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111.
112.
U. Skiba K. J. Hargreaves I. J. Beverland D. H. ONeill D. Fowler J. B. Moncrieff 《Plant and Soil》1996,181(1):139-144
Measurements of N2O emission fluxes from a 3 ha field of winter wheat were measured using eddy covariance and relaxed eddy accumulation continuously over 10 days during April 1994. The measurements averaged fluxes over approximately 105 m2 of the field, which was fertilised with NH4NO3 at a rate of 43 kg N ha-1 at the beginning of the measurements. The emission fluxes became detectable after the first heavy rainfall, which occured 4 days after fertiliser application. Emissions of N2O increased rapidly during the day following the rain to a maximum of 280 ng N m-2s-1 and declined over the following week. During the period of significant emission fluxes, a clear diurnal cycle in N2O emission was observed, with the daytime maximum coinciding with the soil temperature maximum at 12 cm depth. The temperature dependence of the N2O emission was equivalent to an activation energy for N2O production of 108 kJ mol-1. The N2O fluxes measured using relaxed eddy accumulation, averaged over 30 to 270 min, were in agreement with those of the eddy covariance system within 60%. The total emission of N2O over the period of continuous measurement (10 days) was equivalent to about 10 kg N2O-N, or 0.77% of the N fertiliser applied. 相似文献
113.
The fluxes of NO and NO2 between wheat canopy monoliths and the atmosphere were investigated with the dynamic chamber technique. For this purpose monoliths were dug out at different plant growth stages from a field site, transported to the institute, and placed in an environmental growth chamber. The wheat canopy monoliths were exposed over a period of four days to the average ratios of atmospheric NO2 and NO measured at the field site, i.e. NO2 concentration of about 18 mL L-1 plus NO concentration lower than 0.5 nL L-1. Under these conditions NO emission into the atmosphere and NO2 deposition into canopy monoliths was observed. Both fluxes showed diurnal variation with maximum rates during the light and minimum rates during darkness. NO2 fluxes correlated with soil temperature as well as with light intensity. NO fluxes correlated with soil temperature but not with light intensity. From the investigation performed the diurnal variation of the NO and NO2 compensation points, the maximum rates of NO and NO2 emission, and the total resistances of NO and NO2 fluxes were calculated. Under the assumption that the measured data are representative for the whole vegetation period, annual fluxes of NO and NO2 were estimated. Annual NO emission into the atmosphere amounted to 87 mg N m-2 y-1 (0.87 kg ha-1 y-1), annual NO2 deposition into canopy monoliths amounted to 1273 mg N m-2 y-1 (12.73 kg ha-1 y-1). Apparently, the uptake of atmospheric nitrogen by the wheat field from NO2 deposition is about 15 times higher than the loss of nitrogen from NO emission. It can therefore be assumed that even in rural areas wheat fields are a considerable sink for atmospheric nitrogen. The annual sink strength estimated in the present study is ca. 12 kg N ha-1 y-1. The possible origin of the NO emitted and the fate of atmospheric NO2 taken up by the wheat canopy monoliths are discussed.Preliminary results of this paper were presented at the Joint Workshop COST 611/Working Party 3 and EUROTRAC in Delft, The Netherlands (Ludwig et al., 1991). 相似文献
114.
Christopher M. Hylton Kay Denyer Peter L. Keeling Ming-Tang Chang Alison M. Smith 《Planta》1996,198(2):230-237
The effects of waxy mutations on starch-granule-bound starch synthases (EC 2.4.1.18) in the developing endosperm of barley (Hordeum vulgare L.) and maize (Zea mays L.) have been investigated. Three granule-bound starch synthases in barley endosperm were identified by use of antibodies to known starch synthases, by reconstitution and assay of individual proteins from sodium dodecyl sulphate-polyacrylamide gels of granule-bound proteins, and by partial purification of proteins released by enzymic digestion of starch. These are proteins of 60, 77 and 90 kDa. Use of antibodies to known starch synthases and partial purification of proteins released by enzymic digestion of starch indicated that there may be at least four granule-bound starch synthases in maize endosperm: proteins of 59, 74, 77 and 83 kDa. Mutations at the waxy loci of both species affected only the 60- (barley) and 59-(maize) kDa isoforms. No evidence was found that other putative isoforms are altered in abundance or activity by the mutations. The contribution of our results to understanding of the starch synthase activity of intact starch granules and the mechanism of amylose synthesis is discussed.We are very grateful to Dr. Roger Ellis (SCRI, Dundee, Scotland) for the gift of barley seeds, and to Drs Roger Ellis, Alan Schulman and Cathie Martin for helpful advice and comments during the course of this work. 相似文献
115.
