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The hypothesis that outcrossers are competitively superior to close relatives with specialized genetic systems was tested. Interspecific competition between three closely related Oenothera species was examined in common garden environments. Oenothera grandis, an obligate outcrosser, is competitively superior to its derivative, O. laciniata, an obligate chromosomal heterozygote. Both of these species are superior to O. mexicana, a closely related facultative selfer. These relationships were consistent over two levels of density stress. Therefore, in this species triad, the outcrosser has a competitive advantage over its close relatives with derived breeding systems. 相似文献
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AUXIN OF TOMATO FRUIT AT DIFFERENT STAGES OF ITS DEVELOPMENT WITH A SPECIAL REFERENCE TO HIGH TEMPERATURE INJURIES 总被引:1,自引:0,他引:1
Acidic auxin in tomato fruit at various developmental stageswas examined by paper chromatography and Avena curvature test. Auxin activity of the fruit extracts was detected only in thesame Rf zone as that of authentic IAA with four solvent systems,i.e., isopropanol-ammonium hydroxide-water 10:1:1 v/v, n-butanol-ammoniumhydroxide-water 25:1:5 v/v, ethanol-water 7:3 v/v and n-butanol-aceticacid-water 4:1:1 v/v. Auxin content of fruit was the highest on the seventh day afteranthesis, when the two-celled proembryo began to grow rapidlyand the endosperm consisted of multi-cells. The second peakof auxin activity occurred on the 30th day, when the embryo,which consisted of the cotyledons, hypocotyl, and radicle, finishedits most rapid growth. No auxin activity was detected in theripe fruit. Auxin contents in fruit on the fifth, seventh, and tenth daysafter anthesis were lowered by a 4 hr high temperature treatmentat 40 given 03 days after anthesis. The nature of tomato auxin and its possible role in the fruitdevelopment were discussed. (Received June 30, 1966; ) 相似文献
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J. J. Burdon P. H. Thrall A. H. D. Brown 《Evolution; international journal of organic evolution》1999,53(3):704-716
Different patterns of resistance to six pathotypes of Melampsora lini were detected in 11 populations of Linum marginale distributed across two metapopulations. The two metapopulations (mountains and plains of New South Wales, Australia) differed in the annual cycle of disease development, which barely overlapped, and in the growth cycle and mating system of the host. Host populations in the mountains metapopulation were highly inbred, whereas those on the plains showed appreciable levels of outcrossing. Within each metapopulation there was significant variation among component populations in (1) levels of host resistance to individual pathogen isolates; (2) mean levels of resistance to all six isolates; (3) the number of resistance phenotypes present and the evenness of their distribution within the population; and (4) the average number of pathogen lines to which individual hosts were resistant. A more limited comparison of pathogen populations from the two metapopulations (two from each) found greater similarities in the structure of populations and particular virulence frequencies within, rather than among, the two metapopulations. Differences in host outcrossing rates between the two metapopulations are reflected in marked differences in the overall level of resistance, its partitioning within and among populations, the number and distribution of resistance phenotypes in the two areas, and the level of polymorphism for specific virulence factors in the pathogen, with the plains metapopulation showing consistently higher values. However, these differences were not significant. In general, variation for all parameters was just as great among populations within a metapopulation as between the two metapopulations. 相似文献
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A new, single-spored mycetozoan, Schizoplasmodium cavostelioides, was isolated from dead plant materials collected in New Zealand, Australia, Ceylon, North Carolina, and Florida. Its vegetative stage consists of thin, colorless plasmodia that grow vigorously in culture with an unidentified yeast (or yeast and bacterium). Prior to sporulation the plasmodium breaks up into multinucleate prespore cells which develop immediately into simple fruiting bodies, each consisting of a single multinucleate spore on a short stalk. Under proper conditions a gas bubble appears on one side of the spore, enlarges and bursts, thus discharging the spore. Upon germination the spore releases a single small, multinucleate Plasmodium. 相似文献
