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961.
Milan Chytrý Jiří Danihelka Irena Axmanová Jana Božková Eva Hettenbergerová Ching‐Feng Li Zuzana Rozbrojová Lucia Sekulová Lubomír Tichý Marie Vymazalová David Zelený 《植被学杂志》2010,21(6):1125-1137
Questions: Does plant species richness and composition of eastern Mediterranean dwarf shrubland (phrygana) correlate with soil pH? How important is the effect of pH on species diversity in relation to other environmental factors in this ecosystem? What is the evolutionary background of the diversity–pH relationship? Location: Western Crete, Greece. Methods: Species composition of vascular plants, soil and other environmental variables were sampled in 100‐m2 plots on acidic and basic bedrock in phrygana vegetation. The relationships between species composition and environmental variables (including climate) were tested using canonical correspondence analysis, and relationships between species richness and environment using correlation and regression analyses. Data were analysed separately for different plant functional types based on life form and life span. Results: Although soil pH varied across a narrow range (5.9‐8.1), species composition changed significantly along the pH gradient within all plant functional types. For most functional types, the effect of soil pH on species composition was stronger than that of other environmental variables. Species richness of annuals, geophytes and suffruticose chamaephytes increased with soil pH, while richness of hemicryptophytes and shrubs was not correlated with pH. Conclusions: The results are consistent with the evolutionary species pool hypothesis. High numbers of calcicole annuals, geophytes and suffruticose chamaephytes may be a result of the evolution of these groups on base‐rich dry soils in the Mediterranean climate. In contrast, hemicryptophytes, a life form typical of the temperate zone, evolved on both acidic and basic soils and therefore their species numbers do not respond to soil pH across the narrow range studied. The lack of a relationship between shrub species richness and pH is difficult to explain: it may reflect the more diverse or older origin of Mediterranean woody species and their conservative niches. 相似文献
962.
Stefan Dröse Peter J. Hanley Ulrich Brandt 《Biochimica et Biophysica Acta (BBA)/General Subjects》2009
Background
Reactive oxygen species (ROS) are among the main determinants of cellular damage during ischemia and reperfusion. There is also ample evidence that mitochondrial ROS production is involved in signaling during ischemic and pharmacological preconditioning. In a previous study we analyzed the mitochondrial effects of the efficient preconditioning drug diazoxide and found that it increased the mitochondrial oxidation of the ROS-sensitive fluorescent dye 2′,7′-dichlorodihydrofluorescein (H2DCF) but had no direct impact on the H2O2 production of submitochondrial particles (SMP) or intact rat heart mitochondria (RHM).Methods
H2O2 generation of bovine SMP and tightly coupled RHM was monitored under different conditions using the amplex red/horseradish peroxidase assay in response to diazoxide and a number of inhibitors.Results
We show that diazoxide reduces ROS production by mitochondrial complex I under conditions of reverse electron transfer in tightly coupled RHM, but stimulates mitochondrial ROS production at the Qo site of complex III under conditions of oxidant-induced reduction; this stimulation is greatly enhanced by uncoupling. These opposing effects can both be explained by inhibition of complex II by diazoxide. 5-Hydroxydecanoate had no effect, and the results were essentially identical in the presence of Na+ or K+ excluding a role for putative mitochondrial KATP-channels.General significance
A straightforward rationale is presented to mechanistically explain the ambivalent effects of diazoxide reported in the literature. Depending on the metabolic state and the membrane potential of mitochondria, diazoxide-mediated inhibition of complex II promotes transient generation of signaling ROS at complex III (during preconditioning) or attenuates the production of deleterious ROS at complex I (during ischemia and reperfusion). 相似文献963.
Nitrate and nitrite reduction centers in non-nodulated and symbiotic yellow lupine were analyzed. In young seedlings, nitrate
was exclusively accumulated in roots, which also was shown as the main nitrate reduction center. In contrast, leaves were
shown to play a key role in nitrite reduction. A similar distribution of nitrate reductase (NR) and nitrite reductase was
found in nodulated plants. However, in field conditions characterized by low nitrate content, a disproportionately high level
of NR activity in nodules was also observed during all stages of symbiotic growth. This feature was confirmed in nitrate-fed
hydroponic cultures. Nodule NR activity was one order of magnitude higher than in roots, in spite of the small stored nitrate
pool found inside nodules. This suggests that nodule NR activity had been induced not by nitrate itself but indirectly. Since
bacteroids were shown to be responsible for the vast majority of nodule NR activity, the plausible explanation of this effect
seems to be a dissimilatory nature of rhizobial NR. Considering that environmental nitrate could cause hypoxia inside nodules,
this is the proposed way of the observed nodule NR induction. 相似文献
964.
稻田蜘蛛群落的重建及与其种库的相关性 总被引:18,自引:2,他引:18
稻田生态系统是一个不稳定的生态系统,包括稻田和非稻田生境2个部分。随着水稻的移栽与收割,稻田蜘蛛群落周期性地呈现出群落重新形成、群落发展和群落瓦解3个阶段。这一群落的发展不同于自然群落的演替。因此,将稻田生境内蜘蛛群落的重新形成过程定义为群落的重建,而非稻田生境内的蜘蛛群落称之为稻田生境内蜘蛛群落的种库。群落重建是一个季节性的、可重复的动态变化过程,以群落的周期性彻底瓦解和周期性重新形成为最主要特征。种库为群落的重建提供移居者并接受群落瓦解时所迁出的蜘蛛.二者之间呈现出互补的相互关系。保护群落的种库将有助于自然天敌群落的重建。自然天敌群落的重建是自然天敌保护和持续利用的生态学基础的一个重要组成部分,对天敌的保护利用和天敌效能的提高有十分重要的意义。 相似文献
965.
