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1.
Based on a seven-year study of pollen production and release in two different natural populations of Cedrus deodara from Garhwal Himalaya, India, we determined that pollen output follows a two-year cycle. Pollen productivity determinations considered various sources of variability, including the number of pollen strobili per branch, strobili per tree, microsporophylls per tree and pollen grains per tree. Each of these parameters revealed significant year-to-year and population effects. Microsporangium dehiscence took from 2.5 to 3.5 days. Maximum dehiscence was observed between 12:00 and 14:00 h, which coincides with diurnal highest temperature and lowest relative humidity. Annual production of pollen per tree varied from averages of 4.7 × 109, 7.2 × 109 and 5.1 × 109 in years of low production, with alternate high years, producing 12.6 × 109, 14.1 × 109, 13.3 × 109 and 14.0 × 109 pollen grains per tree. Annual pollen production in individual trees of C. deodara ranged from 1.4 × 109 to 22.3 × 109.  相似文献   

2.
This study investigated the effects of dietary Bifidobacterium bifidum (BFD) and mannan-oligosaccharide (MOS), as a synbiotic, on the production performance, gut microbiology, serum biochemistry, antioxidant profile and health indices of broiler chicken. Six dietary treatments were T1 (negative control), T2 (positive control-20 mg antibiotic BMD kg−1 diet; BMD: bacitracin methylene disalicylate), T3 (0·1% MOS + 106 CFU BFD per g feed), T4 (0·1% MOS + 107 CFU BFD per g feed), T5 (0·2% MOS + 106 CFU BFD per g feed) and T6 (0·2% MOS + 107 CFU BFD per g feed). Significantly (P < 0·01) better growth performance and efficiency was observed in birds supplemented with 0·2% MOS along with 106 CFU BFD per g of feed compared to BMD and control birds. Supplementation with 0·2% MOS along with either 106 or 107 CFU BFD per g feed reduced (P < 0·01) the gut coliform, Escherichia coli, total plate count, and Clostridium perfringens count and increased the Lactobacillus and Bifidobacterium count. Significantly (P < 0·01) higher serum and liver antioxidant enzyme pool, serum HDL cholesterol and lower serum glucose, triglyceride, total cholesterol, cardiac risk ratio, atherogenic coefficient and atherogenic index of plasma were observed in birds supplemented with 0·2% MOS along with 106 CFU BFD per g of feed compared to control or BMD supplemented birds. Better production performance, gut microbial composition, serum biochemistry, antioxidant profile and health indices were depicted by broiler chicken supplemented with 0·2% MOS and 106 CFU BFD per g of feed.  相似文献   

3.
I. Kröncke 《Polar Biology》1998,19(6):383-392
Macrofaunal communities of the western Eurasian Arctic Ocean were studied along a transect from the North Pole, across the Amundsen Basin and Gakkel Ridge towards the Morris Jesup Rise and the Yermak Plateau. Samples were collected during autumn 1991, from depths of 560–4411 m, using a box corer. Macrofaunal species numbers varied from 1 to 11 per 0.02 m2 in the basins approaching the Morris Jesup Rise and from 44 to 81 per 0.25 m2 at the Yermak Plateau. Abundances increased from 1 to 31 per 0.02 m2 in the basin and on the Morris Jesup Rise to 24–60 per 0.02 m2 on the Yermak Plateau. Biomass was low in the basin and at the Morris Jesup Rise (0.5–68.9 mg per 0.02 m2) but increased to 116.64 mg per 0.02 m2 at the Yermak Plateau. A total of 108 taxa were recorded. The results contradict the hypothesis that diversity decreases with increasing latitude, and the high species richness at low abundance at intermediate depths was comparable with that observed in Antarctic and tropical regions.  相似文献   

