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771.
In order to study the body size of wild boarSus scrofa Linnaeus, 1758 during the Boreal and Atlantic Chronozones in southern Scandinavia, 12 measurements of teeth and bones from 32 Mesolithic sites from Scania (Sweden) and Zealand and Jutland (Denmark) were analysed. The osteometric analysis revealed that the body size of wild boar from Scania did not change during the period. The results indicate that the changes of ecological conditions during the transition from the Boreal to the Atlantic chronozones did not affect wild boar in the same way as red deer and roe deer, which decreased in body size during the period. The tooth size of wild boar from Zealand is smaller than in wild boar from Jutland and Scania during the Late Atlantic Chronozones, which probably is the result of the isolation of the population when Zealand became an island. Calculations of withers height show that wild boar in southern Scandinavia during the Atlantic Chronozones were of similar body size as recent wild boar from eastern Europe.  相似文献   
772.
We used giving-up densities (GUD) to study patch use decisions of small granivorous passerines throughout the year. We measured GUDs continuously in four sites for a period of 9–10 months per year during 2004 and 2005 in a savannah area in Jos, central Nigeria. The study thus covered a period from the middle of the dry season, through the wet season to the beginning of the next dry season in each year. We placed experimental food patches in both open areas and in cover to investigate possible effects of predation risk and thermal hazard on the foraging behavior of the birds. We found a difference in GUDs between the microhabitats, with a consistently lower GUD in cover throughout the year and for the two years. During both years GUDs followed a pattern coinciding with the seasonal change in local seed availability. An initial decline in GUDs late in the dry season was followed by a steady increase during and after the rains. A similar trend in GUDs observed for both years supports the conclusion that GUDs measure the feeding birds' assessment of environmental quality, possibly in combination with other factors changing predictably during the year. We conclude that food abundance may act with other environmental and ecological factors to affect foraging decisions throughout the year.  相似文献   
773.
774.
Summary The effect of N and S fertilizers on yield, protein content and amino acid composition of the tropical cereal finger millet was studied in field and sand culture experiments. In the field the grain yield measured from 2400 to 4100 kg/ha, and the seed crude protein from 7 to 13% with rates of N up to 150 kg/ha. Seed crude protein was high in methionine and cystine, but contained less sulphur amino acids when the seed was high in protein.Supplies in excess failed to increase the lower methionine and cystine contents of the crude protein.Sulphur deficiency drastically reduced the synthesis of sulphur amino acids, concomitantly raising the aspartic acid/asparagine content of the leaves up to 45 per cent of their total N content. An S:N weight ratio of 1:10 in the seeds and 1:15 in the leaves indicates adequate supply of sulphur. The importance of finger millet for human nutrition is considered in relation to increasing substitution with other crops, use of nitrogen fertilizers, and the actual sulphur status of soils in East Africa.Sponsored by the Norwegian Agency for International Development.Sponsored by the Norwegian Agency for International Development.  相似文献   
775.
776.
Seed germination, growth and flowering of the arctic-alpine annual Koenigia islandica were studied in controlled environment. Intact (unabraded) seeds germinated poorely at temperatures up to 18°C, with an optimum at 24°C (89% in 10 d). Scarified seeds germinated rapidly, and reached 100% germination in 3 d at 21°C, but no >40% germination occurred at 9 and 12°C, The seeds had no light requirement for germination, nor did fluctuating temperatures improve germination
Dry matter production was optimal at 12°C in both short day (SD) and long day (LD) conditions, but was markedly higher in LD than in SD at identical fluences at all temperatures except 21°C where the plants showed symptoms of severe heat stress. The temperature compensation point for net productivity was estimated to 24°C, and negative carbon balance at higher temperatures might be an important physiological mechanism limiting the distribution of K. islandica in Scandinavia.
Flowering was extremely rapid and independent of daylength, even in a high-arctic population from 79°N, In full summer daylight anthesis was reached 24 d after germination and seeds ripened after 36 d at 15°C, Days to anthesis varied little across the temperature range from 6 to 21°C, giving a linear decrease in the heat-sum requirement for the attainment of flowering with decreasing temperature.
