【摘要】 本实验是应用同位素~3H-胸腺嘧啶核苷显微放射自显影技术观察烟草(Nicotiasa tabacumL.)未受粉子房在离体培养初期 DNA 合成的动态,其结果表明:1.幼小子房的胚珠发育主要是来自胎座上外三层细胞,而且在子房上表现出明显的上部生长优势;2.8—12小时以后可观察到胚珠中央的一个细胞活跃地进行 DNA 复制,进而分化为大孢子母细胞,接着形成两个大孢子,四个大孢子,而且它们的 DNA 合成是同步的;3.形成八核胚囊以后,八核之间的 DNA合成速率表现出明显的差异,只有其中一个核具有~3H-胸腺嘧啶核苷的掺入,其它未标记的核逐渐趋于解体和消失;4.在成熟胚囊中仅存卵细胞继续发育并进行旺盛的 DNA 合成,说明未受精的卵细胞处于启动状态,5.观察到未受精的极核亦可进行 DNA 合成和进一步分裂。讨论了未授粉子房在离体培养条件下,单培体植株的起源与子房内各组分 DNA 合成动态之间的关系。更多还原

【Abstract】 DAN synthesis at the initial stage of unpollinated ovary culture was studied with ~3H-thymidine and micro-autoradiography.The results are given as follows: 1.Ovular development of young ovary was mainly derived from the three outer-layer cells on the placenta,and preponderant growth obviously was ob- served on the upper cell of young ovary. 2.After 8-12 hr,a central cell of ovule was actively proceeding on DNA synthesis,and the cell differentiated further into megasporocyte,followed by formation of binucleate and tetranucleate macrospore.Their DNA synthesis were synchronous. 3.After the formation of 8-nucleate emberyo sac their ability of DNA synthesis was strikingly different.It was found that only one nucleate was incorperated with ~3H-thymidine,while other nuclei were not labelled and would gradually collapse. 4.In the mature emberyo sac only an egg cell was actively carrying on DNA synthesis.It suggests that unfertilized egg was in promoter stage. 5.DNA synthesis of unfertilized polar nuclei leading to division were found in culture ovaries. The relation between the origin of unpollinated ovary haploid plants in culture condition and DNA synthesis of various components in the ovary was also discussed.更多还原