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排序方式: 共有201条查询结果,搜索用时 15 毫秒
1.
S. L. Ahuja 《Sexual plant reproduction》1988,1(1):63-64
Summary In 30 genotypes of ramie (Boehmeria nivea L. Gaud.) there were significant genotypic differences in the weight of reproductive parts (male + female flowers), vegetatively propagating parts (clump and rhizome) and non-propagating vegetative parts (leaf and root). The weight of reproductive parts was significantly and positively associated with the weight of vegetatively propagating parts. Path-coefficient analysis revealed that the selection of genotypes with a high weight of reproductive parts should be based on genotypes with a high weight of vegetatively propagating parts. 相似文献
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3.
PETER D. KRUSE 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1996,29(3):213-217
A single specimen of the early Middle Cambrian (Ordian) orthothecimorph hyolith Gudugu-wan hardmani with preserved gut filling has been discovered in the Montejinni Limestone, Wiso Basin, northern Australia. This represents only the eighth such occurrence worldwide. The specimen is unique among orthothecimorphs in retaining the gut filling in combination with the external mould of the operculum and invites revision of the accepted soft-part recon struction in this group, whereby the opercular lateral processes are now recognized to be ventral. Thus orthothecimorph conchs, if horizontal in life, would have been oriented ventral side down, while hyolithomorphs adopted the reverse orientation: horizontal, ventral side up. 相似文献
4.
We have used [2-13C]d-glucose and carbon-13 nuclear magnetic resonance (NMR) spectroscopy to investigate metabolic fluxes through the major pathways of glucose metabolism in intact human erythrocytes and to determine the interactions among these pathways under conditions that perturb metabolism. Using the method described, we have been able to measure fluxes through the pentose phosphate pathway, phosphofructokinase, the 2,3-diphosphoglycerate bypass, and phosphoglycerate kinase, as well as glucose uptake, concurrently and in a single experiment. We have measured these fluxes in normal human erythrocytes under the following conditions: (1) fully oxygenated; (2) treated with methylene blue; and (3) deoxygenated. This method makes it possible to monitor various metabolic effects of stresses in normal and pathological states. Not only has 13C-NMR spectroscopy proved to be a useful method for measuring in vivo flux through the pentose phosphate pathway, but it has also provided additional information about the cycling of metabolites through the non-oxidative portion of the pentose phosphate pathway. Our evidence from experiments with [1-13C]-, [2-13C]-, and [3-13C]d-glucoses indicates that there is an observable reverse flux of fructose 6-phosphate through the reactions catalyzed by transketolase and transaldolase, even in the presence of a net flux through the pentose phosphate pathway. 相似文献
5.
M. Zeches J. Lounkokobi B. Richard M. Plat L. Le Men-Olivier T. Sevenet J. Pusset 《Phytochemistry》1984,23(1):171-174
Fourteen alkaloids were isolated from the stem bark and aerial parts of Melodinus guillauminii. They were 11-hydroxytabersonine, venalstonine, venalstonidine, 14,15-seco-3-oxokopsinal, 3-oxovenalstonine, 11-methoxy-Δ14– vincamenine, 3-oxo-hydroxykopsinine, 11-methoxy-Δ14-vincanol, kopsinine, 15-α-hydroxykopsinine, 11-methoxy- tabersonine, pleiocarpamine, 19-β-hydroxyvenalstonine and guillauminiine. 相似文献
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7.
J. R. Caradus 《Plant and Soil》1992,146(1-2):209-217
Ninety eight white clover genotypes were cloned and grown in pots at two levels of phosphorus (P) supply in soil. After harvest the nitrogen (N) and P content of shoot (leaf, petiole and unrooted stolon), stolon and root tissue was determined. Broad sense heritabilities for %N, %P, and proportion of total N or P in each tissue type were calculated. Heritabilities ranged from 0.22 to 0.68. They were generally higher for %P than %N; and higher in shoot and stolon tissue than root tissue for %P, %N, and proportion of N or P. Level of P in which plants were grown had little effect on heritability values. Genotypes from bred cultivars differed from those collected from hill country pastures for plant size, and partitioning of N and P to shoot, stolon and root. Relationships between plant characters were examined to determine the consequences of selection. 相似文献
8.
《Palaeoworld》2022,31(4):570-581
Rhynchonelliform brachiopods made their first appearance in early Cambrian, and became a major group within the palaeozoic evolutionary fauna since late Cambrian. Exceptionally preserved fossils from the early Cambrian Lagerstätten provide valuable chances to investigate their phylogeny and ecology. Longtancunella is one of the most interesting early rhynchonelliforms, and has been mainly recovered from the Chengjiang Lagerstätte (Series 2, Stage 3). Here, we report a new rhynchonelliform Longtancunella xiazhuangensis n. sp. from the lower Hongjingshao Formation (upper Stage 3) in Yunnan Province, China. These specimens were well preserved with soft parts, including pinnate mantle canal system and a pedicle. It is identified as a new species based mainly on its difference in shell ornamentations, pinnate mantle canals and pedicle morphology from the type species. Its pedicle looks unusually stout with distinct annulated lamellae on the surface, and reveals crucial evidence in illustrating its ecology and settling strategy as an early marine epifauna. The ecological interaction between L. xiazhuangensis and other marine animals also provides insights into the food web structure in the early Cambrian. 相似文献
9.
An NMR spectroscopy study ((31)P, (1)H, (13)C) of the postulated crosslinking mechanism of sodium trimetaphosphate (STMP) on polysaccharides is reported using methyl alpha-D-glucopyranoside as a model. In a first step, reaction of STMP with Glc-OMe gives grafted sodium tripolyphosphate (STPP(g)). On the one hand, STTP(g) can react with a second alcohol functionality to give a crosslinked monophosphate. On the other hand, a monophosphate (grafted phosphate) could be obtained by alkaline degradation of STPP(g). NMR spectroscopy allows to detect the various species formed and to obtain the crosslinking density of STMP-polysaccharides hydrogels. 相似文献
10.
Robert Carlson 《Systems and synthetic biology》2007,1(3):109-117
Biological technologies are becoming an important part of the economy. Biotechnology already contributes at least 1% of US
GDP, with revenues growing as much as 20% annually. The introduction of composable biological parts will enable an engineering
discipline similar to the ones that resulted in modern aviation and information technology. As the sophistication of biological
engineering increases, it will provide new goods and services at lower costs and higher efficiencies. Broad access to foundational
engineering technologies is seen by some as a threat to physical and economic security. However, regulation of access will
serve to suppress the innovation required to produce new vaccines and other countermeasures as well as limiting general economic
growth.
相似文献
Robert CarlsonEmail: |