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61.
Metabolism of nitric oxide and nitrous oxide during nitrification and denitrification in soil at different incubation conditions 总被引:1,自引:0,他引:1
Abstract NO production and consumption rates as well as N2 O accumulation rates were measured in a loamy cambisol which was incubated under different conditions (i.e. soil moisture content, addition of nitrogen fertilizer and/or glucose, aerobic or anaerobic gas phase). Inhibition of nitrification with acetylene allowed us to distinguish between nitrification and denitrification as sources of NO and N2 O. Under aerobic conditions untreated soil showed very low release of NO and N2 O but high consumption of NO. Fertilization with NH4 + or urea stimulated both NO and N2 O production by nitrification. Addition of glucose at high soil moisture contents led to increased N2 and N2 O production by denitrification, but not to increased NO production rates. Anaerobic conditions, however, stimulated both NO and N2 O production by denitrification. The production of NO and N2 O was further stimulated at low moisture contents and after addition of glucose or NO3 − . Anaerobic consumption of NO by denitrification followed Michaelis-Menten kinetics and was stimulated by addition of glucose and NO3 − . Aerobic consumption of NO followed first-order kinetics up to mixing ratios of at least 14 ppmv NO, was inhibited by autoclaving but not by acetylene, and decreased with increasing soil moisture content. The high NO-consumption activity and the effects of soil moisture on the apparent rates of anaerobic and aerobic production and consumption of NO suggest that diffusional constraints have an important influence on the release of NO, and may be a reason for the different behaviour of NO release vs N2 O release. 相似文献
62.
Summary High yields of protoplasts were obtained from leaves of aseptically grown plants and calli originated from different explants, in several cultivars of Cajanus cajan L. The protoplasts divided to form cell clusters in modified KM 8p medium and developed to protocolonies after dilution with liquid Caboche's medium within three to four weeks of culture. The protocolonies proliferated to form green calli on solid Caboche's medium. No shoots or plants were obtained.Abbreviations BAP
6-benzylaminopurine
- NAA
-napthaleneacetic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- Kin
kinetin
- Zea
zeatin
- Adn S
adenine sulphate
- GA 3
gibberellic acid 相似文献
63.
Kenji Kato Su-wan Oh Hiroyuki Yamamoto Takayuki Hanazato Ikuko Yasuda Akira Otuki Masayuki Takahashi 《Ecological Research》1992,7(3):267-276
In order to understand the control mechanisms of a large, stable bacterial standing stock, enclosure experiments were conducted
in a eutrophic lake, where both bacterial productivity and grazing pressure were very high. Total bacterial number in the
different enclosures ranged from 1.2 to 2.7×107 cells mL−1 throughout the experiment. The average bacterial cell production rate estimated from a grazer eliminating experiment was
6.3×105 cells mL−1 h−1. Difference in the bacterial cell production rate between shaded and unshaded enclosures was not apparent. Bacteria showed
a reduction in standing stock of only about 25–30% even after the supply of light was cut to 1%. Bacteria in the shaded enclosures
then recovered their production rate in the first 12 days of perturbation. Grazing pressure in the shaded enclosures was not
less than that for the control. Thus, it was considered a control mechanism of bacterial stable standing stock that the bacteria
shifted their organic substrate from extracellular dissolved organic carbon freshly released from phytoplankton to that already
stocked in the water column, though it is not known whether the dominant bacteria were the same. 相似文献
64.
Anthraquinones produced by suspension cultures of Galium vernum are completely retained intracellularly. Surprisingly, in the presence of some polymeric adsorbents anthraquinones are partially released into the culture medium. The secretion and in situ removal stimulates anthraquinone production in cell cultures of Galium vernum. Best results were obtained with Wofatit ES and Amberlite XAD-2.Abbreviations DW
dry weight
- MS
Murashige & Skoog[7]medium
- NAA
1-naphthaleneacetic acid 相似文献
65.
