Carbon isotope variability and sedimentology of the Upper Permian carbonate rocks and changes across the Permian-Triassic boundary in the Masore section (Western Slovenia)

Carbonate and total organic carbon stable isotope analyses of the Upper Permian and Lower Triassic succession in the Masore section in western Slovenia indicate a high storage of organic matter during the Upper Permian, as well as the well known worldwide light carbon isotope event across the P/Tr boundary. The perturbations in the global carbon cycle observed in the investigated section span an approximately 50 cm thick interval (from –11 cm below to +41 cm above the lithostratigraphically determined P/Tr boundary), and coincide more or less with changes in lithology, as well as with an abrupt disappearance of Upper Permian marine fauna. In this section changes in the sedimentary environment are most probably related to Upper Permian—Lower Triassic sea level changes. The carbonate and organic carbon negative peak anomaly could be explained by accelerated changes in the end Permian carbon cycle, due to some co-occurring events, such as pronounced erosion and oxidation of organic carbon, a possible release of methane from stored hydrates, and volcanic activity, as well as by a sudden reduction in primary productivity triggered by not yet completely satisfactorily explained mechanisms.     

Integrated biostratigraphy based on planktonic foraminifera and dinoflagellates across the Cretaceous/Paleogene (K/Pg) transition at the Izeh section (SW Iran)

The present work is based on semi-quantitative study carried on detailed sampling (samples are spaced by 5, 10 and 15 cm close to the boundary) of an essentially continuous and expanded section crossing the Cretaceous–Paleogene (K/Pg) boundary in Iran. By this work, we attempt to detail biostratigraphy based on planktonic foraminifera biozones and correlate biozones and subzones with dinocyst events. The entire Cretaceous–Paleogene interval contains rich, diversified and well-preserved planktonic foraminifera and dinoflagellate cyst assemblages. Four planktonic foraminiferal biozones have been recognized across the Cretaceous–Paleogene transition (K/Pg): Abathomphalus mayaroensis Biozone including Plummerita hantkeninoides Subzone from the Late Maastrichtian and Guembelitria cretacea (including Hedbergella holmdelensis and Parvularugoglobigerina longiapertura subzones), Parvularugoglobigerina eugubina Biozone and Parasubbotina pseudobulloides Biozone belonging to the Early Danian. These biozones have been correlated with four dinocyst biozones: the Manumiella seelandica Biozone belonging to the Late Maastrichtian and the Alisocysta reticulata, Senoniasphaera inornata and Damassadinium californicum biozones from the Early Danian. At this section, like at the El Kef section (GSSP for the K/Pg) and the auxiliary sections, an Ir anomaly is detected indicating the K/Pg boundary. This geochemical anomaly coincides also with mass extinctions of planktonic foraminifera species. The extinct species are in particular the large, complex tropical and subtropical taxa dwelling in subsurface and lower photic water. The mass extinctions at the Izeh section occurred over a succinct period of time similar to the K/Pg type section at El Kef (Tunisia). These sudden mass extinctions indicate a catastrophic pattern event occurring at the Maastrichtian/Danian boundary. In contrast the organic-walled dinocysts were less affected by the mass extinction and most species crossed the K/Pg boundary without showing mass and sudden extinctions. Nevertheless, they showed changes in their assemblages’ structure beyond the K/Pg boundary. Especially, Manumiella seelandica and M. druggii, typical species of Antarctic Maastrichtian dinocysts assemblages, occur in coeval deposits at the Izeh section; they persist through the Lower Danian and, like in Tunisia (e.g., El Kef section, Ellès section) show an obvious increase in relative abundance.     

‘寒富’苹果二倍体及其同源四倍体叶片超微结构和叶绿素荧光参数特征

采用扫描电镜和石蜡切片法,以‘寒富’苹果二倍体及经秋水仙素加倍获得的同源四倍体植株为材料,比较两种倍性植株叶片超微结构、叶绿素含量及叶绿素荧光参数的日变化规律。结果显示:(1)与二倍体植株相比较,其同源四倍体叶片厚度、栅海比、气孔长、气孔宽、分别增加了15.1%、16.1%、70.5%、27.2%,而气孔密度显著减少了58.7%;其同源四倍体叶保卫细胞中叶绿体数和叶绿素含量分别比二倍体植株高出125.3%、37.7%。(2)‘寒富’苹果同源四倍体与其二倍体的叶绿素荧光参数PSⅡ的原初光能转化效率(Fv/Fm)、PSⅡ的潜在光化学效率(Fv/F0)和以吸收光能为基础的光合性能指数(PI)值的日变化趋势相似,但PI平均值比二倍体显著高出38.6%。研究表明,同源四倍体较二倍体叶片在形态上更大、更厚,气孔更大、密度更小,栅海比更大,表现出抗病的叶片结构;同时同源四倍体较二倍体含有更高的叶绿素含量,表现更优良的光合特性。     