4.
Cyclic variations in nitrogen uptake rate in soybean plants   总被引:1,自引:0,他引:1       下载免费PDF全文
Uptake of NO3 by nonnodulated soybean plants (Glycine max L. Merr. cv Ransom) growing in flowing hydroponic culture at 22 and 14°C root temperatures was measured daily during a 31-day growth period. Ion chromatography was used to determine removal of NO3 from solution during each 24-hour period. At both root-zone temperatures, rate of NO3 uptake per plant oscillated with a periodicity of 3 to 5 days. The rate of NO3 uptake per plant was consistently lower at 14°C than 22°C. The lower rate of NO3 uptake at 14°C during the initial 5 to 10 days was caused by reduced uptake rates per gram root dry weight, but with time uptake rates per gram root became equal at 14 and 22°C. Thereafter, the continued reduction in rate of NO3 uptake per plant at 14°C was attributable to slower root growth.  相似文献   

5.
White clover plants were grown for 97 days under two temperature regimes (20/15°C and 8/5°C day/night temperatures) and were supplied with either small amounts (a total of 80 mg N pot–1) of ammonium (NH 4 + ) or nitrate (NO 3 ) nitrogen, or received no mineral N and relied on N2 fixation. Greatest growth and total leaf area of clover plants occurred in N2 fixing and NO 3 -fed plants grown at 20/15°C and poorest growth occurred in NH 4 + -fed plants grown at 8/5°C. Nodule mass per plant was greater at 8/5°C due to increased nodule numbers rather than increased dry weight per nodule. This compensated to some extent for the reduced N2-fixing activity per unit dry weight of nodule tissue found at the low growth temperature up to 116 d after sowing, but thereafter both activity per nodule dry weight and activity per plant were greater at the low temperature. Highest nitrate reductase activity (NRA) per g fresh weight and total activity per leaf, petiole or root occurred in NO 3 -fed plants at 8/5°C. Low growth temperature resulted in a greater partitioning of total plant NRA to the roots of NO 3 -fed plants. The results are considered in relation to the use of N fertiliser in the spring under field conditions.  相似文献   

6.
Summary The suprachiasmatic nucleus (SCN) of male rats was estimated to contain 16×106 synaptic appositions (unilaterally) or 250×106 appositions in 1 mm3 tissue of the nucleus with an average of 1404 appositions per neuron. There are significantly fewer synaptic appositions in the suprachiasmatic nucleus of female rats (15×106 per SCN or 236×106 in 1 mm3 tissue of SCN with 1264 appositions per neuron on an average). Additionally, numbers of various types of synapses (axo-somatic, invaginated, dendrodendritic and optic) are estimated.Supported by National Health & Medical Research Council of Australia  相似文献   

7.
The aim of this work was to obtain experimental data depending on the properties of calcium stores and SERCAs, to analyse these data in terms of the models based on simulation of the cellular compartments as communicating vessels, and to relate this way the data to the above properties. The main characteristics of the stores and corresponding SERCAs have been estimated. Calcium content in the DTS is ∼1.5 × 106 ions per cell, that in the acidic stores, ∼0.64 × 106 ions per cell. The rate constant of background calcium leakage from the DTS is ∼0.0033 s−1, that from the acidic stores, ∼0.1 s−1. The background activity of SERCA2b is ∼0.22 × 106 s−1 ions per cell, that of SERCA3, ∼2.5 × 106 s−1 ions per cell. The properties of both calcium stores and the SERCAs and the characteristics found might be related to physiological or pathological state of the cells.  相似文献   

