首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 303 毫秒
1.
The possible role of C2H4 metabolism in mediating the responses of plants to C2H4 is re-examined. It is demonstrated that (i) the effects of inhibitors upon C2H4 action do not correspond with their effects on metabolism, (ii) elicitors of C2H4 effects do not have appropriate effects on C2H4 metabolism, (iii) inhibitors of C2H4 metabolism do not affect the response of plants to C2H4. It is concluded that metabolism of C2H4 is not linked to the mode of action of the growth regulator.Abbreviations DTC sodium diethyldithiocarbamate - FW fresh weight  相似文献   

2.
Regulation of growth in stem sections of deep-water rice   总被引:11,自引:0,他引:11  
Ilya Raskin  Hans Kende 《Planta》1984,160(1):66-72
Submergence in water greatly stimulates internodal elongation in excised stem sections of deep-water rice (Oryza sativa L. cv. Habiganj Aman II) and inhibits growth of leaf blades and leaf sheaths. The highest rates of internodal growth have been observed in continuous light. Very little growth occurs in submerged sections kept in darkness or incubated under N2 in the light. The effect of submergence on the growth of deep-water rice is, at least in part, mediated by C2H4, which accumulates in the air spaces of submerged sections. This accumulation results from increased C2H4 synthesis in the internodes of submerged sections and reduced diffusion of C2H4 from the tissue into the water. Increased C2H4 levels accelerate internodal elongation and inhibit the growth of leaves. Compounds capable of changing the rate of C2H4 synthesis, namely aminoethoxyvinylglycine, an inhibitor of C2H4 synthesis, and 1-aminocyclopropane-1-carboxylic acid, the immediate, precursor of C2H4, have opposite effects on growth of internodes and leaves. The enhancement of internodal elongation by C2H4 is particularly pronounced in an atmosphere of high CO2 and low O2. The increase in C2H4 synthesis in internodes of submerged sections is primarily triggered by reduced atmospheric concentrations of O2. The rate of C2H4 evolution by internodes isolated from stem sections and incubated in an atmosphere of low O2 is up to four times greater than that of isolated internodes incubated in air. In contrast, C2H4 evolution from the leaves is reduced under hypoxic conditions. The effect of submergence on growth of stem sections of deep-water rice can be mimicked by exposing non-submerged sections to a gas mixture which is similar to the gaseous atmosphere in the internodal lacunae of submerged sections, namely 3% O2, 6% CO2, 91% N2 (by vol.) and 1 l l-1 C2H4. Our results indicate that growth responses obtained with isolated rice stem sections are similar to those of intact deep-water rice plants.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine  相似文献   

3.
I. Struve  U. Lüttge 《Planta》1987,170(1):111-120
Membrane vesicles were isolated from mesophyll cells of Mesembryanthemum crystallinum in the C3 state and in the crassulacean acid metabolism (CAM) state. The distribution of ATP-hydrolysis and H+-transport activities, and the activities of hydroxypyruvate reductase and Antimycin-insensitive cytochrome-c-reductase on continuous sucrose gradients was studied. For isolations carried out routinely a discontinuous sucrose gradient (24%/37%/50%) was used. Nitrate-sensitive ATP-hydrolysis and H+-transport activities increased several-fold during the transition from C3 photosynthesis to CAM. Nitrate-sensitive ATPase showed a substrate preference for ATP with an apparent Km (MgATP2-) of 0.19–0.37 mM. In both C3 and CAM states the ATPase showed a concentration-dependent stimulation by the anions chloride and malate. However, the pH optima of the two states were different: the ATPase of C3- M. crystallinum had an optimum of pH 7.4 and that of CAM-M. crystallinum an optimum of pH 8.4. The optical probe oxonol-VI was used to demonstrate the formation of MgATP2--dependent electric-potential gradients in tonoplast vesicles.Abbreviations Bistris-Pronane 1,3-bis [tris(hydroxymethyl)-methylaminol propane - CAM Crassulacean acid metabolism - DIDS 4,4-dilsothiocyano-2,2-stilbene disulfonic acid: - DTT dithiothreitol - ER endoplasmic reticulum - Hepes 4-(2-hydroxyethyl)-1-piperazineethane sulfonic acid - HPR hydroxypyruvate reductase - IDPase inosine 5-diphosphatase - OX-VI oxonol VI - Tris 2-amino-2-(hydroxymethyl)-1,3-propanediol  相似文献   

