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1.
Ola Broberg 《Hydrobiologia》1987,150(1):11-24
The acidified lakes Lake Gårdsjön and Lake Stora Hästevatten the reference lake have been monitored since 1979 and 1980 respectively. The lakes are situated in SW Sweden; in an area severly affected by acid deposition. Lake Gårdsjön was limed in spring 1982. This paper analyses changes in nutrient concentrations upon liming of Lake Gårdsjön. The liming of Lake Gårdsjön was followed by a slight increase in ammonium, nitrate, and dissolved organic nitrogen concentrations. A drastic decrease occurred in particulate nitrogen and particulate carbon, whereas dissolved organic carbon increased. Total phosphorus and particulate phosphorus concentrations were similar to pre-limed conditions. The long-term decrease in phosphorus concentration, exhibited by the reference lake, was not identified in Lake Gårdsjön after liming, but total phosphorus concentration was still less than half compared to Lake Gårdsjön in the early 1970's. Additional measures such as phosphorus fertilization, should in certain cases be considered in addition to liming if the goal is to restore lakes to their pre-acidic conditions. 相似文献
2.
Bing Xia Haiping Ke Wei Jiang Masayori Inouye 《The Journal of biological chemistry》2002,277(8):6005-6011
The 5'-end region of cspA mRNA contains a Cold Box sequence conserved among several cold-shock mRNAs. This region forms a stable stem-loop structure followed by an AU-rich sequence. Here we show that the Cold Box region is essential for the normal scale of cspA mRNA induction after cold shock because a deletion of the stem-loop significantly destabilizes the mRNA and reduces the cold shock-induced cspA mRNA amount by approximately 50%. The AU-rich track, however, slightly destabilizes the mRNA. The integrity of the stem is essential for the stabilizing function, whereas that of the loop sequence is less important. Overexpression of a mutant cspA mRNA devoid of both the AUG initiation codon and the coding sequence results in a severe growth inhibition at low temperature along with a derepression of the chromosomal cspA expression. Furthermore, the overexpressed RNA is stably associated with the 30 S and 70 S ribosomes. Our results demonstrate that the AUG initiation codon and the coding region containing the downstream box are not required for cspA mRNA to bind ribosomes and that the 5'-untranslated region by itself has a remarkable affinity to ribosomes at low temperature. 相似文献
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The effect of lysolecithin (lysophosphatidylcholine) on the relaxation of rabbit aortic strip closely resembled that produced by acetylcholine (ACh) which releases the endothelium-derived relaxing factor (EDRF). Relaxation induced by lysolecithin depended on the presence of endothelium and was inhibited by hemoglobin and methylene blue. It appeared to be mediated by the second messenger, c-GMP. Lysolecithin induced relaxation was slower but more persistent than that resulting from the endothelium-derived relaxing factor (EDRF) produced by acetylcholine (ACh). Like lysolecithin, Triton X-100, a non-ionic detergent, also preferentially relaxed aortic strips with intact endothelium. The results demonstrate the importance of phospholipids derived from cell membranes in vascular smooth muscle relaxation. Endothelium-derived relaxing factors appear as a group of heterogeneous substances. 相似文献
7.
Lars Sundström Peter Rådström Göte Swedberg Ola Sköld 《Molecular & general genetics : MGG》1988,213(2-3):191-201
Summary A new gene for trimethoprim resistance, dhfrV, found in several plasmid isolates with different characteristics, was sequenced and found to correspond to a peptide of 157 amino acids showing 75% similarity with the previously characterized, drug resistant dihydrofolate reductase of type I. The sequenced surroundings of dhfrV in plasmid pLMO20, were found to be almost identical with genetic areas surrounding resistance genes in transposon Tn21 and in R plasmid R388. The trimethoprim resistance genes of pLMO20 and R388 and the spectinomycin resistance gene of Tn21 could be regarded as having been inserted, by recombination, into an evolutionary older structure containg the sulfonamide resistance gene, sulI. The latter gene was sequenced and found to correspond to a peptide of 279 amino acids and with a molecular weight of 30126 daltons. The inserted genes were found to be governed by a promoter situated in the highly conserved structure and also controlling expression of sulI. The insertion points of the different resistance genes were precisely defined, and at the 3 ends of the inserted genes inverted repeats allowing the formation of stem and loop structures were found. Similar structures were found at the 3 ends of the antibiotic resistance genes in Tn7, which could indicate similar recombination mechanisms to be effective in the evolutionary construction of all these different resistance elements. 相似文献
8.
Ola Palm W. Lionel Weerakoon M. Ananda P. de Silva Thomas Rosswall 《Plant and Soil》1988,108(2):201-209
Sesbania sesban was evaluated as green manure crop for lowland rice in the Dry Zone of Sri Lanka. The legume was grown during a fallow period
before lowland rice (Oryza sativa) and ploughed under just before transplanting. Weight loss and nitrogen content in litterbags containing leaves, stems and
roots of the legume were monitored. Comparisons were made between rice yields from 20 m2 plots after green manuring in combination with different nitrogen fertilizer levels (0, 2.4, 4.8 and 7.2 gm−2) and nitrogen fertilizer (9.6 gm−2) alone. Above-ground biomass ofS. sesban was 440 gm−2 (dry wt) when ploughed under after 84 days growth. N-content in leaves, stems and roots was 3.76%, 0.41% and 0.73%, respectively.
This gave a N-input fromS. sesban of 9.2 gm−2 (8.3 g from above-ground parts and 0.9 g from roots). The corresponding K and P inputs were 7.3 and 0.6 gm−2 respectively. The nitrogen rich leaves, which contained 88% of the nitrogen in the above-ground parts, decomposed and released
its nitrogen much more rapidly than the stems and roots. After only four days the leaves had released 5.3 g Nm−2 and after 14 days they had released 6.4 g Nm−2. The highest rice yield (505 gm−2) was obtained usingS. sesban and 4.8 gm−2 of N-fertilizer. The yields with only N-fertilizer or onlyS. sesban were 442 gm−2 and 396 gm−2, respectively. Due to the rapid decomposition of the nitrogen rich leaves,S. sesban did not behave as a slow release fertilizer. Thus, it is not necessary to apply nitrogen fertilizers as a basal dose. 相似文献
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水生观赏植物的调查和研究 总被引:2,自引:0,他引:2
倪学明;赵家荣;於炳;周远捷 《武汉植物学研究》1992,10(1):92-100
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。 相似文献