The orchid reproductive strategy, including the formation of numerous tiny seeds, is achieved by the elimination of some stages in the early plant embryogenesis. In this study, we documented in detail the formation of the maternal tissues (the nucellus and integuments), the structures of female gametophyte (megaspores, chalazal nuclei, synergids, polar nuclei), and embryonic structures in Dendrobium nobile. The ovary is unilocular, and the ovule primordia are formed in the placenta before the pollination. The ovule is medionucellate: the two-cell postament and two rows of nucellar cells persist until the death of the inner integument. A monosporic eight-nucleated embryo sac is developed. After the fertilization, the most common central cell nucleus consisted of two joined but not fused polar nuclei. The embryogenesis of D. nobile is similar to the Caryophyllad-type, and it is characterized by the formation of all embryo cells from the apical cell (ca) of a two-celled proembryo. The only exception is that there is no formation of the radicle and/or cotyledons. The basal cell (cb) does not divide during the embryogenesis, gradually transforming into the uninuclear suspensor. Then the suspensor goes through three main stages: it starts with an unbranched cell within the embryo sac, followed by a branched stage growing into the integuments, and it ends with the cell death. The stage-specific development of the female gametophyte and embryo of D. nobile is discussed.

中文翻译：

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Dendrobium nobile (Orchidaceae) 的大孢子发生、大配子发生和胚胎发生

兰花繁殖策略，包括形成许多微小的种子，是通过消除早期植物胚胎发生的某些阶段来实现的。在这项研究中，我们详细记录了母体组织（珠心和珠被）的形成、雌性配子体的结构（大孢子、合点核、增子、极核）和石斛的胚胎结构。子房是单房的，在授粉前在胎盘中形成胚珠原基。胚珠是中核的：两细胞后和两排珠心细胞持续存在，直到内珠被死亡。单孢八核胚囊发育。受精后，最常见的中央细胞核由两个相连但未融合的极核组成。D.胚胎发育 nobile 与 Caryophyllad 型相似，其特征是所有胚胎细胞均由双细胞原胚的顶端细胞 (ca) 形成。唯一的例外是没有形成胚根和/或子叶。基底细胞（cb）在胚胎发生过程中不分裂，逐渐转变为单核悬浮体。然后悬吊经历三个主要阶段：它从胚囊内的未分枝细胞开始，然后是长入珠被的分枝阶段，最后是细胞死亡。讨论了 D. nobile 雌配子体和胚胎的阶段特异性发育。唯一的例外是没有形成胚根和/或子叶。基底细胞（cb）在胚胎发生过程中不分裂，逐渐转变为单核悬浮体。然后悬吊经历三个主要阶段：它从胚囊内的未分枝细胞开始，然后是长入珠被的分枝阶段，最后是细胞死亡。讨论了 D. nobile 雌配子体和胚胎的阶段特异性发育。唯一的例外是没有形成胚根和/或子叶。基底细胞（cb）在胚胎发生过程中不分裂，逐渐转变为单核悬浮体。然后悬吊经历三个主要阶段：它从胚囊内的未分枝细胞开始，然后是长入珠被的分枝阶段，最后是细胞死亡。讨论了 D. nobile 雌配子体和胚胎的阶段特异性发育。