首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   182篇
  免费   9篇
  国内免费   1篇
  2022年   3篇
  2021年   1篇
  2020年   3篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   5篇
  2015年   2篇
  2014年   3篇
  2013年   5篇
  2012年   6篇
  2011年   3篇
  2010年   8篇
  2009年   5篇
  2008年   6篇
  2007年   4篇
  2006年   6篇
  2005年   24篇
  2004年   9篇
  2003年   6篇
  2002年   3篇
  2001年   3篇
  2000年   6篇
  1999年   7篇
  1998年   6篇
  1997年   8篇
  1996年   6篇
  1995年   12篇
  1994年   6篇
  1993年   5篇
  1992年   5篇
  1991年   6篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1985年   5篇
  1984年   1篇
  1977年   1篇
排序方式: 共有192条查询结果,搜索用时 15 毫秒
1.
Barley transformation mediated by Agrobacterium tumefaciens is routinely performed in a number of laboratories. However, elimination of selectable marker genes and formation of plants homozygous for the transgene via conventional segregation is laborious and time-consuming. Here we suggest a concept that includes the production of primary transgenic plants via infection of immature embryos with A. tumefaciens followed by androgenetic generation of a segregating population of entirely homozygous plants. Selectable marker-free, truebreeding plants carrying a single-opy transgene integrant may thus be efficiently and rapidly obtained. However, amenability to Agrobacterium-mediated transformation as well as androgenetic potential is genotype-dependent. Efficient genetic transformation by infection of immature embryos is so far confined to the spring type cultivar ‘Golden Promise’ which, however, turned out to be recalcitrant in pollen embryogenesis. To facilitate androgenetic generation of homozygous segregants from primary transformants, we have established a method for embryogenic pollen culture in cv. Golden Promise that includes conventional cold-treatment and subsequent preculture of immature pollen under starvation conditions prior to transfer to complete nutrient medium. Further we show that conditioning of the pollen culture medium by co-culture of immature wheat pistils as well as addition of pistil-preconditioned medium considerably support androgenetic development. Employment of the established method using immature pollen of primary transgenic plants demonstrates that selectable marker-free, true-breeding transgenic progeny can be rapidly obtained pursuing the concept proposed. The protocol presented will be useful in functional genomics as well as in molecular breeding approaches.  相似文献   
2.
研究了秋水仙碱不同浓度和处理时间对甘蓝型油菜23个基因型离体小孢子胚胎发生的影响.3个基因型的小孢子被10、50和100mg/L秋水仙碱处理24h或48h,胚产量是2.55~14.75胚/蕾,10~50mg/L处理72h则是0.94~2.43胚/蕾.这表明处理72h对小孢子胚发生有抑制作用.用200、400、500和800mg/L处理2个基因型小孢子16~48h,胚产量为0.6~1.33胚/蕾,未处理对照是6.25和9.36胚/蕾.可见200~800mg/L浓度对胚再生有不同程度的阻碍效应.结果还证明,小孢子对秋水仙碱的反应与其基因型有关.当用10、20、50和100mg/L处理48h时,22B5-6和903-3小孢子的胚产量为37.09~69.47胚/蕾,而F1-29、W592和SF10-12是0.28~1.45胚/蕾,相互之间差异很大.秋水仙碱处理小孢子的目的是使其再生植株的染色体高频率加倍,因此应根据胚产量和染色体加倍率来确定秋水仙碱浓度和处理时间.本试验中,采用10~50mg/L处理48h或者用100mg/L处理24h,约80%基因型的小孢子胚产量在5胚/蕾以上,约70%基因型的再生植株加倍率达60%以上,可有效地用于油菜遗传和育种研究等领域.  相似文献   
3.
中国水仙的核型分析和小孢子发生中的细胞学研究   总被引:6,自引:0,他引:6  
中国水仙(Narcissustazettavar.chinensis)只开花不结实,以鳞茎营养繁殖。对中国水仙的染色体倍性有不同的报道。对中国水仙的核型分析,支持它是三倍体的观点,但其核型也显示出了异源三倍体的倾向。在小孢子母细胞减数分裂过程中,染色体的异常行为多表现为:中期出现单个染色体游离在纺锤体外面、在后期出现的染色体桥和落后染色体、在末期出现的单个染色体游离在细胞核外形成微核的现象。这些异常现象引起小孢子的败育,也支持中国水仙为三倍体植物的观点。  相似文献   
4.
