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海南玄武岩砖红壤香蕉园的连作生物障碍严重,轮作是缓解香蕉园连作生物障碍最有效的方式之一。本研究使用主成分分析法结合实测数据,根据不同土壤指标的敏感程度以及指标间的相关度筛选出的土壤pH、速效钾、有效磷、碱解氮、有机质、细菌总数、真菌总数、放线菌总数、线虫数、香蕉枯萎病病原菌数量10项指标对5种轮作模式下的香蕉园土壤质量进行综合评价。结果表明:土壤质量综合评价指数可以较好地反映土壤实际的质量,并能够在一定程度上反映香蕉的产量及发病状况,是较为理想的土壤评价指标;用所得到的综合评价指数对5种轮作模式及香蕉连作进行对比可以发现轮作能有效地提高土壤质量,降低香蕉发病率,提高香蕉产量,其中菠萝、甘蔗、辣椒、冬瓜4种作物相对适合香蕉的轮作。 相似文献
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镉对菠菜生长影响的基因型差异研究 总被引：2，自引：0，他引：2
[目的]研究菠菜对镉的吸收累积基因型差异及镉对菠菜生长的影响,为培育食用部位低镉积累的菠菜品种提供参考。[方法]选取16个品种,采用珍珠岩和蛭石混合培养法种植在镉含量为10mg／L的环境中,研究了镉吸收和积累对菠莱生长及新陈代谢的影响。[结果]结果表明,营养液中镉含量为10mg／L时,可以显著降低菠菜根部和地上部的干重、鲜重和总生物学产量,降低菠菜中叶绿素含量。经镉处理后,菠菜地上部镉含量为129．69～290．15μg／gDW,根部中镉含量为87．26～1487．67μg／gDW。地上部及根部镉含量和镉积累量基因型间存在显著差异。[结论]镉主要累积在菠菜的根部。 相似文献
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Rasmussen M Guo X Wang Y Lohmueller KE Rasmussen S Albrechtsen A Skotte L Lindgreen S Metspalu M Jombart T Kivisild T Zhai W Eriksson A Manica A Orlando L De La Vega FM Tridico S Metspalu E Nielsen K Ávila-Arcos MC Moreno-Mayar JV Muller C Dortch J Gilbert MT Lund O Wesolowska A Karmin M Weinert LA Wang B Li J Tai S Xiao F Hanihara T van Driem G Jha AR Ricaut FX de Knijff P Migliano AB Gallego Romero I Kristiansen K Lambert DM Brunak S Forster P Brinkmann B Nehlich O Bunce M Richards M Gupta R 《Science (New York, N.Y.)》2011,334(6052):94-98
We present an Aboriginal Australian genomic sequence obtained from a 100-year-old lock of hair donated by an Aboriginal man from southern Western Australia in the early 20th century. We detect no evidence of European admixture and estimate contamination levels to be below 0.5%. We show that Aboriginal Australians are descendants of an early human dispersal into eastern Asia, possibly 62,000 to 75,000 years ago. This dispersal is separate from the one that gave rise to modern Asians 25,000 to 38,000 years ago. We also find evidence of gene flow between populations of the two dispersal waves prior to the divergence of Native Americans from modern Asian ancestors. Our findings support the hypothesis that present-day Aboriginal Australians descend from the earliest humans to occupy Australia, likely representing one of the oldest continuous populations outside Africa. 相似文献
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At high pressure the alkali metals potassium, rubidium, and cesium transform to metals that have a d1 electron configuration, becoming transition metal-like. As a result, compounds were shown to form between potassium and the transition metal nickel. These results demonstrate that the chemical behavior of the alkali metals under pressure is very different from that under ambient conditions, where alkali metals and transition metals do not react because of large differences in size and electronic structure. They also have significant implications for the hypothesis that potassium is incorporated into Earth's core. 相似文献
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The distribution and morphology of fibrous astrocytes in the cervical spinal cord of normal horses and horses with chronic compressive myelopathy were demonstrated using immunohistochemical staining for glial fibrillary acidic protein. In the spinal cord from normal horses, astrocytes with stellate cell bodies and short processes were irregularly distributed in grey matter. In the white matter, their cell bodies were small and angular in areas adjacent to grey matter and larger and more stellate-shaped in the subpial area. Astrocyte processes were fine, and evenly distributed in a predominantly radial pattern in transverse sections of cord. Gliosis was marked in the spinal cords of horses with cervical compressive myelopathy. In the grey matter at the level of compression astrocytes were often enlarged and rounded, with short, blunt processes, but the gliosis was generally mild. In the white matter, gliosis was obvious in areas of nerve fibre swelling and degeneration at the level of compression and in areas of ascending and descending Wallerian degeneration. The fine radial pattern of astrocyte fibres was replaced by a dense, irregular arrangement. Gliosis persisted in the cords of chronically affected horses after active nerve fibre degeneration had subsided. The areas of gliosis coincided with the areas of Marchi staining for degenerating myelin and with areas of myelin loss in osmium tetroxide post-fixed tissue. Histological observations were consistent with astrocytes replacing areas of extracellular space that remained after nerve fibre degeneration. it is concluded that astrocytic gliosis is a prominent and persistent alteration of the spinal cord of horses with chronic cervical compressive myelopathy. 相似文献
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