Brzezicka Emilia, Kozieradzka-Kiszkurno Małgorzata
Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdańsk, 59 Wita Stwosza St., 80-308, Gdańsk, Poland.
Protoplasma. 2019 Mar;256(2):537-553. doi: 10.1007/s00709-018-1319-9. Epub 2018 Oct 15.
Available documentation about the development of the female gametophyte of Crassulaceae is very limited. The aim of this study was to extend the embryological knowledge of Crassulaceae by analysing the development of the embryo sac in Sedum sediforme. Transmission electron microscopy and light microscopy including Nomarski optics (DIC) were used to observe individual stages of female gametophyte development. Cytochemical staining enabled detection of lipids, insoluble polysaccharides and proteins in gametophyte cells during their formation. Their increased accumulation was observed during nucellar cell and unfunctional cell degeneration in the embryo sac at the coenocytic and cellular stages (megagametogenesis). The female gametophyte develops in anatropous, bitegmic and crassinucellate ovules. The mature embryo sac is built of seven cells but after antipodes degeneration it is formed by the egg apparatus and a central cell. The monosporic Polygonum type was observed. One megaspore mother cell (MMC) formed three cells after meiosis. A triad was formed from a functional megaspore (placed chalazally), one uninucleate megaspore and a binucleate cell located at the micropylar end. Plasmodesmata with adhering electron-dense dome were noticed in walls of the coenocytic embryo sac and in the outer walls of ephemeral antipodes. Moreover, similar to synergids, antipodes form wall ingrowths. Here, we report new structural features of the antipodal cells (the presence of plasmodesmata with an electron-dense dome) which have not been described before. This new structural observation indicates that these cells participate in substance transport and that this process can probably be additionally regulated.
关于景天科植物雌配子体发育的现有文献非常有限。本研究的目的是通过分析垂盆草胚囊的发育来扩展景天科植物的胚胎学知识。使用透射电子显微镜和包括诺马斯基光学（微分干涉差）的光学显微镜来观察雌配子体发育的各个阶段。细胞化学染色能够在配子体细胞形成过程中检测脂质、不溶性多糖和蛋白质。在合胞体和细胞阶段（大孢子发生）胚囊中珠心细胞和无功能细胞退化期间，观察到它们的积累增加。雌配子体在倒生、具双珠被和厚珠心的胚珠中发育。成熟胚囊由七个细胞组成，但反足细胞退化后由卵器和一个中央细胞组成。观察到单孢子蓼型。一个大孢子母细胞（MMC）减数分裂后形成三个细胞。由一个功能大孢子（位于合点端）、一个单核大孢子和一个位于珠孔端的双核细胞形成一个三分体。在合胞体胚囊壁和短暂反足细胞的外壁中发现了带有附着电子致密穹顶的胞间连丝。此外，与助细胞类似，反足细胞形成壁内突。在这里，我们报告了反足细胞的新结构特征（带有电子致密穹顶的胞间连丝的存在），这是以前没有描述过 的。这一新的结构观察表明这些细胞参与物质运输，并且这个过程可能可以被额外调节。