4.
R. G. Mayne  H. Kende 《Planta》1986,167(2):159-165
The ability of vacuoles prepared from V. faba leaves to convert 1-aminocyclopropane-1-carboxylic acid to C2H4 was destroyed when vacuoles were lysed by passage through a hypodermic needle, freezing and thawing, osmotic shock, treatment with ethanol or with a detergent. Ethylene synthesis in the vacuolar fraction was also inhibited by the uncouplers carbonyl cyanide m-chlorophenyl hydrazone and dinitrophenol and by the ionophores valinomycin, nigericin, and A23187. Ethylene formation increased with increasing pH of the incubation medium over the pH range of 5.0–7.5. These observations support the hypothesis that C2H4 biosynthesis in vacuolar preparations is dependent on membrane integrity, possibly because of the requirement for a transmembrane ion gradient.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AVG aminoethoxyvinylglycine - CCCP carbonyl cyanide m-chlorophenyl hydrazone  相似文献   

5.
A. Yokota  S. Kitaoka  K. Miura  A. Wadano 《Planta》1985,165(1):59-67
The nonenzymatic reaction of glyoxylate and H2O2 was measured under physiological conditions of the pH and concentrations of reactants. The reaction of glyoxylate and H2O2 was secondorder, with a rate constant of 2.27 l mol-1 s-1 at pH 8.0 and 25° C. The rate constant increased by 4.4 times in the presence of Zn2+ and doubled at 35°C. We propose a mechanism for the reaction between glyoxylate and H2O2. From a comparison of the rates of H2O2 decomposition by catalase and the reaction with glyoxylate, we conclude that H2O2 produced during glycolate oxidation in peroxisomes is decomposed by catalase but not by the reaction with glyoxylate, and that photorespiratory CO2 originates from glycine, but not from glyoxylate, in C3 plants. Simulation using the above rate constant and reported kinetic parameters leads to the same conclusion, and also makes it clear that alanine is a satisfactory amino donor in the conversion of glyoxylate to glycine. Some serine might be decomposed to give glycine and methylene-tetrahydrofolate; the latter is ultimately oxidized to CO2. In the simulation of the glycolate pathway of Euglena, the rate constant was high enough to ensure the decarboxylation of glyoxylate by H2O2 to produce photorespiratory CO2 during the glycolate metabolism of this organism.Abbreviations Chl chlorophyll - GGT glutamate: glyoxylate aminotransferase (EC 2.6.1.4) - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - SGT serine: glyoxylate aminotransferase (EC 2.6.1.45) This is the ninth in a series on the metabolism of glycolate in Euglena gracilis. The eighth is Yokota et al. (1982)  相似文献   

6.
Barbehenn RV  Karowe DN  Chen Z 《Oecologia》2004,140(1):96-103
The increasing CO2 concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C3 than C4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C3) and Bouteloua curtipendula C4) at ambient (370 ppm) and elevated (740 ppm) CO2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO2 treatment combinations. As expected, the nutritional quality of the C3 grass declined to a greater extent than did that of the C4 grass at elevated CO2; protein levels declined in the C3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C3 grass grown under elevated CO2. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C3 grass under elevated CO2. Consumption rates of the C3 and C4 grasses were also similar, demonstrating a lack of compensatory feeding on the C4 grass. We also examined the relative efficiencies of nutrient utilization from a C3 and C4 grass by M. sanguinipes to test the basis for the C4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C4 grass than from the C3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C3 grass and the better growth performance of M. sanguinipes on this grass at both CO2 levels, we conclude that C3 grasses are likely to remain better host plants than C4 grasses in future CO2 conditions.  相似文献   

