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61.
Nitrogen losses from perennial grass species 总被引:1,自引:0,他引:1
Nitrogen losses from plants may occur through a variety of pathways, but so far, most studies have only quantified losses of nutrients by above-ground litter production. We used 15N pulse labelling to quantify total nitrogen losses from above- and below-ground plant parts. Using this method we were able to include also pathways other than above-ground litter production. To test the hypothesis that species from nutrient-poor habitats lose less nitrogen than species from more fertile soils, six perennial grasses from habitats with a wide range of nutrient availability were investigated: Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra, F. ovina and Molinia caerulea. The results of an experiment carried out in pots in a green-house at two fertility levels show that statistically significant losses occur through pathways other than above-ground litter production. In the low fertility treatment, most (70%) losses from L. perenne occurred by litter production, but in Ar. elatius, F. rubra, F. ovina and M. caerulea, more than 50% of labelled N losses took place by root turn-over, leaching or exudation from roots. When nutrient supply increased, the 15N losses in above-ground dead material increased in all species and in Ar. elatius, A. odoratum and F. rubra the 15N losses via other pathways decreased. Ranked according to decreasing turnover coefficient the sequence of species was: L. perenne, A. odoratum, F. rubra, F. ovina, Ar. elatius, M. caerulea. These results suggest that species adapted to sites with low availability of nutrients lose less nitrogen (including above- and below-ground losses) than species adapted to more fertile soils. 相似文献
62.
Effects of interleukin-12 on in vitro culture with interleukin-2 of regional lymph node lymphocytes from lung cancer patients 总被引:2,自引:0,他引:2
T. Hanagiri Mitsuhiro Takenoyama Takashi Yoshimatsu Chikashi Hirashima Ichiro Yoshino Kozo Nakanishi Akira Nagashima Kikuo Nomoto Kosei Yasumoto 《Cancer immunology, immunotherapy : CII》1996,43(2):87-93
In the present study, we carried out a functional analysis of regional lymph node lymphocytes (RLNL) from patients with lung
cancer after in vitro activation by interleukin-2 (IL-2) and interleukin-12 (IL-12). IL-12 (100 U/ml) enhanced both the proliferation
and cytotoxic activity of RLNL in a culture with low doses of IL-2 (5 – 10 JRU/ml). After comparing an RLNL culture with a
low dose of IL-2 alone, a higher proportion of CD8+ cells and CD56+ cells and a lower proportion of CD4+ cells were found in the culture with both IL-12 and a low dose of IL-2. Such a combination of the cytokines effectively activated
RLNL in terms of the expression of IL-2 receptors. In the culture condition of IL-12 and a low dose of IL-2, a synergistic
effect was observed in the production of such cytokines as interferon γ, tumor necrosis factor α (TNFα), and TNFβ, as well
as in tumor cytotoxicity. However, the addition of IL-12 inhibited the cytotoxicity of RLNL in the culture with a high dose
of IL-2 (100 JRU/ml). This inhibition is considered to be partially due to the endogenous production of TNFα by lymphocytes,
because the neutralization of TNFα bioactivity partially restored the cytotoxic activities of RLNL. Furthermore, in the presence
of hydrocortisone, IL-12 synergistically enhanced the cytotoxic activity of RLNL cultured with a high dose of IL-2. These
results provide useful information about the improvement of adoptive immunotherapy against cancer using RLNL.
Received: 2 February 1996 / Accepted: 30 July 1996 相似文献
63.
Robert Blackburn Sandra Galoforo Christine M. Berns Mark Ireland Joong M. Cho Peter M. Corry Yong J. Lee 《Molecular and cellular biochemistry》1996,155(1):51-60
We investigated the role of B-crystallin expression in the development of thermotolerance in murine L929 cells. An initial heat-shock of 10 min at 45°C induced thermotolerance in these cells to a heat challenge at 45°C administered 24 h later. The thermotolerance ratio at 10–1 isosurvival was 1.7. Expression of B-crystallin gene was not detected during the 24 h incubation at 37°C following heat shock by either northern or western blots. In contrast, inducible HSP70 synthesis was observed during this time period. Thus, this cell line provided an unique system in which to examine the effects of transfected B-crystallin on thermoresistance and thermotolerance. Cells stably transfected with B-crystallin under the control of an inducible promoter did not show a significant increase in the ability to develop thermotolerance. However, a stably transfected L929 clone expressing high levels of constitutive B-crystallin exhibited an approximately 50% increase in thermal resistance over parental and control cells. Though expression of B-crystallin is not requisite for the development of thermotolerance in L929 cells, overexpression of transfected B-crystallin can contribute to increased thermoresistance. 相似文献
64.
