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991.
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Abstract The differentiation patterns of reproductive systems, including breeding and pollination systems, and perennation strategies of the genus Trillium were critically studied. The pedicellate- and sessile-flowered species with different floral morphologies and ecological distributions exhibited distinct modes of reproductive systems in relation to their habitat conditions. The pedicellate-flowered species occurring in stable mesic temperate deciduous forests reproduce exclusively by seeds, while sessile-flowered species growing in the alluvial flood plain habitats depend to a large extent on vegetative reproduction to compensate for the insufficient sexual reproduction under ecologically unstable conditions, e.g., frequent disturbance due to flooding. These sessile-flowered species are characterized by low ovule numbers, subsequent low seed outputs and low fecundity levels. In contrast to the sessile-flowered species, the pedicellate-erect-flowered species showed very high seed setting rates of over 50%. Breeding experiments for four Japanese species suggest that, although they substantially possess the capability of both inbreeding and outbreeding, the high fecundity levels are maintained by predominant inbreeding system. Furthermore, resource levels in the stock organs of these species obviously determine fecundity levels. As a consequence the amount of reserved food in the rhizomes transferred to the next season is determined, which gurantees a continuous reproductive activity of a given individual plant. 相似文献
994.
Lamont K. Anderson M. Carmen Rayner Frederick A. Eiserling 《Archives of microbiology》1984,138(3):237-243
Mutations affecting pigmentation of the cyanobacterium Synechocystis sp. 6701 were induced with ultraviolet light. Two mutants with phycobilisome structural changes were selected for structural studies. One mutant, UV08, was defective in chromatic adaptation and incorporated phycoerythrin into phycobilisomes in white or red light at a level typical of growth in green light. The other mutant, UV16, was defective in phycobilisome assembly: little phycocyanin was made and none was attached to the phycobilisome cores. The cores were completely free of any rod substructures and contained the major core peptides plus the 27,000 Mr linker peptide that attaches rods to the core. Micrographs of the core particles established their structural details. Phycoerythrin in UV 16 was assembled into rod structures that were not associated with core material or phycocyanin. The 30,500 Mr and 31,500 Mr linker peptides were present in the phycoerythrin rods with the 30,500 Mr protein as the major component. Phycobilisome assembly in vivo is discussed in light of this unusual mutant.Abbreviations PE
phycoerythrin
- PC
phycocyanin
- AP
allophycocyanin
- W
white light
- G
green light
- R
red light
- SDS
sodium dodecyl sulfate
- Na–K–PO4
equimolar solutions of NaH2PO4 · H2O and K2HPO4 · 3 H2O titrated to the desired pH 相似文献
995.
Frederick Hecht 《American journal of human genetics》1972,24(4):487-488
996.
997.
Frederick S. Dellenbaugh 《American anthropologist》1918,20(4):432-436
998.
Frederick A. Kundell 《Origins of life and evolution of the biosphere》2011,41(2):175-198
A suggested pioneer organism for the Wächtershäuser origin of life hypothesis is presented. In this scenario, a cubic pyrite crystal edge serves as a catalytic surface for the production of a proto-nucleic acid. Computational analysis demonstrates how the vacant cubic pyrite edge could be populated by iron(II) and hydrogen phosphate, capped with a distorted iron pentacarbonyl. A bridging iron sulfide then forms blocking one side of the edge. The carbonyl on the other side of the edge can then react with either existing uracil or cytosine, to produce a nitrogen-iron carbonyl intermediate. This intermediate serves as a free radical initiator for a polymerization of carbon monoxide and molecular hydrogen. After the fourth carbon is added to the chain, the polymerization is terminated by ring formation yielding a condensed ribose. The resultant product is a proto-nucleic acid, a pioneer organism. 相似文献
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1000.