7.
The kinetic properties of the phosphate translocator from maize (Zea mays L.) mesophyll chloroplasts have been determined. We have used a double silicone-oil-layer centrifugation system in order to obtain true initial uptake rates in forward-reaction experiments. In addition, it was possible to perform back-exchange experiments and to study the effects of illumination and of preloading the chloroplasts with different substrates on transport. It is shown that the phosphate translocator from mesophyll chloroplasts of maize, a C4 plant, transports inorganic phosphate and phosphorylated C3 compounds in which the phosphate group is linked to the C3 atom (e.g. 3-phosphoglycerate and triose phosphate). The affinities of the transported metabolites towards the translocator protein are about one order of magnitude higher than in mesophyll chloroplasts from the C3 plant, spinach. In contrast to the phosphate translocator from C3-mesophyll chloroplasts, that of C4-mesophyll chloroplasts catalyzes in addition the transport of C3 compounds where the phosphate group is attached to the C2 atom (e.g. 2-phosphoglycerate, phosphoenolpyruvate). The phosphate translocator from both chloroplast types is strongly inhibited by pyridoxal-5-phosphate (PLP), 2,4,6-trinitrobenzenesulfonic acid and 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS). In the case of the spinach translocator protein these inhibitors were shown to react with the same amino-acid residue at the substrate binding site, and one molecule of either DIDS or PLP is obviously required per substrate binding site for the inactivation of the translocation process. In the functionally active dimeric translocator protein only one substrate-binding site appears to be accessible at a particular time, indicating that the site might be exposed to each side of the membrane in turn. Using [3H]-H2DIDS for the labelling of maize mesophyll envelopes the radioactivity was found to be associated with two polypeptides of about 29 and 30 kDa. Since Western-blot analysis showed that only the 30 kDa polypeptide reacted with an antiserum directed against the spinach phosphate translocator protein it is suggested that this polypeptide presumably represents the phosphate translocator from maize mesophyll chloroplasts.Abbreviations DIDS 4,4-diisothiocyanostilbene-2,2-disulfonic acid - PEP phosphoenolpyruvate - 2-,3-PGA 2-,3-phosphoglycerate - PLP pyridoxal-5-phosphate - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - TNBS 2,4,6-trinitrobenzenesulfonic acid - triose P triose phosphate This work was supported by the Deutsche Forschungsgemeinschaft  相似文献   

8.
The extent of photorespiration, the inhibition of apparent photosynthesis (APS) by 21% O2, and the leaf anatomical and ultrastructural features of the naturally occurring C3–C4 intermediate species in the diverse Panicum, Moricandia, and Flaveria genera are between those features of representative C3 and C4 plants. The greatest differences between the photosynthetic/photorespiratory CO2 exchange characteristics of the C3–C4 intermediates and C3 plants occur for the parameters which are measured at low pCO2 (i.e., the CO2 compensation concentration and rates of CO2 evolution into CO2-free air in the light). The rates of APS by the intermediate species at atmospheric pCO2 are similar to those of C3 plants.The mechanisms which are responsible for reducing photorespiration in the C3–C4 intermediate species are poorly understood, but two proposals have been advanced. One emphasizes the importance of limited C4 photosynthesis which reduces O2 fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase, and, thus, reduces photorespiration by a CO2-concentrating mechanism, while the other emphasizes the importance of the internal recycling of photorespiratory CO2 evolved from the chloroplast/mitochondrion-containing bundle-sheath cells. There is no evidence from recent studies that limited C4 photosynthesis is responsible for reducing photorespiration in the intermediate Panicum and Moricandia species. However, preliminary results suggest that some, but not all, of the intermediate Flaveria species may possess a limited C4 cycle. The importance of a chlorophyllous bundle-sheath layer in the leaves of intermediate Panicum and Moricandia species in a mechanism based on the recycling of photorespiratory CO2 is uncertain.Therefore, although they have yet to be clearly delineated, different strategies appear to exist in the C3–C4 intermediate group to reduce photorespiration. Of major importance is the finding that some mechanism(s) other than Crassulacean acid metabolism or C4 photosynthesis has (have) evolved in at least the majority of these terrestrial intermediate species to reduce the seemingly wasteful metabolic process of photorespiration.Abbreviations APS apparent (net) photosynthesis - CAM Crassulacean acid metabolism - CE carboxylation efficiency - T CO2 compensation concentration - IRGA infrared gas analysis - Pi orthophosphate - PEP phosphoenolpyruvate - RuBP ribulose 1,5-bisphosphate Published as Paper No. 7383, Journal Series, Nebraska Agricultural Experiment Station.  相似文献   

