A fossil grass (gramineae: chloridoideae) from the miocene with kranz anatomy

A fossil leaf fragment collected from the Ogallala Formation of northwestern Kansas exhibits features found in taxa of the modern grass subfamily Chloridoideae. These include bullet-shaped, bicellular microhairs, dumbbell-shaped silica bodies, cross-shaped suberin cells, papillae, stomata with low dome- to triangular-shaped subsidiary cells, and Kranz leaf anatomy. The leaf fragment extends the fossil record of plants that show both anatomical and external micromorphological features indicating C(4) photo-synthesis back to the Miocene. On the basis of associated mammals, the leaf fragment is assigned a Hemphillian age (7 to 5 million years ago).     

Plutonium-244: confirmation as an extinct radioactivity

The mass spectrum of xenon from spontaneous fission in a laboratory sample of plutonium-244 is precisely what meteoriticists predicted it would be; this discovery completes a web of proof that this nuclide is a bona fide extinct radioactivity of galactic origin, that r-process nucleosynthesis was ongoing in the galaxy at the time of the birth of the sun, and that the early meteoritic abundances of plutonium-244, heretofore tentative, can be utilized with confidence in models for the chronology of galactic nucleosynthesis. The search for an explanation for anomalous fission-like xenon in carbonaceous chondrites can now be narrowed.     

Wheat streak mosaic virus: incidence in field crops,potential reservoir within grass species and uptake in winter wheat cultivars

Wheat streak mosaic virus(WSMV)has become a re-emerging pathogen in cereal crops in the Czech Republic.WSMV was first reported in the former Czechoslovakia in the early 1980s,and then no record of the virus was documented until 2009.The incidence of the virus was recorded in recent years in several winter wheat fields and many grass species.Here,we surveyed the incidence of WSMV in cereal crops.The results demonstrated the existence of the virus in winter wheat and volunteer wheat during each year of the monitoring period,which spanned from 2013–2016.Although the range of infected samples was low(6.4%of the total tested samples),a high incidence of well-distributed virus was recorded.In at least six fields,the virus reached severe and potentially epidemic levels.In accordance with our previous report detailing WSMV infection of native grasses,we tested several grass species commonly grown in the Czech Republic.We found that some grass species acted as experimental hosts and possible reservoirs of the virus;these included Anthoxanthum odoratum(sweet vernal grass),Arrhenatherum elatius(false oat-grass),Lolium multiflorum(Italian rye-grass),Bromus japonicus(Japanese chess),Echinochloa crus-galli(barnyard grass),Holcus lanatus(meadow soft grass)and Holcus mollis(creeping soft grass).Some of these grass species are also important weeds of cereals,which may be the potential source of WSMV infection in cereal crops.Several widely used winter wheat cultivars were tested in the field after artificial inoculation with WSMV to evaluate virus titre by RT-qPCR.Overall,the tested cultivars had a low virus titre,which is associated with mild disease symptoms and may provide a good level of crop resistance to WSMV.     

Line and grade in the extinct medius species group of sigmodon

Remains of Sigmodon minor and Sigmodon medius, extinct cotton rats comprising the medius species group, have been recovered from both Kansas and Arizona. Sigmodon minor evolved from Sigmodon medius, and the available evidence suggests that Kansas populations of Sigmodon minor were derived from Kansas populations of Sigmodon medius, while Arizona populations of Sigmodon minor were derived from Arizona populations of Sigmodon medius. This multiple origin of a single mammalian species is similar to the origin proposed by Carleton Coon for the races (subspecies) of Homo sapiens.     

Barium isotopes in allende meteorite: evidence against an extinct superheavy element

Carbon and chromite fractions from the Allende meteorite that contain isotopically anomalous xenon-131 to xenon-136 (carbonaceous chondrite fission or CCF xenon) at up to 5 x 10(11) atoms per gram show no detectable isotopic anomalies in barium-130 to barium-138. This rules out the possibility that the CCF xenon was formed by in situ fission of an extinct superheavy element. Apparently the CCF xenon and its carbonaceous carrier are relics from stellar nucleosynthesis.     

Coral skeletons: an explanation of their growth and structure

Coral skeletons are constructed of aragonitic crystals organized into fan systems. A theoretical model for the growth of such fan systems, which depends upon competition between crystals for space in which to grow, is corroborated by vital staining with sodium alizarinesulfonate. Fan systems of crystals compete with each other to form larger fan systems until large, relatively stable fans are produced. It is these relatively stable fan systems that have been observed in optical thin sections of coral skeletons.     

Wadi howar: paleoclimatic evidence from an extinct river system in the southeastern sahara

Field research into the climatic history and shifting of the East Saharan desert has furnished evidence that during Quaternary time the present extremely arid western part of Upper Nubia (northern Sudan)was temporarily linked to the Nile by way of a hitherto unknown 400 kilometer long tributary. From about 9500 to 4500 years ago, lower Wadi Howar flowed through an environment characterized by numerous ground water outlets and freshwater lakes. Savanna fauna and cattle-herders occupied this region, which today receives at most 25 millimeters of rainfall per year. At that period the southern edge of the eastern Sahara was some 500 kilometers further north than today and ground water resources were recharged for the last time.     

Catagonus, an "extinct" peccary, alive in paraguay

A third species of peccary, discovered in the Chaco of Paraguay, is added to the living members of family Tayassuidae. It is assigned to the genus Catagonus Ameghino, heretofore considered confined to the Pleistocene. The new peccary is conspecific with Catagonus wagneri (Rusconi), a species placed in the related extinct genus Platygonus LeConte when it was described from pre-Hispanic archeological deposits of Argentina.     

