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91.
92.
The influence of temperature, shoot age, and medium on gall induction by Subanguina picridis on Russian knapweed (Acroptilon repens) was examined in vitro. The optimal temperature for gall formation was 20 C. Gall induction was delayed as the temperature decreased, and decreased as shoot age increased. Bud primordia (0-day-old shoots and 5-day-old shoots) with an average length of 4.2 mm and 7.9 mm were the most suitable tissues for nematode development and gall formation. Gall formation was more effective on B5G medium than on MSG. Young shoots under slow growth were most suitable for mass rearing of S. picridis. 相似文献
93.
SPA::EcoRI fusion protein was produced by Escherichia coli JM103 carrying the multicopy expression plasmid pMTC48, the multicopy repressor plasmid pRK248, and the multicopy protection plasmid pEcoR4 in a 60-L working volume airlift tower loop reactor on M9 minimal medium with glucose. Cell mass concentration, total cell count, number of colony-forming units, specific growth rate, yield coefficient, and metabolite (acetate, pyruvate, succinate, lactate, ethanol) concentrations were monitored during the growth phase and gene expression. Gene expression was induced by temperature shift or chemically by isopropyl-thiogalactosidase in the airlift tower loop reactor (ALTR) at constant cultivation time and in a small stirred tank reactor at different cultivation times. During induction, the cultivation medium was supplemented with concentrated Luria-Bertani (LB) medium. The intracellular enzyme activity was evaluated as a function of the time after the start of the induction. It was found that the reduction of the glucose concentration and increase of the dissolved oxygen concentration reduced the acetate produced and increased the intracellular enzyme activity. (c) 1993 John Wiley & Sons, Inc. 相似文献
94.
The effect of nitrogen starvation on the NO3-dependent induction of nitrate reductase (NR) and nitrite reductases (NIR) has been investigated in the halophilic alga Dunaliella salina. When D. salina cells previously grown in a medium with NH 4 + as the only nitrogen source (NH 4 + -cells) were transferred into NO 3 ? medium, NR was induced in the light. In contrast, when cells previously grown in N-free medium were transferred into a medium containing NO 3 ? , NR was induced in light or in darkness. Nitrate-dependent NR induction, in darkness, in D. salina cells previously grown at a photon flux density of 500 umol · m?2 s?1 was observed after 4 h preculture in N-free medium, whilst in cells grown at 100 umol · m?2 s?1 NR induction was observed after 7–8 h. An inhibitor of mRNA synthesis (6-methylpurine) did not inhibit NO 3 ? -induced NR synthesis when the cells, previously grown in NH 4 + medium, were transferred into NO 3 ? medium (at time 0 h) after 4-h-N starvation. However, when 6-methylpurine was added simultaneously with the transfer of the cells from NH 4 + to NO 3 ? medium (at time 0 h), NO 3 ? induced NR synthesis was completely inhibited. The activity of NIR decreased in N-starved cells and the addition of NO 3 ? to those cells greatly stimulated NIR activity in the light. The ability to induce NR in darkness was observed when glutamine synthetase activity reached its maximal level during N starvation. Although cells grown in NO 3 ? medium exhibited high NR activity, only 0.33% of the total NR was found in intact chloroplasts. We suggest that the ability, to induce NR in darkness is dependent on the level of N starvation, and that NR in D. salina is located in the cytosol. Light seems to play an indirect regulatory role on NO 3 ? uptake and NR induction due to the expression of NR and NO 3 ? -transporter mRNAs. 相似文献
95.
Using pulses of nitrate, instead of the permanent presence of external nitrate, to induce the nitrate-assimilating system in Hordeum vulgare L., we demonstrated that nitrate can be considered as a trigger or signal for the induction of nitrate uptake, the appearance of nitratereductase activity and the synthesis of mRNA coding for nitrate reductase. Nitrate pulses stimulated the initial rate of nitrate uptake, even after subsequent cultivation in N-free medium, and resulted in a higher acceleration of the uptake rate in the presence of nitrate than in its absence.Abbreviations NR
nitrate reductase 相似文献
96.
Matthew K. Litvak 《Environmental Biology of Fishes》1993,36(2):183-192
Synopsis Many species of shoaling fish are preyed upon by aerial predators. However, to date there has been no analysis of the evasive
response of a group of shoaling fish to an aerial threat or attack. The response of a shoal of fish encompasses a suite of
behaviors starting with a startle response. Shoals of golden shiner, Notemigonus crysoleucas, responded to the threat of aerial predation from a kingfisher model with a startle response, an increase in shoal depth,
an increase in polarity, swimming in the opposite direction under the model predator, shoal compression along the depth axis,
and shoal expansion on the plane perpendicular to the depth axis. It was hypothesized that shoal compression along the depth
axis serves to increase predator confusion by placing more fish in the predator's visual field. This compression was termed
the ‘plane of confusion’. 相似文献
97.