9.
Inhibition of photosynthetic growth of Rhodopseudomonas capsulata by metronidazole was dependent on the nitrogen supply in culture solutions. Cultures fixing dinitrogen were more susceptible to inhibition by low concentrations than those supplied with NH 4 + . Light-dependent C2H2 reduction and H2 production by washed cells were inhibited by 80% and 60% respectively by 1 mM metronidazole. When this compound was first reduced with H2-palladised asbestos prior to assay, it only partially restricted C2H2 reduction in washed cells (33%) compared with unreduced inhibitor (68%). Metronidazole was without effect on other metabolic functions. Thus, even at 40 mM it did not inhibit either (a) dark or light respiration in cells grown under photo- and chemo-heterotrophic conditions; (b) H2-dependent photoreduction of 14CO2; (c) -glutamyltransferase activity of glutamine synthetase in cell-free extracts (25 mM inhibitor).Metronidazole (1 mM) completely inhibited C2H2 reduction by washed cells of Azotobacter vinelandii. The dithionite-dependent C2H2 reduction of a partially purified nitrogenase was only partially inhibited (30%) by 1 mM metronidazole.  相似文献   

10.
Ten isolates of six species of ectomycorrhizal fungi were grown in vitro at nine concentrations of three sodium salts (NaCl, Na2SO4, Na3C6H5O7) for 4 weeks. Colony diamater, biomass and protein content of fungi were evaluated. Isolates of Pisolithus tinctorius and Suillus luteus were more tolerant of NaCl and Na2SO4 than of Na3C6H5O7. Fungi in the genera Cenococcum, Laccaria, and Thelephora were highly intolerant of Na3C6H5O7 and Na2SO4 in vitro. Biomass and protein content of fungi generally declined with increasing substrate salinity in solution culture. In situ ectomycorrhizal colonization by Laccara laccata and P. tinctorius and the dry weight of Pinus taeda seedlings were significantly reduced by 80 mM NaCl after 14 weeks. Only select ectomycorrhizal fungi appear capable of growth and symbiosis in saline soils.  相似文献   

11.
Five strains of heterocystous blue-green algae capable of high rates of growth and nitrogenase activity were isolated from shallow coastal environments. Growth of the organisms was characterized with respect to temperature, NaCl concentration in the medium, and nitrogen source. The temperature optima ranged from 35–42°C, and all but one of the strains displayed a requirement for added NaCl. The generation times under N2-fixing conditions were 5.1–5.9 h, and were as low as 3.4 h for growth on NH4Cl. Nitrogenase activity (C2H2 reduction) was high throughout the logarithmic growth phase of each strain. The maximum value observed for one strain was 65.5 nmoles C2H4 produced/mg protein x min, and the average values for the five strains ranged from 24.5–46.7 nmoles C2H4/mg protein x min. The organisms all belong to the genusAnabaena. The growth and nitrogenase activity of these strains are much higher than those of the heterocystous blue-green algae commonly used for investigation of nitrogen metabolism, and they thus should prove to be useful physiological tools. Their prevalence, as judged by the ease of their enrichment and isolation, in bay and estuarine environments suggests that they are important contributors of combined nitrogen.  相似文献   