The stability and deletion-size-distribution profiles of leading strand (CAG)75 and (CTG)137 trinucleotide repeat arrays inserted in the Escherichia coli chromosome were investigated upon overexpression of the single-stranded DNA-binding protein (SSB) and in mutant strains deficient for the SbcCD (Rad51/Mre11) nuclease. SSB overexpression increases the stability of the (CAG)75 repeat array and leads to a loss of the bias towards large deletions for the same array. Furthermore, the absence of SbcCD leads to a reduction in the number of large deletions in strains containing the (CTG)137 repeat array. 相似文献
966.
Ohad Iosefson 《FEBS letters》2010,584(6):1080-1084
Previous studies have shown that the mammalian mitochondrial 70 kDa heat-shock protein (mortalin) can also be detected in the cytosol. Cytosolic mortalin binds p53 and by doing so, prevents translocation of the tumor suppressor into the nucleus. In this study, we developed a novel binding assay, using purified proteins, for tracking the interaction between p53 and mortalin. Our results reveal that: (i) P53 binds to the peptide-binding site of mortalin which enhances the ability of the former to bind DNA. (ii) An additional previously unknown binding site for mortalin exists within the C-terminal domain of p53.
Structured summary
MINT-7557591: p53 (uniprotkb:P04637) binds (MI:0407) to DnaK (uniprotkb:P0A6Y8) by affinity chromatography technology (MI:0004)MINT-7557644: mortalin (uniprotkb:P38646) binds (MI:0407) to p53 (uniprotkb:P04637) by pull down (MI:0096)MINT-7557580, MINT-7557611: p53 (uniprotkb:P04637) binds (MI:0407) to mortalin (uniprotkb:P38646) by affinity chromatography technology (MI:0004) 相似文献967.
Pierre-Marie Dehé 《FEBS letters》2010,584(17):3725-7513
Recent years have placed fission yeast at the forefront of telomere research, as this organism combines a high level of conservation with human telomeres and precise genetic manipulability. Here we highlight some of the latest knowledge of fission yeast telomere maintenance and dysfunction, and illustrate how principles arising from fission yeast research are raising novel questions about telomere plasticity and function in all eukaryotes. 相似文献
968.
Differential responses of carbon‐degrading enzyme activities to warming: Implications for soil respiration
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Ji Chen Yiqi Luo Pablo García‐Palacios Junji Cao Marina Dacal Xuhui Zhou Jianwei Li Jianyang Xia Shuli Niu Huiyi Yang Shelby Shelton Wei Guo Kees Jan van Groenigen 《Global Change Biology》2018,24(10):4816-4826
Extracellular enzymes catalyze rate‐limiting steps in soil organic matter decomposition, and their activities (EEAs) play a key role in determining soil respiration (SR). Both EEAs and SR are highly sensitive to temperature, but their responses to climate warming remain poorly understood. Here, we present a meta‐analysis on the response of soil cellulase and ligninase activities and SR to warming, synthesizing data from 56 studies. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in SR, while no such relationship was found for cellulase. The warming response of ligninase activity was more closely related to the responses of SR than a wide range of environmental and experimental methodological factors. Furthermore, warming effects on ligninase activity increased with experiment duration. These results suggest that soil microorganisms sustain long‐term increases in SR with warming by gradually increasing the degradation of the recalcitrant carbon pool. 相似文献
969.
970.
1980-2011年川东平行岭谷区农田土壤有机碳动态 总被引:4,自引:0,他引:4
选取重庆市垫江县为川东平行岭谷的典型区,使用1980第二次土壤普查和2011年实测土壤数据,基于土壤类型,运用通用SOC密度/储量计算法和逐步回归分析,对研究区1980—2011年0—20 cm农田SOC动态和动因进行分析,结果表明:(1)1980—2011年农田0—20 cm土层SOC密度/储量总体表现为略有增加态势,单位面积碳增量2307.63 kg C/hm2,碳增汇235945.83 t,增幅为10.74%,年均增长速率为72.11 kg C hm-2a-1;(2)丢碳、固碳和相对平衡面积比37.61∶49.03∶13.36,总体呈西部、西北部高于南部、东南部,更高于东北部和西南部的格局;(3)宏观上1980—2011年农田0—20 cm土层SOC密度/储量变化与土壤类型的分布及利用有很大关系,尤其是黄壤和紫色土在相异的质地本底和不同的扰动下,展现出相反的碳汇/源状态;(4)微观上SOC密度年均变化速率影响最大的因素是SOC密度初始值全N密度C/N比,且全N密度和C/N比拥有正向影响,SOC密度初始值则相反;⑸结果为川东平行岭谷区借助施加适当投入和合适的耕作与管理实践,有效管理农田表层SOC库提供科学依据。 相似文献