8.
Bacterioplankton productivity in Antarctic waters of the eastern South Pacific Ocean and Drake Passage was estimated by direct counts and frequency of dividing cells (FDC). Total bacterioplankton assemblages were enumerated by epifluorescent microscopy. The experimentally determined relationship between in situ FDC and the potential instantaneous growth rate constant (μ) is best described by the regression equation ln μ = 0.081 FDC − 3.73. In the eastern South Pacific Ocean, bacterioplankton abundance (2 × 105 to 3.5 × 105 cells per ml) and FDC (11%) were highest at the Polar Front (Antarctic Convergence). North of the Subantarctic Front, abundance and FDC were between 1 × 105 to 2 × 105 cells per ml and 3 to 5%, respectively, and were vertically homogeneous to a depth of 600 m. In Drake Passage, abundance (10 × 105 cells per ml) and FDC (16%) were highest in waters south of the Polar Front and near the sea ice. Subantarctic waters in Drake Passage contained 4 × 105 cells per ml with 4 to 5% FDC. Instantaneous growth rate constants ranged between 0.029 and 0.088 h−1. Using estimates of potential μ and measured standing stocks, we estimated productivity to range from 0.62 μg of C per liter · day in the eastern South Pacific Ocean to 17.1 μg of C per liter · day in the Drake Passage near the sea ice.  相似文献   

9.
The aim of this study was to develop a useful procedure for laparoscopic insemination (LI) with sex-sorted boar spermatozoa that yields adequate fertility results in farm conditions. In experiment 1, we evaluated the effects of single (oviducts) and double (oviducts and tips of the uterine horns) LI with X-sorted sperm on the reproductive performance of sows. Sows (N = 109) were inseminated once as follows: (1) single LI with 0.5 × 106 unsorted sperm per oviduct; (2) single LI with 0.5 × 106 sex-sorted sperm per oviduct; or (3) double LI with 0.5 × 106 sex-sorted sperm per oviduct and 0.5 × 106 sex-sorted sperm per uterine horn. The farrowing rates were lower (P < 0.05) in sows inseminated with sex-sorted sperm (43.2% and 61.9% for the single and double insemination groups, respectively) than in sows from the unsorted group (91.3%). Within the sex-sorted groups, the farrowing rate tended (P = 0.09) to be greater in sows inseminated using double LI. There were no differences in the litter size among groups. In experiment 2, we evaluated the effect of the number of sex-sorted sperm on the reproductive performance of sows when using double LI. Sows (N = 109) were inseminated with sex-sorted sperm once using double LI with: (1) 0.5 × 106 sperm per oviduct and 1 × 106 sperm per uterine horn; or (2) 1 × 106 sperm per oviduct and 2 × 106 sperm per uterine horn. Similarly high pregnancy (90%) and farrowing (80%) rates were achieved in both groups. The sows inseminated with the highest number of sperm tended (P = 0.09) to have more piglets (10.8 ± 0.7 vs. 9.2 ± 0.6). A high female proportion (number of female births divided by the total of all births ≥0.92) was obtained in both experiments using X-sorted sperm. Our results indicate that the double LI procedure, using between 3 and 6 × 106 sex-sorted sperm per sow produces adequate fertility at the farm level, making sperm-sexing technology potentially applicable in elite breeding units.  相似文献   

10.
At 35°C, the standard and maximal metabolic rates for neonates of four species of goannas (Varanus brevicauda, V. eremius, V. tristis and V. gouldii) are consistently higher than predicted by intraspecific equations for adults. However, this is difficult to demonstrate statistically. The consequence of this is that the data for neonates probably should be excluded from the data used to establish intraspecific allometric regression equations for adults. From an interspecific perspective, neonate V. mertensi have a lower standard (0.16 ml O2 g−1 per h) and maximal (1.18 ml g−1 per h) metabolic rate than neonate V. brevicauda (0.22 ml g−1 per h), V. eremius (0.28 and 2.94 ml g−1 per h, respectively), V. tristis (0.33 and 3.43 ml g−1 per h) and V. gouldii (0.29 and 5.24 ml g−1 per h) at 35°C. Such interspecies differences need to be accounted for in interspecific allometric analysis.  相似文献   

11.

Background

In the clinic, variations in circadian rhythm are evident in patients with cardiovascular disease, and the risk of cardiovascular events increases when rhythms are disrupted. In this study, we focused on the role of the circadian gene period2 (per2) in mobilization and function of endothelial progenitor cells (EPCs) in vitro and in vivo after myocardial infarction (MI) in mice.