Roberto Viola 《Planta》1996,198(2):186-196
Metabolism of radiolabelled hexoses by discs excised from developing potato (Solanum tuberosum L.) tubers was been investigated in the presence of acid invertase to prevent accumulation of labelled sucrose in the bathing medium (Viola, 1996, Planta 198: 179–185). When the discs were incubated with either [U-14C]glucose or [U-14C]fructose without unlabelled hexoses, the unidirectional rate of sucrose synthesis was insignificant compared with that of sucrose breakdown. The inclusion of unlabelled fructose in the medium induced a dramatic increase in the unidirectional rate of sucroses synthesis in the tuber discs. Indeed, the decline in the sucrose content observed when discs were incubated without exogenous sugars could be completely prevented by including 300 mM fructose in the bathing medium. On the other hand, the inclusion of unlabelled glucose in the medium did not significantly affect the relative incorporation of [U-14C]glucose to starch, sucrose or glycolytic products. Substantial differences in the intramolecular distribution of 13C enrichment in the hexosyl moieties of sucrose were observed when the discs were incubated with either [2-13C]fructose or [2-13C]glucose. The pattern of 13C enrichment distribution in sucrose suggested that incoming glucose was converted into sucrose via the sucrose-phosphate synthase pathway whilst fructose was incorporated directly into sucrose via sucrose synthase. Quantitative estimations of metabolic fluxes in vivo in the discs were also provided. The apparent maximal rate of glucose phosphorylation was close to the extractable maximum catalytic activity of glucokinase. On the other hand, the apparent maximal rate of fructose phosphorylation was much lower than the maximum catalytic activity of fructokinase, suggesting that the activity of the enzyme (unlike that of glucokinase) was regulated in vivo. Although in the discs incubated with or without fructose the rates of starch synthesis or glycolysis were similar, the relative partitioning of metabolic intermediates into sucrose was much higher in discs incubated with fructose (0.6% and 32.6%, respectively). It is hypothesised that the equilibrium of the reaction catalysed by sucrose synthase in vivo is affected in discs incubated with fructose as a result of the accumulation of the sugar in the tissue. This results in the onset of sucrose cycling. Incubation with glucose enhanced all metabolic fluxes. In particular, the net rate of starch synthesis increased from 2.0 mol · hexose · g FW–1 · h–1 in the absence of exogenous glucose to 3.7 mol · hexose · g FW–1 · h–1 in the presence of 300 mM glucose. These data are taken as an indication that the regulation of fructokinase in vivo may represent a limiting factor in the utilisation of sucrose for biosynthetic processes in developing potato tubers.Abbreviations ADPGlc
adenosine 5-diphosphoglucose
- Glc6P
glucose-6-phosphate
- hexose-P
hexose phosphate
- NMR
nuclear magnetic resonance
- UDPGlc
uridine 5-diphosphoglucose
Many thanks to L. Sommerville for skillfull assistance and to J. Crawford and J. Liu for useful discussions on flux analysis. The research was funded by the Scottish Office Agriculture and Fisheries Department. 相似文献
116.
Summary The potential of tobacco BY-2 suspension-cultured cells for examining in vivo targeting and import of proteins into plant peroxisomes was shown recently in our laboratory. In the current study, the necessity and sufficiency of putative C-terminal targeting signals on cottonseed malate synthase and bacterial chloramphenicol acetyl-transferase (CAT) were examined in BY-2 cells. Cotton suspension cells also were evaluated as another in vivo peroxisome targeting system. Ultrastructural views of BY-2 cells showed that the peroxisomes were relatively small (0.1-0.3 m diameter), a characteristic of so-called unspecialized peroxisomes, Peroxisomes in cotton and tobacco cells were identified with anti-cottonseed catalase IgGs as distinct immunofluorescent particles clearly distinguishable from abundant immunofluorescent mitochondria and plastids, marked with antibodies to -ATPase and stearoyl-ACP 9 desaturase, respectively. The C-terminal ser-lys-leu (SKL) motif is a well-established peroxisome targeting signal (PTS 1) for mammals and yeasts, but not for plants. Antiserum raised against SKL peptides recognized proteins only in peroxisomes in cotton and tobacco cells. The necessity of SKL-COOH for targeting of proteins to plant peroxisomes had not been demonstrated; we showed that SKL-COOH was necessary for directing cottonseed malate synthase to BY-2 peroxisomes. KSRM-COOH, a conservative modification of SKL-COOH, was shown by others to be sufficient for redirecting CAT in stably-transformed Arabidopsis plants to the leaf peroxisomes. Here we show with the same CAT constructs (e.g., pMON316CAT-KSRM) that KSRM is sufficient for targeting transiently-expressed passenger proteins to unspecialized BY-2 peroxisomes. These results provide new direct evidence for the necessity of SKL-COOH (a type 1 PTS) and sufficiency of a conservative modification of the PTS 1 (KSRM-COOH) for in vivo, heterologous targeting of proteins to plant peroxisomes.Abbreviations CAT
chloramphenicol acetyltransferase
- CHO
cells Chinese hamster ovary cells
- DAB
3,3-diaminobenzidine
- GUS
-glucuronidase
- ICL
isocitrate lyase
- KSRM
lysine-serine-arginine-methionine
- MS
malate synthase
- PBS
phosphate-buffered saline
- PTS
peroxisome targeting signal
- SKL
serine-lysine-leucine
- tobacco BY-2
Bright Yellow-2
Dedicated to Professor Eldon H. Newcomb in recognition of his contributions to cell biology 相似文献
117.
