Pollination biology of yellow starthistle (Centaurea solstitialis) in California

1996 ◽  
Vol 74 (2) ◽  
pp. 262-267 ◽  
Author(s):  
D. M. Maddox ◽  
A. Mayfield ◽  
D. B. Joley ◽  
D. M. Supkoff
Keyword(s):  
Pollination Biology ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Pollen Presentation ◽  
Self Fertilization ◽  
Low Levels ◽  
High Level ◽  
Insect Visitors ◽  
Achene Production ◽  
European Honeybee

Various facets of the pollination biology affecting achene production of Centaurea solstitialis L. were examined. Production of viable achenes commenced in capitula bagged or excised in the late flowering stage (F-2 midstage). In all studies in which capitula were prevented from crossing, only one plant had a high level of achene production, all others producing either a few achenes or none at all. Achene production in plants allowed to cross was high and significantly greater than in plants prevented from crossing. Persistent low levels of self-fertilization in most plants indicated that there was selection against inbreeding. The pollen presentation mechanism for C. solstitialis was similar to that of other Centaurea spp. described previously. The most commonly observed insect visitors of yellow starthistle capitula were Hymenoptera spp., especially the European honeybee. Keywords: Centaurea, pollination, yellow starthistle.

Low levels of outcrossing in Pinus leucodermis: further evidence in artificial stands

1994 ◽  
Vol 72 (9) ◽  
pp. 1289-1293 ◽  
Author(s):  
M. Morgante ◽  
P. Rossi ◽  
G. G. Vendramin ◽  
G. Boscherini
Keyword(s):  
Natural Populations ◽  
Selective Advantage ◽  
Minimum Variance ◽  
Outcrossing Rates ◽  
Self Fertilization ◽  
Low Levels ◽  
High Level ◽  
Germinating Seeds ◽  
Neighbourhood Structure ◽  
Key Words Mating System

Outcrossing rates were estimated in two artificial stands of Pinus leucodermis, a wind pollinated conifer characterized by a relatively high level of selfing. Multilocus outcrossing rates, estimated by assaying five enzyme loci, were lower than 86% in the two stands, using both dormant and germinating seeds, and not different from those observed in two natural populations located in the same area. The lack of relevant differences between single-locus minimum variance means and the multilocus outcrossing rate estimates observed in both the artificial stands indicates that most of the apparent selfing is probably caused by actual self-fertilization. The presence of a high level of self-fertilization in this species seems confirmed also in artificial stands, where the density is higher and neighbourhood structure should be less pronounced. The high level of self-fertilization found in P. leucodermis, which is probably due to the presence of a reduced number of recessive embryonic lethals as a consequence of genetic drift, could represent a selective advantage for this pioneering and precocius species. Key words: mating system, outcrossing rates, artificial stands, Pinus leucodermis.

High world sugar prices: is Asia’s production cycle to blame?

2010 ◽  
pp. 169-173
Author(s):  
Martin Todd
Keyword(s):  
Supply Chain ◽  
Supply And Demand ◽  
Production Cycle ◽  
Low Levels ◽  
High Level ◽  
High World

The current high world sugar prices reflect a major imbalance between global supply and demand, which has reduced stocks to very low levels. Although it remains to be seen whether prices will rise much above current values, it is clear that the supply chain will remain stretched throughout 2010 and this will help to maintain prices at a high level.

scholarly journals Testing Todd: family types and development

2021 ◽  
pp. 1-18
Author(s):  
Jerg Gutmann ◽  
Stefan Voigt
Keyword(s):  
Rule Of Law ◽  
Civil Society Organizations ◽  
The Rule Of Law ◽  
State Fragility ◽  
Family Types ◽  
Low Levels ◽  
Parsimonious Model ◽  
The One ◽  
High Level

Abstract Many years ago, Emmanuel Todd came up with a classification of family types and argued that the historically prevalent family types in a society have important consequences for its economic, political, and social development. Here, we evaluate Todd's most important predictions empirically. Relying on a parsimonious model with exogenous covariates, we find mixed results. On the one hand, authoritarian family types are, in stark contrast to Todd's predictions, associated with increased levels of the rule of law and innovation. On the other hand, and in line with Todd's expectations, communitarian family types are linked to racism, low levels of the rule of law, and late industrialization. Countries in which endogamy is frequently practiced also display an expectedly high level of state fragility and weak civil society organizations.