12.
P. H. Jerie  A. R. Shaari  M. A. Hall 《Planta》1979,144(5):503-507
Isolated cotyledons of Phaseolus vulgaris L. cv. Canadian Wonder accumulated 14C2H4 (0.7–1 l l-1) from air to give partition coefficients of 1 to 4, which greatly exceeded the value obtained with steam killed cotyledons (0.05) and with water (0.11). After 14C2H4 treatment, 98% of the 14C in the tissue remained as 14C2H4. The labelled ethylene accumulated by cotyledons was released only slowly (1–10% h-1) either in an air stream or into toluene. Heating to 60°C for 2 h, but not freezing and thawing, caused the immediate release of 14C2H4 from the tissue. Propylene and vinyl chloride competitively inhibited the accumulation of 14C2H4.Cotyledons emanated endogenous ethylene at a very low rate but after heating (although not freezing and thawing) 13 nl of ethylene per g fresh mass were released within minutes. It was concluded that french bean cotyledons hold ethylene in a compartmented form in sufficient amount to account for at least 200 h of emanation.Abbreviation PPO diphenyloxazole  相似文献   

13.
Thomas  S. M.  Long  S. P. 《Planta》1978,142(2):171-174
The metabolism of 14CO2 in the cool temperate saltmarsh grass Spartina townsendii was investigated in plants grown in their natural habitats at two temperatures. Both in the spring at 10°C and in the late summer at 25°C radioactivity was initially incorporated into the organic acids malate and aspartate and then transferred to 3-phosphoglycerate in the manner characteristic of the C4 pathway of photosynthesis. Metabolism was not disrupted at the lower temperature as in some C4 plants. Radioactivity was transferred more slowly from malate into alanine, glycine and serine at 10°C, but sugars were labelled equally at both temperatures.  相似文献   

14.
15.
Simultaneous measurements of CO2 uptake, transpiration rate, and chlorophyll a fluorescence in leaf strips of C4 plants during the induction phase of photosynthesis are described. The timecourse of CO2 fixation is biphasic with the initial phase occurring within the first 1 to 5 min and the secondary phase consisting of a slow rise to the steady-state rate of photosynthesis. Transpiration rate follows the CO2-fixation timecourse closely but the intercellular CO2 concentration never falls below saturation for C4 plants. Chlorophyll a fluorescence quenching occurs exclusively during the initial fast phase of the CO2-fixation timecourse. The effect of duration of dark pretreatment of leaves on these parameters and the effects of light intensity and CO2 concentration are examined. These results are discussed with respect to the C4 cycle and photochemical and non-photochemical chlorophyll fluorescence quenching.Abbreviations IRGA infra-red gas analyser - NADP-ME, NAD-ME and PEP-CK the three groups of C4 plants utilising the enzymes NADP-malic enzyme, NAD-malic enzyme and phosphoenolpyruvate carboxykinase, respectively, for C4-acid decarboxylation - PEP phosphoenolpyruvate - 3-PGA 3-phosphoglyceric acid  相似文献   

16.
A computational investigation of the sulfur-containing heterocyclic components (substituted thietanes and 1,2-dithiolanes) of Mustela anal sac secretions has been carried out. A cluster analysis of the chemical compositions of Mustela anal sac volatiles reveals little similarity with established phylogenetic relationships between members of the genus. Ab initio calculations [MP2/6–311++G(2df,2p)//B3LYP/6–311++G**] show the lowest-energy C5H10S isomeric thietane to be 2,2-dimethylthietane, which is also the most abundant of the Mustela thietanes. Similarly, 3,3-dimethyl-1,2-dithiolane is the lowest-energy C5H10S2 compound. 2-n-Propylthietane is the highest-energy C6H12S compound, but the most abundant Mustela C6H12S compound produced, whereas cis-2-ethyl-4-methylthietane, the lowest-energy C6H12S thietane, has never been observed in Mustela anal sac secretions. A molecular docking analysis of the Mustela sulfur-containing heterocycles into both porcine and bovine odorant binding proteins reveals the interactions of the docked ligands with the proteins to be largely hydrophobic, and have binding energies generally lower than typical odorant molecules such as linalool or eugenol. Figure Mustela anal sac volatile components, 2,2-dimethylthietane and cis-3,4-dimethyl–1,2-dithiolane.  相似文献   

