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严重缺碘对体质及遗传性状影响的研究 总被引:3,自引:2,他引:1
对严重缺碘地区一个容貌特殊,身材较矮,智力低下的人群进行了体质特征及遗传性状的研究,并与国内有关本地区的调查资料进行了对照,提出人类体质特征和遗传性状除与人种、地理环境异同直接相关外,人体不可缺少的微量元素的摄入水平在一定程度上对其也产生影响。并且认为同一人种、民族居住同一地理位置所产生的体质差异应从水文、地质、生活方式、生活水平的不同进行综合分析。 相似文献
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本文详细描述了菱臼齿兽耳区各个部分的基本结构;并指出了耳区结构与某些啮齿类的相似性,以及中耳鼓泡组成成份与戈壁(犭亚)兽(Anagale gobiensis)的区别。 相似文献
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四川自贡大山铺蜀龙动物群——简报Ⅲ.蜥脚类 总被引:4,自引:2,他引:2
本文记述了中侏罗世蜥脚类一新属种——巴山酋龙(Datousaurus bashanensts gen. et sp. nov.)对李氏蜀龙(Shunosaurus lii)的特征进行了补充,讨论了它们在蜥脚类进化过程中的位置。 相似文献
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The development of the anther wall follows Basic-type. The cytokinesis at the time of pollen mother cell meiosis conforms to successive type. The arrangement of the microspores in the tetrad is referred to isobilateral. The primary wall between the generative cell and the vegetative cell is callose. The callose wall is easily detected under the fluorescence microscope. The mature pollen grain is 2-celled type. The ovule is bitegminous, tenui-nucellar and anatropous. The development of the female gametophyte follows Fritillaria-type. The mature embryo sac. consists of the six cells including the seven nuclei. The fertilization is referred to the premitotic syngamy type. The fusion of the female and male nucleoli is not observed at the end of the fertilization. The division of the primary endosperm nucleus is earlier than that of the zygote. The development of the endosperm is referred to nuclear type. The division of the zygote is transverse of longitudinal, the development of the embryo conforms to Onagradtype. When the seed is mature, the embryo is at the proembryo stage without differentiation and the endosperm cells are not absorbed. 相似文献
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芒苞草形态学和胚胎学研究:Ⅱ.花药和胚珠发育的研究 总被引:3,自引:0,他引:3
芒苞草成熟胚珠为倒生型,薄珠心,双珠被。胎座为侧膜胎座向中轴胎座的过渡类型。胚囊发育为单孢蓼型。 成熟胚囊由印器,具二极核的中央细胞及三个反足细胞组成。助细胞呈倒梨形,极性不明显,珠孔端壁有角状的丝状器。中央细胞的二极核在受精前融合为次生核。 花药具二个小孢子囊,花药壁层为单子叶型,具分泌型绒毡层,小孢子母细胞减数分裂时,胞质分裂为连续型,四分体是左右对称式排列,成熟花粉粒为二细胞的。 在花药与胚珠发育过程中,多糖物质的消长是有规律的变化。 相似文献
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象牙参种子的解剖学和组织化学研究 总被引:3,自引:0,他引:3
象牙参种子解剖学和组织化学的研究结果表明, 种子包括假种皮、种皮、外胚乳、内胚乳和胚。假种皮没有完全包被种子, 由约4~5 层薄壁细胞构成。种皮可以分为外种皮、中种皮和内种皮。外种皮由1 层表皮细胞构成, 细胞壁明显增厚;中种皮包括下皮层、半透明细胞层和3~4层细胞的色素层, 下皮层和色素层细胞均充满红棕色色素;内种皮由1 层体积小、壁局部增厚的砖形薄壁细胞构成。种子在珠孔端分化出珠孔领、孔盖和种阜状结构, 珠孔领为同形型, 孔盖不具石细胞硬层。合点区内种皮出现缺口, 缺口间充满合点区色素细胞, 其整体轮廓成新月形。外胚乳可分为厚区与薄区两部分, 外胚乳细胞壁平直, 细胞内充满淀粉。内胚乳细胞主要含蛋白质, 也有少量脂类物质, 细胞界限不清楚。胚棒状, 两端略膨大, 含大量脂类物质, 也含蛋白质和多糖。 相似文献
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短柄五加大,小孢子发生和雌,雄配子体发育的研究 总被引:6,自引:2,他引:4
短柄五加花药5枚,每个花药四个花粉囊。小孢子母细胞减数分裂时,胞质分裂为同时型,产生正四面体形的四分体。花药壁由表皮、药室内壁、中层和绒毡层四层细胞组成,其发育类型为双子叶型。腺质绒毡层,其细胞为二核。三细胞型花粉。子房5室,每室两个胚珠,上胚珠败育,下胚珠可育。下胚珠倒生,具单珠被,厚珠心。大孢子母细胞减数分裂形成线性排列的四个大孢子,雌配子体发育属蓼型。开花当天,花粉散开,雌配子体尚未成熟,处 相似文献
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糖蜜草(Melinis minutiflora Beauv.)幼穗分化发育.及花和果实形态的研究 总被引:2,自引:0,他引:2
本文对糖密草(MelinisminutifloraBeauv.)的幼穗分化发育及花和果实的形态作了研究,将幼穗分化发育过程划分为以下九个时期:第一苞原基形成期;第一次枝梗原基形成期;第二、三次枝梗原基形成期;小穗及颖花原基形成期;雌、雄蕊原基形成期;花粉母细胞形成期;花粉母细胞减数分裂期;花粉充实期;花粉成熟期。全过程历时约需42d.从抽穗到颖果成熟约需50d。糖蜜草的花序为圆锥花序。每花序有可育花2000—3000朵.小穗是由小穗轴、内外颖片、不育花外稃和小花构成。小花包括有内外稃各一片、一鳞被、雄蕊三枚和一枚雌蕊,颖果千粒重为91mg。 相似文献
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黄土丘陵区子午岭短柄五加群落特征分析 总被引:1,自引:0,他引:1
采用样方法研究了子午岭短柄五加(Acanthopanax brachypus)群落的特征。结果表明:短柄五加群落具有典型的温带植物区系特点,其科属组成分散,种类成分简单,为自然演替和人工改造双重作用下的不稳定群落;群落物种丰富度指数和多样性指数变化趋势基本一致,生态优势度指数表现出相反的趋势;群落垂直结构明显,乔木层以油松、辽东栎和侧柏为主,灌木层中短柄五加占绝对优势,草本层以披针叶苔草为主,该群落可分为油松-短柄五加-披针叶苔草+三褶脉紫菀群丛、油松+辽东栎-短柄五加-披针叶苔草群丛、辽东栎-短柄五加-披针叶苔草群丛、侧柏-短柄五加+铁杆蒿-披针叶苔草群丛4个类型;短柄五加的分布主要受水热条件限制,在水热条件相对较好的地段及林缘长势较好。 相似文献
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利用切片方法观察了猞猁Felislynx肝脏的组织结构,应用免疫组织化学方法检测了表皮生长因子(EGF)在肝脏中的表达。结果显示,肝脏外被覆一层结缔组织薄膜,肝小叶不规则且分界不清,肝板、肝血窦及狄氏间隙围绕中央静脉呈放射状排列,肝板由一排肝细胞构成。肝细胞呈圆形或多边形,多为单核,少数具双核,肝细胞间比较松散。肝血窦发达,内可见血细胞。EGF阳性反应主要定位于肝细胞质中,表明EGF可能参与细胞新陈代谢过程的调控。 相似文献