The influence of pre- and post-zygotic barriers on interspecific Corymbia hybridization

Background and Aims

Corymbia species from different sections hybridize readily, with some of increasing economic importance to plantation forestry. This study explores the locations of reproductive barriers between interspecific Corymbia hybrids and investigates the reproductive success of a wide taxonomic range of C. torelliana hybrid crosses.

Methods

Pollen, pistil and embryo development were investigated for four C. torelliana crosses (×C. torelliana, ×C. citriodora subsp. citriodora, ×C. tessellaris and ×C. intermedia) using fluorescent and standard microscopy to identify the locations of interspecific reproductive isolating barriers. Corymbia torelliana was also crossed with 16 taxa, representing six of the seven Corymbia sections, both Corymbia subgenera and one species each from the related genera, Angophora and Eucalyptus. All crosses were assessed for capsule and seed yields.

Key Results

Interspecific C. torelliana hybridization was controlled by pre-zygotic reproductive isolating barriers inhibiting pollen adhesion to the stigma, pollen germination, pollen tube growth in the style and pollen tube penetration of the micropyle. Corymbia torelliana (subgenus Blakella, sect. Torellianae) was successfully hybridized with Corymbia species from subgenus Blakella, particularly C. citriodora subsp. citriodora, C. citriodora subsp. variegata, C. henryi (sect. Maculatae) and C. tessellaris (sect. Abbreviatae), and subgenus Corymbia, particularly C. clarksoniana and C. erythrophloia (sect. Septentrionales). Attempted intergeneric hybrids between C. torelliana and either Angophora floribunda or Eucalyptus pellita were unsuccessful.

Conclusions

Corymbia hybrids were formed between species from different sections and subgenera, but not with species from the related genera Angophora or Eucalyptus. Reproductive isolation between the interspecific Corymbia hybrid crosses was controlled by early- and late-acting pre-zygotic isolating barriers, with reproductive success generally decreasing with increasing taxonomic distance between parent species. These findings support the monophyly of Corymbia and the close relationships of infrageneric clades. The hybridizing propensity of Corymbia species provides opportunities for breeding but suggests risks of environmental gene flow.     

透射电子显微镜(TEM)技术在大孢子化石超微结构研究中的应用

透射电子显微镜(TEM)具有优异的纳米尺度显微成像性能,因此被广泛应用于材料科学、物理学和生物学等学科的超微结构研究领域。文中根据应用TEM技术研究大孢子化石壁超微结构的实践体会,系统归纳和总结了大孢子化石TEM样品制备的前处理过程,主要步骤包括:材料选取、梯度脱水、包埋剂配比、梯度渗透、包埋、聚合、超薄切片和染色。运用上述TEM实验技术,文中以云南省曲靖市沾益区龙华山剖面中泥盆统吉维特阶上双河组分散拟网龙华山大孢(Longhuashanispora reticuloides Lu and Ouyang, 1978)的壁层超微结构为研究案例,揭示了这类孢子壁主要由三层薄壁组成,包括内部基底层、中部疏松层和外部致密层,其射线唇基底层下部具有近平行排列的多细纹带结构。此类大孢子的多细纹带结构与从加拿大新不伦瑞克省下泥盆统埃姆斯阶Campbellton组同孢植物化石Leclercqia complexa Banks et al., 1972中发现的原位小孢子射线唇基底层下部的多细纹带结构特征非常相似。此外,两者都具有相似的完全弓形脊和远极表面刺瘤状二型纹饰。因此综合外壁超微结构和纹饰形态特征...     

