共查询到20条相似文献,搜索用时 31 毫秒
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Fernando S. Henriques 《The Botanical review》2009,75(3):249-270
This review on chlorophyll a fluorescence starts with an overview of the primary photochemistry occurring at PSII and a characterization of the so-called
“open” and “closed” states of its reaction centers. This provides the theoretical background for understanding the origin
of PSII-emitted fluorescence and how its yield varies with the fraction of open reaction centers. The review proceeds to discuss
the changes in fluorescence emission following illumination of a dark-adapted leaf and to define the PSII intrinsic quantum
yield of photochemistry, which in turn provides an indication of PSII capacity. In light-adapted leaves, it is discussed how
the use of modulated fluorometers and the double lighting technique allow an evaluation of photochemical and non-photochemical
quenching, two parameters that give useful information about the plant’s photosynthetic performance under field conditions.
Finally, it is described how the PSII operational efficiency can be used to calculate the photosynthetic electron transport
rate and the conditions under which this is linearly related to the CO2 assimilation rate. Some requirements for a valid application of the technique as well as some limitations in interpreting
its results are discussed.
相似文献
Fernando S. HenriquesEmail: |
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Peter Godfrey-Smith 《Biology & philosophy》2007,22(3):429-437
Jablonka and Lamb's claim that evolutionary biology is undergoing a ‘revolution’ is queried. But the very concept of revolutionary
change has uncertain application to a field organized in the manner of contemporary biology. The explanatory primacy of sequence
properties is also discussed.
相似文献
Peter Godfrey-SmithEmail: |
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Chi-Li Yu Daniel Ferraro S. Ramaswamy Mark H. Schmitz Wayne F. Schaefer David T. Gibson 《Environmental Biology of Fishes》2008,82(1):51-58
A blue protein present in the mucus coating blue forms of walleye, Sander vitreus, was purified to homogeneity by a combination of ion exchange and hydrophobic interaction chromatography. The purified protein
has a molecular mass of 87,850 and is a homotetramer with a subunit molecular mass of 21,836. Solutions of the protein are
deep blue in color and show absorbance maxima at 383 and 633 nm, respectively. Acetone treatment of the protein releases a
blue chromophore with the spectral characteristics of biliverdin IXα. The results suggest that the blue protein is a new biliprotein
that we have termed Sandercyanin. The function of Sandercyanin is unknown, but limited amino acid sequence analysis suggests
it is a lipocalin that may be involved in the transport of heme degradation products.
相似文献
David T. GibsonEmail: |
5.
Philip Richard Sullivan 《Biology & philosophy》2009,24(1):65-79
This paper demonstrates that the human visual system, the primary sensory conduit for primates, processes ambient energy in
a way that obligatorily constructs the objects that we ineluctably perceive. And since our perceptual apparatus processes
information only in terms of objects (along with the properties and movements of objects), we are limited in our ability to comprehend ‘what
is’ when we move beyond our ordinary world of midsize objects—as, for example, when we address the micro microworld of quantum
physics.
相似文献
Philip Richard SullivanEmail: |
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Sub-Antarctic Marion Island has had a permanent research station for 50 years and the islands Wandering Albatrosses have been intensively studied for 20 years. The reactions of breeding birds to approaches by a human on foot were recorded. Three response variables were calculated: intensity of vocal reaction (IVR), intensity of non-vocal reaction (INR) and overall response index (ORI). At 5 m from the nest, twice as many birds stood and/or vocalised as at 15 m. Nearest neighbour distance, age and gender did not explain individual variability of responses. Study colony birds had higher IVR scores than non-study colony birds; birds at colonies closest to the station had the highest ORI scores. A better breeding record was associated with lower IVR and ORI scores, but a causative relationship remains to be demonstrated. A minimum viewing distance of 25 m is recommended for breeding Wandering Albatrosses.
相似文献
Marienne S. de VilliersEmail: Fax: +27-21-6503434 |
John CooperEmail: |
Peter G. RyanEmail: |
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M. Irfan-Ullah Giriraj Amarnath M. S. R. Murthy A. Townsend Peterson 《Biodiversity and Conservation》2007,16(6):1917-1925
Aglaia bourdillonii is a plant narrowly endemic to the southern portion of the Western Ghats (WG), in peninsular India. To understand its ecological
and geographic distribution, we used ecological niche modeling (ENM) based on detailed distributional information recently
gathered, in relation to detailed climatic data sets. The ENMs successfully reconstructed key features of the species’ geographic
distribution, focusing almost entirely on the southern WG. Much of the species’ distributional potential is already under
protection, but our analysis allows identification of key zones for additional protection, all of which are adjacent to existing
protected areas. ENM provides a useful tool for understanding the natural history of such rare and endangered species.
相似文献
M. Irfan-UllahEmail: Email: |
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The maintenance of exceptionally high numbers of folk varieties by the Piaroa people of the Venezuelan Amazon is considered.
We cataloged 113 manioc folk varieties, their nomenclature, use and relevant characters, revealing significant insights into
the role of manioc in Piaroa social life. Through a qualitative investigation of the cultivation, processing and symbolic
significance of manioc (Manihot esculenta) in two Piaroa regions over a period of 18 years, we have found that such agrobiodiversity can only be fully explained by
a combination of multiple factors, including pragmatic and ecological considerations, the subtle and complex diversity of
Piaroa manioc preparations and a variety of sociocultural factors, such as manioc’s role as a mediator of social relationships
and as a marker of cultural and social heritage.
