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1.
The phylogenetic relationships of species are fundamental to any biological investigation, including all evolutionary studies. Accurate inferences of sister group relationships provide the researcher with an historical framework within which the attributes or geographic origin of species (or supraspecific groups) evolved. Taken out of this phylogenetic context, interpretations of evolutionary processes or origins, geographic distributions, or speciation rates and mechanisms, are subject to nothing less than a biological experiment without controls. Cypriniformes is the most diverse clade of freshwater fishes with estimates of diversity of nearly 3,500 species. These fishes display an amazing array of morphological, ecological, behavioral, and geographic diversity and offer a tremendous opportunity to enhance our understanding of the biotic and abiotic factors associated with diversification and adaptation to environments. Given the nearly global distribution of these fishes, they serve as an important model group for a plethora of biological investigations, including indicator species for future climatic changes. The occurrence of the zebrafish, Danio rerio, in this order makes this clade a critical component in understanding and predicting the relationship between mutagenesis and phenotypic expressions in vertebrates, including humans. With the tremendous diversity in Cypriniformes, our understanding of their phylogenetic relationships has not proceeded at an acceptable rate, despite a plethora of morphological and more recent molecular studies. Most studies are pre-Hennigian in origin or include relatively small numbers of taxa. Given that analyses of small numbers of taxa for molecular characters can be compromised by peculiarities of long-branch attraction and nodal-density effect, it is critical that significant progress in our understanding of the relationships of these important fishes occurs with increasing sampling of species to mitigate these potential problems. The recent Cypriniformes Tree of Life initiative is an effort to achieve this goal with morphological and molecular (mitochondrial and nuclear) data. In this early synthesis of our understanding of the phylogenetic relationships of these fishes, all types of data have contributed historically to improving our understanding, but not all analyses are complementary in taxon sampling, thus precluding direct understanding of the impact of taxon sampling on achieving accurate phylogenetic inferences. However, recent molecular studies do provide some insight and in some instances taxon sampling can be implicated as a variable that can influence sister group relationships. Other instances may also exist but without inclusion of more taxa for both mitochondrial and nuclear genes, one cannot distinguish between inferences being dictated by taxon sampling or the origins of the molecular data.  相似文献   
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Antheridia were induced by exogenously applied GA3 at concentrations between 10−6 and 3 × 10−4 M in very young filamentous protonemata of Lygodium japonicum grown in darkness; the longer the dark preculture of protonemata, the lower was the sensitivity of the protonemata to GA3. Antheridial initials were discernible after 36 hr of GA3 treatment in the most sensitive protonemata, and the timing of antheridial initiation was delayed with increasing protonemal age.
This quantitative response of the protonemata provided the basis for a new method of assaying gibberellins in terms of the degree of antheridial formation. According to this method, all the gibberellins tested and one of their precursors were active in inducing antheridia in the protonemata, and the activity spectrum of the gibberellins was as follows: GA7>GA4>GA9>GA3>GA5>GA1>GA8.