Flavonoids and UV Photoprotection in Arabidopsis Mutants

2001 ◽  
Vol 56 (9-10) ◽  
pp. 745-754 ◽  
Author(s):  
Ken G Ryan ◽  
Ewald E Swinny ◽  
Chris Winefield ◽  
Kenneth R Markham
Keyword(s):  
Crucial Role ◽  
Hydroxycinnamic Acid ◽  
Ultraviolet B ◽  
Uvb Radiation ◽  
Wild Type ◽  
Hydroxycinnamic Acid Derivatives ◽  
Quercetin Glycosides ◽  
Kaempferol Glycosides ◽  
Low Levels ◽  
High Level

AbstractWild-type Arabidopsis L. leaves exposed to low ultraviolet-B (U V B ) conditions contained predominantly kaempferol glycosides, with low levels of quercetin glycosides. The flavonoid level doubled on treatment with UVB and an increase in the ratio of quercetin: kaempferol was observed. These results suggest that flavonols protect Arabidopsis plants from UVB damage, and indicate that the flavonoid 3’-hydroxylase (F3’H) enzyme, which converts dihydrokaempferol to dihydroquercetin, may play a crucial role. The tt7 mutant lacks this gene and, after treatment with sub-ambient UVB, contained kaempferol glycosides exclusively, to a level of total flavonols similar to that in wild-type Arabidopsis. Total flavonols after enhanced UVB treatment were higher in tt7 than in similarly treated wild-type plants, and only kaempferol glycosides were detected. Despite this high level, tt7 plants were less tolerant of UVB radiation than wild-type plants. These observations suggests that kaempferol is a less effective photoprotectant than quercetin. The chalcone isomerase (CHI) mutant (tt5) surprisingly did not accumulate naringenin chalcone, and this suggests that the mutation may not be restricted to the CHI gene alone. The concentration of hydroxycinnamic acid derivatives did not change with UVB treatment in most varieties indicating that their role in UV photoprotection may be subordinate to that of the flavonoids.

scholarly journals Factors Affecting Infection of Yellow Starthistle (Centaurea solstitialis) by Synchytrium solstitiale, Causal Agent of False Rust Disease

Plant Disease ◽  
2006 ◽  
Vol 90 (4) ◽  
pp. 425-428 ◽  
Author(s):  
T. L. Widmer ◽  
F. Guermache
Keyword(s):  
United States ◽  
Classical Biological Control ◽  
The United States ◽  
Carthamus Tinctorius ◽  
Centaurea Solstitialis ◽  
Yellow Starthistle ◽  
Rust Disease ◽  
Invasive Weed ◽  
Factors Affecting ◽  
Centaurea Calcitrapa

Yellow starthistle (Centaurea solstitialis) is an annual invasive weed in the United States with Mediterranean origins. The expense of chemical control and the vast area of invasion make this weed an appropriate target for classical biological control. Observations of a field site in southern France revealed small orange galls on the leaves of yellow starthistle seedlings caused by the fungus Synchytrium solstitiale. Inoculation of yellow starthistle seedlings with a suspension of zoospores released from infected tissue resulted in infection. Ten days after inoculation, typical orange galls appeared on the exposed tissue. Preliminary host range testing showed up to 100% infection of C. solstitialis seedlings from both France and the United States and infection of Carthamus tinctorius, Centaurea americana, C. diffusa, C. rothrockii, C. squarrosa, and Helianthus annuus seedlings. No symptoms were observed on seedlings of Centaurea calcitrapa, C. maculosa, C. sulfurea, Cirsium californica, C. occidentale, Cynera cardunculus, and Taraxacum officinale. Zoospores were released in a pH range between 4.45 and 8.25 and optimally at temperatures between 5 and 15°C. Infection of yellow starthistle seedlings occurred after a minimum 1-h exposure to a zoospore suspension at 20°C.

The dynamics of Holocene monsoon based on meteoric 10Be at Kunlun Pass on the northeastern Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Peng Chen ◽  
Zhongbo Yu ◽  
Markus Czymzik ◽  
Ala Aldahan ◽  
Jinguo Wang ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Early Holocene ◽  
Tibet Plateau ◽  
The Holocene ◽  
Proxy Records ◽  
Low Levels ◽  
High Level ◽  
Qinghai Tibet Plateau

<p>Multiple proxy records have been used for the understanding of environmental and climate changes during the Holocene. For the first time, we here measure meteoric <sup>10</sup>Be isotope of sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate mositure and atmospheric circulation changes during the Holocene. The <sup>10</sup>Be flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP = 4000 years before present). Afterwards, the <sup>10</sup>Be flux remains on a high level during the Late Holocene, but decreases slightly towards today. These <sup>10</sup>Be deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the <sup>10</sup>Be data reveal low levels during the Early Holocene until ~4 ka BP when an obvious increase was indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence for a shift in the dominant pattern of atmospheric circulation at the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.</p>

scholarly journals The Effect of Problem Based Learning Models and Levels of Creativity Toward Student Outcomes in Vocational High School

2019 ◽  
Vol 1 (6) ◽  
Author(s):  
Dasining Dasining ◽  
Supari Muslim ◽  
Sri Handajani
Keyword(s):  
Student Learning ◽  
Learning Outcomes ◽  
Problem Based Learning ◽  
Student Learning Outcomes ◽  
Learning Model ◽  
Higher Learning ◽  
Learning Models ◽  
Low Levels ◽  
Direct Learning ◽  
High Level

