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101.
The Significance of the Obturator in the Control of Pollen Tube Entry into the Ovary in Peach (Prunus persica) 总被引:1,自引:0,他引:1
Changes in the obturator of the peach (Prunus persica) havebeen investigated and related to pollen tube growth in thisregion. At anthesis, the cells of the obturator are active andrich in starch reserves. Twelve days after anthesis these cellsproduce a secretion that stains for carbohydrates and for proteins.As the secretion is produced, starch vanishes from these cellsand they degenerate and collapse as callose is accumulated.Secretion is independent of pollination as it takes place ina similar fashion both in pollinated and in unpollinated flowers. Pollen tube growth along the obturator surface depends on thissecretion for, although pollen tubes reach the base of the styleseven days after pollination, they cannot grow on the obturatoruntil five days later, when the secretion is produced. Thisdiscontinuous secretion taking place at the obturator may providea mechanism that controls the entrance of pollen tubes intothe ovary in the peach. Prunus persica, peach, obturator, pollen tube 相似文献
102.
103.
PHILIP S WANG MATTHIAS ANGERMEYER GUILHERME BORGES RONNY BRUFFAERTS WAI TAT CHIU GIOVANNI DE GIROLAMO JOHN FAYYAD OYE GUREJE JOSEP MARIA HARO YUEQIN HUANG RONALD C KESSLER VIVIANE KOVESS DAPHNA LEVINSON YOSHIBUMI NAKANE MARK A OAKLEY BROWN JOHAN H ORMEL JOSé POSADA-VILLA SERGIO AGUILAR-GAXIOLA JORDI ALONSO SING LEE STEVEN HEERINGA BETH-ELLEN PENNELL SOMNATH CHATTERJI T. BEDIRHAN üSTüN 《World psychiatry》2007,6(3):177-185
Data are presented on patterns of failure and delay in making initial treatment
contact after first onset of a mental disorder in 15 countries in the World
Health Organization (WHO)''s World Mental Health (WMH) Surveys. Representative
face-to-face household surveys were conducted among 76,012 respondents aged
18 and older in Belgium, Colombia, France, Germany, Israel, Italy, Japan,
Lebanon, Mexico, the Netherlands, New Zealand, Nigeria, People''s Republic
of China (Beijing and Shanghai), Spain, and the United States. The WHO Composite
International Diagnostic Interview (CIDI) was used to assess lifetime DSM-IV
anxiety, mood, and substance use disorders. Ages of onset for individual disorders
and ages of first treatment contact for each disorder were used to calculate
the extent of failure and delay in initial help seeking. The proportion of
lifetime cases making treatment contact in the year of disorder onset ranged
from 0.8 to 36.4% for anxiety disorders, from 6.0 to 52.1% for mood disorders,
and from 0.9 to 18.6% for substance use disorders. By 50 years, the proportion
of lifetime cases making treatment contact ranged from 15.2 to 95.0% for anxiety
disorders, from 7.9 to 98.6% for mood disorders, and from 19.8 to 86.1% for
substance use disorders. Median delays among cases eventually making contact
ranged from 3.0 to 30.0 years for anxiety disorders, from 1.0 to 14.0 years
for mood disorders, and from 6.0 to 18.0 years for substance use disorders.
Failure and delays in treatment seeking were generally greater in developing
countries, older cohorts, men, and cases with earlier ages of onset. These
results show that failure and delays in initial help seeking are pervasive
problems worldwide. Interventions to ensure prompt initial treatment contacts
are needed to reduce the global burdens and hazards of untreated mental disorders. 相似文献
104.
High genetic variability in Neotropical myophilous orchids 总被引:1,自引:0,他引:1
MARIA TERESA A. AZEVEDO EDUARDO L. BORBA JOÃO SEMIR VERA N. SOLFERINI 《Botanical journal of the Linnean Society. Linnean Society of London》2007,153(1):33-40
The patterns of genetic variability of seven Bulbophyllum Thouars species were investigated using 14 enzymatic loci, and compared with those of other Neotropical myophilous orchid species. The genetic variability estimated was very high ( H e = 0.39–0.61, P = 86–100%, A = 2.6–3.8), despite the small population sizes, which may be explained by the vegetative reproduction. Of the three species with multiple populations, only B. epiphytum showed moderate values of genetic structuring. Environmental characteristics and seed dispersal mechanisms are important in understanding the differences in the population structure observed. Almost all pairs of species showed low genetic similarity, indicating a long period of divergence. Our results suggest that B. adiamantinum and B. insectiferum , species currently classified in different sections of the genus, are more closely related than previously thought. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 33–40. 相似文献
105.
106.