The amounts of antheridiogen contained in conditioned media were measured by the present bioassay. A semi-logarithmic relation was shown between the percentage of antheridial formation and the concentration of conditioned medium within a certain dilution range. The amounts of antheridiogen secreted by the prothallia were quantitatively compared by transferring samples onto fresh media for a short period of time.  相似文献   
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5-Fluorouracil, 8-azaguanine and ethionine were tested on the orientation of cell division to see whether the two-dimensional development of the fern Adiantum gametophytes was due to newly synthesized protein(s). Using the system in which the orientation of cell division was controlled experimentally by sequential treatment with red light, white light and darkness and by the direction of irradiation, all the inhibitors decreased the rates of cell elongation and cell division of the gametophytes, but did not specifically affect the two-dimensional differentiation at all.  相似文献   
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The requirement of protein synthesis for amoebo-flagellate transformation of Physarum polycephalum was re-examined. When amoebae were grown on nutrient agar in association with live food bacteria and harvested in mid-exponential phase of growth, it took ca. 2 hours for half the cells to form flagella after suspension in phosphate buffer. The transformation was completely inhibited by 5 μg/ml cycloheximide. To the contrary, when the amoebae in mid-exponential phase were starved for 3 hr on non-nutrient agar and then suspended in phosphate buffer, the duration required for this process was shortened to ca. 8 min and it was not inhibited by up to 100 μg/ml cycloheximide. A similar result was obtained using bactobolin, another inhibitor of protein synthesis. When amoebae were starved on non-nutrient agar containing 5 μg/ml cycloheximide, however, the starvation effect described above was not observed. The results indicate that protein(s) necessary for the transformation might be synthesized during the starvation period, and that the amoebo-flagellate transformation may or may not require concomitant protein synthesis depending upon preculture conditions.  相似文献   
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The photo-induced cell division in single-celled protonemata of the fern Adiantum capillus-veneris was studied. When the protonemata were exposed to monochromatic light at 50 nm intervals between 350 and 750 nm, irradiations in the blue and near-ultraviolet regions effectively induced cell division, while wavelengths longer than 550 nm showed no such effect. As reciprocity between duration and intensity was observed within the range of incident energy used, the action spectrum for the frequency of the photo-induced cell divisions 24 h after irradiation was determined between 360 and 510 nm at 10 nm intervals. Furthermore, the previously known effect of phytochrome on the timing of the cell division was minimized by a short exposure to red light given immediately after the monochromatic irradiation. The resulting action spectra showed a peak in the neighborhood of 460 nm with shoulders and another peak in the near-ultraviolet region.  相似文献   
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  • 1 In 4-day-old etiolated rice seedlings, 3 mm of the coleoptile tip did mainly perceive the photostimulus to cause the phytochrome-dependent inhibition of coleoptile elongation. At this age, cell elongation occurred most in the middle portion of coleoptiles in the dark, and was reversibly controlled by a brief exposure of the tip to red and far-red light. Thus, the photoperceptive site was evidently separated from the growing zone in intact rice coleoptiles.
  • 2 The red-light-induced inhibition of coleoptile elongation was nullified by the removal of tip followed by the exogenous application of IAA. The sensitivity of thus treated coleoptiles to IAA was gradually lost during intervening darkness between the irradiation and the decapitation, and a 50% loss was obtained at ca. 6th hour at 26°C.
  • 3 Polar auxin transport from coleoptile tips was remarkably prevented at the period between, at least, 2nd and 4th hour after red irradiation, and it recovered to the level of dark control by the 6th hour. Far-red light given immediately after red irradiation reversed the yield of diffusible auxin up to that of far-red control.
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Fishes of the order Alepocephaliformes, slickheads and tubeshoulders, constitute a group of deep‐sea fishes poorly known in respect to most areas of their biology and systematics. Morphological studies have found alepocephaliform fishes to display a mosaic of synapomorphic and symplesiomorphic characters, resulting in great difficulties when attempting to resolve intra‐ and interrelationships. Molecular data recently added to the confusion by removing Alepocephaliformes from the Euteleostei and placed them as incertae sedis within the Otocephala. In the present study we attempt to further clarify relationships of Alepocephaliformes by adding newly determined whole mitogenome sequences from 19 alepocephaliforms in order to address 1) phylogenetic position of Alepocephaliformes within the Otocephala; and 2) intrarelationships of Alepocephaliformes. The present study includes 96 taxa of which 30 are alepocephaliforms and unambiguously aligned sequences were subjected to partitioned maximum likelihood and Bayesian analyses. Results from the present study support Alepocephaliformes as a genetically distinct otocephalan order as sister clade to Ostariophysi (mostly freshwater fishes comprising Gonorynchiformes, Cypriniformes, Characiformes, Siluriformes and Gymnotiformes). The disputed family Bathylaconidae was found to be an artificial assemblage of the two genera Bathylaco and Herwigia, with the former as the sister group of the family Alepocephalidae and the latter nested within Alepocephalidae. Platytroctidae was found to be monophyletic as sister clade to the rest of Alepocephaliformes. Previously unrecognized clades within the family Alepocephalidae are presented and a clade comprising Alepocephalus, Conocara and Leptoderma was recovered as the most derived. As long as the current classification is being followed, the genera Alepocephalus, Bathytroctes, Conocara and Narcetes were all found non‐monophyletic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 923–936.  相似文献   
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