共查询到20条相似文献，搜索用时 31 毫秒
1.
A primitive enantiornithine bird and the origin of feathers 总被引：2，自引：0，他引：2
A fossil enantiornithine bird, Protopteryx fengningensis gen. et sp. nov., was collected from the Early Cretaceous Yixian Formation of Northern China. It provides fossil evidence of a triosseal canal in early birds. The manus and the alular digit are long, as in Archaeopteryx and Confuciusornis, but are relatively short in other enantiornithines. The alula or bastard wing is attached to an unreduced alular digit. The two central tail feathers are scalelike without branching. This type of feather may suggest that modern feathers evolved through the following stages: (i) elongated scale, (ii) central shaft, (iii) barbs, and finally (iv) barbules and barbicel. 相似文献
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[目的]为了研究"人防"山洞蘑菇栽培技术。[方法]采用荷兰技术,利用"人防"山洞种植双孢蘑菇,对六化建前洞菇房、后洞菇房的生产过程进行总结和分析。[结果]在5 417.6 m2菇床上,采收蘑菇131 105.9 kg,单位面积产量24.2 kg/m2。后洞采菇期自3月11日至5月3日,共54 d,全生产周期123 d,采收鲜菇59 567.0 kg,单位面积产量为23.5 kg/m2。前洞采菇期3月21日至5月4日,共45 d,采收鲜菇71 538.9 kg,单位面积产量24.8 kg/m2。两洞平均采菇期达47.5 d,前洞产量比后洞高出约44%。[结论]利用"人防"山洞种植双孢蘑菇是可行的。 相似文献
3.
Marivaux L Welcomme JL Antoine PO Métais G Baloch IM Benammi M Chaimanee Y Ducrocq S Jaeger JJ 《Science (New York, N.Y.)》2001,294(5542):587-591
In the absence of a comprehensive fossil record, the origin and early evolution of Malagasy lemurs have been subject to much uncertainty. We report here the discovery of a strepsirrhine fossil with strong cheirogaleid lemur affinities, Bugtilemur mathesoni gen. et sp. nov., from early Oligocene deposits of the Bugti Hills (Balochistan, Pakistan). Bugtilemur represents the earliest record of Lemuriformes, which hence appear to have already diversified outside of Madagascar at least 30 million years ago. This fossil clearly enhances the critical role of the Indian subcontinent in the early diversification of lemurs and constrains paleobiogeographic models of strepsirrhine lemur evolution. 相似文献
4.
Jurassic fossil vertebrates collected from the Falla Formation in the Central Transantarctic Mountains included a partial skull and postcranial elements of a crested theropod, Cryolophosaurus ellioti gen. nov. sp. nov. The theropod bears some resemblance to the large tetanurans of the Middle to Late Jurassic but also has primitive ceratosaurian features. Elements from a prosauropod, teeth from scavenging theropods, a pterosaur humerus, and a tritylodont molar were also recovered. The presence of this fauna suggests that a mild climate existed at high paleolatitude in this area of Gondwana during the Early Jurassic. 相似文献
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河西走廊绿洲灌区在农业产业化进程加快的同时,也带来了水资源和生态环境的压力.本文利用养分流动和模型分析的方法,分析河西走廊绿洲灌区典型“农田-食用菌”生产系统(农田-食用菌集约生产模式、农田-食用菌单户生产模式、农田单作)的氮元素流动特征.结果表明:农田作物秸秆通过食用菌体系还田使氮素利用率提高了10％左右,秸秆还田氮输入量(165.6kg· hm-2·a-1)占农田氮素总输入量的37.1％,使化肥氮输入量减少,因此秸秆氮的合理循环利用可作为减少化肥投入的有效途径.但农田氮素仍有盈余,单位面积氮盈余量高达217.0 kg·hm-2· a-1,未能实现循环模式内养分平衡的理想效果,因此优化氮素管理、确定合理的大田作物和食用菌面积、调整农业产业结构是解决该问题的关键. 相似文献
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Shu DG Morris SC Han J Li Y Zhang XL Hua H Zhang ZF Liu JN Guo JF Yao Y Yasui K 《Science (New York, N.Y.)》2006,312(5774):731-734
Ediacaran assemblages immediately predate the Cambrian explosion of metazoans and should have played a crucial role in this radiation. Their wider relationships, however, have remained refractory and difficult to integrate with early metazoan phylogeny. Here, we describe a frondlike fossil, Stromatoveris (S. psygmoglena sp. nov.), from the Lower Cambrian Chengjiang Lagerst?tte (Yunnan, China) that is strikingly similar to Ediacaran vendobionts. The exquisite preservation reveals closely spaced branches, probably ciliated, that appear to represent precursors of the diagnostic comb rows of ctenophores. Therefore, this finding has important implications for the early evolution of this phylum and related diploblasts, some of which independently evolved a frondose habit. 相似文献
7.
