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11.
Summary The combined effect of various temperatures and light intensities on the growth of seven species of antarctic diatoms in culture has been studied. With the exception of Chaetoceros deflandrei whose thermal tolerance is fairly good, these obligatory psychrophils cannot survive in temperatures above 6° to 9° C. Their mean growth rate is relatively low, between 0.24 div d–1 for Corethron criophilum and 0.63 div d–1 for C. deflandrei. Regardless of light intensity, growth rate increased with the temperature to reach a maximum between 3° and 5° C. The highest rates were obtained between 115 and 220 mol m–2 s–1 with 0.38 div d–1 for C. criophilum, 0.56 div d–1 for Synedra sp. and between 0.71 and 0.88 div d–1 for the other 5 species. A reduction in light intensity from 220 to 46 mol m–2 s–1 slowed growth by nearly 50%. These results suggest that the combined effect of temperature and light is one of the factors involved in the limitation of antarctic phytoplankton growth. The low temperatures of the environment do not permit rapid growth, which, even under optimal light conditions remains low. In addition, in the euphotic layer, the overall light energy available for algae is considerably reduced due to turbulence, a factor which exacerbates the reduced growth rate. 相似文献
12.
Carbon and nitrogen partitioning in young nodulated pea (wild type and nitrate reductase-deficient mutant) plants exposed to NH4 NO3 总被引:1,自引:0,他引:1
David C. Taylor Barry J. Shelp Louise M. Nelson Bernard Grodzinski 《Physiologia plantarum》1988,74(4):593-601
Carbon and nitrogen partitioning was examined in a wild-type and a nitrate reductase-deficient mutant (A317) of Pisum sativum L. (ev. Juneau), effectively inoculated with two strains of Rhizobium leguminosarum (128C23 and 128C54) and grown hydroponically in medium without nitrogen for 21 days, followed by a further 7 days in medium without and with 5 mM NH4 NO3 . In wild-type symbioses the application of NH4 NO3 significantly reduced nodule growth, nitrogenase (EC 1.7.99.2) activity, nodule carbohydrates (soluble sugars and starch) and allocation of [14 C]-labelled (NO3 − , NH4 + , amino acids) in roots. In nodules, there was a decline in amino acids together with an increase in inorganic nitrogen concentration. In contrast, symbioses involving A317 exhibited no change in nitrogenase activity or nodule carbohydrates, and the concentrations of all nitrogenous solutes measured (including asparagine) in roots and nodules were enhanced. Photosynthate allocation to the nodule was reduced in the 128C23 symbiosis. Nitrite accumulation was not detected in any case. These data cannot be wholly explained by either the carbohydrate deprivation hypothesis or the nitrite hypothesis for the inhibition of symbiotic nitrogen fixation by combined nitrogen. Our result with A317 also provided evidence against the hypothesis that NO3 − and NH4 + or its assimilation products exert a direct effect on nitrogenase activity. It is concluded that more than one legume host and Rhizobium strain must be studied before generalizations about Rhizobium /legume interactions are made. 相似文献
13.
Richard M. Napier Michael A. Venis Michael A. Bolton Louise I. Richardson Goeffrey W. Butcher 《Planta》1988,176(4):519-526
Binding proteins, thought to be auxin receptors, can be solubilised from maize (Zea mays L.) membranes after acetone treatment. From these crude extracts, receptor preparations of over 50% purity can be obtained by a reliable, straight-forward procedure involving three chromatographic steps — anion exchange, gel filtration and high-resolution anion exchange. Such preparations have been used to immunise rats for subsequent production of monoclonal antibodies. By the further step of native polyacrylamide gel electrophoresis the semi-purified preparations yield homogeneous, dimeric (22-kilodalton, kDa) auxin-binding protein, which has been used to produce a polyclonal rabbit antiserum. The preliminary characterisation of this antiserum and of the five monoclonal antibodies is presented. Two of the monoclonal antibodies specifically recognise the major 22-kDa-binding protein polypeptide whilst the other three recognise, in addition, a minor 21-kDa species. All the monoclonal antibodies recognise the polypeptide rather than the glycan side chain and the polyclonal antiserum also recognises deglycosylated binding protein. The antibodies have been used to quantify the abundance of auxinbinding protein in a number of tissues of etiolated maize seedlings. Root membranes contain 20-fold less binding protein than coleoptile membranes.Abbreviations ABP
auxin-binding protein
- DEAE
diethylaminoethyl
- Ig
immunoglobulin
- kDa
kilodalton
- NAA
naphthalene-1-acetic acid
- Mr
relative molecular mass
- PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulfate 相似文献
14.
A. J. Parr A. C. J. Peerless J. D. Hamill N. J. Walton R. J. Robins M. J. C. Rhodes 《Plant cell reports》1988,7(5):309-312
Transformed roots of Catharanthus roseus were obtained following infection of detached leaves with Agrobacterium rhizogenes. Roots would not grow in full strength Gamborg's B5 medium but would grow satisfactorily if the medium was diluted to one half strength. Little alkaloid appeared in the growth medium but root tissue contained a high level and wide variety of alkaloids. Ajmalicine, serpentine, vindolinine and catharanthine were prominent components. Vinblastine could also be detected by a combination of HPLC and radioimmunoassay, though at a level of only 0.05g/g dry weight.Abbreviations B5
Gamborg's B5 nutrient salts
- LC/MS
combined liquid chromatography/mass spectrometry
- FW
fresh weight
- Kb
kilobase 相似文献
15.
