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1.
Pollen tubes were grown under controlled temperatures in stigmas and styles which had been cut from the flowers at the point of juncture of the style with the ovary. At constant temperatures the tubes compatible with the styles grew rapidly at uniform rates. They showed accelerated growth with increase in temperature within the range 10°–30°C. Growth of incompatible tubes was irregular and slow and was neither measurably accelerated nor depressed within this range of temperatures. Routine tests for compatibility were conducted at 27°C; at this temperature compatible tubes grew through the entire length of the styles (ca. 58 mm) in 9 hours. Much of the incompatible pollen failed to germinate; that which did, grew to a maximum length ofca. 2 mm inca. 4 hours. The incompatible tubes did not even enter the styles but remained confined to the stigmas. ThreeS alleles were involved and conformed in their behavior to the gametophytic system of incompatibility. Colchicine-induced tetraploid derivatives of these plants showed no increase in compatibility. 相似文献
2.
Growth of young sporophytes of the brown algae Laminaria digitata, L. saccharina and L. solidungula from Spitsbergen were measured in the laboratory after being exposed for 21 days to either photosynthetically active radiation
(PAR=P) or to full light spectrum (PAR + UV-A + UV-B=PAB) using of cutoff glass filters. The plants were grown at 8±2°C and
16 h light : 8 h dark cycles with 6 h additional ultraviolet radiation (UVR) exposure in the middle of the light period. Growth
was measured every 10 min using growth chambers with online video measuring technique. Tissue morphology and absorption spectra
were measured in untreated young sporophytes while chlorophyll (Chl) a content and DNA damage were measured in treated thalli at the end of the experiment. In all species, growth rates were significantly
higher in sporophytes exposed to P alone compared to sporophytes exposed to PAB. Tissue DNA damage is dependent on thallus
thickness and absorption spectra characteristics of pigments and UV-absorbing compounds. In sporophytes exposed to UVR, energy
demands for repair of DNA damage and synthesis of UV-absorbing compounds for protection effectively diverts photosynthate
at the expense of growth. Photosynthetic pigment was not significantly different between treatments suggesting a capacity
for acclimation to moderate UVR fluence. The general growth pattern in sporophytes exposed to P alone showed an increasing
growth rate from the onset of light (0500–0900 hours) to a peak at the middle of the light phase (0900–1500 hours), a decline
towards the end of the light phase (1500–2100 hours) and a minimum “low” growth in the dark (2100–0500 hours) relative to
growth during the entire light phase. Under PAB, different growth patterns were observed such as growth compensation at night
in L. digitata, delayed growth recovery in L. saccharina and minimal but continuous growth in L. solidungula. Growth as an integrative parameter of all physiological processes showed that the effect of UVR is correlated to the depth
distribution of these species. 相似文献
3.
Harald Scholz Sepp D. Kohlwein Fritz Paltauf Axel Lezius Friedrich Spener 《Molecular and cellular biochemistry》1990,98(1-2):69-74
Summary The unicellular eukaryotic microorganism, Saccharomyces cerevisiae, transformed with a plasmid containing a cDNA fragment encoding bovine heart fatty acid-binding protein (H-FABP) under the control of the inducible yeast GAL10 promoter, expressed FABP during growth on galactose. The maximum level of immunoreactive FABP, identical in size to native protein as judged from SDS-polyacrylamide gel electrophoresis, was reached after approximately 16 hours of induction. Analysis of particulate and soluble subcellular fractions showed that FABP was exclusively associated with the cytosol. FABP expressed in yeast cells was functional as was demonstrated by its capacity to bind 14C-oleic acid in an in vitro assay. Growth of the transformants on galactose as the carbon source was significantly retarded at 37°C. Whereas the fatty acid pattern of total lipids was not altered in transformed cells, desaturation of exogenously added 14C-palmitic acid was significantly reduced both at 30 and 37°C. The lowest percentage of radioactively labeled unsaturated fatty acids was found in the phospholipid fraction. 相似文献
4.
