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排序方式: 共有252条查询结果,搜索用时 31 毫秒
1.
Induction kinetics of delayed fluorescence of sun and shade leaves ofFagus sylvatica in the ms-range
U. Stein C. Buschmann R. Blaich H. K. Lichtenthaler 《Radiation and environmental biophysics》1990,29(2):119-128
Summary Induction kinetics of luminescence (=delayed chlorophyll fluorescence or delayed light emission) were measured with sun and shade leaves of a tall beech tree (Fagus sylvatica pendula, weeping beech). The kinetics detected in the ms-range are contrasted for the upper and the lower leaf side. The influence of the following parameters is demonstrated: time of dark-adaptation prior to the measurement, intensity of the excitation light and photoinhibitory treatment. The effects are discussed with respect to chlorophyll concentration, absorption of the excitation light, reabsorption of the luminescence and photosynthetic activity of the leaf tissue. It is shown that the luminescence signal and its kinetic are determined mainly by the properties of the mesophyll parenchyma facing the detector. Thus the more densely packed palisade parenchyma at the upper leaf side exhibits a lower luminescence and a slower kinetic than the spongy parenchyma at the lower leaf side, which is characterized by many aerial interspaces. Our study shows that luminescence kinetics can be applied to interpret the physiological state of a specific leaf tissue. They may serve as an indicator of disorders in the photosynthetic function. 相似文献
2.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
3.
Agar yield and quality of Gracilaria chilensis (Gigartinales,Rhodophyta) in tank culture using fish effluents 总被引:1,自引:0,他引:1
Tank cultivation of Gracilaria using fish effluents has permitted a production of 48 kg m–2 yr–1 and can reduce the dissolved nitrogen loads in the seawater. We report the yield, gel strength, gelling and melting point of agar from Gracilaria cultivated in tanks with seawater previously utilized in intensive, land-based salmon cultures and compared to a control using directly pumped seawater, over a study period of 22 months. The results show that the highest agar yield (20 to 22%) was obtained when Gracilaria was cultivated with pure seawater as compared to the fish effluents. The gel strength, gelling and melting point were higher in the agar obtained from algae cultured with fish effluents. During the spring, the gel strength, gelling and melting point increased in tanks with fish effluents and decreased in tanks with a supply of pure seawater. 相似文献
4.
5.
A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
6.
Hypercalcemia is a frequent complication of cancer. Recently, parathyroid hormone-related protein has been isolated from tumors associated with this syndrome. In the present study, the effects of tumor-derived hypercalcemic factor and bovine parathyroid hormone (PTH) on bone were compared in an organ culture system using calvarial bones from newborn mice. Mouse calvaria were incubated for 72 h with control medium or media containing 0.15 mg/m tumor extract (TE) or 2 x 10(-9) M PTH. Bone resorption, as assessed by the amount of calcium released into the medium and the number of osteoclasts counted on light microscopy, was increased by both PTH and TE. On electron microscopy, areas for cytoplasm, ruffled border and clear zone were statistically increased in PTH- and TE-treated calvaria as compared to control. These values were not significantly different between PTH- and TE-treated calvaria. The study therefore demonstrates that the ultrastructural changes in osteoclasts induced by the hypercalcemia-producing TE are similar to those induced by PTH. 相似文献
7.
8.
Martin Blumenberg Richard Seifert Bernd Buschmann Steffen Kiel Volker Thiel 《Geomicrobiology journal》2013,30(1):66-75
The steep biogeochemical gradients near deep sea hydrothermal vents provide various niches for microbial life. Here we present biosignatures of such organisms enclosed in a modern and an ancient hydrothermal sulfide deposit (Turtle Pits, Mid-Atlantic Ridge, Recent; Yaman Kasy, Russia, Silurian). In the modern sulfide we found high amounts of specific bacterial and archaeal biomarkers with δ13C values between ?8 and ?37‰ VPDB. Our data indicate the presence of thermophilic members of the autotrophic Aquificales using the reductive tricarboxylic acid (rTCA) cycle as well as of methanogenic and chemolithoheterotrophic Archaea. In the ancient sample, most potential biomarkers of thermophiles were obscured by compounds derived from allochthonous organic matter (OM), except for an acyclic C40 biphytane and its C39 breakdown product. Both samples contained high amounts of unresolved complex mixtures (UCM) of hydrocarbons. Apparently, OM in the sulfides had to withstand high thermal stress, indicated by highly mature hopanes, steranes, and cheilanthanes with up to 41 carbon atoms. 相似文献
9.
Oylum Erkus Victor CL de Jager Maciej Spus Ingrid J van Alen-Boerrigter Irma MH van Rijswijck Lucie Hazelwood Patrick WM Janssen Sacha AFT van Hijum Michiel Kleerebezem Eddy J Smid 《The ISME journal》2013,7(11):2126-2136
Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty. 相似文献
10.
Irisin was first identified in muscle cells. We detected irisin immunoreactivity in various organs of the crested porcupine (Hystrix cristata). In the epidermis, irisin immunoreactivity was localized mainly in stratum basale, stratum spinosum and stratum granulosum layers; immunoreactivity was not observed in the stratum corneum. In the dermis, irisin was found in the external and internal root sheath, cortex and medulla of hair follicles, and in sebaceous glands. Irisin immunoreactivity was found in the neural retina and skeletal muscle fibers associated with the eye. The pineal and thyroid glands also exhibited irisin immunoreactivity. 相似文献