匍枝根黴生殖過程之超微研究

Abstract

本研究係以光學顯微鏡及掃描式、穿透式電子顯微鏡觀察匍枝根黴Rhizopus stolonifer(Ehrenb.：Fr.) Vuill.的有性生殖構造--接合孢子及無性生殖構造--孢子囊孢子的發育過程，並注意到孢子成熟後中軸的變化。 接合孢子的發育是由接合孢子梗互相接近開始，其頂端相接觸後，形成接合壁。接著接合孢子梗膨大而成棍棒狀的原配子囊，再由原配子囊壁向內形成配子囊壁，而將原配子囊分隔成配子囊及配子囊柄。壁上有很多胞間連絲，連通兩邊。配子囊內有大的液胞。配子囊壁完成後，接合壁開始由中央部分向外分解。在接合孢子囊初形成時，在配子囊壁的兩側見有密集的網狀內質網，伴隨著許多油滴的顆粒出現，這些油滴並向中央移動，均勻分佈至整個接合孢子囊，而液胞則逐漸縮小。 接合孢子囊壁的增厚，除了原來的原配子囊壁--初生壁外，並有次生壁與三次壁的增厚。其中次生壁包含接合孢子囊表面凸出的疣狀突起。而初生壁後來被膨大的接合孢子囊撐破。三次壁則形成於次生壁的內側。三次壁及接合孢子壁初形成時，表面均為平坦狀。但當接合孢子成熟時，接合孢子壁及三次壁表面均有突起向外陷入疣狀突起中。接合孢子壁厚，此壁在電子顯微鏡下有分層的現象，最多可分二十幾層。成熟的接合孢子內部充滿油滴，粒線體不活躍，液胞幾乎沒有，處於脫水休眠的狀態下。 孢子囊孢子的形成始於分裂前中期出現的分裂囊胞。由於分裂囊胞膨大、向四周延伸，而構成了分裂裝置，並由於其間的互相接合，而把細胞質和內部的胞器分割成獨立的細胞。此時除了原有分裂裝置膜外，內側又出現一層襯層。幼孢子的原生質膜包括分裂裝置膜及孢子囊原生質膜。隨後孢子壁開始增厚，並由於色素的堆積轉成黑色。成熟的孢子壁厚，分三層。表面有脊狀突起，內貯藏很多油滴。 中軸的發育與孢子的分割同步，也由分裂裝置的接合而在分裂後期，將孢子囊中央部份分隔出一個拱形的中軸。也以分裂裝置膜為中軸的原生質膜。完成的中軸，呈卵形、有纖維狀的壁，項端部分較厚，而下方漸變薄。並隨之在內側產生次生壁。中軸在初分隔時，內部即已充滿液胞，但靠近中軸壁處有很多核與其他胞器，接著開始有液胞出現，並有液胞的吞噬作用和胞器的分解作用出現，其中有酸性磷酸?的活性發現。當分解作用進行至末期，中軸內部幾乎全空。 文中比較匍枝根黴生殖構造發育過程與其他毛徽目真菌之異同，並討論中軸內部變化與其塌陷情形之關係。

The sexual and asexual processes in Rhizopus stolonifer (Ehrenb.:Fr.) Vuill. were studied by light, transmission and scanning electron microscopy. Zygosporangium formation was initiated by copulation of two compatible zygophores. Setting down of a gametangial septum delimited the carrot shaped progarnetangium into a gametangium and a suspensor. plasrnodesmata were distributed throughout the gametangial septum. Dense endoplasmic reticula were found along the gametangium septum. Oil droplets were formed within this area then dispersed into zygosporangiuxn. Developing zygosporangia contained several large vacuoles but this feature was not discernible in mature zygosporangia. Electronopaque fluted warts developed within the secondary zygosporangial wall followed by tertiary zygosporangial wall formation. A mature zygospore contained organelles as in earlier stages but was distinguished by the presence of large quantity of oil droplets and a multi-layered zygospore wall. A fully formed sporangiuin was bounded by an amor-phous sporangial wall. In sporangium at mid-pre-cleavage stage, various shaped cleavage vesicles were found throughout the sporangium except in the central region. Later, enlargement and mutual fusion of cleavage vesicles occurred to form a cleavage apparatus. Protoplast cleavage was effected by the mutual fusion of cleavage vesicle membranes and fusion of cleavage vesicle membrane with the plasmalemma. The columella zone was delimited by cleavage vesicle in late-cleavage stage and separated from the sporogenous zone by a fibrillar wall. Later a electron-opaque secondary wall was formed. Acid phosphatase activity was found in degenerated columella. Recently delimited spore protoplast was bounded by a plasmalemma which was derived from cleavage apparatus membranes and sporangial plasmalemma. This plasmalemma was surrounded by an outer layer derived from lining layers of cleavage apparatus. The spore wall was formed between the outer layer and the plasmalemma. Mature thick spore wall was three-layered. Information obtained in this study was compared mainly with other taxa of Mucorales.