相似文献
Stanford ZentEmail: |
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Natalia V. Ivanova Aron J. Fazekas Paul D. N. Hebert 《Plant Molecular Biology Reporter》2008,26(3):186-198
Many plant species are considered difficult for DNA isolation due to their high concentrations of secondary metabolites such
as polysaccharides and polyphenols. Several protocols have been developed to overcome this problem, but they are typically
time-consuming, not scalable for high throughput and not compatible with automation. Although a variety of commercial kits
are available for plant DNA isolation, their cost is high and these kits usually have limited taxonomic applicability. In
a previous study we developed an inexpensive automation-friendly protocol for DNA extraction from animal tissues. Here we
demonstrate that a similar protocol allows DNA isolation from plants.
相似文献
Natalia V. IvanovaEmail: |
11.
Paul F. Cannon Nigel L. Hywel-Jones Norbert Maczey Lungten Norbu Tshitila Tashi Samdup Phurba Lhendup 《Biodiversity and Conservation》2009,18(9):2263-2281
The insect-pathogenic fungus Ophiocordyceps sinensis (better known as Cordyceps sinensis) is harvested over much of the Himalayan plateau as a highly prized remedy in traditional Oriental medicine. Over the past
10 years its financial value has increased dramatically, with collectors paid as much as US $12,500 kg−1 for top-quality material. This is causing significant distortion to local economies, and there is widespread concern that
the current rate of collection is unsustainable. This paper introduces the fungus and its insect hosts, documents some of
the biological and social constraints to achieving sustainability, describes the socioeconomic climate within which harvest
and sale occurs in Bhutan, and details the measures put in place by the Royal Government of Bhutan to promote wise management
of this valuable natural resource.
相似文献
Paul F. CannonEmail: |
12.
Large-scale scientific computing applications frequently make use of closely-coupled distributed parallel components. The
performance of such applications is therefore dependent on the component parts and their interaction at run-time. This paper
describes a methodology for predictive performance modelling and evaluation of parallel applications composed of multiple
interacting components. In this paper, the fundamental steps and required operations involved in the modelling and evaluation
process are identified—including component decomposition, component model combination, M×N communication modelling, dataflow analysis and overall performance evaluation. A case study is presented to illustrate the
modelling process and the methodology is verified through experimental analysis.
相似文献
Stephen A. JarvisEmail: |
13.
Debates over adaptationism can be clarified and partially resolved by careful consideration of the ‘grain’ at which evolutionary
processes are described. The framework of ‘adaptive landscapes’ can be used to illustrate and facilitate this investigation.
We argue that natural selection may have special status at an intermediate grain of analysis of evolutionary processes. The
cases of sickle-cell disease and genomic imprinting are used as case studies.
相似文献
Peter Godfrey-SmithEmail: |
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The recent contribution by Jarmila Kukalová-Peck on Hennigian phylogenetics and hexapod limb evolution is critically evaluated.
相似文献
Michael S. Engel (Corresponding author)Email: |
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We tested the pathogenicity of 18 Metarhizium anisopliae (Metschn.) Sorokin isolates and 22 Beauveria bassiana (Balsamo) Vuillemin isolates against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae) larvae and adults. The efficacy of the most virulent isolate—M. anisopliae K—was evaluated in containers with a concrete bottom covered with wood shavings, under simulated poultry house conditions.
Application of conidia of this isolate to the shavings or directly to the concrete bottom reduced the yield of larvae in 8–15
time compared with the control. In another test, the mortality of mature larvae placed on previously inoculated shavings or
bottom reached 80–90% within 14 days, compared with 14% in the control. The residual activity of conidia kept at 28°C retained
its initial level during 14 days post-inoculation, but declined after three weeks. Based on our data M. anisopliae has considerable potential for the control of A. diaperinus.
相似文献
Michael SamishEmail: Email: |
19.
The presence of several types of allelochemicals has been reported from Ajuga, a Labiatae genus comprising more than 40 species of wide distribution in extratropical regions of both hemispheres. The
genus is of great medicinal and economic importance and among the biological properties of the secondary metabolites, the
antifeedant activity against pest insects appears to be related to the presence of neo-clerodane type diterpenes. This review focuses on the isolation and structural elucidation of this type of compounds from
Ajuga species and the hemisynthetic compounds of closely related structure obtained. The reported biological activity of crude
extracts and isolated diterpenes will be briefly commented.
相似文献
Josep CollEmail: |
20.
Aggregations of juvenile whale sharks (<Emphasis Type="Italic">Rhincodon typus</Emphasis>) in the Gulf of Tadjoura,Djibouti 总被引:1,自引:0,他引:1
D. Rowat M. G. Meekan U. Engelhardt B. Pardigon M. Vely 《Environmental Biology of Fishes》2007,80(4):465-472
A total of 23 whale sharks were identified over a 5 d period in the Arta Bay region of the Gulf of Tadjora, Djibouti. Most
of the sharks aggregating in this area were small (<4 m TL) males. Individuals were identified using photographs of distinctive
scars and spot and stripe patterns on the sides of the animals. Of these, 65% had scarring that was attributable to boat or
propeller strikes. Most of the whale sharks we encountered were feeding on dense accumulations of plankton in shallow water
just off (10–200 m) the shoreline. This food source may account for the aggregation of sharks in this area. One 3 m male shark
was tagged with an ARGOS (Splash) satellite tag for 9 d. During this time the shark traversed to the shoreline on the opposite
side of the Gulf (a distance of 14 km) and then returned to the Arta Bay area before retracing his path to the other shore.
The shark spent most of the daylight hours at the surface, while at night dives were more frequent, deeper and for longer
durations.
相似文献
D. RowatEmail: |