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41.
The present study aimed to investigate the morphological and genetic differentiation of lowland and montane populations of the Pieris napi species complex in Norway and to make inferences about the subspecific status of Pieris napi adalwinda and Pieris napi napi . We measured 22 morphological characters on 228 individuals from eight populations in Central Norway (20–1100 m a.s.l.). In addition, lowland and mountain animals were reared at a high altitude locality. Half the animals from either locality were reared on mountain plant, and the other half on a lowland plant. Finally, a fragment of the mitochondrial cytochrome b gene was sequenced for individuals from Central and South-eastern Norway and Germany. Principal component analysis of morphological characters showed a zone of abrupt change from lowland to mountain morphological character states between populations at 506 m and 730 m a.s.l., respectively. The transplant experiment showed that the morphological differences have a genetic basis and that food plants have no impact on morphology. Limited, but significant, molecular genetic differentiation was found between lowland and mountain animals, but the phylogenetic analysis, however, showed that the lowland form ( P. n. napi ) is paraphyletic and the montane form ( P. n. adalwinda ) is monophyletic. Further study is required before taxonomic recognition can be applied.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 727–745.  相似文献   
42.
In the past, practice in mental health was guided by the belief that individuals with serious mental illnesses do not recover. The course of their illness was either seen pessimistically, as deteriorative, or optimistically, as a maintenance course. Research over the past thirty to forty years has indicted that belief and shown that a vision of recovery can be achieved for many individuals. People with serious mental illnesses have themselves published accounts of their own recovery as well as advocated for the development of recovery promoting services. In North America and other regions, policies have been developed to make recovery the guiding vision of services. Today, particularly in the United States, much effort is going into the transformation of services and systems to achieve recovery outcomes. Despite these trends, the idea of recovery remains controversial and, some say, even illusory. This article clarifies the meaning of the term "recovery", reviews the research and first person accounts providing a rationale for recovery, and sets out implications for developing recovery oriented services.  相似文献   
43.
Individuals ofArabidopsis thaliana, collected in different naturalpopulations, were grown in controlled and elevated CO2in a glasshouse.Following germination, root growth of progeny of different linesof these populations was studied in control and elevated atmosphericCO2. No significant direct effect of atmospheric CO2concentrationcould be demonstrated on root growth. An important parentaleffect was apparent, namely that root length and branching weredecreased in seeds collected from a mother plant which had beengrown in elevated CO2. This was correlated with smaller seeds,containing less nitrogen. These parental effects were geneticallyvariable. We conclude that CO2may affect plant fitness via parentaleffects on seed size and early root growth and that the geneticvariability shown in our study demonstrates thatArabidopsispopulationswill evolve in the face of this new selective pressure.Copyright1998 Annals of Botany Company Root growth, root branching, seed, elevated CO2, natural population,Arabidopsis thaliana, parental effect.  相似文献   
44.
Climate change is expected to affect the high latitudes first and most severely, rendering Antarctica one of the most significant baseline environments for the study of global climate change. The indirect effects of climate warming, including changes to the availability of key environmental resources, such as water and nutrients, are likely to have a greater impact upon continental Antarctic terrestrial ecosystems than the effects of fluctuations in temperature alone. To investigate the likely impacts of a wetter climate on Antarctic terrestrial communities a multiseason, manipulative field experiment was conducted in the floristically important Windmill Islands region of East Antarctica. Four cryptogamic communities (pure bryophyte, moribund bryophyte, crustose and fructicose lichen‐dominated) received increased water and/or nutrient additions over two consecutive summer seasons. The increased water approximated an 18% increase in snow melt days (0.2°C increase in temperature), while the nutrient addition of 3.5 g N m?2 yr?1 was within the range of soil N in the vicinity. A range of physiological and biochemical measurements were conducted in order to quantify the community response. While an overall increase in productivity in response to water and nutrient additions was observed, productivity appeared to respond more strongly to nutrient additions than to water additions. Pure bryophyte communities, and lichen communities dominated by the genus Usnea, showed stronger positive responses to nutrient additions, identifying some communities that may be better able to adapt and prosper under the ameliorating conditions associated with a warmer, wetter future climate. Under such a climate, productivity is overall likely to increase but some cryptogamic communities are likely to thrive more than others. Regeneration of moribund bryophytes appears likely only if a future moisture regime creates consistently moist conditions.  相似文献   
45.