Sefton Louise Arnaud Danielle Goodfellow Peter N. Simmler Marie-Christine Avner Philip 《Mammalian genome》1992,2(1):21-31
The irradiation and fusion gene transfer (IFGT) procedure provides a means of isolating subchromosomal fragments for use in the mapping of loci and for cloning probes from a particular area of a chromosome. Using this procedure, two large panels of somatic cell hybrids that contain mouse X Chromosome (Chr) fragments have been generated. These hybrid panels were generated by irradiating the monochromosomal mouse-hamster hybrid HYBX, which retains the mouse X Chr, with either 10 K or 50 K rads of X-irradiation followed by fusion with a recipient Chinese hamster cell line. IFGT hybrids retaining mouse material were generated at high frequency. These hybrids were used to orient loci in the X-inactivation center region that had not been resolvable in our interspecies backcross panel and also to map, within the terminal region of the X Chr, repeat elements detected by the probe p15-4. These hybrids not only complement existing interspecies meiotic mapping panels for the detailed analysis of specific regions of particular chromosomes, but also provide a potential source of material for chromosome-specific probe isolation. 相似文献
16.
Susannah Louise Varmuza 《Development genes and evolution》1992,201(3):142-148
Summary LTXBO mice develop ovarian teratomas at high frequency. The phenotype of tumour tissues is unusual in that most contain trophoblast elements. Since the tumours are derived from parthenogenetically activated oocytes, they would not be expected to produce trophoblast. The developmental potential of parthenogenetic cells from these mice was tested in aggregation chimeras. No contribution to trophoblast tissues was observed. However, a high incidence of morphological abnormalities was seen, suggesting that the parthenogenetic cells exerted a teratogenic effect. 相似文献
17.
The introduction of new technology and increased effort from around the world is driving the completion of the human gene map. In parallel with the creation of the map, we are beginning to see the bio-medical benefits that are a direct consequence of learning more about our own genome. 相似文献
18.
Patricia A. James F. Louise Lavender Gillian M. Lawrence Deryck G. Walker 《Biochemical genetics》1985,23(7-8):525-538
Partially purified preparations of the hepatic glucokinase from C3H/He and C58 inbred mice have been used to explore the molecular basis for the observed twofold difference in activity between the strains. The single codominant gene that appears to regulate activity, the alleles of which are designated Gka and Gkb, respectively, for the two strains, could represent a structural gene change. This now seems unlikely because the mouse enzyme, although showing small differences from rat glucokinase, appeared to be identical in the two strains with respect to thermal stability, electrophoretic mobility in agarose gels, and kinetic properties such as the apparent K
m values for MgATP2– and glucose and the unique cooperative interaction with the latter substrate. The enzymes also reacted identically in a range of immunological tests (double-diffusion, immunoelectrophoresis, immune precipitation and immune inhibition assays) and ELISA immune inhibition assays indicated that the twofold difference in activity was due to a similar difference in antigenically active enzyme. Genetic control over the physiologically significant regulation of enzyme amount is therefore probable.This work has been supported in part by a grant from the British Diabetic Association and a Training Studentship to PAJ from the Medical Research Council (U.K.). 相似文献
19.
Addition of a mixture of EGF + insulin to quiescent cell cultures synergistically stimulates the cells to reinitiate DNA synthesis and cell division. We have previously demonstrated that this mixture rapidly increases ATP turnover in quiescent cells. The present work shows that each of the two growth factors, EGF and insulin, when added separately to quiescent cells was able to stimulate the phosphorylation of the organic acid-soluble compounds (Po) pool and ATP turnover. The stimulation of ATP turnover was closely correlated with the increase in phosphorylation of the Po pool which suggests that Po labelling reflects the ATP turnover. In many experiments, the synergy between the two growth factors on the early increase in phosphorylation of the Po pool was clearly shown. Doubling the concentration of EGF (12-24 ng/ml) or insulin (50-100 ng/ml) did not increase early stimulation of phosphorylation of the Po pool, whereas simultaneous addition of the two growth factors induced a greater stimulation than that of each growth factor separately added. The augmentation in Po labelling after addition of EGF or insulin alone was transient. The synergistic effect of the two growth factors was more significant when determined 150 or 300 min after growth-factor addition. In our experimental conditions, each of the two growth factors, EGF and insulin, was able to induce a stimulation of DNA synthesis. However, the best stimulatory effect was observed with the mixture of the two which synergistically increased DNA synthesis determined between 6 and 24 h after growth-factor addition. The comparison between DNA replication and Po labelling suggests a correlation between the increase in DNA replication and in the total ATP synthesized in the first 5 h after cell stimulation by growth factors added separately or in combination. 相似文献
20.
J. D. Hamill D. Pental E. C. Cocking 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1985,71(3):486-490
Summary Somatic hybrid plants, produced between Nicotiana rustica and N. tabacum by heterokaryon isolation and culture and also by mutant complementation, were examined regarding their ability to set seed. From a total of seventeen independent somatic hybrids, three were found to be partially self-fertile while the others did not set seed. Differences regarding the methods of hybrid selection, parental varieties and chloroplast composition of hybrids did not appear to be significant regarding the ability of plants to set seed. Much variation in fertility was observed in subsequent generations and by recurrent selection of the most fertile, over two generations, it was possible to increase the level of self-fertility in some of the progeny. One R2 derivative possessed approximately a tenfold higher level of self-fertility than it's somatic hybrid parent. The presence of genetic markers from both parents were observed in all progeny indicating their hybrid nature. 相似文献