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121.
Summary Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C3 plant) and Amaranthus retroflexus L. (C4 plant) were maintained under open air conditions in standard soil at low and high nitrogen supply levels.A comparison of shoot dry weight and shoot length in the various series shows that the growth of the aboveground parts of both species was severely reduced under low N conditions. In both pure and mixed cultures the differences resulting from low N vs. high N conditions was less pronounced with Atriplex (C3 plant) than with Amaranthus (C4 plant). The root dry weight of the two species was not reduced so much under low N conditions as was the shoot dry weight. The low N plants were found to contain a larger proportion of their biomass in the roots than did the high N plants. In general the root proportion of Atriplex was greater than that of Amaranthus. The contents of organic nitrogen and nitrate and the nitrate reductase activity (NRA) per g dry weight of both species decreased continually throughout the experiments. With the exception of young plants, the low N plants always had tower contents of organic nitrogen and nitrate and nitrate reductase activities than did the high N plants. The highest values of NRA were measured in the leaf laminae. The eaves also exhibited the highest concentrations of organic nitrogen. The highest nitrate concentrations, however, were observed in the shoot axis, and in most cases the lowest nitrate values were found in the laminae. At the end of ne growing season this pattern was found to have been reversed with Atriplex, but not with Amaranthus. Thus Atriplex was able to maintain a higher NRA in the laminae than Amaranthus under low N conditions.The transpiration per leaf area of the C4 plant Amaranthus during the course of a day was substantially lower than that of the C3 plant Atriplex. There were no significant differences in transpiration between the low N and high N series of Amaranthus. The low N plants of Atriplex, however, clearly showed in most cases higher transpiration rates than the corresponding high N plants. These different transpiration rates of the high N and the low N Atriplex plants were also reflected in a distinct 13C discrimination.The sum of these results points to the conclusion that the C3 plant Atriplex hortensis can maintain a better internal inorganic nitrogen supply than the C4 plant Amaranthus retroflexus under low N conditions and an ample water supply, due to the larger root proportion and the more pronounced and flexible transpiration of the C3 plant.Dedicated to Prof. Dr. Karl Mägdefrau, Deisenhofen, on the ocasion of his 80th birthday 相似文献
122.
Summary In the neutral lipid fraction of Hydrogenomonas eutrapha strain H 16, two esters of phthalic acid were found and separated by column chromatography.By totally labelling chemolithotrophically growing bacteria with 14CO2 it was demonstrated that these phthalic acid esters are not genuine bacterial products but of exogenous origin.It is supposed that these esters which are used as plasticizers for various plastics originate from such materials used in the preparation and storage of demineralized water. 相似文献
123.
S. Katsura W. Fukuda S. Inawashiro N. M. Fujiki R. Gebauer 《Cell biochemistry and biophysics》1987,11(1):309-319
The integral equation for the distribution function of effective field of the ±J random Ising model in the pair (Bethe) approximation is investigated. Its exact solutions atH (magnetic field)=0,T (temperature)=0 and forz (coordination number)=3 expressed as superpositions of 2N+1 (more than 3), delta functions are considered. Then the integral equation is reduced to a system of algebraic equations ofz ?1th degree withN+1 unknowns. The system of the equations is solved by the Gröbner basis method withN=1, 2, 3, 4. The number of physically acceptable solutions for a givenN is ω(N)+1 where ω(N) is the number of divisors ofN. The ground-state energy and entropy for these are calculated. They are very close in value (entropies are positive), and it is suggested that a number of physically acceptable solutions correspond to local stationary spin-glass states, as discussed in the literatures. 相似文献
124.
Ronald E. Bontrop Marcel G. J. Tilanus Marlies M. A. Mikulski Dienne G. Elferink Annemarie Termijtelen Rene R. P. de Vries Jon J. van Rood Marius J. Giphart 《Immunogenetics》1988,27(1):40-45
HLA-DR molecules were isolated from HLA-DR3, –5, and –w6 positive homozygous B-cell lines by immunoprecipitation with monoclonal antibodies and analyzed by gel electrophoretic techniques. DNA isolated from the same cell lines was digested with the restriction enzyme Taq I and hybridized with a DR beta full-length cDNA probe. We demonstrated that certain DR
I alleles are found in combination with different DR
III alleles as defined by Southern blotting, protein chemistry, a functional assay using purified protein derivative-specific T-cell lines, and, in one case, also alloreactive T-cell reagents. Our results indicate that within the family of HLA-DRw52-associated haplotypes DR beta chain genes may have been transferred from one haplotype to another. The implications of these findings are discussed. 相似文献
125.