Impact of residue quality on the C and N mineralization of leaf and root residues of three agroforestry species 总被引:6,自引:1,他引:5
A laboratory incubation experiment with 15N labeled root and leaf residues of 3 agroforestry species (Leucaena leucocephala, Dactyladenia barteri and Flemingia macrophylla) was conducted under controlled conditions (25 C) for 56 days to quantify residue C and N mineralization and its relationship with residue quality.No uniform relation was found between the chemical composition of the above and below residues. The leucaena and dactyladenia roots contained more lignin (8 and 26% respectively) and less N (2.0 and 1.0% respectively) than the respective leaves (2 and 13% lignin and 2.9 and 1.4% N, respectively), whereas the differences between the lignin and N contents of the flemingia leaves and roots were not significant (4.6 and 3.0% lignin and 2.63 and 2.68% N, respectively). The leucaena leaves contained more polyphenols than the roots (6.4 and 3.6%), while the polyphenol content of the leaves and roots of the other residues was similar (5.0 and 5.1% for dactyladenia and 4.0 and 3.5% for flemingia).Three patterns of N mineralization could be distinguished. A first pattern, followed by residues producing the highest amounts of CO2, showed an initial immobilization of soil derived N, followed by a net release of both soil and residue derived N after 7 days of incubation. A second pattern, followed by the flemingia leaf residues which produced intermediate amounts of CO2 and had an intermediate quality, showed no significant immobilization of soil derived N, and significant mineralization of residue N. A third pattern, followed by both low quality dactyladenia residues, showed a low release of residue derived N and a continued inmobilization of soil derived N.Residue C mineralization was significantly (p<0.05) correlated with the residue lignin content, C-to-N ratio, and polyphenol-to-N ratio. The proportion of residue N mineralized (immobilized) after 56 days of incubation was significantly correlated with the residue N content (p<0.01) and the C-to-N ratio (p<0.05). The relations were quadratic, rather than linear. The ratio of the proportion of residue N mineralized (immobilized) over the proportion of residue C mineralized after 56 days was highly significantly correlated with the lignin content (p<0.01) and C-to-N (p<0.001), lignin-to-N (p<0.01), polyphenol-to-N (p<0.01) and (lignin+polyphenol)-to-N ratios (p<0.01) in a linear way. This indicates that due to the low availability of the residue C, relatively less N is immobilized for the very low quality residues ((lignin+polyphenol)-to-N ratio: 29.7) than for the residues with a relatively higher quality ((lignin+polyphenol)-to-N ratios between 3.3 and 12.5). 相似文献
65.
The current study investigated the short-term physiological implications of plant nitrogen uptake of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) under both greenhouse and field conditions. 15N labelled urea amended with 0.0, 0.01, 0.1 and 0.5% nBTPT (w/w) was surface applied at a rate equivalent to 100 kg N ha–1 to perennial ryegrass in a greenhouse pot experiment. Root, shoot and soil fractions were destructively harvested 0.75, 1.75, 4, 7 and 10 days after fertilizer application. Urease activity was determined in each fraction together with 15N recovery and a range of chemical analyses. The effect of nBTPT amended urea on leaf tip scorch was evaluated together with the effect of the inhibitor applied on its own on plant urease activity.nBTPT-amended urea dramatically reduced shoot urease activity for the first few days after application compared to unamended urea. The higher the nBTPT concentration the longer the time required for shoot activity to return to that in the unamended treatment. At the highest inhibitor concentration of 0.5% shoot urease activity had returned to that of unamended urea by 10 days. Root urease activity was unaffected by nBTPT in the presence of urea but was affected by nBTPT in the absence of urea.Transient leaf tip scorch was observed approximately 7–15 days after nBTPT + urea application and was greatest with high concentrations of nBTPT and high urea-N application rates. New developing leaves showed no visual sign of tip necrosis.Urea hydrolysis of unamended urea was rapid with only 1.3% urea-N remaining in the soil after 1.75 days. N uptake and metabolism by ryegrass was rapid with 15N recovery from unamended urea, in the plant (shoot + root) being 33% after 1.75 days. Most of the 15N in the soil following the urea+0.5% nBTPT application was still as urea after 1.75 days, yet 15N plant recovery at this time was 25% (root+shoot). This together with other evidence, suggests that if urea hydrolysis in soil is delayed by nBTPT then urea can be taken up by ryegrass as the intact molecule, albeit at a significantly slower initial rate of uptake than NH4
+-N. Protein and water soluble carbohydrate content of the plant were not significantly affected by amending urea with nBTPT however, there was a significant effect on the composition of amino acids in the roots and shoots, suggesting a difference in metabolism.Although nBTPT-amended urea affected plant urease activity and caused some leaf-tip scorch the effects were transient and short-lived. The previously reported benefit of nBTPT in reducing NH3 volatilization of urea would appear to far outweigh any of the observed short-term effects, as dry-matter production of ryegrass is increased. 相似文献
66.
