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Adaptations of animals to the xeric environment have been studied in various taxonomic groups and across several deserts. Despite the impressive data that have been accumulated, the focus in most of these studies is mainly on the significance of one variable at a time. Here, we attempt to integrate between responses of several physiological systems, challenged by increasing diet and water salinity and extreme temperatures, acquired in different studies of thermo and osmo‐regulatory adaptations, of small rodents, to the xeric environment. Studies have shown differential thermoregulatory responses to increased dietary salinity, which were attributed to habitat and habits of the relevant species. In the thermoregulatory studies, a potential adaptive significance of low metabolic rate was demonstrated. From an evolutionary point of view, the most important adaptation is in the timing of reproduction, as it enables the transfer of genetic properties to the next generation in an unpredictable ecosystem, where reproduction might not occur every year. Results in this aspect show that increased dietary salinity, through an increase in vasopressin plasma levels, plays an important role as a regulator of the reproductive system. We assume that the amount of food existing in the habitat and the amount of reserves in the animal in the form of white adipose tissue are important for reproduction. Photoperiod affects all studied physiological responses, emphasizing the importance of pre‐acclimation to seasonal characteristics. We summarize the existing data and suggest neuro‐endocrine pathways, which have a central role in these adaptations by affecting thermoregulation, osmoregulation and reproduction to create the optimal response to xeric conditions. These hypotheses can be used as the basis for future studies. 相似文献
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Wenju Liang Yocheved Pinhasi-Adiv Hagit Shtultz Yosef Steinberger 《Arid Land Research and Management》2013,27(2):183-192
The effects of soil conditions on nematode populations were investigated in a field study at the Avdat Research Farm, Israel. Soil samples from the upper soil layer (0-10 cm) were collected monthly during November 1997 and October 1998, under the canopy of three halophyte shrubs: Zygophyllum dumousum, Hammadetum scopariae and Reaumuria negevensis. Ecological indices such as fungivore to bac terivore ratio (F/B), ratio of fungivores and bacterivores to plant parasites (WI), trophic diversity (TD) and Shannon index (H') were used to assess and compare the response of nematode populations to the soil conditions. The mean numbers of total nematodes during January 1998 April 1998 were less under Z. dumosum than under H. scoparia, and those of total nematodes during April 1998 October 1998 were higher under R. negevensis than under the control soil. Bacterivores under the three shrubs were the most abundant trophic group. Significant differences were found between months and between treatments for total nematodes, bacterivores and plant parasites. The content of K + exhibited a positive correlation with total nematodes, bacterivores, plant parasites and omnivores-predators, and that of Ca 2+ presented a negative correlation with bacterivores. F/B, WI, TD, and H' were effetive in distinguishing differences in nematode populations during the study period. 相似文献
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S Bauer H Sorek VD Mitchell AB Ibáñez DE Wemmer 《Journal of agricultural and food chemistry》2012,60(33):8203-8212
Miscanthus giganteus lignin was extracted by an organosolv process under reflux conditions (4 h) with varying concentrations of ethanol (65%, 75%, 85%, 95%) and 0.2 M hydrochloric acid as catalyst. The resulting lignin was extensively characterized by size exclusion chromatography (SEC), Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC/MS), two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR), and chemical analysis (residual sugars, Klason lignin, ash). The predominant linkage units present were β-O-4' (82-84%), resinol (6-7%), and phenylcoumaran (10-11%). The 65% ethanol solvent system gave the lowest lignin yield (14% of starting biomass) compared to 29-32% of the other systems. Increasing ethanol concentration resulted in decreasing carbohydrate content of the lignins (3.6-1.1%), a higher solubility in tetrahydrofuran (THF), a slight reduction of the molecular weight (M(w) 2.72-2.25 KDa), an increasing α-ethoxylation, and an increase in ethoxylated phenylpropenoic compounds (p-coumaric and ferulic acid), but the S/G ratio of the monolignols (0.63, GC/MS) and Klason lignin content (86-88%) were unaffected. An extraction method for these ethyl-esterified phenylpropenoids and smaller molecular weight lignin compounds was developed. The effect of reaction time (2, 4, and 8 h) was investigated for the 95% ethanol solvent system. Besides increased lignin yield (13-43%), a slight increase in M(w) (2.21-2.38 kDa) and S/G ratio (0.53-0.68, GC-MS) was observed. Consecutive extractions suggested that these changes were not from lignin modifications (e.g., condensations) but rather from extraction of lignin of different composition. The results were compared to similar solvent systems with 95% acetone and 95% dioxane. 相似文献
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Dhruv Aditya Srivastava Mariana Yakubov Reut Feldbaum Nimrod Tish Hagit Shoyhet Ekaterina Manasherova Eswari P. J. Pandaranayaka Dalia Rav-David Yigal Elad Arye Harel 《Phytoparasitica》2018,46(4):569-581
The necrotrophic fungus Botrytis cinerea, known as the causal agent of gray mold, is ranked second for its phytopathological global-impact. The disease is controlled by cultural means and fungicides, however, these techniques have variable effect on different fungal isolates due to the plasticity of the pathogen populations. Here we studied and characterized the genetic and virulence associated variability of B. cinerea isolates from different sources. Starting from initial survey of 31 B. cinerea isolates, collected from seven hosts in different locations of Israel, we have focused on 10 isolates that exhibited potential phytopathogenic variability. Two genetic markers (microsatellite) Bc1 and Bc7, were able to differentiate between these isolates. Our analysis demonstrates significant variability in saprophytic growth rate, necrotrophic growth rate on tomato leaves and stems, and in the incidence of infection on leaves of whole plants. Following the observation of significant correlation between saprophytic growth rate, and necrotrophic growth on leaves, we have studied normalized (by saprophytic growth) virulence. Utilization of normalized necrotrophic growth rate enabled to indicate on the presence of virulence mechanisms other than growth rate, for several isolates. Exploration of this direction illustrated variability in resistance to paraquat (associated with resistance to oxidation), which was associated with high and low superoxide dismutase (SOD) gene expression for selected isolates showing high or low paraquat resistance, respectively. Finally, we have used unsupervised learning (clustering analysis) to explore patterns in the multivariable space, which demonstrated two modes of pathogenicity in the tested B. cinerea isolates. 相似文献
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The global spread of wireless networks brings a great opportunity for their use in environmental studies. Weather, atmospheric conditions, and constituents cause propagation impairments on radio links. As such, while providing communication facilities, existing wireless communication systems can be used as a widely distributed, high-resolution atmospheric observation network, operating in real time with minimum supervision and without additional cost. Here we demonstrate how measurements of the received signal level, which are made in a cellular network, provide reliable measurements for surface rainfall. We compare the estimated rainfall intensity with radar and rain gauge measurements. 相似文献
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