果肉和埋土深度对新疆野杏种子萌发与幼苗生长的影响

为探明新疆野杏（Armeniaca vulgaris）种子萌发与幼苗生长对果肉和埋土深度的响应,以期为新疆野杏的天然更新与实生苗培育提供理论参考。通过2种果皮结构（有果肉和无果肉）的种子在不同埋土深度（地表至18.0 cm的14个梯度）对新疆野杏种子萌发和幼苗生长进行研究,旨在揭示果皮结构和埋土深度对新疆野杏种子萌发与成苗能力的影响。结果表明：果肉和埋土深度显著影响野杏种子的萌发、幼苗生长与质量（P<0.05）。埋土深度<3.0 cm不利于成苗,埋土深度>6.0 cm时,萌发能力与幼苗生长量随埋土深度的增加而降低,3.0～6.0cm为适宜埋土深度。无果肉种子萌发优于有果肉种子,萌发率、萌发指数、成苗率、活力指数分别增长了37.18%、3.88%、37.18%、26.59%,幼苗高、基径、叶片数量、根冠比、幼苗质量指数分别增长了36.99%、7.48%、68.69%、20.61%、14.29%,其萌发能力与幼苗生长量显著高于有果肉种子（P<0.05）。有无果肉种子的萌发和幼苗生长指标与埋土深度呈显著负相关（P<0.05）。研究结果表明,无果肉处理对新疆野杏种...     

Structural Base for Enzymatic Cyclodextrin Hydrolysis

Cyclodextrins resist hydrolysis by burying all bridge oxygens at their interior. Still, the rings can be opened by a small group of specialized enzymes, the cyclomaltodextrinases. Among them, the enzyme from Flavobacterium sp. no. 92 was mutated, crystallized and soaked with cyclodextrins, giving rise to four complex structures. One of them showed an α-cyclodextrin at the outer rim of the active center pocket. In the other complexes, α-, β-and γ-cyclodextrins were bound in a competent mode in the active center. The structures suggest that Arg464 functions as a chaperone guiding the substrates from the solvent into the active center. Over the last part of this pathway, the cyclodextrins bump on Phe274, which rotates the glucosyl group at subsite (+1) by about 120° and fixes it in the new conformation. This induced fit was observed with all three major cyclodextrins. It makes the bridging oxygen between subsites (+1) and (−1) available for protonation by Glu340, which starts the hydrolysis. The mechanism resembles a spring-lock. The structural data were supplemented by activity measurements, quantifying the initial ring opening reaction for the major cyclodextrins and the transglucosylation activity for maltotetraose. Further activity data were collected for mutants splitting the tetrameric enzyme into dimers and for active center mutants.     

Regio-Specific N-Glycome and N-Glycoproteome Map of the Elderly Human Brain With and Without Alzheimer’s Disease

The proteins in the cell membrane of the brain are modified by glycans in highly interactive regions. The glycans and glycoproteins are involved in cell–cell interactions that are of fundamental importance to the brain. In this study, the comprehensive N-glycome and N-glycoproteome of the brain were determined in 11 functional brain regions, some of them known to be affected with the progression of Alzheimer’s disease. N-glycans throughout the regions were generally highly branched and highly sialofucosylated. Regional variations were also found with regard to the glycan types including high mannose and complex-type structures. Glycoproteomic analysis identified the proteins that differed in glycosylation in the various regions. To obtain the broader representation of glycan compositions, four subjects with two in their 70s and two in their 90s representing two Alzheimer's disease subjects, one hippocampal sclerosis subject, and one subject with no cognitive impairment were analyzed. The four subjects were all glycomically mapped across 11 brain regions. Marked differences in the glycomic and glycoproteomic profiles were observed between the samples.     

The evolutionary consequence of the individualistic response to climate change

The Quaternary fossil record has abundant evidence for ecologically nonanalogue communities made up of combinations of modern taxa not seen in sympatry today. A brief review of the literature detailing these nonanalogue communities is given with a discussion of their various proposed causes. The individualistic, Gleasonian, response of species to climate and environmental change is favoured by many. The degree to which communities are nonanalogue appears to increase with greater time depth, and this progressive process is a necessary outcome of the individualistic response of species to climate change through time. In addition, it is noted that populations within species, as well as the species as a whole, respond individualistically. This paper proposes that many elements of nonanalogue communities are extinct populations, which may explain their environmentally anomalous combinations. These extinct populations are, by definition, lineages without descendents. It is further proposed that the differential extinction of populations, as a result of continuous ecological reassembly, could amount to a significant evolutionary phenomenon.     