Switching skeletons: hydrostatic support in molting crabs

Skeletal support systems are essential for support, movement, muscular antagonism, and locomotion. Crustaceans shed their rigid exoskeleton at each molt yet are still capable of forceful movement. We hypothesize that the soft water-inflated body of newly molted crabs may rely on a hydrostatic skeleton, similar to that of worms and polyps. We measured internal hydrostatic pressure and the force exerted during claw adduction and observed a strong correlation between force and hydrostatic pressure, consistent with hydrostatic skeletal support. This alternation between the two basic skeletal types may be widespread among arthropods.     

日照市野生草类资源主要种类调查

在辖区内根据不同的地理条件,采用实地调查和访问调查的方式,共调查到野生草类资源42科155属209种,分布在农田、山川、河流、沼泽及旱地。有可以利用的良好药材资源107种,绿化及水土保持用草15种,牧草类12种,农作物育种资源5种。经初步访问调查,数量在逐渐减少的有28种,数量呈上升趋势的有9种,茜草数量极少。该项调查为开展有益草类资源的保护和利用,为农业部门有针对性地进行农田杂草防除,防止外来物种入侵提供技术支持。     

Variable porosity in siliceous skeletons: determination and importance

Gas adsorption data were used to obtain the specific surface area and specific pore volume for a variety of biogenically precipitated silica semples. The results suggest that this material is finely divided and porous. This interpretation was corroborated by the use of transmission electron microscopy at magnifications up to 180,000.     

Ross sea region in the middle miocene: a glimpse into the past

Fossil diatoms and pollen from sea-floor sediments beneath the Ross Ice Shelf indicate that a permanent ice cover was not present in the Ross Sea and that vegetation including angiosperms, gymnosperms, and ferns existed on at least some parts of the largely glaciated Antarctic mainland in the late middle Miocene.     

A Cambrian peak in morphological variation within trilobite species

Morphological variation within species is a raw material subject to natural selection. However, temporal change in morphological diversity has usually been studied in terms of variation among rather than within species. The distribution of polymorphic traits in cladistic character-taxon matrices reveals that the frequency and extent of morphological variation in 982 trilobite species are greatest early in the evolution of the group: Stratigraphically old and/or phylogenetically basal taxa are significantly more variable than younger and/or more derived taxa. Through its influence on evolutionary tempo, high intraspecific variation may have played a major role in the pronounced Cambrian diversification of trilobites.     

广西石漠化地区适生牧草品种的筛选

为筛选出适合广西石漠化地区种植的牧草品种,试验引进14个牧草品种在广西石漠化地区种植,观察生长适应情况,测量株高、产量以及土壤养分变化。结果表明,紫色象草、合萌、山毛豆、宽叶雀稗、柱花草表现较优,覆盖度高达80%～100%,与杂草竞争力强;种植当年,紫色象草鲜草产量达15.63 t/667 m²,合萌、宽叶雀稗、柱花草鲜草产量分别为2.01、2.51、1.96 t/667 m²,年可刈割3～4次;对土壤理化性能具有改善作用,尤其是柱花草可以明显提高土壤有机质含量,与对照相比提高了7.12%,同时土壤的水解氮含量也得到了提高,与对照相比提高了13.68%。山毛豆由于种子硬实,第一年萌发较少,但是第二年的覆盖度也达到了80%,水土保持能力强。紫色象草、合萌、山毛豆、宽叶雀稗、柱花草适合在广西石漠化地区种植,对石漠化治理效果较好,同时饲料牧草可用于牛羊养殖,发展石漠化山区畜牧业。     

北京地区不同草种的草坪质量变化及影响因素分析

在北京地区对5个冷季型和1个暖季型草种共112个品种的草坪质量变化及影响因素进行了研究,结果表明,在5个冷季型草种中,多年生黑麦草和剪股颍建植速度最快,草地早熟禾建植速度最慢,暖季型草种狗牙根是6个参试草种中建植速度最慢的一个,暖季型和冷季型草种的草坪质量在季节上存在明显差异,暖季型草坪草在最热的7、8月份表现最佳,而冷季型草坪草在春季和秋季表现良好,气候的季节变程和草种是影响草坪质量最重要的因素,而品种之间的变差较小,其贡献大小和重复间的贡献相当。     

4种禾本科牧草在川东北地区适应性研究初探

对川东北地区的扁穗雀麦、苇状羊茅、“广益”牛鞭草、“重高”牛鞭草等4种禾本科牧草的生长速度、产草量、叶宽和叶长等性状进行了研究。结果显示,4个材料都能适合该地区的气候和土壤条件,扁穗雀麦的生长速度最大,其次为“广益”,“重高”、苇状羊茅最小;另外,扁穗雀麦的叶片长度和宽度都显著高于其他材料;从产量上来看,“广益”最高,达26493．0kg／hm^2,“重高”和扁穗雀麦次之,分别为26040．0和21103．5kg／hm^2,苇状羊茅最低,为15768kg／hm^2。由此表明,牛鞭草和扁穗雀麦均适宜在川东北丘陵地区栽培,具有较高的推广价值。     

Gibberellic Acid: effects of feeding in an artificial diet for honeybees

Complete larval and pupal development occur in colonies of honeybees when adult bees are allowed to feed upon an artificial diet containing gibberellic acid. In the absence of gibberellic acid larvae die in the 3rd or 4th day of development.     

Scaling in tensile "skeletons": structures with scale-independent length dimensions

Skeletal structures that resist only tensile forces can scale differently than compression resisting structures that fail in bending or buckling. The tensile structures examined scalelike simple ropes: length and diameter of the structure are not correlated, and in three of four cases, length is independent of scale or load, but diameter is dependent on scale. These relations suggest that similarity in stress rather than strain, or deformational behavior, is the basis for mechanical adaptation in the gross dimensions of these tensile structures.