Studies on blastospore production in different liquid media were conducted with three strains of Metarhizium anisopliae var. anisopliae (M. a.) derived from various countries (M. a. 43: Austria, M. a. 57: Brazil, M. a. 97: Philippines). Variation of six fermentation parameters (cornsteep products, carbohydrates, pH values, temperature, Tween 80, and polyethyleneglycol (PEG) 200) disclosed that the three strains of M. anisopliae differed in their growth pattern and physiology. In standard medium and in all tests, M. a. 57 produced the highest number of blastospores invariably amounting to > 108 per ml, while mycelial pellets were never formed. The preferred carbohydrates were glucose and fructose. Blastospore production of M. a. 43 was increased by growth at 30°C, at pH 6.5 or by addition of 5% PEG 200. However, it was impaired by different concentrations of Tween 80 or higher concentrations of PEG 200 (10–15%). M. a. 97 produced most blastospores at 30°C, and the strain preferred basic (pH 8.0) as well as acid (pH 4.5) media. Blastospore production was increased by the addition of 5% PEG 200 or 0.4–1.2% Tween 80. Moreover, PEG 200 suppressed pellet formation effectively. Altogether, our results showed that for optimal blastospore production of Metarhizium anisopliae, suitable strain‐specific parameters have to be evaluated. 相似文献
66.
P. N. Nehete N. K. Shah V. Ramamurthy R. M. Kothari 《World journal of microbiology & biotechnology》1992,8(4):446-450
An economical protocol, which is simple, rapid and reproducible for the production of maltose by enzymatic hydrolysis of tapioca starch, has been optimized. The protocol involves liquefaction of 35% (w/w) tapioca starch by bacterial -amylase at 78±2°C to 3 to 5% (w/w) reducing sugars, followed by maximal (85±3% w/w maltose equivalent) saccharification with barley -amylase and pullulanase at 50°C for 24 to 30 h. The post-saccharification recovery protocol comprised decolourization by charcoal, de-dextrinization by denatured spirit precipitation, de-ionization by passage through cation and anion exchangers and dehydration by vacuum drying. A white crystalline maltose powder was obtained with specifications comparable to commercial high purity maltose. The protocol yields at least 60% (w/w) recovery of maltose and is suitable for use by the pharmaceutical industry. The protocol is unique in that it utilizes cheap and easily hydrolysed tapioca starch, leaves no mother liquor, enabling higher recovery of maltose, and allows almost quantitative recovery of limit maltodextrins, a value-added marketable by-product. 相似文献
67.
Thousands of tonnes of dry oil palm trunks will be produced annually in Malaysia after about 1990. A project was initiated to study the feasibility of converting palm trunks into charcoal. Carbonisation was done at terminal temperatures of 400–550°C with holding times of 1–3 h and at two heating rates. From laboratory-scale pyrolysis studies, it was found that holding time does not affect the quantity and quality of the charcoal produced, while heating rate has a minor influence. However, as terminal temperature increases, both yield and volatile content decrease while the fixed carbon content increases. The calorific value and ash contents are independent of the parameters studied and their respective values are 4032 kcal/kg and 37.2%. Since the calorific value is low and the ash content high, it is concluded that oil palm trunks are not suitable for the production of charcoal fuel. 相似文献
68.
Sarah J. Holden D. Layne Coppock Mulugeta Assefa 《Human ecology: an interdisciplinary journal》1991,19(1):35-59
Surveys of pastoral households in a semi-nomadic Borana community during 1987–1988 were used to test the hypothesis that poorer families living closest to a market town would be most affected by the enhanced opportunity to sell dairy products, which would intensify competition between people and calves for milk and have negative implications for calf management. These poorer families indeed reported the highest rates of milk offtake per cow, and the milk increment was probably sold to purchase more grain for human consumption at the expense of milk intake for the calf. Consequently, this strategy may increase the susceptibility of malnourished calves to disease, especially those from lower-producing dams. Benefits of improved human energy intake from grain and retention of livestock capital must be weighed against risks of calf death and possible malnutrition of people from milk restriction when assessing dairy marketing trade-offs that are most acute for the poor. Opportunity to sell dairy products at favorable terms of trade helps the poorest people survive, and their risks could be mitigated by policies that facilitate grain marketing in the rangelands and interventions that improve calf feeding management, diversify human diets, and create alternative opportunities for women to generate income. The households postulated to be most at risk were identified from a complex, but logical, interaction among factors of distance to market, household wealth, and the quality of milking cows held. This indicates that targeting such needy groups for development assistance may require a more detailed and interdisciplinary analysis of production systems than is commonly practiced. 相似文献
69.
