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231.
以腐熟的甘蔗渣( SB)、木薯皮( CP)、花生壳( PS)和火炭灰( BA)及园土( GS)为原料,按照不同体积比配制成9种混配基质,并以等体积比泥炭和园土混配基质为对照,对各基质的理化性质及基质中油茶( Camellia oleifera Abel)幼苗的生长状况进行比较;在对基质理化指标和油茶幼苗的壮苗指数进行线性回归分析和通径分析的基础上,采用主成分分析和综合评价法对各基质的育苗效果进行综合评价。结果表明:9种农林废弃物混配基质的容重、总孔隙度和毛管孔隙度分别为0.23~0.47 g·cm-3、60.90%~67.23%和46.53%~58.27%, pH 6.72~pH 7.14,各基质的速效氮含量、速效磷含量、速效钾含量、pH值、电导率和通气孔隙度均高于或显著高于对照,容重则显著低于对照。在不同基质中油茶幼苗的茎粗、单株叶片数、叶长、叶宽、叶绿素相对含量( SPAD)、单株茎叶干质量、单株根干质量和壮苗指数均存在一定差异,而株高和根冠比却无显著差异;其中S9混配基质也V( SB):V( CP):V( BA)=2:1:1页中幼苗的大部分生长指标较高,表现出明显的生长优势。线性回归和通径分析结果显示:除通气孔隙度外,基质的其他8个理化指标基本涵盖了影响幼苗壮苗指数的关键因素;其中,速效钾含量是对壮苗指数直接影响最大的负相关因子,而速效磷含量、电导率和总孔隙度对壮苗指数则有较大的正向直接作用,并且三者通过速效钾含量对壮苗指数产生较大的负向间接作用;此外,基质容重对壮苗指数也有一定的负向直接作用。综合评价结果显示:S9和S7混配基质也V( SB):V( BA):V( GS)=4:3:3页对油茶育苗效果的综合得分较高,分别为14.363和14.337,建议将S9混配基质作为油茶育苗的首选替代基质,S7混配基质作为备选基质。  相似文献   
232.
Homomorphic self‐incompatibility is a well‐studied example of a physiological process that is thought to increase population diversity and reduce the expression of inbreeding depression. Whereas theoretical models predict the presence of a large number of S‐haplotypes with equal frequencies at equilibrium, unequal allele frequencies have been repeatedly reported and attributed to sampling effects, population structure, demographic perturbation, sheltered deleterious mutations or selection pressure on linked genes. However, it is unclear to what extent unequal segregations are the results of gametophytic or sexual selection. Although these two forces are difficult to disentangle, testing S‐alleles in the offspring of controlled crosses provides an opportunity to separate these two phenomena. In this work, segregation and transmission of S‐alleles have been characterized in progenies of mixed donors and fully compatible pollinations under field conditions in Prunus avium. Seed set patterns and pollen performance have also been characterized. The results reveal paternal‐specific distorted transmission of S‐alleles in most of the crosses. Interestingly, S‐allele segregation within any given paternal or maternal S‐locus was random. Observations on pollen germination, pollen tube growth rate, pollen tube cohort size, seed set dynamics and transmission patterns strongly suggest post‐pollination, prezygotic sexual selection, with male–male competition as the most likely mechanism. According to these results, post‐pollination sexual selection takes precedence over frequency‐dependent selection in explaining unequal S‐haplotype frequencies.  相似文献   
233.
The evolution of plant defence in response to herbivory will depend on the fitness effects of damage, availability of genetic variation and potential ecological and genetic constraints on defence. Here, we examine the potential for evolution of tolerance to deer herbivory in Oenothera biennis while simultaneously considering resistance to natural insect herbivores. We examined (i) the effects of deer damage on fitness, (ii) the presence of genetic variation in tolerance and resistance, (iii) selection on tolerance, (iv) genetic correlations with resistance that could constrain evolution of tolerance and (v) plant traits that might predict defence. In a field experiment, we simulated deer damage occurring early and late in the season, recorded arthropod abundances, flowering phenology and measured growth rate and lifetime reproduction. Our study showed that deer herbivory has a negative effect on fitness, with effects being more pronounced for late‐season damage. Selection acted to increase tolerance to deer damage, yet there was low and nonsignificant genetic variation in this trait. In contrast, there was substantial genetic variation in resistance to insect herbivores. Resistance was genetically uncorrelated with tolerance, whereas positive genetic correlations in resistance to insect herbivores suggest there exists diffuse selection on resistance traits. In addition, growth rate and flowering time did not predict variation in tolerance, but flowering phenology was genetically correlated with resistance. Our results suggest that deer damage has the potential to exert selection because browsing reduces plant fitness, but limited standing genetic variation in tolerance is expected to constrain adaptive evolution in O. biennis.  相似文献   
234.
