The emergence of transgenic potatoes as commercial products and tools for basic science

The potato has tremendous potential as a transgenic crop and is a good model system by which to analyse metabolic regulation and gene expression. The potato’s difficult genetics, but ease of genetic transformation and its clonal means of propagation make it ideal for applied agricultural molecular genetics. Thus, the next 4 years promise to put the potato (with a diversity of transgenic constructs expressed) in the limelight as many of the first transgenic agricultural products enter the marketplace.     

小兴凯湖的水生植被及其生态作用

本文论述了小兴凯湖水生植物的种类组成、植被类型、生物量及其在湖泊淤积和渔业中的作用。该湖属老年期湖泊,水生维管束植物共有25科56种,优势种为竹叶眼子菜、荇菜、芦、菰等。植被类型可划分为沉水植被、浮叶植被和挺水植被等三个亚型,包括12个主要植物群丛。全湖水生植物总生物量(湿重)为196380吨;以植物现存量计算,草食性鱼类的年生产力应为78.75吨。由于水生植物大量繁殖,为减缓湖泊的垫平作用,可适量放养草食性鱼类,控制住水生植物的过量繁殖;同时引种一些经济水生植物,压住水中杂草的生长。     

水生观赏植物的调查和研究

水生绿化观赏植物是美化园林水景的重要植物材料,作者通过几年的调查研究和引种栽培,提出了28种(其中荷花含18个品种,睡莲含20个品种)水生绿化观赏植物,同时介绍了20种(其中荷花含6个品种)观赏价值较高的水生绿化观赏植物。     

Structure and expression of the Chlorobium vibrioforme hemA gene

The green sulfur bacterium, Chlorobium vibrioforme, synthesizes the tetrapyrrole precursor, -aminolevulinic acid (ALA), from glutamate via the RNA-dependent five-carbon pathway. A 1.9-kb clone of genomic DNA from C. vibrioforme that is capable of transforming a glutamyl-tRNA reductase-deficient, ALA-dependent, hemA mutant of Escherichia coli to prototrophy was sequenced. The transforming C. vibrioforme DNA has significant sequence similarity to the E. coli, Salmonella typhimurium, and Bacillus subtilis hemA genes and contains a 1245 base open reading frame that encodes a 415 amino acid polypeptide with a calculated molecular weight of 46174. This polypeptide has over 28% amino acid identity with the polypeptides deduced from the nucleic acid sequences of the E. coli, S. typhimurium, and B. subtilis hemA genes. No sequence similarity was detected, at either the nucleic acid or the peptide level, with the Rhodobacter capsulatus or Bradyrhizobium japonicum hemA genes, which encode ALA synthase, or with the S. typhimurium hemL gene, which encodes glutamate-1-semialdehyde aminotransferase. These results establish that hemA encodes glutamyl-tRNA reductase in species that use the five-carbon ALA biosynthetic pathway. A second region of the cloned DNA, located downstream from the hemA gene, has significant sequence similarity to the E. coli and B. subtilis hemC genes. This region contains a potential open reading frame that encodes a polypeptide that has high sequence identity to the deduced E. coli and B. subtilis HemC peptides. hemC encodes the tetrapyrrole biosynthetic enzyme, porphobilinogen deaminase, in these species. Preliminary evidence was obtained for the existence of a 3.0-kb polycistronic meassge that includes the hemA sequence, in exponentially growing C. vibrioforme cells. Results of condon usage analysis for the C. vibrioforme hemA gene indicate that green sulfur bacteria are more closely related to purple nonsulfur bacteria than to enteric bacteria. Sequences corresponding to a polyadenylation signal and a poly(A) attachment site were found immediately downstream from the 3 end of the hemA open reading frame.     

Ecological comparison of the pre- and post-impoundment macrophyte flora of the river Niger and Lake Kainji,Nigeria

The floristic composition of the macrophyte vegetation of Lake Kainji was investigated and compared with the vegetation of the river Niger before impoundment.Of 18 hydatophytes, 40 tenagophytes and 57 trichophytes listed for the Niger, 18 tenagophytes, 12 trichophytes and 7 hydatophytes were found growing in the lake 17 years after impoundment. Fourteen new tenagophytes, 3 new hydatophytes and 1 new trichophyte were recorded. The hydatophytes which were expected to colonize the lake are limited in number and range.The failure of the hydatophytes to colonize the lake, as predicted by Cook (1968), is discussed in relation to the inflow-to-volume ratio of the lake.Nomenclature follows Hutchinson & Dalziel (1952–1972). Flora of West Tropical Africa.     

