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51.
Curtiss D. Hunt Edward S. Halas Marilou J. Eberhardt 《Biological trace element research》1988,16(2):97-113
The purpose of this study was threefold: 1. to determine the long-term effects of interactions between lactational zinc deficiency
and gender on bone mineral composition in repleted rat offspring, 2. to determine the nutritional efficacy of the second of
two commercially designed, modified Luecke diets (ML2) during the gestational and lactational stress, and 3. determine the
ultratrace element contents of Ralston Rodent Laboratory Chow #5001. The ML2 basal diet, based on dextrose, sprayed egg white,
and corn oil contained 0.420 μg Zn/g, was supplemented with Zn (as zinc acetate) at 0 (diet 0ML2) or 30 (diet 30ML2) μg/g,
and was mixed and pelleted commercially. all rat dams were fed the 30ML2 diet ad libitum during gestation. Beginning at parturition,
the dams were fed either the 1. 0ML2, 2. 30ML2 (food restricted), or 3. 30ML2 (ad libitum) diets. All pups were fed the 30ML2
diet ad libitum from 23 to 40 d of age. From d 40 to 150, all pups were fed Ralston Rodent Laboratory Chow. The 30ML2 diet
was found to be nutritionally efficacious; litter size and pup growth were normal and pup mortality was only 1.2%. Pups (ZD)
with access to the 0ML2 diet until 23 d of age and nursed by dams fed the 0ML2 diet, when compared to pups (PF) fed restricted
amounts of the 30ML2 diet, exhibited increased mortality and decreased concentrations of tibial zinc but no change in growth.
Inadequate zinc nutriture during infancy, despite postlactational zinc repletion, induced imbalances in adult bone mineral
metabolism. Thus, at 150 d of age, the ZD pups exhibited increased levels of bone P and Mg and decreased concentrations of
K as compared to the PF pups. 相似文献
52.
The effect of biotin deficiency on the metabolism of cholesterol was studied in rats fed cholesterol-free and cholesterol-containing
diet. Biotin deficiency induced by feeding raw egg-white resulted in higher cholesterol in the serum and aorta, and higher
high density lipoprotein cholesterol and low density lipoprotein + very low density lipoprotein cholesterol. In the liver,
cholesterol increased only in the cholesterol diet group but not in the cholesterol-free diet group. Levels of triglycerides
were lower in the biotindeficient, cholesterol-free diet group, but triglycerides were elevated in the cholesterol diet group.
Concentration of bile acids in the liver and activity of lipoprotein lipase in the heart and adipose tissue were significantly
decreased in the biotin-deficient rats. Release of lipoproteins into the circulation, incorporation of [1,2-14C] acetate into cholesterol, and activity of plasma lecithin: cholesterol acyl transferase were higher. 相似文献
53.
H. S. Bachelard R. S. Badar-Goffer K. J. Brooks S. J. Dolin P. G. Morris 《Journal of neurochemistry》1988,51(4):1311-1313
We report the first measurement of the free intracellular calcium level in an actively metabolising intact cerebral tissue preparation. To this end, we applied the recently developed 19F-nuclear magnetic resonance calcium chelator, 5,5'-F2-1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), in superfused cerebral cortical slices to give values for the intracellular Ca2+ concentration of 350 and 480 nM, at external calcium concentrations of 1.2 and 2.4 mM, respectively. Under both conditions, the intracellular Ca2+ concentration was increased by depolarisation using a high external K+ concentration. Interleaved 31P spectra showed that the presence of the 5FBAPTA had a deleterious effect on the metabolic state of the tissue with an external Ca2+ concentration of 1.2 mM, but normal viability was maintained using 2.4 mM. 相似文献
54.
55.
Maize (Zea mays L.) and ricebean (Vigna umbellata [Thumb.] Ohwi and Ohashi) were grown in intercrop and monoculture on Tropaqualf soils under rainfed conditions in Northern
Thailand yearly from 1983 to 1986. De Wit's replacement design was used to compare intercrops and monocultures with a constant
plant density equivalent to 80 000 maize or 160 000 ricebean plants ha−1. Combined nitrogen was applied at varying levels to 200 kg N ha−1. In the final two seasons the intercrop ratio of maize: ricebean was also varied. At the time of maize maturity intercrops
yielded upt 49 kg ha−1 more N in the above ground plant parts than the best monoculture. Dry matter, grain and nitrogen yield of maize and ricebean
in intercrop relative to their monoculture yields (RY, relative yield) were significantly greater than their respective share
of the plant population. Relative yield totals (RYT) for grain, dry matter and nitrogen were always greater than 1.
