台灣蘆竹接合子之微細構造

Ultrastructure of The Zygote in Arundo formosana Hack

台灣蘆竹（Arundo formosana Hack.）之卵與接合子於胞器分佈之極性上有所不同。本篇報告主要是利用光學與電子顯微鏡觀察台灣蘆竹接合子之細胞質內含物之變化與移動。接合子內兩性細胞核融合完成時間較初生胚乳細胞早。細胞核融合初完成時，接合子之細胞核位於細胞中央位置，而大部分細胞質胞器則集聚於細胞核的一側。新胞器於近珠孔端大量形成，其中增加最多者為粒線體，內質網與核醣體。隨著發育，胞器分佈之極性開始變化，先是細胞質胞器而後是細胞核移向近合點端。於胚乳細胞進入自由核分裂期時，接合子與胚乳細胞交接處有細胞壁物質的堆積。細胞壁之形成是從珠孔端以片斷方式往合點端延伸，而於接合子分裂前，細胞壁完全形成。接合子第一次分裂為橫向，產生一較大之基部細胞和一較小之頂端細胞。液胞多分佈於基部細胞之珠孔端，而頂端細胞則少有液胞。基部細胞有較多之高爾基氏體與油滴，而頂端細胞則有有較濃之細胞質。細胞質內富含胞器，胞器分佈均勻。細胞質連絡絲只存在於頂端細胞與基部細胞之間，而此兩細胞與胚囊之間則無。

The polarity in the zygote of Arundo formosana Hack. differs from that in the egg. This report mainly describes the changes and shift of the cytoplasmic contents in the zygote of Arundo formosana Hack. as observed by both light and electron microscopies. The nuclear fusion in zygote occurs earlier than that in the primary endosperm. The nucleus of the zygote is centrally located and the majority of cytoplasmic organelles become aggregated on one side of the nucleus at the end of nuclear fusion. The new cytoplasmic organelles are formed in great qunatities at the micropylar half of the zygote. Mitochondria, endoplasmic reticulum and ribosomes increase more rapidly than other organelles. As the development takes place, most organelles as well as the nucleus move towards the chalazal pole resulting in the change of polarity in zygote. When the endosperm undergoes nuclear division, electron dense wall materials deposite between the zygote and young endosperm. Wall formation progresses from the micropylar pole to the chalazal pole discontinously. The wall formation completes before the first division of the zygote. The first division in zygote is transverse forming a large basal cell and a small terminal cell. Vacuoles are distributed at the micropylar half of the basal cell and seldom present in the terminal cell. The basal cell contains more dictyosomes and oil drops, whereas the terminal cell contains denser cytoplasm. The cytoplasm of the two-celled proembryo is rich in organelles which are uniformly distributed. Plasmodesmata are found between two cells of proembryo, but not in the walls associated with the two-celled proembryo and developing endosperm.