E. Flipse C. J. A. M. Keetels E. Jacobsen R. G. F. Visser 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1996,92(1):121-127
A gene-dosage population was obtained by crossing two genotypes that were duplex for the GBSS allele. Nulliplex, simplex, duplex or triplex/quadruplex plants could be identified by monitoring the segregation of red and blue microspores after staining with iodine. GBSS activity was significantly different for all groups and showed an almost linear dosage effect for the wildtype GBSS gene. A dosage effect was found for amylose content that was not linear. The amylose content was similar for both the duplex and triplex/quadruplex group. Within the simplex group, differences in amylose content were found, which might be due to a different genetic background. There was no linear correlation between GBSS activity and amylose content. A certain level of GBSS activity led to a maximum amount of amylose, and further increase in GBSS activity did not result in a further increase in amylose content. The presence of one or more wildtype GBSS allele(s), and therefore the presence of amylose in the starch granules, had a great influence on the physico-chemical properties of the starch suspensions. 相似文献
118.
Culture of rat mesenteric arteriolar smooth muscle cells: effects of platelet-derived growth factor, angiotensin, and nitric oxide on growth 总被引:1,自引:0,他引:1
We cultured smooth muscle cells as explants from rat mesenteric arterioles (40–200m in diameter) obtained by injecting a suspension of iron oxide intraarterially and magnetically separating the arterioles after collagenase digestion of adventitial tissue. In third-passaged cells we ascertained smooth muscle purity of >98% by characteristic morphology, contraction responses, and specific immunofluorescence staining. Treatment of growth-arrested (in 0.4% fetal calf serum) cells with platelet-derived growth factor (0.3–7.5 nM) or angiotensin II (0.001–1000 nM) induced 3H-thymidine incorporation and cell proliferation in a dose-dependent manner (P<0.01). S-nitroso-N acetylpencillamine (0.05–0.5 mM), a nitric oxide-generating compound, inhibited 10% fetal calf serum-induced 3H-thymidine incorporation (P<0.05) and cell proliferation (P<0.01). The antimitogenic effect of S-nitroso-N-acetylpencillamine was significantly reduced by hemoglobin and potentiated by superoxide dismutase (P<0.01). In addition to a new technique for culturing mesenteric arteriolar smooth muscle cells, these findings provide evidence that platelet-derived growth factor, angiotensin II, and nitric oxide may be involved in their growth control. 相似文献
119.
Gilbert Berben 《Antonie van Leeuwenhoek》1996,69(1):305-315
Cytochrome c oxidase (EC 1.9.3.1) is one of the components of the electron transport chain by which Nitrobacter, a facultative lithoautotrophic bacterium, recovers energy from nitrite oxidation. The genes encoding the two catalytic core subunits of the enzyme were isolated from a Nitrobacter winogradskyi gene library. Sequencing of one of the 14 cloned DNA segments revealed that the subunit genes are side by side in an operon-like cluster. Remarkably the cluster appears to be present in at least two copies per genome. It extends over a 5–6 kb length including, besides the catalytic core subunit genes, other cytochrome oxidase related genes, especially a heme O synthase gene. Noteworthy is the new kind of gene order identified within the cluster. Deduced sequences for the cytochrome oxidase subunits and for the heme O synthase look closest to their counterparts in other -subdivision Proteobacteria, particularly the Rhizobiaceae. This confirms the phylogenetic relationships established only upon 16S rRNA data. Furthermore, interesting similarities exist between N. winogradskyi and mitochondrial cytochrome oxidase subunits while the heme O synthase sequence gives some new insights about the other similar published -subdivision proteobacterial sequences.Abbreviations COI
cytochrome oxidase subunit I
- COII
cytochrome oxidase subunit II
- COIII
cytochrome oxidase subunit III
- HOS
Heme O synthase
- ORF
open reading frame
- SDS
sodium dodecyl sulfate 相似文献
120.
Is there a gas (general adaptation syndrome) response to various types of environmental stress? 总被引:6,自引:0,他引:6
A hypothesis of existence of a general adaptation syndrome (GAS), in which different types of stress evoke similar coping
mechanisms, resulting in adaptations, is tested for plants. As stress coping mechanisms, oxy-free radical scavengers and antioxidants,
osmoregulation, the role of abscisic acid, jasmonates, nitric oxide, synthesis of heat shock proteins and phytochelatins as
heavy metal detoxifiers are discussed.
The authors would like to thank the Netherlands Organization for Scientific Research (NWO) which enabled their collaboration
and the formulation of some of the concepts here presented. 相似文献