The uptake of Manganese-54 by green algae (Protococcoidal chlorella), Daphnia magna,and fathead minnows (Pimephales promelas) 总被引:1,自引:1,他引:0
Concentration factors (CF) of 54Mn for three aquatic species: green algae (Protococcoidal chlorella), Daphnia magna, and fathead minnows (Pimephales promelas) were determined following direct exposure to the isotope in solution. The maximum accumulation (CF = 911) in P. chlorella was reached at 48 hours of exposure; the maximum uptake (CF = 65) in Daphnia was reached at 8 hours of exposure; and the maximum accumulation (CF = 22.6) in fathead minnows was at 128 hours of exposure. The data indicate that 54Mn accumulation decreases with ascent up a theoretical aquatic food chain when water is the only source of contamination. 相似文献
5.
Summary Growth ofCandida albicans strain B 311-10 was observed in a minimal synthetic biotin-free medium, using different glucose concentrations, during the first 30 hours of its development at 28 °C. The yeast's growth was observed spectrophotometrically at 675 nm reading its optical density every hour. The minimal medium of Shepherdet al. [12], with glucose (15 g/L) and biotin was modified: this vitamin was eliminated and the concentration of glucose was gradually lowered to 0.5 g/L. At 5 g/L of glucose and without biotin very good growth was obtained. Based on our results during the first 30 hours of growth, biotin has no influence on the yeast's growth. This medium would be useful for the study of the physiology ofC. albicans during the first period of its development. 相似文献
6.
The Rhizobium sp., isolated from the root nodules of the leguminous fodder herb Melilotus alba, produced large amounts of extracellular polysaccharides (EPS) (963.5 μg/ml) in a yeast extract mannitol medium. Growth and EPS production started simultaneously, but EPS production reached its maximum during the stationary phase of growth of the bacteria, at 20 hours. EPS production was increased with all of the thirteen sugars tested. Different nitrogen sources, such as nitrates, glutamic acid, casamino acid and L-asparagine, increased the EPS production although it was inhibited by glycine, nitrite and ammonium salts. Among the vitamins and metal ions, only pyridoxal phosphate and ZnSO4 promoted EPS production. Attempts were made to optimize the cultural requirements for growth and maximum EPS production. Maximum EPS production (1457.0 μg/ml) was obtained when the medium was supplemented with glucose (1%), pyridoxal phosphate (2 μ g/ml), ZnSO4 × 7 H2O (10 μg/ml) and glutamic acid (0.1%). Under these conditions, the production was increased by 254.3% compared to the control. The EPS contained arabinose, xylose and rhamnose monomers. The presence of arabinose and xylose in the EPS produced by a Rhizobium sp. was uncommon. 相似文献
7.
A Kademi L Fakhreddine N Aït-Abdelkader J C Baratti 《Journal of industrial microbiology & biotechnology》1999,23(3):188-193
Growth and esterase production (activity on p-nitrophenyl caprylate) by the newly isolated Bacillus circulans MAS2 bacterial strain were studied. The growth rate at 50°C was high (0.9 h-1) on LB medium with glucose added. Esterase production followed growth with the majority of activity being intracellular during
exponential growth phase. During stationary phase, the esterase activity was released in the culture medium. The strain was
able to grow at 35– 55°C with maximum growth rate at 50°C, showing a pattern typical of a moderate thermophile. Growth occurred
at pH 6–9 with a maximum at 8, with a similar pattern for the esterase production. Addition of glucose, fructose, sucrose
or sodium acetate greatly promoted both growth and esterase production while starch, inulin, tributyrin or glycerol showed
no effect. Complex nitrogen sources such as tryptone or yeast extract increased growth and esterase production while mineral
sources (ammonium chloride or sulfate), glycine or glutamate showed no effect. An increase of tryptone plus yeast extract
and glucose concentrations stimulated growth and esterase production which reached 160 U L−1.
Received 17 March 1999/ Accepted in revised form 25 June 1999 相似文献
8.
Jaap Dorgelo 《Aquatic Ecology》1976,10(1):30-30
In two brooks, at about 1000 m altitude, drift rates were measured at hourly intervals during 48 hours.Hydracarina were day-active with a maximum drift rate coincidently starting with the increasing phase of the sinusoidal water temperature curve. Nymphs ofEphemeroptera andPlecoptera as well as gammarids were night-active with maximum numbers of animals caught that start and end shortly after the greatest changes in light intensity during resp. sunset and sunrise. Analysis of the activity during 48 hours of a drifting ephemeroptean and a non-drifting trochopteran did not reveal a periodical pattern. The results have been discussed. The relationship between periodically occurring increases in drift and activity, with attention to exogenous control and endogenous rhythms, deserves thorough experimental studies. 相似文献
9.