A spatially explicit representation of conservation agriculture for application in global change studies

Conservation agriculture (CA) is widely promoted as a sustainable agricultural management strategy with the potential to alleviate some of the adverse effects of modern, industrial agriculture such as large‐scale soil erosion, nutrient leaching and overexploitation of water resources. Moreover, agricultural land managed under CA is proposed to contribute to climate change mitigation and adaptation through reduced emission of greenhouse gases, increased solar radiation reflection, and the sustainable use of soil and water resources. Due to the lack of official reporting schemes, the amount of agricultural land managed under CA systems is uncertain and spatially explicit information about the distribution of CA required for various modeling studies is missing. Here, we present an approach to downscale present‐day national‐level estimates of CA to a 5 arcminute regular grid, based on multicriteria analysis. We provide a best estimate of CA distribution and an uncertainty range in the form of a low and high estimate of CA distribution, reflecting the inconsistency in CA definitions. We also design two scenarios of the potential future development of CA combining present‐day data and an assessment of the potential for implementation using biophysical and socioeconomic factors. By our estimates, 122–215 Mha or 9%–15% of global arable land is currently managed under CA systems. The lower end of the range represents CA as an integrated system of permanent no‐tillage, crop residue management and crop rotations, while the high estimate includes a wider range of areas primarily devoted to temporary no‐tillage or reduced tillage operations. Our scenario analysis suggests a future potential of CA in the range of 533–1130 Mha (38%–81% of global arable land). Our estimates can be used in various ecosystem modeling applications and are expected to help identifying more realistic climate mitigation and adaptation potentials of agricultural practices.     

Relative preferences of carcinogenic aromatic nitrenium ions for adduct formation with different DNA base sites: Theoretical elucidations

The ultimate carcinogenic form of aromatic amines, the nitrenium ions, interact with DNA bases in order to exert their carcinogenic effects.Experimental findings have indicated the general trend to produceN (deoxy guanin-8-yl) as the major adduct and the minor adduct involving the extra cyclicN ² of guanine and the carbon in a -position of the amine nitrogen.The adduct formation with DNA bases by aromatic amines has been studied with several contributing factors in view. The theoretically computed values of these factors serve as clues to rationalize experimentally observed findings concerning this adduct formation.     

Long‐term nitrous oxide fluxes in annual and perennial agricultural and unmanaged ecosystems in the upper Midwest USA

Differences in soil nitrous oxide (N₂O) fluxes among ecosystems are often difficult to evaluate and predict due to high spatial and temporal variabilities and few direct experimental comparisons. For 20 years, we measured N₂O fluxes in 11 ecosystems in southwest Michigan USA: four annual grain crops (corn–soybean–wheat rotations) managed with conventional, no‐till, reduced input, or biologically based/organic inputs; three perennial crops (alfalfa, poplar, and conifers); and four unmanaged ecosystems of different successional age including mature forest. Average N₂O emissions were higher from annual grain and N‐fixing cropping systems than from nonleguminous perennial cropping systems and were low across unmanaged ecosystems. Among annual cropping systems full‐rotation fluxes were indistinguishable from one another but rotation phase mattered. For example, those systems with cover crops and reduced fertilizer N emitted more N₂O during the corn and soybean phases, but during the wheat phase fluxes were ~40% lower. Likewise, no‐till did not differ from conventional tillage over the entire rotation but reduced emissions ~20% in the wheat phase and increased emissions 30–80% in the corn and soybean phases. Greenhouse gas intensity for the annual crops (flux per unit yield) was lowest for soybeans produced under conventional management, while for the 11 other crop × management combinations intensities were similar to one another. Among the fertilized systems, emissions ranged from 0.30 to 1.33 kg N₂O‐N ha^?1 yr^?1 and were best predicted by IPCC Tier 1 and ΔEF emission factor approaches. Annual cumulative fluxes from perennial systems were best explained by soil pools (r² = 0.72) but not so for annual crops, where management differences overrode simple correlations. Daily soil N₂O emissions were poorly predicted by any measured variables. Overall, long‐term measurements reveal lower fluxes in nonlegume perennial vegetation and, for conservatively fertilized annual crops, the overriding influence of rotation phase on annual fluxes.     

黄土旱塬区免耕玉米田土壤呼吸对降雨的响应

在多年定位试验的基础上,采用LI-8150-16多通道土壤碳通量测量系统对传统耕作和免耕处理下玉米田的土壤呼吸进行了连续观测,以探讨不同耕作措施处理下土壤呼吸对降雨的响应。结果表明:降雨发生瞬间,土壤呼吸受应激反应影响迅速降低,传统耕作和免耕处理下分别较降雨前降低62.9%—92.9%和35.8%—56.9%;降雨后,传统耕作和免耕处理土壤呼吸的降幅范围分别为31.5%—89.2%和15.7%—59.9%;土壤体积含水量接近于18%时,传统耕作下土壤呼吸比免耕下高51.8%,当土壤体积含水量高于30%时,传统耕作下土壤呼吸比免耕处理下低43.0%,表明传统耕作土壤呼吸更易受土壤水分的影响,波动幅度大;传统耕作处理下土壤呼吸随土壤温度的升高而增大,免耕处理下土壤呼吸随土壤温度的升高变化不明显;土壤体积含水量较小(20%)时,不同耕作处理下土壤呼吸均随土壤含水量增加而增加,含水量较高(30%)时则均随土壤含水量的升高而减小,两种情况下均为免耕处理的变化速率更大;双因子线性模型可较好地描述玉米田土壤呼吸对温度和水分变化的响应。     

Marine reserves indirectly affect fine‐scale habitat associations,but not overall densities,of small benthic fishes

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.