Methods and Results

MI was produced by surgical ligation of the left anterior descending coronary artery in mice with and without per2 deficiency. Trans-thoracic echocardiography was used to evaluate cardiac function in mice. Per2−/− mice with MI showed decreased cardiac function and increased infarct size. The number of CD34+ cells and capillary density were decreased in the myocardium of per2−/− mice on immunohistochemistry. Flow cytometry revealed decreased number of circulating EPCs in per2−/− mice after MI. In vitro, per2−/− EPCs showed decreased migration and tube formation capacity under hypoxia. Western blot analysis revealed inhibited activation of extracellular signal-regulated kinase and Akt signaling in the bone marrow of per2−/− mice and inhibited PI3K/Akt expression in per2−/− EPCs under hypoxia.

Conclusions

Per2 modulates EPC mobilization and function after MI, which is important to recovery after MI in mice.  相似文献   

12.
Evidence for a Terpene-Based Food Chain in the Gulf of Alaska   总被引:5,自引:5,他引:0       下载免费PDF全文
A mixture of 14C-terpenes was prepared from conifer seedlings and introduced into fresh seawater samples taken near Seward, Alaska. Initial rates of oxidation by the indigenous bacteria were linear and faster than the rates of toluene oxidation. Turnover times were 4 to 19 days. Autoradiographic measurements with 3H-terpenes indicated that at least 10% of the 0.6 × 109 to 2.7 × 109 bacteria per liter present could catabolize terpenes. The rate of terpene oxidation, 24 μg of terpenes per g of cells per h with 3 μg of terpenes added per liter, was a constant function of bacterial biomass. The specific affinity of the process was estimated to be between 8.1 and 81 liters/g of cells per h, indicating a high state of induction and the probable presence of terpenes. Terpene-oxidizing bacteria were grown on [14C]alanine and added to fresh seawater samples. Transfer of the bacterial radioactivity into larger particles at a rate of 146 pg/liter per h from the 2.3 × 109 organisms added indicated that any terpenes present would participate in the food chain.  相似文献   

13.
Specific activity of aquatic bacteria, which indicates average heterotrophic activity per bacterial cell, was determined asV max per bacterium and turnover rate per bacterium for glucose mineralization at different sites (river and estuary) in north Humberside, northeast England.V max per bacterium ranged from 0.05×10−13 to 52.2×10−13 mg/h and turnover rate per bacterium from 0.05×10−8 to 88.3×10−8 ml/h. Highest mean values were found at river sites and the lowest at an outer estuary site, although there was considerable variation at each site and ranges from all sites overlapped. Also, ranges ofV max per bacterium from Humberside sites in general overlapped published ranges for sites in other geographical areas.V max per bacterium and turnover rate per bacterium were significantly correlated with some environmental variables, which suggests that they are of ecological significance.  相似文献   

14.
1. Unfertilized eggs of Chaetopterus consume about 2.4 mm.3 O2 per hour per 10 mm.3 eggs at 21°C. 2. In the 1st hour after fertilization, the fertilized eggs consume oxygen at about 53 or 54 per cent of this rate, which is about 1.3 mm.3 O2 per hour per 10 mm.3 eggs at 21°C. 3. For the first 6 hours after fertilization, at 21°C., the curve of the rate of oxygen consumption is slightly asymmetrically sigmoid. The prefertilization rate is regained between 4½ and 5 hours after fertilization. Soon after 6 hours, ciliary activity begins, and the rate of oxygen consumption rises rapidly. 4. The unfertilized eggs of Arbacia punctulata consume about 0.36–0.5 mm.3 O2 per hour per 10 mm.3 eggs at 21°C. The absolute determination is difficult as these eggs are highly sensitive to shaking in the manometer vessels, and these difficulties are discussed. 5. The fertilized eggs of Arbacia punctulata consume oxygen at the rate of about 2.0 mm.3 O2 per hour per 10 mm.3 21°C. At 1 hour after fertilization the rate is already rising. 6. A comparison of the absolute rates of oxygen consumption, and the changes in rate at fertilization of these and a number of other eggs, together with a theoretical discussion, and a discussion of discrepancies in measurements on the eggs of Arbacia punctulata, is contained in the fifth paper of this series (21).  相似文献   