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This paper presents a detailed report on the developmental progresses of the microsporangium and its microspores in Azolla filiculoides Lam., and shows the morphologicaI structures of the respective developmental stares with the aid of scanning electron photographs. The entire developmental progress may be divided into six stages: ( 1 ) The microspore mother cell initiating stage The microsporangium initial on the placenta of the sporocarp gave rise a sporogenous cell, and then divided four times to form sixteen microspore mother cells; (2) The meiotic stage–The microspore mother cells initiated meiosis inside their calIose walls. The radial and inner tangential walls of the tapetum were dissolved at the same time and followed by the formation of a sporoplasmodium; (3) The microspore shrinking Ⅰ–After the callose walls of tetrads was dissolved, those microspores that just released from the callose walls shrunk intensely and became spherical later again. The sporoderm of microspores was principally synthesized in this stage, and the volume of microspores became evidently increased. The microspores then gradually moved to the periphery of the sporoplasmodium; (4) The microspore shrinking Ⅱ-Each microspore formed a large vacuole and gave rise the second contraction. The periphery of the sporoplasmodium was gradually dissolved; (5) The massulae forming stage–The sporoplasmodium was dissolved successivelly, and the undissolvable granules and organelle membrane residues. became aggregated into the compartmental layer, and the microsporangium was divided into several large vesicles, each vesicle will form a massulae; (6) The microspore germinating stage–The ,natured microspores inside the massulae each gave rise an androgonial initial which divided two times to form four antherozoid mother cells and then gave rise the antherozoids. The relationships between the various morphological structures and their functions in the microsporangium developmental progress have breify discussed. In addition, our viewpoints have compared with those of previous investigations. 相似文献
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P. godefroyae is one of the diandrous species of rather primitive orchids. The cytokinesis of PMCs conforms to simultaneous type. The arrangement of microspores in a tetrad is tetrahedral or isobilateral. The first mitosis in a pollen grain is unequal and results in the formation of two unequal cells. The small one is the generative cell and the large one, the vegetative cell. The wall material between them is callose which is easily detectable under the fluorescence microscope. When the generative cell detaches from the microspore wall and migrates into the cytoplasm of the vegetative cell, the callose wall disappears and a thin PAS-positive wall Was observed around the generative cell. The PAS-positive wall remains untill anthesis. The tapetum is of secretory type and its cells are binucleate. With the degradation of the tapetal cells, they discharge a lot of yellow, amorphous, sticky mass into the pollen sac. The pollens distribute in it to form a sticky pollen mass. The ovule has single integument and one layered nucellus around the magaspore mother cell. The mature embryo sac consists of eight or six cells and conforms to the Allium type. The interval between pollination and fertilization is about 45 days and the normal double fertilization has been observed. The primary endosperm cell undergoes one division only and results in the formation of 2 nucleate endosperm. The dormancy period of zygote lasts 45–50 days. During the development of the embryo, a suspensor consisting of a row of two to four cells is formed. It takes more than six months from the pollination to the maturation of the seed. The embryo in the mature seed is just an ellipsoidal mass of 120–140 cells without differentiation. The endosperm and suspensor are all degenerated in the mature seed. 相似文献
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应用扫描电镜(SEM)与透射电镜(TEM)观察了黄姑鱼和大黄鱼精子的超微结构。结果显示,黄姑鱼和大黄鱼精子无论在形态、大小还是超微结构上都十分相似。黄姑鱼和大黄鱼精子均由头部、中段和尾部(鞭毛)3部分组成。精子头部形状近似椭圆形,无顶体,细胞核呈肾形。中心粒复合体位于细胞核背侧,近、远端中心粒相互垂直,远端中心粒分化成基体并形成轴丝。中段的袖套呈筒状,4~5个圆形的线粒体围绕轴丝呈环形排列。精子尾部为单鞭毛,轴丝为典型“9+2”结构,鞭毛表面质膜形成不规则侧鳍。 相似文献