It is concluded that conservative seed germination strategy, tininess and rapid development, low temperature optima for growth and reproduction, and daylength indifference of flowering are important adaptations for success of an annual plant in high-arctic and high-alpine environments, Daylength neutrality has facilitated the wide-latitudinal distribution of K. islandica. including the penetration of the species to the southern hemisphere.  相似文献   
777.
Ola Vahl 《Oecologia》1981,51(1):53-56
Summary The possibility for a trade-off between age-specific residual reproductive value (RRV) and reproductive effort (RE) was investigated. Different ways of estimating RE did not affect conclusions which were: a) there is no clear trade-off between RRV and RE until the scallop has reached an age of about 13 years, i.e. after a reproductive life of about eight years; b) the larva of C. islandica is more important as a means of dispersal than as a means of maintaining the parent population.  相似文献   
778.
Indole-3-acetic acid (IAA) was purified by high performance liquid chromatography (HPLC) and identified by gas chromatography - mass spectrometry (GC-MS) in leaf extracts of Begonia × cheimantha Everett cv. Nova. The content of IAA and of gibberellins A4, A9, A19 and A20 (GAs) previously identified in this material, were quantified by GC-MS in leaves of Begonia plants grown under different temperature and daylength conditions, using deuterated compounds as internal standards. GA1, which was also identified, was present in too low quantities for reliable quantitation. Rapid and significant decreases (within 2–4 days) occurred in the content of both IAA and GAs when the plants were transferred from conditions which are non-inductive for adventitious bud formation and flowering (24°C/long day) to inductive conditions (24°C/short day, 15°C/long day or 15°C/short day). GA4 and GA9 were affected by photoperiod only, whereas IAA, GA19 and GA20 were affected by both photoperiod and temperature. The data suggest that biosynthesis of GA9 and GA4 are blocked in short days at a step located before GA9. Conversion of GA19 to GA20 seemed to be blocked by both short days and low temperature, while an additional block located before GA19 seemed to be imposed in 15°C/short day. The results confirm earlier results and support the hypothesis that photoperiod and temperature effects in Begonia are mediated by endogenous hormones.  相似文献   
779.
Cytokinin activity has been obtained in ethanol extracts of Begonia and Bryophyllum plants. Begonia x cheimantha Everett yielded 30 to 300 μg kinetin equivalents per kg of fresh leaves in the tobacco callus bioassay. Short day conditions appeared to increase the extractable cytokinin content in the tissue. Purification by fractionation on Dowex 50 H+ columns followed by organic solvent extraction, silver precipitation, and repeated paper chromatography yielded an apparently homogeneous product which accounted for most of the activity in the Begonia extracts. It was indistinguishable from zeatin in chromatograms developed with six solvent systems. Other cytokinin active fractions were also obtained from both Begonia and Bryophyllum. Crystalline picrate preparations of active products were insufficient for identification by mass spectrometry.  相似文献   
780.
Abstract

Purpose: The Fourth Universal Definition of Myocardial Infarction (MI) has highlighted the different pathophysiological mechanisms that may lead to ischaemic and non-ischaemic myocardial injury and has emphasised that the diagnosis of myocardial infarction requires the presence of acute myocardial ischaemia in the setting of acute myocardial injury. This case based review intends to illustrate basic principles on how to apply this new, revised definition in clinical practice.

Methods and Results: The distinction between different types of MIs (type 1 or type 2) and the delineation of MI from acute non-ischaemic myocardial injury may be challenging in individual patients, which is illustrated by presenting and discussing real-life routine cases.

Conclusions: Type 1?MI is a consequence of coronary plaque rupture or erosion with intracoronary thrombus formation that is usually apparent on coronary angiography. Plausible triggering mechanisms causing myocardial oxygen supply/demand mismatch must be identified for the diagnosis of type 2?MI and its treatment should focus initially on management of the underlying disease attributable to acute myocardial ischaemia.  相似文献   
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