刘海龙 《生物信息学》2019,26(11):64-70
美国州立公园与国家公园相比,更强调满足州内居民就近户外休闲游憩需求的功能,这使得其在美国整体公共户外休闲空间体系中占据特殊的位置。在中国第一次全面地研究了美国州立公园体系的发展、特征及与国家公园体系的关系,特别是以部分州为例研究了美国州立公园的分类、质量评估、可达性与空间分布评估等关键问题。研究认为,州立公园的意义在于既缓解了美国国家公园面临的巨大旅游游憩压力,也满足了大众户外休闲游憩的需求。这值得中国在目前构建国家公园与自然保护地体系的同时予以借鉴。最后基于中国的实际需求与挑战,探讨了在省域/区域层次加强构建地方公园、保护地和游憩地体系建设的必要性与途径。  相似文献   
235.
为探讨信号分子过氧化氢(H2O2)增强裸燕麦盐碱耐性的作用及其生理机制,以裸燕麦品种‘定莜6号’为材料,在日光温室内用珍珠岩培养幼苗至三叶一心期时叶面喷施0.01 mmol·L-1 H2O2的同时根部浇灌75 mmol·L-1盐碱混合溶液(NaCl:Na2SO4:NaHCO3:Na2CO3=12:8:9:1)或添加H2O2淬灭剂二甲基硫脲(DMTU),研究对幼苗生长及叶片光合色素含量、活性氧代谢和渗透调节物质积累的影响。结果表明:喷施H2O2能够缓解盐碱混合胁迫对裸燕麦幼苗生长的抑制,提高幼苗根长、株高和植株干重及叶片叶绿素a、叶绿素b、总叶绿素、类胡萝卜素含量和超氧化物歧化酶、过氧化物酶、过氧化氢酶、抗坏血酸过氧化物酶活性,降低超氧阴离子、H2O2、丙二醛、抗坏血酸、谷胱甘肽和游离氨基酸含量,促进抗氧化物质类黄酮、总酚和原花青素及渗透调节物质可溶性蛋白质、可溶性糖和脯氨酸积累。添加DMTU部分或完全逆转了H2O2的上述作用。采用隶属函数综合评价显示,喷施H2O2提高了盐碱混合胁迫下裸燕麦幼苗的综合评价值D,添加DMTU完全逆转了H2O2D值的提升作用。表明外源H2O2通过参与活性氧代谢和渗透调节物质积累等生理代谢调控缓解盐碱混合胁迫诱导的氧化伤害和生长抑制,从而提高裸燕麦对盐碱胁迫的适应能力。  相似文献   
236.
Metallic potassium (K) is a desirable anode for potassium secondary batteries due to its low electrode potential in nonaqueous electrolytes and high theoretical capacity. Nevertheless, instability caused by dendritic growth, large volume changes, and parasitic side reactions hamper its practical application. Here, an anode containing metallic K is fabricated by infiltrating an aligned carbon nanotube membrane (ACM) with molten K because of its good wettability to molten K due to the strong capillary forces. The K metal is spatially distributed on the 3D ACM framework, which offers sufficient electrode/electrolyte contact for charge transfer. The robust ACM host provides a large number of K nucleation sites and physically confines the K deposited there, thus mitigating dimensional changes during cycling. The pathways for electrons and ions in the anode are associated to form a mixed conducting network, which is beneficial for the electrochemical redox. Consequently, the anode shows stable plating/stripping profiles with low polarization in symmetric cells using conventional carbonate‐based electrolytes. In addition, dendrite growth is suppressed, and the anode demonstrates excellent suitability when paired with a Prussian blue cathode in a full cell. This design strategy is expected to provide a way to address the problems with using metallic K anodes.  相似文献   
237.
