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181.
Barbara L. Gartner 《American journal of botany》1991,78(10):1345-1353
Because of the different mechanical constraints on vines and self-supporting plants, vines are thought to differ from trees and shrubs in a variety of their growth characteristics. I tested the hypotheses that vines grow faster than shrubs and that supported shoots have delayed leaf expansion relative to stem elongation, using western poison oak, Toxicodendron diversilobum (T. & G.) Greene, a plant that grows as a vine when externally supported but otherwise as a shrub. In the field, supported shoots (vines) had significantly higher aboveground biomass and relative growth rates than did their paired unsupported shoots (shrubs) growing nearby. This was not due to differences in leaf phenology, but may have resulted from vines growing into more favorable habitats for growth. In contrast, whereas 2-yr-old cloned plants in a common garden differed in their stem and internode lengths, they had the same aboveground dry weight, proportion of dry weight that was leaf, and relative rate of increase in primary stem length whether grown with stakes (vines) or without stakes (shrubs). These results suggest that there is no inherent requirement of vines to grow faster than shrubs. As hypothesized, leaf elongation was more delayed relative to stem elongation in staked than unstaked individuals in 19 paired plants (each pair cloned from a different source plant). Thus, physical cues resulting from the presence of support can alter the plant's spatial and temporal patterns of development, but do not necessarily dictate the quantity of biomass that will be produced. 相似文献
182.
Astrid Löffler Justyna Wolinska Barbara Keller Karl-Otto Rothhaupt Piet Spaak 《Freshwater Biology》2004,49(10):1372-1380
1. We investigated whether Daphnia galeata × hyalina hybrids of Lake Constance and Lake Greifensee show the same pattern of life history parameters as previously reported for D. galeata × cucullata hybrids and whether such a pattern is consistent between Daphnia populations from those two lakes. 2. Hybrids in Lake Constance were intermediate in size compared with the parental species. Hybrids in Lake Greifensee were smaller than D. galeata. The intrinsic growth rate (r) of hybrids from Lake Constance was not significantly different from the faster growing parental taxon D. galeata. However, r of hybrids from Lake Greifensee was significantly lower than that of D. galeata. 3. The observed juvenile body length differences between the taxa varied with the clutch number. The first clutch juvenile lengths of the three taxa did not differ for Lake Constance. First clutch juveniles of Lake Greifensee D. galeata were smaller than hybrid first clutch juveniles. The third clutch juvenile length did not differ between taxa from Lake Greifensee, but D. galeata juveniles from Lake Constance were bigger than those of D. hyalina. 4. The life history pattern found in Lake Constance corresponds to previous findings from other studies. The hybrids in this lake combine the faster population growth of one parental species with a relatively small size. In the case of Lake Greifensee hybrids, the relatively large size of first clutch juveniles and the small size of the adults could be interpreted as dual adaptations to invertebrate and fish predation. We speculate that the lower population growth rate of the hybrids is a trade‐off for this twofold protection. 相似文献
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184.
Barbara Seliger Rudolf Lichtenfels Roland Kellner 《Briefings in Functional Genomics and Prot》2003,2(3):194-212
Proteome analysis has rapidly developed in the post-genome era and is now widely accepted as the complementary technology for genetic profiling. It has been shown to be a powerful tool for studying human diseases and for identifying novel prognostic, diagnostic and therapeutic markers. This review focuses on the identification of new biomarkers and therapeutic targets for renal cell carcinoma using different 'ome'-based technologies. 相似文献
185.
Sigrun Skjelseth Arne Moksnes Eivin Røskaft H. Lisle Gibbs Michael Taborsky Barbara Taborsky Marcel Honza Oddmund Kleven 《Journal of avian biology》2003,35(1):21-24
Microsatellite DNA markers were used to investigate parentage relationships in a population of common cuckoo Cuculus canorus . Thirty adults and 55 nestlings were genotyped at six loci from blood samples collected over a four-year period. To test whether each cuckoo female specialises in parasitising one single host species (Host Preference Hypothesis), the maternal relationships were used to record each female's host choice. The results supported the Host Preference Hypothesis since no female (N=3) was recorded to have parasitised more than one of four congeneric host species breeding in the area. In contrast, the males (N=4) did not show such specialisation since two of them sired offspring reared by different host species. 相似文献
186.