基于稳定同位素技术的塔里木河下游不同林龄胡杨的水分利用来源

水分是制约很多陆地生态系统植物生长和繁殖的重要因素, 在干旱地区尤为明显。利用稳定同位素技术探究塔里木河下游不同林龄胡杨(Populus euphratica)的水分来源情况, 了解生态输水背景下荒漠河岸林的水分利用循环与利用策略, 可为生态输水提供科学依据, 同时也可对同类地区的生态恢复提供借鉴。本研究通过测定塔里木河下游胡杨茎干水和各潜在水源(土壤水、地下水)的稳定氢氧同位素值(δD、δ¹⁸O), 应用多源线性混合模型(IsoSource)分析了各潜在水源对不同林龄胡杨的贡献比例, 并结合3种林龄胡杨不同土壤深度含水量的变化, 分析了胡杨的主要吸水层位。结果表明: (1)不同林龄胡杨样地的不同深度区间上的土壤水δ¹⁸O值存在显著差异(P < 0.05): 胡杨幼龄木、成熟木、过熟木木质部δ¹⁸O分别为-7.83 ± 0.07‰、-8.53 ± 0.11‰、-9.36 ± 0.21‰; 而δD值不存在显著差异(P > 0.05)。可据此来推断胡杨的主要吸水层位。(2)总体上, 三种林龄胡杨土壤水δ¹⁸O值随土壤深度增加而减小, 并趋于接近地下水的δ¹⁸O值。其中, 0-60 cm土壤水受蒸发影响比较大, 其同位素组成经历了强烈的蒸发分馏过程, 土壤含水量极少, 土壤水δ¹⁸O值偏正。(3)不同林龄胡杨所利用的水分来源不同: 胡杨幼龄木对于地表80 cm以下的土壤水以及地下水均有一定程度的利用, 对80-140 cm、140-220 cm和220-340 cm的土壤水平均利用比率依次为16.2%、21.4%和24.6%, 对地下水平均利用比率为24.5%; 成熟木主要利用220-340 cm的土壤水及地下水, 平均利用比率分别为36.9%和42.3%; 过熟木主要利用140-340 cm的土壤水及地下水, 平均利用比率分别为32.8%和49.3%。     

Vigilance and grouping in the southern African ground squirrel (Xerus inauris)

Animals may form groups in response to the foraging–vigilance trade‐off, through enhanced predator detection (collective detection hypothesis) or reduced predation risk to the individual (dilution hypothesis), allowing individuals to decrease vigilance levels. Both hypotheses predict decreasing individual vigilance levels with increasing group size; however, the collective detection hypothesis also predicts increasing overall group vigilance with increasing group size. However, in species in which vigilance and foraging are not mutually exclusive, where vigilance may not be as costly, neither of these hypotheses may apply. Here, we examine the relationship between group size and vigilance in the social Cape ground squirrel (Xerus inauris), a species that can combine foraging and vigilance behaviours. Ten groups were observed using scan sampling, measuring both group and individual vigilance and group size. A negative relationship existed between individual vigilance and group size and a positive relationship between group vigilance and group size. Therefore, in Cape ground squirrels, vigilance seems to be costly even though it can be combined with foraging behaviours. Furthermore, group vigilance behaviour gives support to the collective detection hypothesis, whilst individual vigilance gives support to both hypotheses.     

锯缘青蟹精巢发育的组织学观察

组织学观察表明,锯缘青蟹（Scylla serrata)精巢发育周期可以分为精原细胞期,精母细胞期,精子细胞期,精子期和休止期5个时期。在划分精巢发育期的基础上,结合生精小管直径的成熟节段比例这2个指标,可以较准确地反映锯缘青解精巢的发育状况。而成熟节段比例可以作为锯缘青蟹精巢发育的表征指标。     

ESEEM and Mössbauer studies of the ferriheme model compound bis(3-aminopyrazole)tetraphenylporphyrinatoiron(III) chloride, [TPPFe(NH2PzH)2]Cl

A model heme complex, bis(3-aminopyrazole)tetraphenylporphinatoiron(III) chloride, [TPPFe (NH₂PzH)₂]Cl, for which the EPR g-values lead to a rhombicity V/Δ=1.2 if g _zz is the largest g-value, have been investigated by electron spin echo envelope modulation (ESEEM) and Mössbauer spectroscopies. The ESEEM studies focus on the proton sum frequency peaks at near twice the proton Larmor frequency. Analysis of the distant proton peak (mainly due to the pyrrole-H) at exactly twice the proton Larmor frequency shows conclusively that g _zz is aligned along the normal to the porphyrin plane, and thus the electron configuration is (d _xy )²(d _xz ,d _yz )³, with g _zz >g _yy >g _xx . This system is thus another violation to Taylor's "proper axis system" rule. The near proton (the α-H and N-H of the axial ligands) peaks provide distance information for those protons from the metal. Magnetic Mössbauer studies of the same complex confirm the (d _xy )²(d _xz ,d _yz )³ ground state and indicate that, as is the case for cytochrome P450_cam, A _xx is the largest magnitude A-value, and is negative in sign. Other low-spin iron(III) porphyrinates also have A _xx of negative sign, but usually the magnitude is only about half that of A _zz , which is always positive in sign.