Grain yield, symbiotic N2 fixation and interspecific competition for inorganic N in pea-barley intercrops 总被引:4,自引:0,他引:4
Erik Steen Jensen 《Plant and Soil》1996,182(1):25-38
The effect of mixed intercropping of field pea (Pisum sativum L.) and spring barley (Hordeum vulgare L.), compared to monocrop cultivation, on the yield and crop-N dynamics was studied in a 4-yr field experiment using 15N-isotope dilution technique. Crops were grown with or without the supply of 5 g 15N-labeled N m-2. The effect of intercropping on the dry matter and N yields, competition for inorganic N among the intercrop components, symbiotic fixation in pea and N transfer from pea to barley were determined. As an average of four years the grain yields were similar in monocropped pea, monocropped and fertilized barley and the intercrop without N fertilizer supply. Nitrogen fertilization did not influence the intercrop yield, but decreased the proportion of pea in the yield. Relative yield totals (RYT) showed that the environmental sources for plant growth were used from 12 to 31% more efficiently by the intercrop than by the monocrops, and N fertilization decreased RYT-values. Intercrop yields were less stable than monocrop barley yields, but more stable than the yield of monocropped pea. Barley competed strongly for soil and fertilizer N in the intercrop, and was up to 30 times more competitive than pea for inorganic N. Consequently, barley obtained a more than proportionate share of the inorganic N in the intercrop. At maturity the total recovery of fertilizer N was not significantly different between crops, averaging 65% of the supplied N. The fertilizer N recovered in pea constituted only 9% of total fertilizer-N recovery in the intercrop. The amount of symbiotic N2 fixation in the intercrop was less than expected from its composition and the fixation in monocrop. This indicates that the competition from barley had a negative effect on the fixation, perhaps via shading. At maturity, the average amount of N2 fixation was 17.7 g N m-2 in the monocrop and 5.1 g N m-2 in the intercropped pea. A higher proportion of total N in pea was derived from N2 fixation in the intercrop than in the monocrop, on average 82% and 62%, respectively. The 15N enrichment of intercropped barley tended to be slightly lower than of monocropped barley, although not significantly. Consequently, there was no evidence for pea N being transferred to barley. The intercropping advantage in the pea-barley intercrop is mainly due to the complimentary use of soil inorganic and atmospheric N sources by the intercrop components, resulting in reduced competition for inorganic N, rather than a facilitative effect, in which symbiotically fixed N2 is made available to barley.Abbreviations MC
monocrop
- IC
intercrop
- PMC
pea monocrop
- BMC
barley monocrop
- PIC
pea in intercrop
- BIC
barley in intercrop 相似文献
67.
Specific molecular marker of the genes controlling linolenic acid content in rapeseed 总被引:4,自引:0,他引:4
C. Jourdren P. Barret D. Brunel R. Delourme M. Renard 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,93(4):512-518
In rapeseed, which is an agronomically important oilseed, variation in the linolenic acid content of the oil has been obtained through chemical mutagenesis treatment. Conventional breeding of this quantitative trait, however requires specific molecular markers. By means of biochemical experiments, we have established that the induced variation in linolenic acid content is associated with the fad3 gene encoding the microsomal 15 desaturase. Using a pair of primers specific to this gene and a doubled haploid progeny derived from a low linolenic x high linolenic acid F1hybrid, we have identified a polymorphism of the fad3 alleles between the low- and the high-linolenic acid genotypes. The structure exon/intron of the fad3 DNA sequence seems to be very similar to that of the Arabidopsis fad3 gene. The choice of the primer pair allows specific amplification of one of the two rapeseed fad3 genes. The value and contribution of specific markers to conventional plant breeding is discussed. 相似文献
68.