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《Electromagnetic biology and medicine》2013,32(1):107-113
The present study aimed to investigate the effects of microwaves (MW) emitted by cellular phones (CPs) on peripheral blood parameters and birth weights of rats. Thirty-six albino rats were divided into four groups, male (n = 6) and female sham-exposed groups (n = 12) and male (n = 6) and female experimental groups (n = 12). No blood parameters differed following exposure (p > 0.05). The birth weight of offspring in the experimental group was significantly lower than in the sham-exposed group (p < 0.001). No significant differences were observed between rectal temperatures of rats in the sham and experimental groups (p > 0.05). The specific absorption rate (SAR) was found to be 0.155 W/kg for the experimental groups. All parameters investigated were normal in the next generation of rats (p > 0.05). 相似文献
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Edward J. Klekowski Jr. 《American journal of botany》1973,60(6):535-544
Meiosis in homosporous ferns allows chromosomes to pair within homoeologous sets rather than restricting pairing to homologs; this allows homozygous spore mother cells to give rise to genetically heterogeneous meiospores. It is envisioned that such a meiotic system has evolved in homosporous ferns in response to a life cycle which allows the attainment of total homozygosity in one generation of selfing. 相似文献
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生于蒙古栎(Quercus mongolica)和波罗栎(Q.Dentata)上的齿裂菌属一新种,即异襄齿裂菌(Coccomycesdimorphus)。该种因子囊同时以两种状态存在而明显区别于齿裂菌属其它成员。主、副模式标本保藏于安徽农业大学森林保护教研室(AAUFP)。 相似文献
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Robert W. Baxter 《American journal of botany》1959,46(3):163-169
Baxter , ROBERT W. (U. Kansas, Lawrence.) A new cordaitean stem with paired axillary branches. Amer. Jour. Bot. 46(3) : 163-169. Illus. 1959.—A cordaitean stem tip from the middle Pennsylvania of Kansas is described as a new species, Mesoxylon birame sp. nov. The most distinctive feature of the new species is the presence of paired branches in the axil of each leaf. The possibility that these twin branches represent axes of Cordaianthus cones is discussed. 相似文献
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本文根据Henri Romagnesi(1967)的分类系统就作者在广东地区所采集到的红菇属Russula33个种作了分类上的研究。其中新种1种即广东红菇Russula guangdongensis Bi & T.H.Li,sp.nov.,新变种一种即小小红菇Russula minutula var.minor Bi var.nov.和12种国内新记录种。文中有新种及新变种的形态描述及微观图,分种及所属亚组的检索表。 相似文献
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A new genus and species of the Protosteliida (Mycetozoa), Ceratiomyxella tahitiensis, was isolated from dead plant material—var. tahitiensis from Tahiti and var. neotropicalis from Brazil and Colombia. The sporocarps have deciduous spores borne singly on slender hollow stalks; zoocysts with anteriorly flagellate planonts are produced. The trophic stage is comprised of uninucleate to plurinucleate amoeboid cells and reticulate plasmodia; the uninucleate cells become flagellate in water. The prespore cells and spores are plurinucleate. Sexuality has not been demonstrated. Var. tahitiensis has globose spores and produces its zoocysts just after spore germination, whereas var. neotropicalis has subglobose spores and forms zoocysts later in the life cycle. The species is thought to show phylogenetic relationships with Ceratiomyxa, which was recently transferred to the Protosteliida by Olive. 相似文献
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Benton M. Stidd Michael O. Rischbieter Tom L. Phillips 《American journal of botany》1985,72(4):501-508
A new lyginopterid pollen organ is described based upon specimens occurring in a single coal ball from the Providence, Kentucky locality. Seven to nine beaked sporangia are fused together at their proximal ends forming a common synangial chamber; synangia are joined together in clusters of two or three. In situ prepollen is similar to Cyclogranisporites and Verrucosisporites sporae dispersae. The thick exine has a lamellate nexine and a prominent alveolate sexine. 相似文献