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941.
Anther form and structure across the taxonomic groups inVerticordia were examined. The three anther types which were recognised — rectangular, oblong and saccate, accord well with the three subgenera into which the genus has been divided. The sporogenous part of the anther has a fairly typical angiosperm anatomy. However in many species there is a small or large gland in the upper filament/connective which contains lipidic contents. The anatomy of this structure is based on that of the oil glands which are ubiquitous in Myrtaceae primary tissues. However the gland is usually much larger than these and is schizolysigenous in origin. Evolutionary development of the anthers in the genus is related to pollination systems and the development of secondary pollen presentation from the upper style in some groups. Anther glands may have originally had a protective function for the sporogenous tissue. However in different groups the function has changed or the gland has disappeared. In some species in subgenusChrysoma (which does not have secondary pollen presentation) the gland contents seem to be an additional food source for pollinators. In other groups, with the development of secondary pollen presentation the protective function has become redundant and anther glands have either disappeared or produce contents which have become part of the process of pollen dispersal. 相似文献
942.
Livestock grazing is often perceived as being detrimental to the quality and functioning of dryland ecosystems. For example, a study in a semiarid Kenyan savanna proposed that cattle form bare spaces throughout the landscape, which indicate ecosystem degradation. Other studies, conducted in north‐eastern Spain, where climatic conditions range between semiarid and Mediterranean subhumid, reported that sheep and goat trails have increased the emergence of rill erosion processes. Sometimes, this negative perception is extended to include wild, large ungulate herbivores as well. Here, we challenge this perception by highlighting the generally nonadverse and even ameliorative impacts of moderate animal rate on geoecosystem functioning of hilly drylands. Specifically, trampling routes (also known as treading paths, livestock terracettes, cattle trails, migration tracks, cowtours, etc.) formed across hillslopes by grazing animals—being either domesticated livestock or native large herbivores—transform the original two‐phase vegetation mosaic of shrubby patches and interpatch spaces into a three‐phase mosaic. The animal routes increase the complexity of ecosystem, by strengthening the spatial redistribution of water and soil resources at the patch scale and decreasing hydrological connectivity at the hillslope scale. As a consequence, the animal routes improve functioning of hilly drylands and increase their resilience to long‐term droughts and climatic change. Therefore, instead of viewing the animal routes as degraded spots, they should be perceived at a wider perspective that allows to properly understand their overall role in sustaining dryland geoecosystems. 相似文献
943.
基于连续10年的观测,本文对比研究了3种植被类型的地表径流效应,证明了混交林的水文效益无论从哪方面都较桉树林和裸地明显,并且随着年度的的推移,混交林的水文效益更加突出。发生产流的最小降雨量条件为:混交林30.2mm,桉树林5.1mm,裸地6.0mm。产流发生时饱和上层厚度分别为12.6mm,3.4mm,和6.3mm。理论上,作者阐明了3种植被类型下的产流类型,提出了桉树林下地表更易形成击实层这样一个设想,这就为水土保持林的营造提供了一个极富实际意义的例子,为在海岸台地这样一个特殊生境下综合研究水土保持效益提供了资料。 相似文献
944.
Pollen analysis resulted from 111 core samples from Diaojiao (DJ) Lake Inner Mongolia have shown the highest value of total pollen accumulati6n rate was more than 20000 grains · cm-2 · a-1 and lowest was 80~90 grains ·cm-2 · a- 1. In general, the arboreal pollen was more than 50%, up to 80%, including the following families and genera: Pinus, Betula, ,Picea, Carpinus, Ouercus, Ulrnus etc. The non-arboreal pollen consist of 27 types, which mainly include Artemisia, Ephedra, Chenopodiaceae, Compositae, Gramineae, Leguminosae, Labiatae, Nitraria. Polygonaceae, Ranunculus, Thalictrurn, Umbelliferae, Caryophyllaceae and Cyperaceae etc. Fern spores, aquatic pollen and algae were also observed off and on in the DJ core. A pollen diagram, of five pollen assemblage zones was established through stratigraphically constrained cluster analysis,using the method of incremental sum of squares. It shows two peaks appearing at about 6.3 and 5.1 ka BP in the curve of total pollen accumulation rate. The first peak reflects a humid period and the second an arid period. The study indicated that Holocene climatic and vegetational changes in Inner Mongolia can be recongnized at different time scales (e. g. thousands, hundreds of years, or even much shorter time scale). In addition, the humidity in that area during those time was higher than today, with dominent climate humid-cool or humid-warm during most of the Holocene time on account of the lower vaporization and high altitude (1800 ma. s. 1. ). 相似文献
945.