Identification of potentially embryogenic microspores in Brassica napus   总被引:1,自引:0,他引:1  
Studies were undertaken with Brassica napus L. cv. Topas to identify buds containing microspores predisposed to embryogenesis in vitro and to investigate bud and microspore development in relation to this process. No significant correlation was found between the final embryo number and bud components. There appears to be a developmental window of less than 8 h duration during which microspores are very likely to form embryos: over 70% of the microspores can undergo division and up to 70% of these can form embryos. Embryos were mainly obtained from late uninuucleate to early binucleate microspores: the former contained mainly a G2 or M phase nucleus located at the microspore periphery and the latter a generative nucleus (associated with the intine) and a vegetative nucleus. Observations indicated that only the vegetative nucleus contributed to embryo formation. The first embryogenic division occurred between 8 and 16 h for uninucleate- and between 8 and 48 h for binucleate-derived embryos.  相似文献   
5.
Significant improvements were achieved in the production of haploid and doubled haploid plants from isolated microspore culture of wheat c.v. Chris on a defined media. Procedures found to be of benefit included: A 7-day pretreatment of anthers in 0.4M mannitol plus the macronutrients from FHG medium; the inclusion of 4.5 mg/liter abscisic acid in the pretreatment solution; the isolation of microspores from pretreated anthers by vortexing; and the use of phenylacetic acid (PAA) as the auxin source in MS medium. The best response was achieved with 4.0 mg/liter PAA in MS medium containing 90 g/liter maltose as the sugar source. Under these conditions, 68% of viable microspores underwent division, and an average of 93 embryos and 92 green plants were regenerated per 100 anthers used. The root-tip chromosome number and the fertility of 114 regenerating green plants revealed that 75% were completely fertile spontaneously doubled haploids.  相似文献   
6.
7.
Pretreatment of anthers in mannitol prior to isolation of microspores by glass rod homogenization was effective for in vitro induction of embryogenesis in barley cv. Igri. A procedure for separation of viable microspores using centrifugation on 20% maltose was developed. The concentration of microspores was important and greatly increased the number of developing structures. Initial culture of microspores on FHG medium containing 62 g l-1 maltose, 4.4 M (1 mg l-1) BA and 200 g l-1 Ficoll-400 resulted in high frequencies of plant regeneration. Albino plant frequency was correlated to length of time in culture. Stock plant condition appeared to be a major factor influencing induction frequency. From 868 to 1738 green plants per 100 anthers were produced. The number of calli and embryos obtained and the number of green plantlets regenerated were improved by increasing the Ficoll concentration from 100 g l-1 to 400 g l-1 during the culture period compared to continuous culture on FHG Ficoll 200 g l-1.Abbreviations BA benzyladenine  相似文献   
8.
9.
不同萝卜品种游离小孢子的诱导及培养体系优化研究   总被引:1,自引:0,他引:1  
以19个萝卜品种为试验材料,研究各种因素对萝卜游离小孢子培养的影响.结果表明:(1)13个品种可诱导出胚状体,诱导率达到68.4%,但不同品种间产胚量存在较大差异,其中路路通翠雪产胚量可达每蕾10个,而圆白萝卜的产胚量最小为每蕾0.125个,进一步培养有8个品种得到再生植株;(2)在NLN-13液体培养基中添加活性炭和6-BA对萝卜游离小孢子出胚有较好的促进作用,小孢子分离30d后将胚状体转移至固体MS培养基上,子叶型胚可获得大量的再生植株,而畸形胚状体转移后不能获得正常的再生植株.  相似文献   
10.
In this paper we describe the isolation and characterization of a genomic clone (Bp4) from Brassica napus which contains three members of a pollen-specific multigene family. This family is composed of 10 to 15 closely related genes which are expressed in early stages of microspore development. The complete nucleotide sequence of the clone Bp4 and of three homologous cDNA clones is reported. One of the genes (Bp4B) contained in the genomic clone is believed to be non-functional because of sequence rearrangements in its 5 region and intron splicing sites. The remaining genes (Bp4A and Bp4C), as well as the cDNA clones, appear to code for small proteins of unique structure. Three different types of proteins can be predicted as a result of the deletion of carboxy or amino terminal portions of a conserved core protein. These proteins all share a common alternation of hydrophobic and hydrophilic domains. A fragment of the genomic clone containing the gene Bp4A, as well as the non-functional gene Bp4B, was introduced into tobacco plants via Agrobacterium-mediated transformation. The functional gene Bp4A is expressed in transgenic tobacco plants and shows spatial and temporal regulation consistent with the expression patterns seen in Brassica napus.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号