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A high-resolution pollen analysis has been carried out on the Lupoaia section (SW Romania) in order to check whether the repetitive clay–lignite alternations correspond to cyclic changes in climate. Increases in altitudinal tree pollen content appear to have been caused by drops in temperature, while developments of thermophilous elements correspond to rises in temperature, still under humid conditions. Such repeated changes in vegetation, on the whole consistent with the clay–lignite alternations, have been forced by cycles in eccentricity. On the basis of a comparison between the Lupoaia pollen record and (1) European climatostratigraphy (based on reference pollen diagrams documenting global changes), and (2) global climatic curves (eccentricity, δ18O), the age of the section has been reconsidered. The Lupoaia section (i.e. from lignite IV to lignite XIII) starts just before the C3n.3n Chron and probably ends just before the C3n.1n Chron. The section represents a time span of about 600 kyr, i.e. from about 4.90 Ma to about 4.30 Ma. 相似文献
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For pollination studies of forest species it is sometimes only possible to work on those flowers nearest to the ground. We test whether using low flowers introduces bias, by measuring height effects on bird visitation and fruit set in one mistletoe species pollinated by bellbirds in New Zealand. At this site, previous studies have shown fruit set near the ground to be pollen limited. We measured fruit set on 32 mistletoes at different heights in 11 host trees. Mistletoe fruit set varied significantly among host trees but did not vary with height. Although bellbirds generally forage preferentially in the upper part of the forest, mistletoe flowers appear to be attractive enough to ensure adequate visitation and fruit set at all heights. 相似文献
34.
Francisco José González Minero Isabel Iglesias Victoria Jato Maria Jesús Aira Pilar Candau Julia Morales Carmen Tomas 《Aerobiologia》1998,14(2-3):117-129
A comparative study is presented of the pollen emissions of Urticaceae, Plantaginaceae and Poaceae, collected during 1995
with Hirst samplers (Burkard or Lanzoni) at five sites in western Spain: two Mediterranean sites located in the south (Huelva
and Seville) and three Atlantic sites in the north (Orense, Vigo and Santiago). The annual pollen of Poaceae and Plantaginaceae
collected in the Atlantic cities was found to be twice that in the Mediterranean sites, and the total amount of Urticaceae
was higher at sites with an urban environment and subject to sea influence (Vigo, Huelva and Seville). At all the sites, the
start of the main pollination periods (MPP) took place in the following order: Urticaceae, Plantaginaceae and Poaceae. It
was also observed that the MPP of these three pollen types began earlier in Huelva and Seville, where the mean temperatures
necessary for the beginning of pollen emissions are recorded very early. Regarding the variation in pollen concentrations
throughout the year, Urticaceae presented peaks of maximum concentration in March (Huelva, Seville, Vigo and Orense) and June
(Santiago); Plantaginaceae in March (south) and June (north); and Poaceae in May (south) and June–July (north). At northern
sites, pollen emissions of Urticaceae and Plantaginaceae continued throughout the summer, while in the south they decreased
considerably from May onwards. From the allergenic point of view, the indices of reactivity described for Urticaceae and Poaceae
were exceeded more often at northern sites, in particular at Vigo. The meteorological conditions associated with periods of
highest pollen emission of these three herbaceous types are a rise in mean temperature, light or absent rainfall, and abundant
sunshine. The statistical correlations between pollen emissions and meteorological factors were not well-defined, either for
the stations or for all the taxa, although they were clearer for the Atlantic cities and for Urticaceae. 相似文献
35.
The influence of fruit ingestion by the bat, Sturnira lilium, on germination of the seeds of the tree Solanum riparium was studied in a secondary rain forest in northwestern Argentina. Bat frequencies in disturbed areas were analyzed by mist net captures. Germination rates were determined for seeds collected from trees and bat feces. S. lilium was the most abundant fruit bat in the study area. Fruit digestion and the passage of seeds through the intestine did not significantly affect germination in S. riparium. In this case the fruit bats, therefore, probably provide only seed dispersal. 相似文献
36.
J. Tomkova D. Friedecky P. Vyskocilova T. Adam 《Nucleosides, nucleotides & nucleic acids》2013,32(6-7):656-660
Inosine triphosphate pyrophosphohydrolase (ITPase) catalyzing the pyrophosphohydrolysis of inosine triphosphate, deoxyinosine triphosphate and xanthosine triphosphate is involved in the metabolism and tolerance of thiopurine drugs. ITPase activity plays an important role in the prediction of toxicity to thiopurine therapy. Activities in dry blood spots were compared with fresh erythrocytes. Samples were incubated with inosine triphosphate, then inosine monophosphate was determined by a capillary electrophoresis method. Calculated enzyme activities obtained from dry blood spots were in good accordance with activity in fresh erythrocytes. 相似文献
37.
Roberto A. Saenz Paula Medone Natalia di Clemente Anthony Tongen Jorge Rabinovich 《Physiological Entomology》2017,42(4):336-345
The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus. 相似文献
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Subregional variability in the response of New England vegetation to postglacial climate change 下载免费PDF全文
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