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Species of the Marsileaceae represent a unique group of pteridophytes of uncertain origin. The polyphenolic profiles of representative species, which include flavonol-3-O-mono- and diglycosides, C-glycosylflavones and C-glycosylxanthones, have chemical features in common with the primitive leptosporangiate ferns, especially the Hymenophyllaceae. Intergeneric relationships in the family based on morphology, cytology, fossil evidence and polyphenolic profiles are discussed.  相似文献   

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The shoot apex of Dennstaedtia cicutaria consists of three zones—a zone of surface initials, a zone of subsurface initials, and a cup-shaped zone that is subdivided into a peripheral region and central region. A diffuse primary thickening meristem, which is continuous with the peripheral region of the cup-shaped zone, gives rise to a broad cortex. The roots occurring on the rhizomes are initiated very near the shoot apex in the outer derivatives of the primary thickening meristem. The roots that occur on the leaf bases also differentiate from cortical cells. Eventually, those cortical cells situated between the newly formed root apical cell and the rhizome procambium (or leaf trace) differentiate into the procambium of the root trace, thus establishing procambial continuity with that of the rhizome or leaf trace. Parenchymatous root gaps are formed in the rhizome stele and leaf traces when a few of their procambial cells located directly above the juncture of the root trace procambium differentiate into parenchyma. As the rhizome procambium or leaf trace continues to elongate, the parenchyma cells of the gap randomly divide and enlarge, thus extending the gap.  相似文献   

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本文研究长跑锻练对老年人血浆白细胞介素-1(IL-1)活性的影响及其和糖皮质激素受体(GR)的可能关系。IL-1活性用刺激C_(57)小鼠胸腺细胞增生后~3H-胸腺嘧啶核苷参入量的多少来表示,GR用~3H-地塞米松特异结合表示。结果表明:长跑锻练10年以上老年人(n=6)安静时血浆IL-1活性在14.7-18.7,3.8-7.0以及1.5-2.6KD之间出现三个淋巴细胞增生峰,分别为对照组老年人(n=4)的209%,223%和145%(P<0.05);而外周血白细胞GR水平较对照老年人降低,约为对照组的65%。本文对IL-1的活性和GR含量的关系和生理意义进行了讨论。  相似文献   

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The arrangement and numbers of vascular bundles were documented for the species of the Allium cernuum Roth, Allium validum Wats., and Allium kunthii G. Don alliances. These characters proved consistent and diagnostically useful in the A. cernuum and A. validum alliances, but inconsistent in the A. kunthii alliance.  相似文献   

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The efficiency of weak ELF (extremely low frequency) EMF on living systems can be explained by taking into account the nonstationary processes that arise when ions pass part of the intermembrane distance during the EMF period. The periodic movement of ions in the heterogeneous medium would result in the nonlinear effects influencing the ionic strength and pH near the membrane and the release of some peripheral proteins to the water phase. Based on this notion, we studied the effects of EMF treatment (30 or 50 Hz, 30 mT) at different stages of imbibition of wheat seeds. The treatment at the stage of activation of esterases increased the leakage of the products of esterase reaction with its following retardation, which contrasts with the linear kinetics for untreated seeds and for seeds treated at earlier stages. The treatment also led to a reliable increase in pH near the embryo surface. When the wheat seeds with germinability of 50% were treated at the stage of root formation, a significant increase in the number of seeds with roots was observed. The sprout length reliably increased after this treatment with respect to seeds treated later and untreated seeds. In the latter case, only the number of seeds with sprouts increased. Long treatment of seeds during the second day of imbibition reduced the length of sprouts. The observed effects are discussed on the basis of this proposed mechanism.  相似文献   

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The following Lolium species were shown to have 14 chromosomes: L. canariensis Steud. (= L. gracile Parl.), L. loliaceum (Bory and Chaub.) Hand.-Mazz., L. multiflorum Lam., L. perenne L., and L. temulentum L. B-chromosomes in addition to the normal complement were observed during metaphase I and anaphase I for L. persicum Boiss. and Hohen., L. remotum Schrank, L. rigidum Gaud., L. strictum Presl. (= L. rigidum?), and for several synthesized interspecific hybrids. General absence of B-chromosomes in diakinesis suggested that they originated by misdivision of A-chromosomes during prometaphase I. The B-chromosomes reached a maximum of eight but the number varied for microsporocytes of the same plant. B-chromosomes appeared spontaneously in progenies from sibbing of hybrid plants without supernumeraries but were also eliminated in the F2 from other sibbings. Degree of chromosome pairing during meiosis was unrelated to the subsequent presence of B-chromosomes. Normal pairing of seven bivalents was typical for L. perenne × L. multiflorum, L. perenne × L. rigidum, L. multiflorum × L. loliaceum, and L. rigidum × L. loliaceum. Between five and seven bivalents were recorded for L. multiflorum × L. persicum, L. multflorum × L. remotum, L. multiflorum × L. strictum, L. rigidum × L. persicum, L. rigidum × L. remotum, L. rigidum × L. strictum, and L. rigidum × L. temulentum. The results indicated that these Lolium species have a common and generally undifferentiated genome suggesting relatively recent speciation.  相似文献   

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猴及人胎儿延髓内脏带的化学神经解剖学   总被引:1,自引:0,他引:1  
本实验采用免疫组织化学ABC法,观察儿茶酚胺类(以酪氨酸羟化酶-TH作标记物)、5-羟色胺及神经肽(P物质、亮氨酸-脑啡肽、胆囊收缩素、神经肽Y、生长抑素)在猴及人胎儿延髓内脏带的分布及形态特点。结果发现,上述物质均程度不同地集中分布于猴及人胎儿延髓内脏带,即位于延髓中尾段的一条从背内侧至腹外侧的弧形带状区。这表明猴及人胎儿延髓内脏带是一个相对独立的机能结构区,其化学构筑具有独特特点。  相似文献   

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Walker , S. (Liverpool Univ., England.) Further studies in the genus Dryopteris: the origin of D. clintoniana, D. celsa and related taxa. Amer. Jour. Bot. 49(5): 497–503. Illus. 1962.—Cytogenetic studies of 5 Dryopteris species, from North America, together with wild and synthesized hybrids between some of them, show that D. clintoniana and D. celsa are allohexaploid and allotetraploid respectively. Cytological and morphological evidence points to D. cristata and D. goldiana being parental to D. clintoniana, whilst D. goldiana and D. ludoviciana are parental to D. celsa. The taxon D. X australis is triploid and has been synthesized; it is the backcross between D. celsa and D. ludoviciana.  相似文献   

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The genus Tricolia(Phasianellidae) in the Eastern Atlantic andMediterranean is reviewed on the bases of radular morphology,shell characters and polychromatism. The taxa included within the T. pullus (L.) group are not clearlyseparable and are treated as geographical subspecies:T. pulluspullus (L.), T. pullus picta (da Costa), T. pullus azorica (Dautzenberg),T. pullus canarica Nordsieck. The case of T. tenuis (Michaud)is problematic since it is clearly separable from sympatricT. pullus pullus in most parts of the Mediterranean but transitionalto T. pullus picta, towards the Atlantic. Other taxa are considered as having specific status since theyare consistently separable when found in sympatric populations.These include T. speciosa (Muhlfeldt), T. miniata (Monterosato),T. tingitana n.sp., T. petiti (Craven), T. nordsiecki (Talavera)and T. algoidea (Pallary). The last two species are stated forthe first time as belonging to the Phasianellidae. The genusEpheriella Pallary, based on T. algoidea, is synonymized withTricolia. (Received 6 April 1981;  相似文献   

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