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121.
1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO2 . We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula ) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius ) of elevated CO2 treatment ( c. 700 μl litre–1 ) under mean QFD of less than 11 μmol m–2 s–1 , all species produced more biomass (25–76%) under elevated CO2 .
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m–2 s–1 ) but the relative stimulation by elevated CO2 was higher at low QFD except in Pharus .
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO2 . An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO2 continues to rise. 相似文献
2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m
3. Non-structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%).
4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO
122.
人肾上腺内肽能神经的超微结构 总被引:1,自引:0,他引:1
殷树仪 《中国组织化学与细胞化学杂志》1994,(1)
应用抗生蛋白链菌素一生物素一过氧化物酶复合物的免疫电镜技术,在相邻切片中,分别观察人肾上腺内NPY、VIP、SP和CGRP免疫反应神经纤维的超微结构和免疫反应物的定位。NPY和VIP免疫反应物位于小颗粒羹泡和线粒体外膜,部分嗜铬细胞呈NPY免疫反应阳性。SP和CGRP免疫反应物主要定位于大颗粒囊泡内。SP和CGRP免疫反应轴突与嗜铬细胞形成对称性或非对称性的轴体突轴。测量了这4种肽能神经末梢的直径,从而推测其来源,并讨论了该4种神经肽对人肾上腺的作用。 相似文献
123.
Restriction-map variation at the zeste-tko region in natural populations of Drosophila melanogaster 总被引:4,自引:0,他引:4
Restriction-map variation in 64 X chromosome lines extracted from three
different natural populations of Drosophila melanogaster was investigated
with seven six-nucleotide-recognizing enzymes for a 20-kb region including
the zeste and tko genes. Ten restriction-site and four length polymorphisms
(two insertions and two deletions) were detected. Contrary to the predicted
lower level of variation for genes on the X chromosome, the level of
variation attributable to nucleotide substitution (estimated
heterozygosity/nucleotide = 0.004) was similar to that previously reported
for autosomal loci. The amount of insertion/deletion variation in the
studied region was within the range observed in autosomal regions and thus
not explainable by a simple selection model against the effects of
insertional mutations. A general lack of linkage disequilibrium between
polymorphic sites was observed.
相似文献
124.
The impact of gender and/or hormone variations on a wide variety of neural functions makes the choice between studying males or females (or both) of a given species difficult. Although female rats are widely used experimentally, few studies control for the stage of estrus. More detailed information about how to distinguish the various stages of the estrous cycle is needed. For the present study, vaginal smears were obtained once a day and stained using an adaptation of the Papanicolaou (PAP) procedure. Images are provided of unstained “wet” samples and the corresponding PAP stained smears illustrating the cellular profile for each stage of the cycle as well as post-ovariectomy. The different cell populations across the cycle were quantified and ratios determined to show trends between the predominant and other cell types in each stage of the estrous cycle. Both stained and unstained images and cell quantification data provide valuable guidelines for distinguishing the stages of the estrous cycle. 相似文献
125.
126.
127.
Interspecific variation in neighbour–stranger discrimination in ants of the Neoponera apicalis complex
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BORIS YAGOUND MATHILDE CROWET CHLOÉ LEROY CHANTAL POTEAUX NICOLAS CH ÂLINE 《Ecological Entomology》2017,42(2):125-136
1. The ecological success of social insects lies in their ability to prevent the exploitation of colony resources by competitors or parasites. Nestmate recognition is therefore of crucial importance in maintaining the integrity of the colony. Furthermore, inter‐colony competitive relationships are often complex, as many species discriminate between neighbours and strangers, with reduced (the dear enemy phenomenon) or increased levels of aggression towards nearby colonies, depending on the species. In this context, between‐species comparisons could be particularly helpful to investigate the proximate causes underlying this context‐dependent phenomenon, but these are notoriously lacking. 2. Here an attempt was made to circumvent this drawback by studying three closely related sympatric ant species with very similar life histories that belong to the Neoponera apicalis complex. The present study investigated how nestmate recognition and inter‐colony competitive relationships were influenced by spatial, chemical and genetic distances between colonies. 3. It was found that one species, N. apicalis morph 7, showed a clear dear enemy phenomenon with no influence of chemical and genetic distances, suggesting the existence of a learning process. In contrast, N. apicalis morph 4 and Neoponera verenae morph 1 failed to show any strong discrimination between close and distant non‐nestmates. 4. These results are discussed in the light of the observed interspecific variation in nesting preferences, possibly constraining the opportunities of familiarisation between nearby nests, and modulating the competition for resources between colonies. 5. It is argued that this study further reinforces the relative threat level hypothesis as an ultimate explanation for neighbour–stranger discrimination processes. 相似文献
128.
129.
The paper presents a new approach for medical image segmentation. Exudates are a visible sign of diabetic retinopathy that is the
major reason of vision loss in patients with diabetes. If the exudates extend into the macular area, blindness may occur. Automated
detection of exudates will assist ophthalmologists in early diagnosis. This segmentation process includes a new mechanism for
clustering the elements of high-resolution images in order to improve precision and reduce computation time. The system applies
K-means clustering to the image segmentation after getting optimized by Pillar algorithm; pillars are constructed in such a way
that they can withstand the pressure. Improved pillar algorithm can optimize the K-means clustering for image segmentation in
aspects of precision and computation time. This evaluates the proposed approach for image segmentation by comparing with Kmeans
and Fuzzy C-means in a medical image. Using this method, identification of dark spot in the retina becomes easier and the
proposed algorithm is applied on diabetic retinal images of all stages to identify hard and soft exudates, where the existing pillar
K-means is more appropriate for brain MRI images. This proposed system help the doctors to identify the problem in the early
stage and can suggest a better drug for preventing further retinal damage. 相似文献
130.
Maria Hoffmann Eric W Brown Peter CH Feng Christine E Keys Markus Fischer Steven R Monday 《BMC microbiology》2010,10(1):1-14