Maria Ermakova Russell Woodford Zachary Taylor Robert T. Furbank Srinivas Belide Susanne von Caemmerer 《Plant biotechnology journal》2023,21(6):1206-1216
Sorghum is one of the most important crops providing food and feed in many of the world's harsher environments. Sorghum utilizes the C4 pathway of photosynthesis in which a biochemical carbon-concentrating mechanism results in high CO2 assimilation rates. Overexpressing the Rieske FeS subunit of the Cytochrome b6f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO2 assimilation in the model C4 plant Setaria viridis. To test whether productivity of C4 crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor Tx430 plants with increased Rieske content. The transgenic plants showed no marked changes in abundances of other photosynthetic proteins or chlorophyll content. The steady-state rates of electron transport and CO2 assimilation did not differ between the plants with increased Rieske abundance and control plants, suggesting that Cytochrome b6f is not the only factor limiting electron transport in sorghum at high light and high CO2. However, faster responses of non-photochemical quenching as well as an elevated quantum yield of Photosystem II and an increased CO2 assimilation rate were observed from the plants overexpressing Rieske during the photosynthetic induction, a process of activation of photosynthesis upon the dark–light transition. As a consequence, sorghum with increased Rieske content produced more biomass and grain when grown in glasshouse conditions. Our results indicate that increasing Rieske content has potential to boost productivity of sorghum and other C4 crops by improving the efficiency of light utilization and conversion to biomass through the faster induction of photosynthesis. 相似文献
98.
Olga V. Beluzhenko Galina V. Bogdanova Vitalii A. Tumenev Yurii A. Zhdanov 《Chirality》1993,5(6):455-463
To control stereoselectivity in aldol-like reactions with chiral carbohydrate templates, we studied the interaction between completely protected dialdo compounds and magnesium enediolates of arylacetic acids. Diastereomeric mixtures of the highly functionalized acids obtained were esterified to isolate individual methyl uronates. It was found that all the diastereomeric esters exhibit Cotton effects of the same positive sign in the 220–230 nm region and so possess the same S configuration of the aryl chiral center C(6). Chiral center C(5) configurational assignments were performed using IR and ORD spectroscopy. We separated and specified four pairs of diastereomeric methyl uronates. It follows that the precursory acids have the same 5R*, 6S (major isomers) and 5S*, 6S (minor isomers) configurations. A tentative mechanism for complexation and possible models of Mg2+ -protected dialdose intermediate complexes has been proposed. We have concluded that a kind of orbital steering is realized, accompanied by some “tuning” of molecular assembly conditioned by two-point coordination between Mg2+ and potential cation-binding sites in the substrate molecules. Thus it has been demonstrated that reasonable diastereo-selectivity can be achieved even through the use of small matrix molecules using rather small functional groups, which do not impose any stringent steric requirements. © 1993 Wiley-Liss, Inc. 相似文献
99.
We have used [2-13C]d-glucose and carbon-13 nuclear magnetic resonance (NMR) spectroscopy to investigate metabolic fluxes through the major pathways of glucose metabolism in intact human erythrocytes and to determine the interactions among these pathways under conditions that perturb metabolism. Using the method described, we have been able to measure fluxes through the pentose phosphate pathway, phosphofructokinase, the 2,3-diphosphoglycerate bypass, and phosphoglycerate kinase, as well as glucose uptake, concurrently and in a single experiment. We have measured these fluxes in normal human erythrocytes under the following conditions: (1) fully oxygenated; (2) treated with methylene blue; and (3) deoxygenated. This method makes it possible to monitor various metabolic effects of stresses in normal and pathological states. Not only has 13C-NMR spectroscopy proved to be a useful method for measuring in vivo flux through the pentose phosphate pathway, but it has also provided additional information about the cycling of metabolites through the non-oxidative portion of the pentose phosphate pathway. Our evidence from experiments with [1-13C]-, [2-13C]-, and [3-13C]d-glucoses indicates that there is an observable reverse flux of fructose 6-phosphate through the reactions catalyzed by transketolase and transaldolase, even in the presence of a net flux through the pentose phosphate pathway. 相似文献
100.
BothPseudomonas putida F1 and a mixed culture were used to study TCE degradation in continuous culture under aerobic, non-methanotrophic conditions. TCE mass balance studies were performed with continuous culture reactors to determine the total percent removed in the reactors, and to quantify the percent removed by air stripping and biodegradation. Adsorption of TCE to biomass was assumed to be negligible. This research demonstrated the feasibility of treating TCE-contaminated water under aerobic, non-methanotrophic conditions with a mixed-culture, continuous-flow system.Initially glucose and acetate were fed as primary substrates. Pnenol, which has been shown to induce TCE-degrading enzymes, was fed at a much lower concentration (20mg/L). Little degradation of TCE was observed when acetate and glucose were the primary substrates. After omitting glucose and acetate from the feed and increasing the phenol concentration to 50mg/L, TCE biotransformation was observed at a significant level (46%). When the phenol concentration in the feed was increased to 420mg/L, 85% of the incoming TCE was estimated to have been biodegraded. Under the same conditions, phenol utilization by the mixed culture was greater than that ofP. putida F1, and TCE degradation by the mixed culture (85%) exceeded that ofP. putida F1 (55%). The estimated percent-of-TCE biodegraded by the mixed culture was consistently greater than 80% when phenol was fed at 420mg/L. Biodegradation of TCE was also observed in mixed-culture, batch experiments. 相似文献