17.
The apparent photosynthetic Km (CO2) of air-grown Dunaliella salina is 2 M as measured both by the filtering centrifugation technique and by O2 electrode. These cells are capable of accumulating inorganic carbon (Cinorg) up to 20 times its concentration in the medium. It is suggested that air-grown Dunaliella cells are able to concentrate CO2 within the cell. Analysis of the efflux of Cinorg from cells previously loaded with H14CO 3 - demonstrated the existence of an internal pool which has an half-time of depletion of 2.5–7 min depending on the conditions of the experiment. This finding indicates that the internal Cinorg pool is not readily exchangeable with the external medium. Furthermore, the influence of the presence or absence of unlabelled Cinorg in the medium during the efflux experiment on the half-time observed indicate that efflux of Cinorg is not a simple diffusion process but is rather carrier-mediated.Abbreviation Cinorg inorganic carbon  相似文献   

18.
A. Sellstedt 《Planta》1986,167(3):382-386
Acetylene reduction, 15N2 reduction and H2 evolution were measured in root systems of intact plants of grey alder (Alnus incana (L.) Moench) in symbiosis with Frankia. The ratios of C2H2: 15N2 were compared with C2H2:N2 ratios calculated from C2H2 reduction and H2 evolution, and with C2H2:N2 ratios calculated from accumulated C2H4 production and nitrogen content. It was possible to calculate C2H2:N2 ratios from C2H2 reduction and H2 evolution because this source of Frankia did not show any hydrogenase activity. The ratios obtained using the different methods ranged from 2.72 to 4.42, but these values were not significantly different. It was also shown that enriched 15N could be detected in the shoot after a 1-h incubation of the root-system. It is concluded that the measurement of H2 evolution in combination with C2H2 reduction represents a nondestructive assay for nitrogen fixation in a Frankia symbiosis which shows no detectable hydrogenase activity.  相似文献   

19.
Proton-proton coupling constants for terminal -l-iduronate residues in tetrasaccharides obtained from heparan sulphates by complete nitrous acid deaminative cleavage were shown to vary with experimental conditions. It is proposed that the iduronate residue is in a conformational equilibrium between the1C4 chair and either the2So skewboat or possibly the2H3 half-chair conformers. It was not possible to discriminate between the two non-chair forms empirically. The position of the equilibrium is sensitive to temperature, pH and sulphation of neighbouring residues. The likelihood of iduronate residues within glycosaminoglycans existing in the4C1 conformer in addition to the1C4 and2So forms is discussed.  相似文献   

20.
The sporangiophore of the fungus Phycomyces blakesleeanus has the property of growing away from a barrier which is few mm from the growing zone of the sporangiophore (avoidance or autochemotropic response). A model has been published (Cohen, R.J., Jan, N.Y., Matricon, J., Delbrück, M.: J. Gen. Physiol. 66, 67–95 (1975)). To explain the avoidance response which postulates that the sporangiophore emits and readsorbs a volatile growth-promoting effector (gas X) and that the barrier modifies the effector distribution by acting as an aerodynamic obstacle, causing a higher concentration of gas X on the side of the sporangiophore closer to the barrier. From this model we deduced three properties of the gas X. Of the several gases tested (N2, CO2, CH4, C2H2, C2H4, C2H6) only ethylene (C2H4) had all these three properties, a finding which suggests that it has a role in the avoidance response (autochemotropism).Abbreviation Spph Sporangiophore  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号