Leildo M. Carilo Filho Bruno T. de Carvalho Bruna K. A. Azevedo Luis M. GutirrezPesquera Caio V. MiraMendes Mirco Sol Victor G. D. Orrico 《Ecology and evolution》2021,11(23):16462
In the Brazilian Atlantic Rainforest (AF), amphibians (625 species) face habitat degradation leading to stressful thermal conditions that constrain animal activity (e.g., foraging and reproduction). Data on thermal ecology for these species are still scarce. We tested the hypothesis that environmental occupation affects the thermal tolerance of amphibian species more than their phylogenetic relationships. We evaluated patterns of thermal tolerance of 47 amphibian species by assessing critical thermal maxima and warming tolerances, relating these variables with ecological covariates (e.g., adult macro‐ and microhabitat and site of larval development). We used mean and maximum environmental temperature, ecological covariates, and morphological measurements in the phylogenetic generalized least squares model selection to evaluate which traits better predict thermal tolerance. We did not recover phylogenetic signal under a Brownian model; our results point to a strong association between critical thermal maxima and habitat and development site. Forest species were less tolerant to warm temperatures than open area or generalist species. Species with larvae that develop in lentic environment were more tolerant than those in lotic ones. Thus, species inhabiting forest microclimates are more vulnerable to the synergistic effect of habitat loss and climate change. We use radar charts as a quick evaluation tool for thermal risk diagnoses using aspects of natural history as axes. 相似文献
946.
Binding of receptor-recognized forms of tetrameric human α2-macroglobulin (α2M*) to a macrophage signaling receptor induces cAMP synthesis, increases in inositol 1,4,5-triphosphate (IP3) synthesis, and a concomitant rise in cytosolic free calcium ([Ca2+]i). The α2M* signaling receptor is coupled to a pertussis-toxin insensitive G protein. Binding of α2M* also occurs to the low density lipoprotein receptor-related protein/α2M receptor (LRP/α2MR), but this binding does not induce signal transduction. Rat α1-inhibitor-3 (α1I3) is a monomeric member of the α-macroglobulin/complement superfamily. Like α2M, it can react with proteinases or methylamine which induces a conformational change causing activated α1I3 to bind to LRP/α2MR. We now report that α1I3-methylamine binds to the macrophage α2M* signaling receptor inducing a rapid rise in the synthesis of IP3 with a subsequent 1.5- to 3-fold rise in [Ca2+]i. α1I3-methylamine binding to macrophages also caused a statistically significant elevation in cAMP. Native α1I3, like α2M, was unable to induce signal transduction. α1I3 forms a complex with α1-microglobulin, which has a distinct conformation from α1I3 and is recognized by LRP/α2MR. This complex also induces an increase in [Ca2+]i comparable to the effect of α1I3-methylamine on macrophages. It is concluded that activation of α1I3 by methylamine or binding of α1-microglobulin causes similar conformational changes in the inhibitor, exposing the receptor recognition site for the α2M* signaling receptor, as well as for LRP/α2MR. © 1996 Wiley-Liss, Inc. 相似文献
947.
