摘要
在含有２ｍｇ／ＬＩＡＡ和３ｍｇ／ＬＢＡＰ的改良Ｎ６培养基上，香雪兰（ＦｒｅｓｉａｒｅｆｒａｃｔａＫｌａｔ）花序外植体经直接体细胞胚胎发生途径再生出新的植株。在这一形态发生过程中，一个引人注意的现象是，所有的体细胞胚都出现在花序轴切段的原形态学下端（称为胚发生端，ＥＥ），而在形态学上端（称为非胚胎发生端，ＮＥＥ）无体细胞胚形成。这一形态发生的极性与地心引力的方向和外植体在培养基上的放置位置无关。在培养的早期，仅于胚发生端观察到了起始细胞的分裂。ＳＤＳ聚丙烯酰胺凝胶电泳结果表明，在培养了１ｄ的外植体的胚发生端出现了两个特殊的多肽成分，而在非胚发生端则未检测到这两种多肽。高效液相色谱分析表明，培养前外植体切段两端的内源激素（ＩＡＡ）的含量无显著差别。但经过一段时间的培养，胚发生端的ＩＡＡ含量明显高于非胚发生端的ＩＡＡ含量，表明内源激素在体细胞胚胎发生的诱导过程中起着关键的作用。在香雪兰体细胞胚胎发生诱导的过程中，由于花序轴切段两端在分子水平和生理水平上均存在差异，使这一系统有可能成为研究体细胞胚胎发生机理的有用实验材料。
Inflorescence explants of Freesia refracta Klatt placed on modified N6 medium supplemented with 2 mg/L indole3acetic acid (IAA) and 3 mg/L 6benzyl aminopurine (BAP) might undergo direct somatic embryogenesis leading to plant regeneration. A noticeable phenomenon observed in this morphogenetic process was that all the somatic embryos appeared exclusively at the original morphological lower end of the segments cut from the inflorescence axes (termed the embryogenic end,EE),while no embryos were formed at the morphological upper end (termed the nonembryogenic end,NEE),irrespective of the gravity of earth and the position of the explants placed on the medium. Divisions of embryogenic initial cells were observed solely at the EEs of the segments in the early stages of culture.Sodium dodecyl sulphatepolyacrylamide gel electrophoresis showed that two polypeptides appeared specifically at the EEs of the explanted segments after one day in culture,but they were undetectable at the NEEs. Four polypeptides detectable at both ends of the explants at day 1 of culture disappeared from the NEEs at late stages of culture.There was no significant difference in the distribution of the endogenous IAA before culture between the two ends of the segments as measured by highperformance liquid chromatography. However,the level of IAA was remarkably higher at the EE than at the NEE after a certain period of culture. This result showed that the endogenous hormone might play a key role in the process of somatic embryogenesis. The differences in molecular composition and physiological status between the two morphological ends of the explant in relation to the induction of the somatic embryogenesis in F.refracta may be considered as a useful marker in studying the mechanisms of this in vitro morphogenesis.
关键词
香雪兰
体细胞
胚胎发生
外植体极性
Freesia refracta, Somatic embryogenesis, Polarity of explant