Blandine Laferrre Susan K. Fried Tom Osborne F. Xavier Pi‐Sunyer 《Obesity (Silver Spring, Md.)》2000,8(7):481-486
Objective: We have previously shown that morning administration of dexamethasone in combination with food induces a doubling of serum leptin levels starting at 7 hours after dexamethasone administration, with a maximum effect at 10 hours, the latest time point that we have studied. However, dexamethasone given in the absence of food had no effect on serum leptin at 10 hours. The present experiment was undertaken to determine the duration of the effect of dexamethasone on 24‐hour serum leptin under fasted and fed conditions in humans. Research Methods and Procedures: Six healthy non‐obese male volunteers were studied under the following four conditions: 1) dexamethasone (2 mg intravenously, given at 0900 hours) with fasting; 2) dexamethasone with food (1700 kcal, 55% carbohydrate, 15% protein, and 30% fat, given in one meal 2 hours after dexamethasone administration at 1100 hours); 3) saline with food (same meal); 4) saline with fasting. Serum leptin, glucose, insulin, and cortisol were monitored every 30 minutes for 24 hours. Results: 1) Under the fasting condition, dexamethasone increased leptin nocturnal secretion between 2100 and 2400 hours. 2) A single meal (1700 kcal) at 1100 hours increased nocturnal leptin secretion when compared with the fasting condition. The peak increase of leptin was 123% over baseline between 2100 and 2400 hours, 10 to 14 hours after the meal. 3) In the fed + dexamethasone condition, leptin levels increased from baseline starting 8 hours after dexamethasone injection, reached a maximum increase of 260% between 2100 and 2400 hours, then decreased thereafter, remaining elevated compared to baseline for 16 hours. There was a correlation between 24‐hour leptin secretion and insulin secretion after a single morning meal. Discussion: A single bolus of dexamethasone, given before a single large meal, produces a delayed (6‐hour) but long‐lasting increase in serum leptin (over 16 hours). Under fasted conditions, dexamethasone does not increase daytime leptin but does increase leptin during the night. 相似文献
10.
Coleoptile sections from Avena sativa L. were exposed to non-lethal concentrations of peroxyacetyl nitrate (PAN). The sections were then incubated in solutions of 50 mM glucose plus 2.5 mM potassium phosphate with various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D). Growth after 4 hours was measured. A corresponding series of experiments was carried out and the effect of the 2,4-D treatments on enzymes utilizing uridine diphosphate glucose (14C-glucose) to form glucolipid and β-glucans including cellulose was determined. Growth in the PAN-treated sections was inhibited less at optimal and superoptimal auxin levels than at low auxin levels. Glucolipid synthetase activity was only slightly inhibited by PAN pretreatment and was reduced by increasing levels of auxin. Responses of alkali-soluble glucan and cellulose synthetases were similar to growth in both control and PAN treated tissues. It was concluded that the earlier reported response of cell wall metabolism in vivo probably is due to effects on these enzyme levels. 相似文献
11.
The growth of a thermophilic Clostridium sp. and the production of α-glucosidase, α-amylase and pullulanase were studied under anaerobic conditions using different carbon and nitrogen sources and varying pH values and temperatures. Growth and enzyme activities were highest with soybean meal as the nitrogen source. The optimum concentration was 2.5% [w/v] for the production of α-amylase as well as pullulanase and 2% [w/v] for α-glucosidase. The best carbon source proved to be soluble starch for α-amylase, and pullulanase and maltose for α-glucosidase. Growth and enzyme production reached their optimum at pH 6.5 to 7.0 and 70°C. Under these conditions, the enzyme activities followed exponential growth with maximum yields of α-glucosidase, α-amylase and pullulanase at 28, 36, and 44 h. 相似文献
12.
Daniel H. Pope Reginald J. Soracco Helen K. Gill Carl B. Fliermans 《Current microbiology》1982,7(5):319-321
Environmental and clinical isolates ofLegionella pneumophila were grown in minimal-salts media (no organic compounds added) in associated with various green algae and cyanobacteria. Growth was observed to level off after a period of hours to days with no subsequent significant loss in the numbers of viableL. pneumophila even several days after growth had ceased. Transfer to new algal or cyanobacterial cultures resulted in a new burst of growty by theL. pneumophila. 相似文献
13.