Nitrogen uptake per maize plant increased with progressive replacement of maize by ricebean plants. This increase was similar
to that obtained by applying combined N. Available soil nitrogen tended to decrease with increasing maize:ricebean ratio.
Increasing the maize:ricebean ratio increased the % of nitrogen derived from fixation in ricebean, the increase being equivalent
to that obtained by decreasing combined nitrogen application. Approximately the same amount of fertilizer and soil nitrogen
was taken up by maize plus ricebean in intercrop as the maize monoculture. The results suggest that the improved nitrogen
economy of the intercrop resulted from the strong competitiveness of maize in the use of mineral nitrogen and the enhancement
of nitrogen fixation in intercropped ricebean which made it less dependent on the depleted pool of soil nitrogen. 相似文献
56.
Before starting a breeding program aimed at improving the nitrogen nutrition ofVicia faba, the authors tried an alternative technique to the acetylene reduction assay, to measure some genetic variability in the
plant material. The quantity of dinitrogen fixed by several cultivars ofVicia faba was estimated using a low enrichment15N tracer method and high precision15N mass spectrometry. The fababeans were cultivated for two years in two different soils.
The percentage of fixed dinitrogen in the seed varied between genotypes from 40 to 83% of the total nitrogen and was positively
correlated with the total seed nitrogen (r=0.64 to 0.86). A highly significant positive correlation was also found between
the total seed nitrogen and the quantity of fixed dinitrogen in the seed (r=0.95 to 0.99).
The technique used to measure dinitrogen fixation proved to be useful and reliable enough to discriminate between various
genotypes, grown over a period of two years in two different soils. However, several non-fixing control plants showed significant
differences in their15N enrichment and the problem of choosing a good reference plant was raised and discussed. 相似文献
57.
Laboratory incubation and field experiments were conducted to evaluate thiourea, ATC (4-amino-1, 2, 4 triazole hydrochloride)
and N-Serve 24 E (2-chloro-6-trichloromethyl-pyridine) as inhibitors of nitrification of fertilizer N. In the incubation experiment,
most of the added aqueous NH3 or urea was nitrified at 14 days on both soils, but addition of the inhibitors to fertilizer N decreased the conversion of
NH4−N to NO3−N markedly. There was less nitrification for ATC and thiourea but not for N-Serve 24 E when the fertilizers and the inhibitors
were placed at a point as opposed to when mixed into soil. After 28 days, ATC and N-Serve 24 E were more effective in inhibiting
nitrification than thiourea. ATC and N-Serve 24 E also inhibited release of mineral N (NH4−N+NO3−N) from native soil N. In the uncropped field experiment, which received N fertilizers in the fall, nitrification of fall-applied
N placed in the 15-cm bands was almost complete by early May in the Malmo soil, but not in the Breton soil. When ATC or thiourea
had been applied with urea, nitrification of fall-applied N was depressed by May and the recovery of applied N as NH4−N was greater with increasing band spacing to 60 cm or placing N fertilizer in nests (a method of application where urea
prills were placed at a point in the soil in the center of 60×60 cm area). In late June, the percentage recovery of fall-applied
N in soil as NH4−N or mineral N increased with wide band spacing, or nest placement, or by adding ATC to fertilizer N on both soils. These
results indicate that placing ammonium-based N fertilizers in widely-spaced bands or in nests with low rates of inhibitors
slows nitrification enough to prevent much of the losses from fall-applied N.
Scientific Paper No. 552, Lacombe Research Station, Research Branch, Agric, Can. 相似文献
58.