中国梅(Prunus mume)的植物学分类与园艺学分类 总被引：8，自引：0，他引：8
本文系在对梅所作之分类总结基础上所提出的一套全新方案。梅的植物学分类包括对已发表的29个变种、变型的整理,并增添了新发表的3变种、1变型;其园艺分类则将不同品种(栽培变种)纳入中国梅分类系统(1991)中。新系统的特点有二:一是把植物学分类与园艺学分类既区分开又适当联系起来,二是对果梅与花梅品种实行统一的2元(演化关系为主,形态、应用为次)4级(4系、7类、14组,24型)分类。 相似文献
8.
食用菌常见病害及预防 总被引：3，自引：0，他引：3
从制种、代料栽培、段木栽培和子实体培养几个方面阐述了危害食用菌的常见病害。食用菌病害的防治应以“预防为主,综合防治”,才能收到较好的效果。 相似文献
9.
Sparse coding presents practical advantages for sensory representations and memory storage. In the insect olfactory system, the representation of general odors is dense in the antennal lobes but sparse in the mushroom bodies, only one synapse downstream. In locusts, this transformation relies on the oscillatory structure of antennal lobe output, feed-forward inhibitory circuits, intrinsic properties of mushroom body neurons, and connectivity between antennal lobe and mushroom bodies. Here we show the existence of a normalizing negative-feedback loop within the mushroom body to maintain sparse output over a wide range of input conditions. This loop consists of an identifiable "giant" nonspiking inhibitory interneuron with ubiquitous connectivity and graded release properties. 相似文献
10.
[目的]研究亳菊茎尖组织培养技术,为亳菊产业化生产提供科学依据。[方法]在不同的MS培养基中,考察不同浓度的6-BA、NAA对亳菊茎尖愈伤组织、丛生芽、再生植株诱导的影响。[结果]茎尖诱导愈伤组织的最佳培养基为MS＋1.00 mg/L6-BA＋0.30mg/L NAA,以MS＋0.50 mg/L6-BA＋0.10 mg/L NAA为芽的诱导培养基,芽诱导率达100%;最佳的生根培养基为1/2MS＋0.30 mg/L IBA。[结论]通过亳菊茎尖愈伤组织培养技术,可以达到快速繁殖的目的。 相似文献
11.
蒲螨是食用菌栽培中最为重要的害螨。自1983年以来,我们对上海地区的蘑菇、香菇、平菇、草菇等食用菌及稻草、粪肥、棉籽等栽培材料上的蒲螨种类进行了调查研究。经鉴定共计有4科7属16种,其中包括一新记录。文中列有属种名录和分种检索表。本研究结果表明:兰氏布伦螨[Brennandania lambi(Krcz(?)l,1964)]是上海地区蘑菇生产的主要害螨,蘑菇严重减产乃至毫无收成的情况80～90％是由它造成的,而菌种带螨是其大面积发生的主要原因。矩形拟矮螨[Pseudo pygmephorus quadratus(Ewing,1917)]在蘑菇房中颇为常见。费氏穗螨[Siteroptus flechtmanni(Wicht,1970)〕在各种食用菌上常见,但并未见其造成严重的产量损失。 相似文献
12.