Abstract: The pentameric subunit composition of a large population (36%) of the cerebellar granule cell GABAA receptors that show diazepam (or clonazepam)-insensitive [3 H]Ro 15-4513 binding has been determined by immunoprecipitation with subunit-specific antibodies. These receptors have α6 , α1 , γ2S , γ2L , and β2 or β3 subunits colocalizing in the same receptor complex. 相似文献
69.
Etsuro Ito Kotaro Oka Carlos Collin Bernard G. Schreurs Manabu Sakakibara Daniel L. Alkon 《Journal of neurochemistry》1994,62(4):1337-1344
Abstract: Tumor necrosis factor-a (TNF-α), interferon-γ (IFN-7), and interleukin-6 (IL-6), but not TNF-β, can induce the in vitro differentiation of the neuroblastoma cell line N103 in a dose-dependent manner. Differentiation of N103 was accompanied by the arrest of cell growth and neurite formation. The induction of neuroblastoma cell differentiation by TNF-α and IFN-γ can be specifically inhibited by a nitric oxide (NO) synthase inhibitor, l -NG -monomethylarginine. In contrast, the differentiation of N103 cells by IL-6 was not affected by l -NG -monomethylarginine. These results indicate that TNF-α and IFN-γ, but not IL-6, induce the differentiation of neuroblastoma cells via NO. This is confirmed by the finding that the culture super- natants of N103 cells induced by TNF-α and IFN-γ, but not that by IL-6, contained high levels of NO2 − , the production of which was inhibited by l - N G -monomethylarginine. Furthermore, the differentiation of N103 cells can be induced directly in a dose-dependent manner by the addition of nitroprusside, a generator of NO, into the culture medium. These data therefore indicate that NO may be an important mediator in the induction of neuronal cell differentiation by certain cytokines such as TNF-α and IFN-γ and that neuronal cells, in addition to the macrophagelike brain cells, can be induced by immunological stimuli to produce large quantities of NO. 相似文献
70.
Bi-directional transfer of nitrogen between alfalfa and bromegrass: Short and long term evidence 总被引:2,自引:0,他引:2
Transfer of N from legumes to associated non-legumes has been demonstrated under a wide range of conditions. Because legumes
are able to derive their N requirements from N2 fixation, legumes can serve, through the transfer of N, as a source of N for accompanying non-legumes. Studies, therefore,
are often limited to the transfer of N from the legume to the non-legume. However, legumes preferentially rely on available
soil N as their source of N. To determine whether N can be transferred from a non-legume to a legume, two greenhouse experiments
were conducted. In the short-term N-transfer experiment, a portion of the foliage of meadow bromegrass (Bromus riparius Rhem.) or alfalfa (Medicago sativa L.) was immersed in a highly labelled 15N-solution and following a 64 h incubation, the roots and leaves of the associated alfalfa and bromegrass were analyzed for
15N. In the long-term N transfer experiment, alfalfa and bromegrass were grown in an 15N-labelled nutrient solution and transplanted in pots with unlabelled bromegrass and alfalfa plants. Plants were harvested
at 50 and 79 d after transplanting and analyzed for 15N content. Whether alfalfa or bromegrass were the donor plants in the short-term experiment, roots and leaves of all neighbouring
alfalfa and bromegrass plants were enriched with 15N. Similarly, when alfalfa or bromegrass was labelled in the long-term experiment, the roots and shoots of neighbouring alfalfa
and bromegrass plants became enriched with 15N. These two studies conclusively show that within a short period of time, N is transferred from both the N2-fixing legume to the associated non-legume and also from the non-legume to the N2-fixing legume. The occurrence of a bi-directional N transfer between N2-fixing and non-N2-fixing plants should be taken into consideration when the intensity of N cycling and the directional flow of N in pastures
and natural ecosystems are investigated. 相似文献