Solid‐state sodium batteries (SSSBs) are promising electrochemical energy storage devices due to their high energy density, high safety, and abundant resource of sodium. However, low conductivity of solid electrolyte as well as high interfacial resistance between electrolyte and electrodes are two main challenges for practical application. To address these issues, pure phase Na3Zr2Si2PO12 (NZSP) materials with Ca2+ substitution for Zr4+ are synthesized by a sol‐gel method. It shows a high ionic conductivity of more than 10?3 S cm?1 at 25 °C. Moreover, a robust SSSB is developed by integrating sodium metal anodes into NZSP‐type monolithic architecture, forming a 3D electronic and ionic conducting network. The interfacial resistance is remarkably reduced and the monolithic symmetric cell displays stable sodium platting/striping cycles with low polarization for over 600 h. Furthermore, by combining sodium metal anode with Na3V2(PO4)3 cathode, an SSSB is demonstrated with high rate capability and excellent cyclability. After 450 cycles, the capacity of the cell is still kept at 94.9 mAh g?1 at 1 C. This unique design of monolithic electrolyte architecture provides a promising strategy toward realizing high‐performance SSSBs.  相似文献   
238.
Solar‐driven water splitting is in urgent need for sustainable energy research, for which accelerating oxygen evolution kinetics along with charge migration is the key issue. Herein, Mn3+ within π‐conjugated carbon nitride (C3N4) in form of Mn–N–C motifs is coordinated. The spin state (eg orbital filling) of Mn centers is regulated by controlling the bond strength of Mn–N. It is demonstrated that Mn serves as intrinsic oxygen evolution reaction (OER) site and the kinetics is dependent on its spin state with an optimized eg occupancy of ≈0.95. Specifically, the governing role of eg occupancy originates from the varied binding strength between Mn and OER intermediates. Benefiting from the rapid spin state‐mediated OER kinetics, as well as extended optical absorption (to 600 nm) and accelerated charge separation by intercalated metal‐to‐ligand state, Mn–C3N4 stoichiometrically splits pure water with H2 production rate up to 695.1 µmol g?1 h?1 under simulated sunlight irradiation (AM1.5), and achieves an apparent quantum efficiency of 4.0% at 420 nm, superior to most solid‐state based photocatalysts to date. This work for the first time correlates photocatalytic redox kinetics with the spin state of active sites, and suggests a nexus between photocatalysis and spin theory.  相似文献   
239.
Two types of all‐small‐molecule ternary solar cells consisting of two small‐molecule donors and one acceptor (fullerene/non‐fullerene) are developed. Interestingly, both these devices have a common component: a carefully designed medium bandgap small molecule, which possesses appropriate energy levels and displays good compatibility with the host donor. In the fullerene system, the charge‐relaying role of the additive donor is confirmed by the improved charge transportation and suppressed charge recombination. While in the non‐fullerene system, the mixed face‐on and edge‐on orientation of the ternary film induced by the additive donor dominates the promotion of charge transportation. Accordingly, both ternary devices deliver higher short‐circuit current density, fill factor, and power conversion efficiencies of over 10% compared to binary ones. This work offers a promising guideline on the construction of high‐performance all‐small‐molecule ternary solar cells by incorporating a miscible small‐molecule donor.  相似文献   
240.
Majority of type 2 diabetes mellitus (T2DM) patients are highly susceptible to several forms of cognitive impairments, particularly dementia. However, the underlying neural mechanism of these cognitive impairments remains unclear. We aimed to investigate the correlation between whole brain resting state functional connections (RSFCs) and the cognitive status in 95 patients with T2DM. We constructed an elastic net model to estimate the Montreal Cognitive Assessment (MoCA) scores, which served as an index of the cognitive status of the patients, and to select the RSFCs for further prediction. Subsequently, we utilized a machine learning technique to evaluate the discriminative ability of the connectivity pattern associated with the selected RSFCs. The estimated and chronological MoCA scores were significantly correlated with R = 0.81 and the mean absolute error (MAE) = 1.20. Additionally, cognitive impairments of patients with T2DM can be identified using the RSFC pattern with classification accuracy of 90.54% and the area under the receiver operating characteristic (ROC) curve (AUC) of 0.9737. This connectivity pattern not only included the connections between regions within the default mode network (DMN), but also the functional connectivity between the task-positive networks and the DMN, as well as those within the task-positive networks. The results suggest that an RSFC pattern could be regarded as a potential biomarker to identify the cognitive status of patients with T2DM.  相似文献   
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