Population ecology of a Stratiotes aloides l. stand in a riverside lagoon in N. Sweden

A stand of Stratiotes aloides L. in a riverside lagoon, Abborravan on the Vindelälven river in N Sweden, was studied for 3 years (1975–1977). The stand was vegetative, at all times submerged and therefore never flowering. On average each plant produced 3 adventitious roots and 40 leaves. One or two turions were also produced each year, together with stolons and associated offsets. At the beginning of June 1977 the population density was 42 plants/m² and the biomass was 290 kg/ha (dry wt. basis). At the end of September that year the respective values were 90/m² and 756 kg/ha. The dry wt./fresh wt. ratio of the biomass changed little during that period, from 6.4 to 6.5%. These and other results are compared with the respective data for Stratiotes stands in Central European lakes. In Abborravan Stratiotes seems well-adapted to survive the prevailing, hard, winter conditions. Freezing in situ is quite normal and is only lethal if the overwintering basal rosettes become frozen solid. The turions are quite frost-hardy.     

Leishmania tarentolae: streptomycin and chloramphenicol resistance of promastigotes.

Stable mutant strains of Leishmania tarentolae promastigotes resistant to chloramphenicol (CAP) were isolated by replica-plating techniques. In addition, cell lines stress-adapted to streptomycin and to high culture temperature (33 C) were obtained. Drug resistance was influenced by temperature, culture media, and plating technique. Inhibition of amino acid incorporation into protein occurs in CAP-resistant cells when exposed to 600 μg CAP/ml but this inhibition was 50–80% lower than that found in wild type sensitive cells. The primary site of CAP action appears to be inhibition of protein synthesis. CAP also adversely affected proline oxidation.     

Production of gluconic acid and 2-ketogluconic acid by Klebsiella aerogenes NCTC 418

2-Ketogluconic acid and, to a lesser extent, gluconic acid were found to be major products of glucose catabolism by phosphate-limited cultures of Klebsiella aerogenes NCTC 418, and together accounted for up to 46% of the glucose carbon that was metabolized.Although the concentrations of both acids increased sub-stantially at low growth rates, their specific rates of synthesis decreased markedly, as did the proportion of glucose converted into these products.Determination of the affinity constant, for glucose, of phosphate-limited organisms showed it to be not significantly different from that of glucose-limited organisms (K _s 50 M), indicative of the phosphotransferase uptake system. And since these organisms possessed an active glucose 6-phosphate dehydrogenase, and had no detectable glucose dehydrogenase activity, it was concluded that gluconic acid and 2-ketogluconic acid arose from their corresponding phosphorylated metabolites, and not directly from glucose.     

Plantlet Regeneration from Protoplasts lsolated from an Embryogenic Suspension Cultureof Cotton(Gossypium hirsutum L.)

Protoplasts were isolated from an embryogenic suspension culture of commercial cotton cv. The protoplasts were released enzymatically and isolated by centrifugation on a sucrose cushion. The isolated protoplasts were initially cultured in a liquid medium with K3 mineral salts and modified Km8p organic compositions, supplemented with 0.05–0.1 mg/l 2,4-D, 0.2–0.5 mg/l 2ip in the dark. The regenerated plantlets from protoplasts of coker312 and coker 201 cv. were obtained. Embryogenesis from protoplast of Jin4 cv. and microcolonies form protoplasts of JiHe321 and Lul cv. were observed.     

SCREENING OF IRON- AND ZINC-ENRICHED YEAST STRAIN AND OPTIMIZATION OF CULTIVATION CONDITIONS

Saccharomyces cerevisiae LN-17 was selected from 26 kinds of primary yeast strains that belong to different genera and species. The iron- and zinc-enriched capability of strain LN-17 was higher than the others. The highest iron and zinc contents of the strain were obtained when the strain grew up under the following conditions: The strain was incubated (5%, v/v) in 50 mL wort medium (pH 6.0) with 100 mg/L Fe ion and 120 mg/L Zn ion. The medium was loaded into a 250-mL Erlenmeyer flask and shaken in a rotary shaker (200 rpm) at 30°C for 60 h. Ferrous sulfate and zinc sulfate were chosen as the source of Fe and Zn. The Fe and Zn contents of the dry cells were determined by atomic absorption spectrum analysis. Under the optimized cultivation conditions, the Fe and Zn contents reached 7.854 mg/g dry cells and 4.976 mg/g dry cells.     

Intraspecific variation in the status of ant symbiosis on a myrmecophyte,<Emphasis Type="Italic"> Macaranga bancana,</Emphasis> between primary and secondary forests in Borneo

A tree species, Macaranga bancana , distributed in South East Asian tropics has a mutualistic relationship with specific symbiotic ant species, which defend the plant from herbivores. To examine the intraspecific variation in the status of the ant-plant symbiosis among microhabitats of different light conditions, we investigated the species composition of nesting ants and the herbivory damage on M. bancana saplings by field observations and sampling in primary and secondary forests in Sarawak. In addition, the effectiveness of non-ant (physical and chemical) defenses were estimated by feeding the larvae of a polyphagous lepidopteran with M. bancana leaves from saplings in the two types of forests. All saplings in the primary forest were colonized by two Crematogaster ant species that had been known to be the obligate symbionts of M. bancana, while in the secondary forest, about half of the saplings were occupied by several ant species that were not obligate symbionts. There was little herbivory damage on saplings colonized by the two Crematogaster symbiont ants in both forest types, while the saplings colonized by the other ant species suffered a 10–60% loss of leaf area. Larval mortality of the polyphagous lepidopteran Spodoptera litura was significantly higher when larvae fed on leaves of M. bancana saplings in the secondary forest than when fed on leaves of M. bancana saplings in the primary forest. These results suggest that the symbiosis between ants and M. bancana is looser and the non-ant-defenses are stronger in secondary forests, where light is more intense, than in primary forests.     

银杏根系甲醇溶提物对离体培养条件下丛枝菌根真菌生长发育的研究

银杏根系甲醇溶提物对离体培养条件下丛枝菌根真菌生长发育的试验结果表明,银杏根系甲醇溶提物对离体条件下丛枝菌根真菌(Glonus mosseae,Gigaspora margarita)生长发育有明显的促进作用,能显著提高孢子萌发率,增加菌丝生长长度。与对照相比,浓度为20％～100％的甲醇溶提物均可显著促进丛枝菌根真菌的生长发育,80％甲醇溶提物效果最明显,银杏根系甲醇溶提物中含丰富的黄酮类化合物,溶提物中黄酮类物质的含量与甲醇洗脱剂的浓度有关,当浓度为80％时,黄酮含量最高,对银杏根系甲醇溶提物中黄酮类化合物含量与丛枝菌根真菌生长发育相关性分析发现,溶提物中黄酮类化合物含量与离体条件下丛枝菌根真菌孢子的生长发育表现为极显著的正相关关系,溶提物中黄酮含量越高,其对丛枝菌根真菌孢子的生长发育促进作用越大。