Mayla Daiane Correa Molinari Renata Fuganti-Pagliarini Daniel de Amorim Barbosa Silvana Regina Rockenbach Marin Daniel Rockenbach Marin Elíbio Leopoldo Rech Liliane Marcia Mertz-Henning Alexandre Lima Nepomuceno 《Genetics and molecular biology》2022,45(1)
Soybean is a key crop in many countries, being used from human food to the animal industry due to its nutritional properties. Financially, the grain chain moves large sums of money into the economy of producing countries. However, like other agricultural commodities around the world, it can have its final yield seriously compromised by abiotic environmental stressors, like drought. As flowers imply in pods and in grains inside it to minimize damages caused by water restriction, researchers have focused on understanding flowering-process related genes and their interactions. Here a review dedicated to the soybean flowering process and gene network involved in it is presented, describing gene interactions and how genes act in this complex mechanism, also ruled by environmental triggers such as day-light and circadian cycle. The objective was to gather information and insights on the soybean flowering process, aiming to provide knowledge useful to assist in the development of drought-tolerant soybean lines, minimizing losses due to delays or anticipation of flowering and, consequently, restraining financial and productivity losses. 相似文献
948.
《Biotechnic & histochemistry》2013,88(6):385-396
AbstractWe assessed the time-dependent effects of intraperitoneal (i.p.) and intravenous (i.v.) application of dexamethasone (Dexa) on the mean arterial blood pressure (MAP), heart rate (HR) and total blood volume (TBV). We evaluated also the relation between the effects and immunoreactivities of transforming growth factor-beta (TGF-β), epithelial nitric oxide synthase (eNOS), interleukin-1 beta (IL1-β) and vascular endothelial growth factor (VEGF) in rat brain, lung and kidney tissues. Rats were anesthetized and while still breathing spontaneously, a tracheotomy and femoral vein and artery catheterizations were performed. To determine TBV using the hemodilution method, 2 ml albumin-electrolyte solutions were applied by i.v. injection. Group 1 (control group) received a 1 ml bolus injection of physiologic saline, Group 2 received 15 mg/kg and Group 3 received 75 mg/kg Dexa i.p. The hematocrit was measured at 10, 20, 60 and 120 min. For each animal, the values of MAP, HR and TBV were measured within 2 h. For immunohistochemical evaluation, anti-TGF-β, anti-eNOS, anti-IL1-β and anti-VEGF primary antibodies were tested using the avidin-biotin-peroxidase method. TBV was decreased in Group 1 and the increase in MAP was statistically significant. HR values increased slightly. None of the values changed significantly in Group 2. Although TBV was unchanged in Group 3, the decrease in MAP was statistically significant. HR values increased, but the increase was not statistically significant. Mild IL1-β immunoreactivity and moderate TGF-β, eNOS and VEGF immunoreactivities were observed in the brain, lung and kidney samples in Group 1. Increased eNOS immunoreactivity in the kidney samples were observed in Group 2. eNOS immunoreactivity was as strong in the brain and the kidney samples in Group 3. Decreased VEGF immunoreactivity was observed in the lung and kidney tissues in Group 3. Significantly decreased TGF-β immunoreactivity was observed in all tissue samples in Group 3. The decreased MAP values in Group 3 differed from those in Groups 1 and 2. Despite increased eNOS immunoreactivity, especially in brain and kidney, the decrease in VEGF immunoreactivity in Group 3, especially lung and kidney, were consistent with a drop in blood pressure. 相似文献
949.
950.
J.-F. David S. Devernay G. Loucougaray E. Le Floc'h 《Biodiversity and Conservation》1999,8(6):753-767
Millipedes and woodlice were sampled at 27 sites in a mosaic landscape in order to establish the extent to which the macroarthropod community changed with different plant formations. Multivariate analyses conducted on abundance data for ten species revealed four main types of macroarthropod communities. This classification was highly correlated with vegetation structure and particularly the degree of openness of the sites. Communities dominated by Ommatoiulus rutilans (Julidae) occurred in open grassland; those dominated by Glomeris marginata (Glomeridae) plus Porcellio gallicus (Porcellionidae) were found at the least open sites, with a high oak cover; communities with a high proportion of the endemic glomerid Glomeris annulata occurred in semi-open sites with a substantial cover of shrubs. Species diversity was significantly higher at the semi-open sites, this being interpreted as an edge effect. Population density and biomass were lower at wooded sites. In the context of a regional trend towards woodland expansion, the results are discussed from the viewpoint of conserving the pool of millipede and woodlouse species and of maintaining the abundance of saprophagous macroarthropods in the region's ecosystems. 相似文献