Kees Kersting 《Hydrobiologia》1978,59(2):113-120
Some results of studies with Daphnia magna are presented. These results can be used as background information for toxicologists, but the techniques referred to might well be used for toxicity tests. Daphnia magna is a filter-feeder. With the Coulter Counter it was shown that the feeding mechanism is aselective for size of the food particles. It was also shown that algal cells can pass the gut of Daphnia magna several times before being completely digested. The uptake of food is proportional to the food concentration up to a critical concentration. Above this concentration the food uptake is constant. Respiration is also dependent on the food concentration, and has a maximum value at food concentrations near the critical concentration of the feeding process. Growth efficiency is independent of the food concentration. The effect of temperature on the feeding process is different for low and high food concentrations. Growth efficiency is maximal at 10°C and above 22°C growth efficiency was negative, which means that the population cannot survive under the experimental conditions used, at temperatures above 22°C. 相似文献
14.
Phytoplankton growth rates in the Ross Sea, Antarctica, determined by independent methods: temporal variations 总被引:1,自引:0,他引:1
The development of the seasonal phytoplankton bloom in the Ross Sea was
studied during two cruises. The first, conducted in November-December 1994,
investigated the initiation and rapid growth of the bloom, whereas the
second (December 1995-January 1996) concentrated on the bloom's maximum
biomass period and the subsequent decline in biomass. Central to the
understanding of the controls of growth and the summer decline of the bloom
is a quantitative assessment of the growth rate of phytoplankton. Growth
rates were estimated over two time scales with different methods. The first
estimated daily growth rates from isotropic incorporation under simulated
in situ conditions, including
14C, 15N and
32Si uptake measurements combined with estimates of
standing stocks of particulate organic carbon, nitrogen and biogenic
silica. The second method used daily to weekly changes in biomass at
selected locations, with net growth rates being estimated from changes in
standing stocks of phytoplankton. In addition, growth rates were estimated
in large-volume experiments under optimal irradiances. Growth rates showed
distinct temporal patterns. Early in the growing season, short-term
estimates suggested that growth rates of in situ
assemblages were less than maximum (relative to the temperature-limited
maximum) and were likely reduced due to low irradiance regimes encountered
under the ice. Growth rates increased thereafter and appeared to reach
their maximum as biomass approached the seasonal peak, but decreased
markedly in late December. Differences between the major taxonomic groups
present were also noted, especially from the isotopic tracer experiments.
The haplophyte Phaeocystic antarctica was dominant in
1994 throughout the growing season, and it exhibited the greatest growth
rates (mean 0.41 day-1) during spring. Diatom
standing stocks were low early in the growing season, and growth rates
averaged 0.100 day-1. In summer diatoms were more
abundant, but their growth rates remained much lower (mean of 0.08
day-1) than the potential maximum. Understanding
growth rate controls is essential to the development of predictive models
of the carbon cycle and food webs in Antarctic waters.
相似文献
15.
Use of whey for production of exocellular polysaccharide by a mutant strain ofXanthomonas campestris
Growth and kinetics of the production of exocellular polysaccharide was studied in a mutant strain ofXanthomonas campestris lac
+ during cultivation in a submerged culture in a medium containing whey. The maximum production of the polymer was observed
at the initial stage of the stationary growth phase of the culture. The mean production yield was about 1.4%. The results
were comparable with those obtained during cultivation on a lactose medium.
Translated by Č. Novotny 相似文献
16.
Dorte Haubjerg S?gaard Per Juel Hansen S?ren Rysgaard Ronnie N?hr Glud 《Polar Biology》2011,34(8):1157-1165
The effect of salinity, pH, and dissolved inorganic carbon (TCO2) on growth and survival of three Arctic sea ice algal species, two diatoms (Fragilariopsis nana and Fragilariopsis sp.), and one species of chlorophyte (Chlamydomonas sp.) was assessed in controlled laboratory experiments. Our results suggest that the chlorophyte and the two diatoms have
different tolerance to fluctuations in salinity and pH. The two species of diatoms exhibited maximum growth rates at a salinity
of 33, and growth rates at a salinity of 100 were reduced by 50% compared to at a salinity of 33. Growth ceased at a salinity
of 150. The chlorophyte species was more sensitive to high salinities than the two diatom species. Growth rate of the chlorophyte
was greatly reduced already at a salinity of 50 and it could not grow at salinities above 100. At salinity 33 and constant
TCO2 concentration, all species exhibited maximal growth rate at pH 8.0 and/or 8.5. The two diatom species stopped growing at
pH > 9.5, while the chlorophyte species still was able to grow at a rate which was 1/3 of its maximum growth rate at pH 10.