15.
Zhu GL  Steudle E 《Plant physiology》1991,95(1):305-315
A double pressure probe technique was used to measure simultaneously water flows and hydraulic parameters of individual cells and of excised roots of young seedlings of maize (Zea mays L.) in osmotic experiments. By following initial flows of water at the cell and root level and by estimating the profiles of driving forces (water potentials) across the root, the hydraulic conductivity of individual cell layers was evaluated. Since the hydraulic conductivity of the cell-to-cell path was determined separately, the hydraulic conductivity of the cell wall material could be evaluated as well (Lpcw = 0.3 to 6.10−9 per meter per second per megapascal). Although, for radial water flow across the cortex and rhizodermis, the apoplasmic path was predominant, the contribution of the hydraulic conductance of the cell-to-cell path to the overall conductance increased significantly from the first layer of the cortex toward the inner layers from 2% to 23%. This change was mainly due to an increase of the hydraulic conductivity of the cell membranes which was Lp = 1.9.10−7 per meter per second per megapascal in the first layer and Lp = 14 to 9.10−7 per meter per second per megapascal in the inner layers of the cortex. The hydraulic conductivity of entire roots depended on whether hydrostatic or osmotic forces were used to induce water flows. Hydrostatic Lpr was 1.2 to 2.3.10−7 per meter per second per megapascal and osmotic Lpr = 1.6 to 2.8.10−8 per meter per second per megapascal. The apparent reflection coefficients of root cells (σs) of nonpermeating solutes (KCI, PEG 6000) decreased from values close to unity in the rhizodermis to about 0.7 to 0.8 in the cortex. In all cases, however, σs was significantly larger than the reflection coefficient of entire roots (σsr). For KCI and PEG 6000, σsr was 0.53 and 0.64, respectively. The results are discussed in terms of a composite membrane model of the root.  相似文献   

16.
L. K. Wiersum 《Plant and Soil》1987,100(1-3):361-370
Summary A number of data on root performance of six different crop species during development were measured. The plants wre cultivated in nutrient solution. Normal plant requirements were in the range of 4 mg O2 per g dry root per hour, 0.2–4μg K per cm2 total root surface per hour,2 0.2–2μg NO3 per om2 total root surface per hour. An attempt was made to establish a ratio between forced water entry and total root surface as a measure of functional root surface. The indication is that the relative surface of permeable root remains dominant during the phase of exponential growth and declines thereafter. The data collected are considered to be representative of normal requirements. They compare well with results published in the literature.  相似文献   

17.
Rate equations and kinetic parameters were obtained for various reactions involved in the bacterial oxidation of pyrite. The rate constants were 3.5 μM Fe2+ per min per FeS2 percent pulp density for the spontaneous pyrite dissolution, 10 μM Fe2+ per min per mM Fe3+ for the indirect leaching with Fe3+, 90 μM O2 per min per mg of wet cells per ml for the Thiobacillus ferrooxidans oxidation of washed pyrite, and 250 μM O2 per min per mg of wet cells per ml for the T. ferrooxidans oxidation of unwashed pyrite. The Km values for pyrite concentration were similar and were 1.9, 2.5, and 2.75% pulp density for indirect leaching, washed pyrite oxidation by T. ferrooxidans, and unwashed pyrite oxidation by T. ferrooxidans, respectively. The last reaction was competitively inhibited by increasing concentrations of cells, with a Ki value of 0.13 mg of wet cells per ml. T. ferrooxidans cells also increased the rate of Fe2+ production from Fe3+ plus pyrite.  相似文献   

