板栗(Castanea mollissima Bl.)的胚胎学研究 Ⅱ雌配子体的超微结构

Embryological Study on Castanea mollissima Bl.ⅡThe Ultrastructure of the Female Gametophyte

受精前的助细胞是代谢活跃的细胞,具丰富的线粒体、高尔基体和质体,内质网大多为光滑型且库槽膨大,极少淀粉粒;助细胞向合点端的壁是不连续的。卵细胞的壁与助细胞的相似,合点端也是不连续的;卵细胞质中线粒体,高尔基体和内质网均较少,但游离核糖体很丰富。中央细胞除具大量各种细胞器外,质体中还常有小淀粉粒。反足细胞壁在与中央细胞间及各反足细胞间是间断的,并具大量胞间连丝,细胞质中也富含各种细胞器,表明其代谢活动十分活跃;反足细胞中观察到核物质穿壁现象。珠心柱(postment)中部细胞在形态和结构上都与其外部细胞不同,显示了其功能的差异。文中并讨论了助细胞、反足细胞在胚囊营养中的作用以及胚囊营养物质供应的途径。

Before fertilizatio, the metabolically active synergids are rich in mitochondria, dictyosomes plastids and predominantly smooth dilated ER. Few starch grains are observed and the synergid wall at the chalazal end is discontinuous . The egg is rich in free ribosomes but scarce in ER, mitochondria, dictyosomes, and plastids, and .the egg wall ,at the chalazal end is also discontinuous. The central cell is rich in cyto-plastic organelles and small strch grains. Numerous well developed pla-smodesmata between the central cell and antipodals, in which there are plenty of cytoplasmic organelles, indicate an active metabolism. The migration of the nucleus from the antipodals into the central cell suggests that antipodals provide the central cell with nutrition. The central part of the postament is composed of slender elongated cells which differ from those of the outer part suggesting that they play an important role in embryo sac nutrition. Therefore, the conclusion may be drawn that synergids in Castanea mollissima Bl, , play little, or no role in embryo sac nutrition and that available food sources enter the sac at the chalazal end through the postament.