Summary The opisthonephric kidney of the rainbow trout was investigated by light- and electron microscopy and a fluorescent-histochemical technique for biogenic amines was used. Preglomerular sphincters at the origin of afferent arterioles are present in this euryhaline teleost. The branching point of the afferent arteriole is characterized by (i) the formation of a right angle with the parent vessel, (ii) circularly arranged smooth muscle cells of the tunica media, (iii) additional circularly arranged smooth muscle cells intercalated between endothelium and tunica media, and (iv) a collar-like arrangement of several large endothelial cells with elaborate marginal folds and abundant myoendothelial junctions. A dense adrenergic innervation displaying specific fluorescence was found along the terminal arterioles and afferent arterioles, and conspicuously at the preglomerular sphincters. These results are suggestive of a neural participation in kidney function. They are discussed on the basis of recent evidence from pharmacological and physiological experiments for neural involvement in glomerular intermittency. 相似文献
126.
Pollination Biology of Piperaceae Species in Southeastern Brazil 总被引:3,自引:2,他引:1
Phenology, floral biology and breeding system are describedfor 14 Piperaceae species at two sites covered by semi-deciduousforest in southeastern Brazil. Flowering occurred continuouslythroughout the year, with a peak during the windy months. Allspecies had minute odorous and nectarless flowers visited byinsects; five of them showed a substantial degree of self-compatibility,and one was andromonoecious. Seven species were wind pollinated,and three were exclusively pollinated by insects. Flower visitorswere mainly hoverflies and bees. Copyright 2000 Annals of BotanyCompany Piper spp., Ottonia spp., Pothomorphe umbellata, pepper family, phenology, floral biology, breeding system, ambophily, semi-deciduous forest 相似文献
127.
This paper discusses archaeobotanical remains from the settlement mound of Kursakata, Nigeria, comprising both charred and uncharred seeds and fruits as well as charcoal. In addition, impressions of plant tempering material in potsherds were analysed. The late Stone Age and Iron Age sequence at Kursakata is date from 1000 cal. B.C. to cal. A.D. 100. DomesticatedPennisetum (pearl millet), wild Paniceae and wild rice are the most common taxa. Kernels from tree fruits were regularly found including large numbers ofVitex simplicifolia—a tree which is absent from the area today. A distinct change in plant spectra can be observed between the late Stone Age and the Iron Age. Although domesticated pearl millet was already known at the beginning of the settlement sequence of Kursakata, it only gained greater economic importance during the Iron Age. Besides farming, pastoralism and fishing, gathering of wild plants always played a major role in the subsistence strategy of the inhabitants of Kursakata. The charcoal results show that firewood was mainly collected from woodlands on the clay plains, which must have been more diverse than today. The end of the late Stone Age in the Chad Basin was presumably accompanied by the onset of drier environmental conditions from ca. 800 cal. B.C. onwards. 相似文献
128.
We examined the extent to which carbon investment into secondary compounds in loblolly pine (Pinus taeda L.) is changed by the interactive effect of elevated CO2 and N availability and whether differences among treatments are the result of size-dependent changes. Seedlings were grown
for 138 days at two CO2 partial pressures (35 and 70 Pa CO2) and four N solution concentrations (0.5, 1.5, 3.5, and 6.5 mmol l−1 NO3NH4) and concentrations of total phenolics and condensed tannins were determined four times during plant development in primary
and fascicular needles, stems and lateral and tap roots. Concentrations of total phenolics in lateral roots and condensed
tannins in tap roots were relatively high regardless of treatment. In the smallest seedlings secondary compound concentrations
were relatively high and decreased in the initial growth phase. Thereafter condensed tannins accumulated strongly during plant
maturation in all plant parts except in lateral roots, where concentrations did not change. Concentrations of total phenolics
continued to decrease in lateral roots while they remained constant in all other plant parts. At the final harvest plants
grown at elevated CO2 or low N availability showed increased concentrations of condensed tannins in aboveground parts. The CO2 effect, however, disappeared when size differences were adjusted for, indicating that CO2 only indirectly affected concentrations of condensed tannins through accelerating growth. Concentrations of total phenolics
increased directly in response to low N availability and elevated CO2 in primary and fascicular needles and in lateral roots, which is consistent with predictions of the carbon-nutrient balance
(CNB) hypothesis. The CNB hypothesis is also supported by the strong positive correlations between soluble sugar and total
phenolics and between starch and condensed tannins. The results suggest that predictions of the CNB hypothesis could be improved
if developmentally induced changes of secondary compounds were included.
Received: 27 March 1997 / Accepted: 25 July 1997 相似文献
129.
130.
H.-D. Bartsch L. M. de Azevedo Moreira G. Röhrborn U. Claussen H.-J. Gebauer 《Human genetics》1980,54(3):319-322
Summary The possible derivation of a small supernumerary marker chromosome was investigated by means of different staining techniques and the frequency of satellite associations. It could be demonstrated that the marker chromosome participates at satellite association more than randomly. The marker chromosome is supposed to derive from 2 of chromosomes 13, 14, 21, or 22.Who died accidentally in 1978 相似文献