18.
The divalent cation, Ca2+, plays crucial roles in plant growth, development and stress resistance. Limonium bicolor seedlings were treated with 200 mM NaCl combined with three levels of Ca2+ (0 mM, 5 mM and 20 mM) for 15 days to study the effects of Ca2+ on development and salt-secretion rates of salt glands. It was shown that the 4th leaf areas of L. bicolor seedlings under 20 mM Ca2+ treatment were significantly higher than those under 0 mM and 5 mM Ca2+ treatments. The total number and the densities of salt glands per leaf increased markedly with increased Ca2+ concentrations. The diameters of salt glands increased by 59% and 63% as Ca2+ concentration increased from zero to 5 mM and 20 mM, respectively. Under 20 mM Ca2+ treatment, the salt-secretion rate per leaf was obviously higher than that treated with 5 mM Ca2+, but there was no significant difference in the salt-secretion rates per salt gland between the two groups. Under 0 mM Ca2+ treatment, leaf-cell membrane permeability increased significantly, which led to serious leakage of ions and a significant increase in Na+ loss rate. The results showed that the increase of Ca2+ concentration markedly enhanced development and salt-secretion rates of salt glands in the leaves of L. bicolor, the increase of salt secretion per leaf is due to the efficiency of the secretion process per salt gland and the number of salt glands, the salt-secretion rates per salt gland have a relationship with the diameters of salt glands.  相似文献   

19.
The acute effects of aqueous solutions of As, Cd, Cu, Pb, F, and Zn ions at concentrations from 0.01 to 100 micrograms per milliliter and solutions adjusted to pH 2 to 6 with nitric or sulfuric acid were studied with respect to acetylene reduction, net photosynthesis, respiration rate, and chlorophyll content in Vernal alfalfa (Medicago sativa L. cv. Vernal). The effects of the various treatments on acetylene reduction varied from no demonstrable effect by any concentration of F and 42% inhibition by 100 micrograms Pb2+ per milliliter, to 100% inhibition by 10 micrograms Cd2+ per milliliter and 100 micrograms per milliliter As, Cu2+, and Zn2+ ions. Zn2+ showed statistically significant inhibition of activity at 0.1 micrograms per milliliter. Acid treatments were not inhibitory above pH 2, at which pH nitric acid inhibited acetylene reduction activity more than did sulfuric acid. The inhibition of acetylene reduction by these ions was Zn2+ > Cd2+ > Cu2+ > AsO3 > Pb2+ > F. The sensitivity of acetylene reduction to the ions was roughly equal to the sensitivity of photosynthesis, respiration, and chlorophyll content when Pb2+ was applied, but was 1,000 times more sensitive to Zn2+. The relationship of the data to field conditions and industrial pollution is discussed.  相似文献   

20.
The response of the planktonic heterotrophic bacterial community to the buildup and breakdown of a semipermanent, crusted, floating cyanobacterial mat, or hyperscum, that covered 1 to 2 ha was studied in a hypertrophic lake (Hartbeespoort Dam, South Africa). The initial response of bacteria in the main basin to the release of dissolved organic carbon (DOC) from the hyperscum 1 km away was an increase in activity per cell from 35 × 10−12 to 153 × 10−12 μg of C cell−1 h−1 for total cell counts, while activity per cell for metabolically active cells increased from 19 × 10−11 to 85 × 10−11 μg of C cell−1 h−1. No major population growth occurred at this stage. Later, with the continuous supply of DOC from the hyperscum, total bacterial numbers increased from 6.6 × 106 to 20 × 106 cells ml−1, while the activity per cell declined. Metabolically active bacteria followed the same trend. Shorter-term DOC increases caused only increases in bacterial activity per cell. The data from Hartbeespoort Dam demonstrate an interesting and little-documented mechanism by which aquatic bacteria respond to increased DOC concentration and which may be universal for aquatic systems.  相似文献   

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