Thus, Chlamydomonas sp. was able to grow at high pH levels in the succession experiment and therefore outcompeted the two diatom species. Complementary
experiments indicated that growth was mainly limited by pH, while inorganic carbon limitation only played an important role
at very high pH levels and low TCO2 concentrations. 相似文献
17.
E. Paasche 《Physiologia plantarum》1968,21(1):66-77
The diatoms Ditylum brightwellii and Nitzschia turgidula were grown in semi-continuous culture under various combinations of light intensity, temperature and daylength (photoperiod). Growth was strongly limited by light intensities below 0.03 cal/em2. min in both species. Above this intensity, light saturation of growth was rapidly approached in Nitzschia but only gradually so in Ditylum. The growth rate in continuous light was never significantly higher than with 16 hours of light plus 8 hours of dark. In Ditylum, continuous light above 0.03 cal/cm2. min caused a strong inhibition of growth at all temperatures. The chlorophyll concentration in the cells was greater the shorter the photopceriod. In cultures synchronised by different combinations of light intensity and photoperiod, cell division generally took place in the light. Synchrony was best under short photoperiods of bright light. Time courses are shown for chlorophyll synthesis and photosynthesis in synchronised cultures. 相似文献
18.
Growth of Saccharomyces cerevisiae on non-fermentable medium was more sensitive to inhibition by vanadate than growth of fermentable medium. The frequency of petite mutants increased in cultures grown for 18 hours in fermentable medium containing vanadate. However, oxygen uptake markedly increased in yeast cultures grown in the presence of vanadate, a similar effect being produced by phosphate. It was also found that oligomycin toxicity was relieved by vanadate. These results suggest that vanadate may interact with the mitochondria of S. cerevisiae. 相似文献
19.
S Belia S Fulle S Antonioli A M Salvatore G Fano 《Physiological chemistry and physics and medical NMR》1991,23(1):35-41
The aim of this work is to examine if the membrane-bound Phospholipase C system is correlated with the differentiative action of Nerve Growth Factor in PC12 cells. We found that the activity of membrane-bound Phospholipase C system increased with the presence of Nerve Growth Factor at two different phases. The early phase occurs during the first minutes after the formation of Nerve Growth Factor-receptor complex and it is completed within one hour. The later phase starts two hours after Nerve Growth Factor introduction and lasts for at least a total of 48 hours. The inositol-triphosphate levels measured in intact cells by radioimmunoassay show the same pattern of activation. We think that this dual response to Nerve Growth Factor could be due to either a double separated activation of the same enzyme or the presence of two different forms of membrane-bound Phospholipase C. 相似文献
20.
Effect of 2,4-D on Cell Wall Metabolism of Peroxyacetyl Nitrate Pretreated Avena Coleoptile Sections
Avena coleoptile sections were exposed to nonlethal concentrations of peroxyacetyl nitrate (PAN). The sections were then incubated in solutions of 50 mM glucose plus 2.5 mM poassium phosphate with various concentrations of 2,4-dichlorophenoxycetic acid (2,4-D). Growth after 4 hours was measured. A corresponding series of experiments was carried out with glucose-14C (U) in the subsequent incubation medium and the effect of the 2,4-D treatments on 14C incorporation into various cell wall components was determined. Growth in the PAN-treated sections, although still partially inhibited, was greater at auxin levels normally superoptimal for growth than at the former optimum. Incorporation into all cell wall fractions was similar to growth in the case of control treated tissue. Most of the cell wall constituents, but particularly cellulose and less soluble noncellulosic polysaccharides, tended to show higher incorporation at the levels where PAN-treated growth was also higher. It was concluded that effects by PAN on cell wall metabolism in growing tissue are similar to the effects on growth and that the mechanism of alleviation of growth inhibition is probably through decreased inhibition of wall metabolism. 相似文献