The ultrastructure of the frontal gland complex of six species of Macrostomida is investigated. In all species it comprises an array of discretely emerging gland necks of at least two gland types, including one with rhammite secretion granules and one with rhahdite granules. Moreover, mucous glands and glands containing other secretion granules are found in Microstomum sp. No intermeditate form which would allow bridging of the present lack of ultrastructural, histochemical and positional similarities between the Macrostomida and the Acoela is found in the examined species. Therefore, the probability of homology between the frontal organs of the Acoela and the frontal glands of the Macrostomida remains low. Even though two or three tyes of sensory receptors are found distributed over the anterior end of all examined species, the frontal gland complex does not appear to be sensory. Because of the uniformity in frontal gland ultrastructure. relationships within the Macrostomida based on this character alone cannot be detected.  相似文献   
46.
In the present study we investigated by electron microscopy whether melanin granules derived from choroidal melanocytes and retinal pigment epithelium of cattle could be degraded in the phagolysosomes of cultured murine macrophages. It was found that degradation of ocular melanin is possible by the lysosomes of these macrophages. During degradation of the melanin granules an internal gridwork of fine concentric, highly ordered membranes, 3-4 nm thick, became visible. These membranes may represent remnants of the melanin polymer in the original melanosome or may result from self-assembly of degradation products. Early-stage melanosome-like structures also appeared during digestion of these melanin granules. Melanin granules that seemed to break down into smaller fragments without any visible internal structure were also observed.  相似文献   
47.
AteIF5A3, one of three genes encoding eukaryotic translation initiation factor 5A (eIF5A) in Arabidopsis thaliana, and corresponding genes PdeIF5A3 from Populus deltoides (eastern cottonwood) and SleIF5A4 from Solanum lycopersicum (tomato) were constitutively over‐expressed in A. thaliana. The resultant transgenic plants exhibited enhanced vegetative and reproductive growth. Indeed, the increase in seed yield relative to empty vector controls for the PdeIF5A3 over‐expressing plants ranged from 50% to 300% depending on the line. The PdeIF5A3 over‐expressing plants also exhibited enhanced fitness when exposed to osmotic and nutrient (N, P and K) stress. The spatial localization of AteIF5A3 was visualized by confocal microscopy using transgenic plants expressing PAteIF5A3:GFP‐AteIF5A3. GFP fluorescence reflecting expression of AteIF5A3 was detectable in the phloem, particularly companion cells, of roots, stems and leaves, in the epidermal cells of the root tip, in the columella cells of the root cap and in the chalazal tissue of fertilized ovules, which all play a pivotal role in nutrient or hormone translocation. Thus, AteIF5A3 appears to be involved in supporting growth and to play a regulatory role in the response of plants to sub‐lethal osmotic and nutrient stress.  相似文献   
48.
The genus Scalesia is endemic to the Galápagos Islands. Scalesia cordata is a tree occurring only in the southern part of Isabela as small, remnant populations of larger forests. We studied the reproductive ecology of a population protected in an enclosure in order to reveal the extent to which the reproductive system limits the recruitment of young individuals. Pollinator observations revealed that each capitulum received, on average, 2.5 visits per hour and exposed receptive stigmas received many pollen grains. Even so, the seed set and recruitment of trees was poor. Crossing experiments showed that S. cordata produced about twice as many fertile seeds after outcrossing than after selfing. In addition, self‐pollinated capitula flowered for a longer time than outcrossed capitula (3.8 ± 1.1 days vs. 2.1 ± 0.8 days). These results may suggest that the species is partly self‐incompatible, as other species of the genus. The small population size, with its potential derived consequences, is most certainly a prominent threat to S. cordata. The pressure from introduced plant species found in the enclosure also contributes to the seemingly poor condition of the population. To recover S. cordata, we suggest enlarging the enclosure, removing the introduced plant species and continuing to cultivate plants as a genetic reserve. Introducing new genetic material is likely to increase the seed set of the population. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 162 , 496–503.  相似文献   
49.
Analysis of the stem vasculature of the American climbing palm Desmoncus reveals structural features differing significantly from the Old World rattan genus Calamus . Desmoncus has a more directly continuous vascular system but nevertheless shows a vessel distribution that makes for high hydraulic resistance in the axial xylem. Desmoncus is like Calamus in having a single very wide metaxylem vessel in each central axial bundle and is also without direct vascular contact between protoxylem and metaxylem tracheary elements. However, in Desmoncus the stem vascular bundle system resembles that in tree palms (as has been described in the model palm Rhapis excelsa ) in having a continuing axial bundle that branches from each outgoing leaf trace together with a large number of bridge connections between leaf traces and peripheral axial bundles. Resistance to axial water transport is, however, evident in the narrowness of the continuing metaxylem elements in the peripheral stem vascular region. Desmoncus has scalariform perforation plates with few thickening bars in the metaxylem vessels, unlike the simple perforation plates found in Calamus . Thus, Desmoncus shows only limited convergence in stem vascular architecture toward the extreme modifications found in Calamus . This is not unexpected since it is clear that the climbing habit evolved independently in the two genera.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142 , 243−254.  相似文献   
50.
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