Morphological evidence for a close interaction of chromaffin cells with cortical cells within the adrenal gland 总被引:3,自引:0,他引:3
Stefan R. Bornstein Monika Ehrhart-Bornstein Henning Usadel Michael Böckmann Werner A. Scherbaum 《Cell and tissue research》1991,265(1):1-9
Summary The adrenal medulla appears to exert a regulatory influence on adrenocortical steroidogenesis. We have therefore studied the morphology of rat, porcine and bovine adrenals in order to characterize the contact zones of adrenomedullary and adrenocortical tissues. The distribution of chromaffin cells located within the adrenal cortex and of cortical cells located within the adrenal medulla was investigated. Chromaffin cells were characterized by immunostaining for synaptophysin and chromogranin A, both being considered specific for neuroendocrine cells. Cortical cells were characterized by immunostaining for 17-hydroxylase, an enzyme of the steroid pathway. Cellular contacts of chromaffin cells and cortical cells were examined at the electron microscopical level. In rat and porcine adrenals, rays of chromaffin cells, small cell clusters and single chromaffin cells or small invaginations from the medulla could be detected in all three zones of the cortex. Chromaffin cells often spread in the subcapsular space of the zona glomerulosa. In porcine and bovine adrenals, 17-hydroxylase immunoreactive cells were localized within the medulla. Single cortical cells and small accumulations of cells were spread throughout this region. At the ultrastructural level, the chromaffin cells located within the cortex in pig and rat adrenals formed close cellular contacts with cortical cells in all three zones. Our morphological data provide evidence for a possible paracrine role of chromaffin cells; this may be important for the neuroregulation of the adrenal cortex. 相似文献
70.
James B. Russell 《Archives of microbiology》1991,155(6):559-565
Glucose-limited, continuous cultures (dilution rate 0.1 h-1) of Streptococcus bovis JB1 fermented glucose at a rate of 3.9 mol mg protein-1 h-1 and produced acctate, formate and ethanol. Based on a maximum ATP yield of 32 cells/mol ATP (Stouthamer 1973) and 3 ATP/glucose, the theoretical glucose consumption for growth would have been 2.1 mol mg protein-1 h-1. Because the maintenance energy requirement was 1.7 mol/mg protein/h (Russell and Baldwin 1979), virtually all of the glucose consumption could be explained by growth and maintenance and the YATP was 30. Glucose-limited, continuous cultures produced heat at a rate of 0.29 mW/mg protein, and this value was similar to the enthalpy change of the fermentation (0.32 mW/mg protein). Batch cultures (specific growth rate 2.0 h-1) fermented glucose at a rate of 81 mol mg protein-1 h-1, and produced only lactate. The heat production was in close agreement with the theoretical enthalpy change (1.72 versus 1.70 mW/mg protein), but only 80% of the glucose consumption could be accounted by growth and maintenance. The YATP of the batch cultures was 25. Nitrogen-limited, glucose-excess, non-growing cultures fermented glucose at a rate of 6.9 mol mg protein-1 h-1, and virtually all of the enthalpy for this homolactic fermentation could be accounted as heat (0.17 mW/mg protein). The nitrogenlimited cultures had a membrane potential of 150 mV, and nearly all of the heat production could be explained by a futile cycle of protons through the cell membrane (watts = amperes x voltage where H+/ATP was 3). The membrane voltage of the nitrogen-limited cells was higher than the glucose-limited continuous cultures (150 versus 80 mV), and this difference in voltage explained why nitrogen-limited cultures consumed glucose faster than the maintenance rate. Batch cultures had a membrane potential of 100 mV, and this voltage could not account for increased glucose consumption (more than growth plus maintenance). It appears that another mechanism causes the increased heat production and lower growth efficiency of batch cultures. 相似文献