The15N abundance of plants usually closely reflects the15N abundance of their major immediate N source(s); plant-available soil N in the case of non-N2-fixing plants and atmospheric N2 in the case of N2 fixing plants. The15N abundance values of these sources are usually sufficiently different from each other that a significant and systematic difference in the15N abundance between the two kinds of plants can be detected. This difference provides the basis for the natural15N abundance method of estimating the relative contribution of atmospheric N2 to N2-fixing plants growing in natural and agricultural settings. The natural15N abundance method has certain advantages over more conventional methods, particularly in natural ecosystems, since disturbance of the system is not required and the measurements may be made on samples dried in the field. This method has been tested mainly with legumes in agricultural settings. The tests have demonstrated the validity of this method of arriving at semi-quantitative estimates of biological N2-fixation in these settings. More limited tests and applications have been made for legumes in natural ecosystems. An understanding of the limits and utility of this method in these systems is beginning to emerge. Examples of systematic measurements of differences in15N abundance between non-legume N2-fixing systems and neighbouring non-fixing systems are more unusual. In principle, application of the method to estimate N2-fixation by nodulated non-legumes, using the natural15N abundance method, is as feasible as estimating N2-fixation by legumes. Most of the studies involving N2-fixing non-legumes are with this type of system (e.g., Ceanothus, Chamabatia, Eleagnus, Alnus, Myrica, and so forth). Resuls of these studies are described. Applicability for associative N2-fixation is an empirical question, the answer to which probably depends upon the degree to which fixed N goes predominantly to the plant rather than to the soil N pool. The natural15N abundance method is probably not well suited to assessing the contribution of N2-fixation by free-living microorganisms in their natural habitat, particularly soil microorganisms.This work was supported in part by subcontracts under grants from the US National Science Foundation (DEB79-21971 and BSR821618) 相似文献
59.
Kucey R. M. N. Snitwongse P. Chaiwanakupt P. Wadisirisuk P. Siripaibool C. Arayangkool T. Boonkerd N. Rennie R. J. 《Plant and Soil》1988,108(1):33-41
Controlled environment and field studies were conducted to determine relationships between various measurements of N2 fixation using soybeans and to use these measures to evaluate a number ofBradyrhizobium japonicum strains for effectiveness in N2 fixation in Thai soils.15N dilution measurements of N2 fixation showed levels of fixation ranging from 32 to 161 kg N ha−1 depending on bacterial strain, host cultivar and location. Midseason measures of N2 fixation were correlated with each other, but not related measures taken at maturity. Ranking ofB. japonicum strains based on performance under controlled conditions in N-free media were highly correlated with rankings based on soybean
seed yields and N2 fixation under field conditions. This study showed that inoculation of soybeans with effectiveB. japonicum strains can result in significant increases in yield and uptake of N through fixation. The most effective strains tested
for use in Thai conditions were those isolated from Thai soils; however, effective strains from other locations were also
of benefit. 相似文献
60.
Growth response of barley and tomato to nitrogen stress and its control by abscisic acid,water relations and photosynthesis 总被引:14,自引:0,他引:14
Barley (Hordeum vulgare L.) and tomato Lycopersicon esculentum Mill.) were grown hydroponically and examined 2, 5, and 10 d after being deprived of nitrogen (N) supply. Leaf elongation rate declined in both species in response to N stress before there was any reduction in rate of dryweight accumulation. Changes in water transport to the shoot could not explain reduced leaf elongation in tomato because leaf water content and water potential were unaffected by N stress at the time leaf elongation began to decline. Tomato maintained its shoot water status in N-stressed plants, despite reduced water absorption per gram root, because the decline in root hydraulic conductance with N stress was matched by a decline in stomatal conductance. In barley the decline in leaf elongation coincided with a small (8%) decline in water content per unit area of young leaves; this decline occurred because root hydraulic conductance was reduced more strongly by N stress than was stomatal conductance. Nitrogen stress caused a rapid decline in tissue NO
3
-
pools and in NO
3
-
flux to the xylem, particularly in tomato which had smaller tissue NO
3
-
reserves. Even in barley, tissue NO
3
-
reserves were too small and were mobilized too slowly (60% in 2 d) to support maximal growth for more than a few hours. Organic N mobilized from old leaves provided an additional N source to support continued growth of N-stressed plants. Abscisic acid (ABA) levels increased in leaves of both species within 2 d in response to N stress. Addition of ABA to roots caused an increase in volume of xylem exudate but had no effect upon NO
3
-
flux to the xylem. After leaf-elongation rate had been reduced by N stress, photosynthesis declined in both barley and tomato. This decline was associated with increased leaf ABA content, reduced stomatal conductance and a decrease in organic N content. We suggest that N stress reduces growth by several mechanisms operating on different time scales: (1) increased leaf ABA content causing reduced cell-wall extensibility and leaf elongation and (2) a more gradual decline in photosynthesis caused by ABA-induced stomatal closure and by a decrease in leaf organic N.Abbreviation and symbols ABA
abscisic acid
- ci
leaf internal CO2 concentration
- Lp
root hydraulic conductance 相似文献