解和负理想解来进行排序,能够客观地比较和评价不同样本点综合指标的优劣。本文根据生态效率和循环经济理论,结合《综合类生态工业园区标准（试行）》,建立工业园区循环经济评价指标体系,运用TOPSIS方法对苏州高新区、苏州工业园区生态工业园和无锡新区生态工业示范园区的生态效率进行综合评价,结果表明：三者的生态效率综合排名由高到低依次为：无锡新区生态工业示范园区> 苏州工业园区生态工业园> 苏州高新区,且3园区在经济发展、资源能源利用率、物质循环利用、环境污染控制等子系统有所优劣。并针对各园区的各自存在的不足提出了相应的改进和发展建议。     

QTL analysis of leaf morphology in tetraploid Gossypium (cotton)

Molecular markers were used to map and characterize quantitative trait loci (QTLs) determining cotton leaf morphology and other traits, in 180 F₂ plants from an interspecific cross between a Gossypium hirsutum genotype carrying four morphological mutants, and a wild-type Gossypium barbadense. The prominent effects of a single region of chromosome 15, presumably the classical ”Okra-leaf” locus, were modified by QTLs on several other chromosomes affecting leaf size and shape. For most traits, each parent contained some alleles with positive effects and others with negative effects, suggesting a large potential for adapting leaf size and shape to the needs of particular production regimes. Twenty one QTLs/loci were found for the morphological traits at LOD≥3.0 and P≤0.001, among which 14 (63.6%) mapped to D-subgenome chromosomes. Forty one more possible QTLs/loci were suggested with 2.0≤LOD<3.0 and 0.001<P≤0.01. Among all of the 62 possible QTLs (found at LOD≥2.0 and P≤0.01) for the 14 morphological traits in this study, 38 (61.3%) mapped to D-subgenome chromosomes. This reinforces the findings of several other studies in suggesting that the D-subgenome of tetraploid cotton has been subject to a relatively greater rate of evolution than the A-subgenome, subsequent to polyploid formation. Received: 26 April 1999 / Accepted: 30 July 1999     

志贺菌对HeLa细胞侵袭力的研究

通过使用噬斑形成试验、透射电镜及检测志贺菌蛋白表达等方法,研究志贺菌对Hela细胞的侵袭能力。研究发现:37℃培养条件下,胞质内出现成堆的志贺菌;30℃培养条件下,细菌主要分布在细胞外。SDS-PAGE显示,与30℃培养条件相比,在37℃培养下,志贺菌表达蛋白质的种类和数量明显增加。噬斑形成发现,12株福氏志贺菌强毒株,有9株噬斑数>1000个／ml,而2株弱毒株噬斑数则在50个／ml以下。透射电镜证实了志贺菌对细胞的黏附、侵入和释放过程。结果表明:志贺菌对细胞的侵袭能力受温度的影响;不同志贺菌流行株对细胞的侵袭力存在着差异:实验也显示,应用HeLa细胞研究志贺菌侵袭力是一种简便易行且价廉的方法。     

Viral fusion peptides and identification of membrane-interacting segments

Viral envelope glycoproteins promote infection by mediating fusion between viral and cellular membranes. Fusion occurs after dramatic conformational changes within fusion proteins, leading to the exposure of a short stretch of mostly apolar residues, termed the fusion peptide, which is presumed to insert into the membrane and initiate the fusion process. The typical global composition of fusion peptides, rich in hydrophobic but also in small amino acids such as alanine and glycine, was used here as bait to detect other peptidic segments that can insert into membranes. We so evidenced a similar composition in several cytotoxic peptides, which promote pore formation such as peptides involved in amyloidoses and hydrophobic alpha-hairpins of pore-forming toxins. It is suggested that the structural plasticity observed for several membrane active peptides can be conferred by this particular global amino acid composition, which could be thus used to predict such functional behavior from genome data.     

The Life Cycle of Cryptochlora perforans (Chlorarachniophyta)

Observations on the behaviour of different life cycle stages, gamete fusions, and measurements of nuclear DNA contents in Cryptochlora perforans resulted in a first concept concerning life histories in Chlorarachniophyta: the life cycle of Cr. perforans is diplohaplontic (gamete fusion with karyogamy - mitosis - meiosis - mitosis). In the haploid as well as in the diploid life cycle phases amoeboid and coccoid stages occur. The isomorphic gametes are modified amoebae frequently without filopodia. Only haploid flagellate stages are known representing mito- or meiozoospores. Diploid coccoid stages have a granular cytoplasmic structure and may be somewhat larger than haploid ones. Nevertheless, positive identification of haploid (gametophytic) and diploid (sporophytic) stages is only possible on the basis of nuclear DNA contents.