This study aims to determine the level of creativity of students who are taught using problem based learning models and students who are taught using direct learning models. To find out the learning outcomes of students who have a high level of creativity and creativity level of creativity is low. The method used in this study is Quasi Experimental. The design used is a 2x2 factorial design, because this design can be used to see student learning outcomes before administering treatments and after giving treatments. The results of the study found: (1) the level of creativity of students who study using a learning model based on higher learning outcomes compared to students who learn with the direct learning model; (2) student learning outcomes with a high level of creativity, significantly higher than students who have low levels of creativity; and (3) there is an interaction between the use of learning models and the level of creativity on student learning outcomes. This study concludes that: (1) problem based learning models can improve student creativity; (2) students who have a high level of creativity, higher learning outcomes than students who have low levels of creativity; and (3) there is an interaction between the use of learning models and the level of creativity on student learning outcomes.

scholarly journals Identifying Pollen Donors and Success Rate of Individual Pollinizers in European Plum (Prunus domestica L.) Using Microsatellite Markers

Agronomy ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 264
Author(s):  
Meland ◽  
Frøynes ◽  
Fotiric Akšić ◽  
Pojskić ◽  
Kalamujić Stroil ◽  
...  
Keyword(s):  
Microsatellite Markers ◽  
Success Rate ◽  
Genetic Characterization ◽  
Prunus Domestica ◽  
Tissue Samples ◽  
Self Pollination ◽  
Self Fertilization ◽  
High Level ◽  
Very High ◽  
Simple Sequence

European plum cultivars (Prunus domestica L.) are hexaploid and partially self-fertile or self-sterile requiring compatible pollinizers with overlapping bloom times. Therefore, inter-planting of different pollinizer cultivars is recommended. In order to identify successful pollinizers of the plum cultivars ‘Edda’, ‘Opal’ (self-fertile), ‘Jubileum’, ‘Reeves’, ‘Mallard’, ‘Avalon’, ‘Cacanska Lepotica’ (self-fertile), and ‘Valor’, 60 fruits per cultivar were collected from nine orchards in 2017 and 2018, all of which were located in Ullensvang, western Norway. DNA extraction was subsequently conducted from the obtained embryos, followed by genetic characterization using seven microsatellite markers. Tissue samples from all possible pollinizers were collected during the summer of 2017 and the same DNA approach was conducted. Results showed that ‘Opal’ was the most successful pollinizer among the investigated plum cultivars. The main exception was ‘Cacanska Lepotica’, which consistently displayed very high level of self-pollination. The most successful foreign pollinizer of ‘Opal’ was ‘Mallard’. However, in more than two thirds of embryos extracted from ‘Opal’ fruits self-fertilization was determined. ‘Reeves’ was identified as the most successful pollinizer among embryos collected from ‘Valor’. Among the five cultivars (‘Edda’, ‘Jubileum’, ‘Reeves’, ‘Mallard’, and ‘Avalon’) that did not display self-pollination, the pollinizer success rate of ‘Opal’, ranged from 36.5% (‘Mallard’) to 93.5% (‘Edda’) in 2017, while in 2018 this rate ranged from 43.5% (‘Jubileum’ and ‘Reeves’) up to 96.5% (‘Edda’). Overall, genotyping embryos using SSRs (simple sequence repeats) proved an effective method in determining the success rate of individual pollinizers among European plum cultivars.

Objectives and Review of the International Milk Fluoridation Program

1995 ◽  
Vol 9 (2) ◽  
pp. 110-111 ◽  
Author(s):  
G.N. Pakhomo
Keyword(s):  
Dental Caries ◽  
National Level ◽  
Data Bank ◽  
Epidemiological Studies ◽  
Weighted Mean ◽  
Number Of Children ◽  
The World ◽  
Low Levels ◽  
High Level ◽  
Very High

The WHO Global Oral Data Bank (GODB) demonstrates wide varieties of dental caries levels. During the last 10 years, dental caries prevalence in many countries has decreased from very high and high to moderate and low levels. However, there also are countries where dental caries has increased from very low and low to a moderate level. In total in 1993, of the 158 countries for which the WHO GODB has data available, 16 countries indicate a very low level (69 - low, 53 - moderate, 17 - high), and only three a very high level of dental caries. Very high levels of dental caries have been recorded in Costa Rica, Jamaica, and Uruguay. All these data, based on the weighted mean of DMF in 12-year-old children, have been obtained from national surveys or collected from published papers on oral health surveys conducted in selected areas of the countries. Very often, these papers indicated an increase (or decrease) in dental caries in people living in different areas of a particular country; however, the DMF weighted mean at the national level is still without change. One of the most populated countries in the world, China, shows clear evidence from several recent epidemiological studies that the level of dental caries in the urban population is persistently increasing. Dental caries still remains one of the most common diseases affecting a substantial number of children and adults around the world. There is evidence that water or

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