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31.
Shoots of Hygrophila sp., which are decussate and have budsof unequal size at a node, were grown in liquid culture. Inexcised nodes it is known that the larger (+) bud inhibits thesmaller () bud in the axil of the opposite leaf, andonly one shoot grows out; in nodes split longitudinally bothbuds grow out. When nodes were split and grafted together again(+/ grafts), in general only one bud grew out; if aluminiumfoil was introduced at the nodal region both buds grew out.Thus the inhibitory effect of a + on a bud is laterallytransmissible across a graft union. In +/ grafts of half-nodesdiffering in age by two plastochrones, a higher proportion yieldedtwo shoots, suggesting that the age differential had some importance.This view is supported by observations on sectioned material.Grafts having two + or two buds (+/+ grafts) were madebetween half-nodes differing in age by two plastochrones; inthe majority both buds grew out. Thus a + bud inhibits a bud but usually not another + bud; in either case a considerabledifference in stage of development of the half-nodes may affectthe results. It is concluded that bud dominance resembles apicaldominance, and is probably mediated by hormonal means. 相似文献
32.
Apoptosis was measured in mammary glands during whole organ culture, to determine whether regression resulting from hormone withdrawal results in epithelial cell death as in vivo involution. Glands were evaluated for morphology and DNA degradation prior to whole organ culture, after lobulo-alveolar development and 2, 4, or 6 days after hormone withdrawal. The data indicated that mammary regression during whole organ culture mimics in vivo involution and results in part from apoptosis of epithelial tissue. 相似文献
33.
MENG‐HSUEN CHIU I‐HSUAN CHEN DAVID C. BAULCOMBE CHING‐HSIU TSAI 《Molecular Plant Pathology》2010,11(5):641-649
Previous evidence has indicated that the P25 protein encoded by Potato virus X (PVX) inhibits either the assembly or function of the effector complexes in the RNA silencing‐based antiviral defence system (Bayne et al., Cell‐to‐cell movement of Potato Potexvirus X is dependent on suppression of RNA silencing. Plant J. 44 , 471–482). This finding prompted us to investigate the possibility that P25 targets the Argonaute (AGO) effector nuclease of RNA silencing. Co‐immunoprecipitation and Western blot analysis indicated that there is a strong interaction between P25 and AGO1 of Arabidopsis when these proteins are transiently co‐expressed in Nicotiana benthamiana. P25 also interacts with AGO1, AGO2, AGO3 and AGO4, but not with AGO5 and AGO9. As an effective suppressor, the amount of AGO1 accumulated in the presence of P25 was dramatically lower than that infiltrated with HcPro, but was restored when treated with a proteasome inhibitor MG132. These findings are consistent with the idea that RNA silencing is an antiviral defence mechanism and that the counter‐defence role of P25 is through the degradation of AGO proteins via the proteasome pathway. Further support for this idea is provided by the observation that plants treated with MG132 are less susceptible to PVX and its relative Bamboo mosaic virus. 相似文献
34.
印楝素对亚洲玉米螟幼虫生长发育的影响 总被引:18,自引:1,他引:18
本文报道印楝素对亚洲玉米螟Ostrinia furnacalis Guene幼虫生长发育的抑制作用和引起幼虫各器官的病变症状。用含20ppm印楝素的人工饲料饲喂亚洲玉米螟3—4龄幼虫2天,然后换入正常饲料,可使幼虫期显著延长,最后不能化蛹而死亡。印楝素对幼虫的作用是缓慢的,虫体受药后还可发育一个龄期。处理幼虫的行为失常,取食动作逐渐消失,主要靠消耗体内的水分和脂肪来维持生命。幼虫的胸足变黑,胸部出现褐色斑,这些部位的表皮分层不正常,真皮细胞坏死或自溶。处理幼虫的大脑萎缩,生殖器官和前胸腺肿大,前胸腺细胞膜厚而松散,血淋巴中β-蜕皮酮含量显著降低。从整个中毒症状来看,印楝素可能作用于亚洲玉米螟幼虫的神经和内分泌系统,从而逐渐引起各器官的病变。 相似文献
35.
An automatic bandwidth selector for kernel density estimation 总被引:4,自引:0,他引:4
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黄杜鹃提取物对亚洲玉米螟生物活性的研究 总被引:4,自引:0,他引:4
本文报道了闹羊花素 - ( Rhodojaponin- ,简称 R- )和黄杜鹃花乙酸乙酯 ( Et OAc)提取物对亚洲玉米螟 Ostrenia furnacalis Guenée3龄幼虫的拒食、生长抑制和毒杀作用。以饲料柱法测定 R- 和 Et OAc提取物的非选择性拒食作用 AFC50 为 77.0 2和 384 .30 mg/ kg,而以虫重法表示时 ,则分别为15.60和 2 55.4 4 mg/ kg。以 R- 2 0 0 mg/ kg连续饲喂 4天后 ,换为无毒饲料至 15天 ,试虫死亡率为86.67% ,L T50 为 2 .99天 ;以 Et OAc提取物 2 0 0 0 mg/ kg处理时 ,同期的死亡率 66.67% ,LT50 为 3.85天。R- 和 Et OAc提取物的生长抑制中浓度 IC50 分别为 9.30和 39.64mg/ kg。文中还讨论了亚洲玉米螟拒食作用的测定方法和 R- “取食后效应”等作用特点 相似文献
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40.
心房钠尿因子对豚鼠窦房结自律性的影响 总被引:2,自引:0,他引:2
用微电极技术研究表明,分别灌流心房钠尿因子(ANF)0.025和0.05μmol/L 7min 后,豚鼠窦房结细胞的自发节律无明显变化,而用0.1μmol/L 灌流时,其自发节律明显降低7%(P<0.01)。但当上述三种浓度 ANF 和异丙肾上腺素混合液灌流时,自发节律分别降低4,12和22%。这些结果表明,ANF 能抑制异丙肾上腺素的阳性变时效应。其机理可能与 ANF 阻滞窦房结细胞的 T 型钙通道电流有关。 相似文献