Ingestion of Salmonella enterica Serotype Poona by a Free-Living Nematode, Caenorhabditis elegans, and Protection against Inactivation by Produce Sanitizers
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Krishaun N. Caldwell Barbara B. Adler Gary L. Anderson Phillip L. Williams Larry R. Beuchat 《Applied microbiology》2003,69(7):4103-4110
Free-living nematodes are known to ingest food-borne pathogens and may serve as vectors to contaminate preharvest fruits and vegetables. Caenorhabditis elegans was selected as a model to study the effectiveness of sanitizers in killing Salmonella enterica serotype Poona ingested by free-living nematodes. Aqueous suspensions of adult worms that had fed on S. enterica serotype Poona were treated with produce sanitizers. Treatment with 20 μg of free chlorine/ml significantly (α = 0.05) reduced the population of S. enterica serotype Poona compared to results for treating worms with water (control). However, there was no significant difference in the number of S. enterica serotype Poona cells surviving treatments with 20 to 500 μg of chlorine/ml, suggesting that reductions caused by treatment with 20 μg of chlorine/ml resulted from inactivation of S. enterica serotype Poona on the surface of C. elegans but not cells protected by the worm cuticle after ingestion. Treatment with Sanova (850 or 1,200 μg/ml), an acidified sodium chlorite sanitizer, caused reductions of 5.74 and 6.34 log10 CFU/worm, respectively, compared to reductions from treating worms with water. Treatment with 20 or 40 μg of Tsunami 200/ml, a peroxyacetic acid-based sanitizer, resulted in reductions of 4.83 and 5.34 log10 CFU/worm, respectively, compared to numbers detected on or in worms treated with water. Among the organic acids evaluated at a concentration of 2%, acetic acid was the least effective in killing S. enterica serotype Poona and lactic acid was the most effective. Treatment with up to 500 μg of chlorine/ml, 1% hydrogen peroxide, 2,550 μg of Sanova/ml, 40 μg of Tsunami 200/ml, or 2% acetic, citric, or lactic acid had no effect on the viability or reproductive behavior of C. elegans. Treatments were also applied to cantaloupe rind and lettuce inoculated with S. enterica serotype Poona or C. elegans that had ingested S. enterica serotype Poona. Protection of ingested S. enterica serotype Poona against sanitizers applied to cantaloupe was not evident; however, ingestion afforded protection of the pathogen on lettuce. These results indicate that S. enterica serotype Poona ingested by C. elegans may be protected against treatment with chlorine and other sanitizers, although the basis for this protection remains unclear. 相似文献
187.
188.
189.
Plankton composition, abundance and dynamics in a severely stressed cooling reservoir 总被引:1,自引:0,他引:1
The effects of severe thermal stress imposed by the intermittentoperation of a nuclear reactor on plankton abundance and dynamicswere investigated in Pond C, a cooling reservoir on the SavannahRiver Site in South Carolina, USA. Temperatures in Pond C rangedup to 58°C during reactor operation. The thermal effluenteliminated zooplankton from regions where the temperature exceeded45°C, reduced zooplankton abundance by 13 ordersof magnitude and typically halved the number of taxa. Reactoroperation also reduced phytoplankton biovolume, often by >70%.During intermittent reactor operation, the rotifer Filinia longisetadominated the zooplankton and two cladocerans of the genus Moinawere abundant. These species were not abundant during extendedreactor shutdowns. The success of Filinia and Moina was dueprimarily to their tolerance of high temperatures. Sparse phytoplanktonprobably limited some zooplankton taxa, although other taxa,such as Filinia may have utilized bacterial resources. Reactoroperation may have intensified predation on crustacean zooplanktonwhen fish were concentrated in refuge areas with zooplankton.Processes by which zooplankton repopulated the reservoir afterreactor shutdown were inferred from zooplankton distributionpatterns, and population growth and birth rates. Repopulationtypically occurred within a few days due to rapid growth ofpopulations from refuge areas within the reservoir and colonistsbrought in through a tributary canal. Mechanisms of zooplanktonrepopulation in Pond C suggest that refuges or colonizationcorridors should be maintained when the re-establishment ofcommunities following cessation of stresses is desired. 相似文献
190.
Ana María Bravo-Angel Heinz-Albert Becker Reinhard Kunze Barbara Hohn Wen-Hui Shen 《Molecular & general genetics : MGG》1995,248(5):527-534
A reverse genetic system for studying excision of the transposable elementDs1 in maize plants has been established previously. In this system, theDs1 element, as part of the genome of maize streak virus (MSV), is introduced into maize plants via agroinfection. In the presence
of theAc element, excision ofDs1 from the MSV genome results in the appearance of viral symptoms on the maize plants. Here, we used this system to study DNA
sequences requiredin cis for excision ofDs1. TheDs1 element contains theAc transposase binding motif AAACGG in only one of its subterminal regions (defined here as the 5′ subterminal region). We showed
that mutation of these motifs abolished completely the excision capacity ofDs1. This is the first direct demonstration that the transposase binding motifs are essential for excision. Mutagenesis with
oligonucleotide insertions in the other (3′) subterminal region resulted in elements with either a reduced or an increased
excision efficiency, indicating that this subterminal region also has an important function. 相似文献