Basidiomycetes with branched, water-borne conidia

A number of water-borne fungi with branched conidia have been shown to be basidiomycetes. These fungi resemble aquatic hyphomyectes in their habitat, conidial morphology and ontogeny. Their conidia are typically tetraradiate or elaborately branched. Ingoldiella hamata and Taeniospora gracilis, which produce clamped, tetraradiate conidia, are anamorphs connected to the teleomorphs Sistotrema hamalum and Leptosporomyces galzinii, respectively. Both teleomorphs are members of the Corticiaceae. Dendrosporomyces prolifer and D. splendens, which produce non-clamped conidia resembling the aquatic hyphomycete Dendrospora, have binucleate conidia and typical dolipore septa are present. Other water-borne fungi with basidiomycete affinities include Ingoldiella fibulata and Tricladiomyces malaysianum.     

元江干热河谷山地五百年来植被变迁探讨

元江河谷是云南省最干热地区之一,在海拔800—900米以下的山地上广泛分布着稀树灌草丛。根据《元江府志》(1714年编纂)、《元江州志》(1826年编纂)、《元江志稿》(1922年编篡)及对现存植被的考察,本文探讨了元江干热河谷山地五百年来植被的变迁。 元江县森林复盖率的减少与人口的增加有密切关系,十七世纪中期以前,森林复盖率在75％以上,十八、十九世纪时为70％左右,1958年为61.5％,1975年为27.3％,至1982年则为19.3％。研究表明,在十九世纪以前,这个地区分布的主要植被是热带季雨林,甚而热带季节雨林,以后热带稀树灌草丛则迅速发展。植被的历史变化与土壤流失密切相关。植物群落的演变是由以乔木树种为优势演变为以灌木种类为优势,再演变为以多年生草木植物为优势,而最后则成为裸地。本文也讨论了这个地区植被恢复的方法。     

Successful transfer of embryos recovered from a cow with chronic cervicitis of mixed aerobic and anaerobic bacterial aetiology a case report

An imported 13-year-old Simmentaler cow was presented with severe purulent cervicitis and endometritis from which Corynebacterium pyogenes , Fusobacterium necrophorum , Bacteroides melaninogenicus and an untyped Clostridium perfringens were isolated. The endometritis responded to treatment but the cervix did not and remained fibrous, continuously patent and purulent. Natural pregnancy was considered unlikely and the cow was prepared as an embryo transfer donor. Eight embryos were recovered and six transferred, resulting in five confirmed pregnancies and four live births.     

The chorologic pattern of European Nardus-rich communities

Two types of Nardus-rich communities may be distinguished in Europe according to their geographic pattern:I. Communities of high mountains showing discontinuous variation. Different florogenesis in island-like high mountains results in a number of alliances characteristic for particular mountain systems: Trifolion humilis Quézel 57 (Atlas, N Africa), Plantaginion thalackeri Quézel 53 (Sierra Nevada), Campanulo-Nardion Rivaz-Martinez 63 (mountains of the central Iberian peninsula), Nardion Br.-Bl. 26 (from Pyrenees, Auvergne to W and E Carpathians), Potentillo ternatae-Nardion Simon 58 (S Carpathians, Pirin, Rila), Jasionion orbiculatae Lakui 66 (Dinarids), Trifolion parnassi Quézel 64 (S Greece), Nardo-Caricion rigidae Nordhagen 37 (Iceland, Scotland, Scandinavia, W Sudeten).II. Communities at lower altitudes with continuous variation, where particular syntaxa are difficult to distinguish. Along the climatic gradient from a subatlantic to a subcontinental climate, a cline in floristic composition of the communities under discussion is found. Towards the eastern borderline, the communities are poorer in characteristic species. Here only one alliance is considered-Violion caninae Schwickerath 44. A Similar situation occurs along the altitudinal gradient in mountains. Only in mountains with a belt of alpine communities the montane Nardeta are saturated with alpine species. This thpe of communities was described as Nardo-Agrostion tenuis by Sillinger (1933).     

Eutrophication of Lakes Leman and Neuchâtel (Switzerland) indicated by oligochaete communities

In 1978–80, oligochaete communities of meso-eutrophic Lake Léman (Lake of Geneva) were compared to those of mesotrophic Lake Neuchâtel. Worm species were classified into three groups corresponding to their increasing tolerance to eutrophication: (1) oligotrophic species, mostly Peloscolex velutinus, Stylodrilus heringianus; (2) mesotrophic species, mostly Potamothrix vejdovskyi, P. bedoti; (3) eutrophic species, mostly Potamothrix hammoniensis, P. heuscheri, Tubifex tubifex. In both lakes, eutrophic species constituted the bulk of the communities in terms of absolute abundance. However, relative abundance of mesotrophic and eutrophic species was higher in Lake Léman; oligotrophic species were more important in Lake Neuchâtel. These data confirmed the trophic classification of lakes based on chemical parameters. The number of zero values, which perturbated statistical analysis, was reduced by using species groupings instead of isolated species. Thus, making the lakes more comparable even if different species were present in each one. Relative density values based on all samples were distributed among 4 density classes for the 3 species groupings. The 12 resulting frequencies described the community structure expressed in terms of eutrophication. Furthermore, these frequencies may be used for comparison of eutrophication levels in several lakes.