Land clearing and the biofuel carbon debt 总被引：8，自引：0，他引：8
Increasing energy use, climate change, and carbon dioxide (CO2) emissions from fossil fuels make switching to low-carbon fuels a high priority. Biofuels are a potential low-carbon energy source, but whether biofuels offer carbon savings depends on how they are produced. Converting rainforests, peatlands, savannas, or grasslands to produce food crop-based biofuels in Brazil, Southeast Asia, and the United States creates a "biofuel carbon debt" by releasing 17 to 420 times more CO2 than the annual greenhouse gas (GHG) reductions that these biofuels would provide by displacing fossil fuels. In contrast, biofuels made from waste biomass or from biomass grown on degraded and abandoned agricultural lands planted with perennials incur little or no carbon debt and can offer immediate and sustained GHG advantages. 相似文献
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研究了三唇属线虫(Trilabiatus spp.)对蘑菇菌丝生长的影响,以确定其对蘑菇生产的危害性。分别在甘肃省天水市秦州区(2006年8月中下旬)和浙江省温州市苍南县(2009年8月初和2010年2月)调查有退菌现象的蘑菇菇床及基质(草粪培养料)、鉴定线虫类群、统计线虫数量、纯化三唇线虫并接种于黑木耳及双孢蘑菇斜面培养基。退菌现象严重的木耳和双孢蘑菇基质中三唇属线虫数量多;三唇线虫可在供试的两种食用菌菌丝上大量繁殖,接种2或3周后,线虫数量可分别扩增365倍和208倍;线虫的体表细菌可协助线虫加速对菌丝生长的危害,但不单独危害菌丝。三唇属线虫可造成黑木耳和双孢蘑菇菌丝过早萎缩、变黄、变褐,影响其正常发育。 相似文献
15.
Mellett JS 《Science (New York, N.Y.)》1974,185(4148):349-350
Small-mammal bone found in Recent carnivore droppings (scat) is identical in appearance with that in many Mesozoic and Tertiary microvertebrate fossil collections. Such fossil specimens passed into or through the digestive tracts of carnivores before being left as scat that was later reworked into sedimentary rocks. The term "coprocoenosis" is proposed for such an assemblage. Caution is urged in drawing conclusions about the composition of paleocommunities because carnivores can catch prey representing several different communities and leave a mixed assemblage in a particular depositional environment. 相似文献
16.
系统研究了分布于中国、印度和尼泊尔的直翅目蚱科尖顶蚱属Teredorus昆虫种类共计22种,其中有2个新种,即太白尖顶蚱Teredorus taibeiensis sp.nov.和短背尖顶蚱Teredorus brachinota sp.nov.,并有1个新组合,即格尖顶蚱Teredorus graveli(Gunther,1939)com.nov.,同时提供了尖顶蚱属昆虫的分种检索表和分布地区。模式标本保存于陕西师范大学动物研究所昆虫标本室。 相似文献
17.
观赏南瓜有机栽培基质配方研究 总被引：3，自引：0，他引：3
以观赏珍珠南瓜为试材,研究了观赏南瓜有机基质栽培的合理基质配方,选用炉渣、菇渣、蛭石、珍珠岩和泥炭等作为基质,不同基质按体积比组合,4个处理分别为珍珠岩∶蛭石∶泥炭=2∶1∶3,珍珠岩∶蛭石∶菇渣=2∶1∶3,炉渣∶蛭石∶泥炭=2∶1∶3,炉渣∶蛭石∶菇渣=2∶1∶3,对照为土壤。结果表明,各配方的理化性质均优于对照,其中珍珠岩∶蛭石∶菇渣=2∶1∶3和炉渣∶蛭石∶菇渣=2∶1∶3两配方观赏南瓜植株中叶绿素含量、全磷、全钾含量较高,果实中全氮、全磷、维生素C、氨基酸、β-胡萝卜素的含量较高,但还原糖、可溶性糖、淀粉及粗纤维的含量较低。说明在基质中添加菇渣可以明显促进观赏南瓜的生长并改善品质。 相似文献
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Silicified specimens of the Vendian (late Precambrian) "index fossil" Conophyton gaubitza from South Kazakstan contain a diverse assemblage of well-preserved cyanophytic and apparently eukaryotic algae, the first stromatolitic microbiota to be reported from the Soviet Union. Unlike the stromatolites in which they occur, the microorganisms that apparently built this form of Conophyton did not become extinct at the end of the Precambrian. 相似文献