Psychophysically, spatial summation can be demonstrated as a decrease in threshold accompanying an increased field of stimulation. The present study examined to what extent different mechanically evoked percepts (pressure, sharpness, and pain) show spatial summation. Various probes were used to apply prescribed forces to the dorsal surface of the digits of 19 healthy subjects. The threshold for three perceptual qualities showed differing degrees of spatial summation: sharpness showed no statistically significant spatial summation; pain demonstrated some significant summation (46% on average); pressure showed the greatest degree of spatial summation (76% on average). The lack of significant spatial summation for sharpness threshold is consistent with the theory that perceived sharpness can be evoked by near threshold activity of a single nociceptor. The modest amount of spatial summation for pain implies that distinctly suprathreshold activation of nociceptors is required for mechanically evoked pain perception, and such input summates centrally, but not completely. The greater spatial summation observed for pressure vs. pain thresholds implies a greater degree of central summation for slowly adapting mechanoreceptors vs. nociceptors. 相似文献
107.
PAULO M. FARIA E SILVA ANTONIO M. SOLÉ-CAVA MAURILIO J. SOARES MARIA CRISTINA M. MOTTA JOÁTO E. FIORINI WANDERLEY DE SOUZA 《The Journal of eukaryotic microbiology》1991,38(5):489-494
The trypanosomatid previously described as Crithidia roitmani is characterized here at the ultrastructural and biochemical levels. The data indicates that the parasite belongs to the Herpetomonas genus, and we therefore suggest the flagellate to be denominated as Herpetomonas roitmani n. comb. Cladistic analysis of isoenzyme data generated by eight different enzymes showed that the parasite presented a distinct banding pattern and could be grouped with some Herpetomonas spp., but not with Crithidia spp., used as reference strains. Accordingly, when the parasites were grown for longer periods in Roitman's defined medium, expontaneous differentiation from promastigotes to opisthomastigotes (typical of the Herpetomonas genus) occurred. Transmission electron microscopy revealed the presence of bacterium-like endosymbionts in the cytoplasm of all evolutive forms of the parasite. All morphological alterations characteristic of endosymbiont-bearing trypanosomatids could be observed. 相似文献
108.
NEVES MARIA C. P.; DIDONET AGOSTINHO D.; DUQUE FERNANDO F.; DO?BEREINER JOHANNA 《Journal of experimental botany》1985,36(8):1179-1192
Neves, M. C. P, Didonet, A. D., Duque, F. F. and Dobereiner,J. 1985. Rhizobium strain effects on nitrogen transport anddistribution in soybeans.J. exp. Bot. 36: 11791192. The role of six Rhizobium strains in the nitrogen metabolismof soybeans (Glycine max Merril) was studied under glasshouseand field conditions. The strains could be divided into twogroups, group I which produced a large nodule mass with relativelylow efficiency and group II which produced less nodule massbut which fixed the same amount of nitrogen. Plants inoculatedwith group I strains remobilized nitrogen faster from leavesbut also lost more nitrogen in senesced leaves. Although thetotal nitrogen transported in the xylem was similar for allstrains, plants inoculated with group I strains contained lessnitrogen in ureides in the xylem sap during the whole growthcycle. This difference was reflected in the nitrogen partitioningwithin the shoot, and smaller nitrogen harvest indexes wereobserved in these plants than in those inoculated with strainsof group II. The role of ureides in the nitrogen partitioningand grain yield was confirmed by the significant correlationbetween mean ureide content in xylem sap and nitrogen partitioningor yield. Further, nodules formed with group I strains evolvedmore hydrogen than those formed with group II strains and thepossible significance of this is discussed. Key words: Ureides, hydrogen evolution, grain yield, grain yield, harvest index, nitrogen fixation 相似文献
109.
MARCO CORTI CARLA MARIA CIABATTI ERNESTO CAPANNA 《Biological journal of the Linnean Society. Linnean Society of London》1990,41(1-3):203-214
Chromosomal races of the house mouse ( Mus domesticus ) occur extensively in Italy. The present paper reports results of studies on a hybrid zone in Central Italy on a chromosomal race with a 2 n = 22 karyotype and surrounding populations with a standard 2 n = 40 karyotype. Karyotypic and morphometric patterns of variation in this area are discussed in an attempt to contribute to an understanding of the chromosomal speciation in this species. Data are compared, where possible, with other findings on the same hybrid zone. Finally, it is suggested that changes in behavioural traits (inter-male aggression and female socio-sexual preferences) may help in promoting complete genetic isolation. 相似文献
110.
GABRIELLA CORSI ANNA MARIA PAGNI 《Botanical journal of the Linnean Society. Linnean Society of London》1990,104(4):381-388
The ontogeny, morphology, histochemistry and nuclear structure of glandular hairs in Valeriana officinalis L. subsp. collina (Wallr.) Nyman were investigated. An interesting characteristic of these glandular hairs is their remarkable variability, not only in morphology, but in their chromatin activity, and the reactions of the secretions to histochemical tests. 相似文献