烏藥的胚胎學

Abstract

烏藥(Lindera aggregata Kosterm)分布於中國大陸的中部至南部、越南、菲律賓和台灣，在台灣為稀有種。常綠灌木至小喬木、花單性、雌雄異株，3月開花，漿果於8-9月間成熟，成熟時紅至黑色。 雄花序原體約在8月中旬於葉腋處出現，10月中旬，花藥原體形成。雄蕊為2小孢子囊。花藥壁包含，一層細胞的表皮層、一層細胞的內壁層、兩層細胞的中間層及一層細胞的營養層，此藥壁發育方式可歸類為基本型。營養層性質屬於類變形蟲營養層型。小孢子母細胞約在11月上旬行減數分裂，胞質分裂屬於連續型，產生之小孢子四分體大部分為兩側對稱形，少為四面體形。成熟花粉粒為2細胞，無溝孔之形成，直徑約22-25 μm。3月開花時，雄花花藥瓣裂。 10月中旬，雌花出現心皮原體。10月下旬，胚珠原體形成。胚珠倒生、具雙珠被，厚珠心型。約在11月上旬，成熟胚珠的外珠被約4-5層細胞厚，內珠被約2-3層細胞厚，大孢子母細胞距離珠心頂端表皮約有3-6層細胞，珠心帽約約2-4層細胞厚。 胚乳之發育為核型。約在7月下旬，成熟種子只具有非常微量之胚乳，以及兩枚子葉、胚軸及胚根。

Lindera aggregata Kosterm is distributed in central to south mainland China, Vietnam the Philippines and Taiwan. This species is rare in Taiwan. They are evergreen, dioecious shrubs to small trees. Unisexual flowers are produced in March. Berry fruits are reddish-brown to black at maturity during August to September. Axillary inflorescence primordia occur in mid-August. Anther primordia are formed in staminate flowers by mid-October. The anther is bisporangiate. The anther wall layers consist of the epidermis, the endothecium of one cell-layer, the middle layers of two cells and the tapetum of one-layer. The wall formation of the anther conforms to the basic type. The tapetum is amoeboid type of characteristics. Microspore mother cells undergo meiosis through successive cytokinesis in early November and give rise to tetrads of microspores, which are mostly isobilaterally arranged, and occasionally tetrahedrally. Mature pollen grains are 2-celled, acolpate and non-aperturate, and about 22-25 μm in size. Anther dehisceces with valves in March. Carpel primordia are formed in pistillate flowers in mid-October. Ovule primordia are formed in late October. The ovules are anatropous, bitegmie and crassincellate. In early November, the outer integument in mature embryo is of 4-5 layers of cells in thickness, while the inner integument is composed of 2-3 layers of cells. The developing megaspore mother cell is located at 3-6 layers of cells beneath the epidermis of the nucellus top end. The nucellar cap is of 2-4 cell-layers in thickness. The development of embryo sac is of the polygonum type. Developing endosperm is of the nucellar type. In late July, mature seeds contain very less endosperm and a big embryo with 2 massive cotyledons,the hypocotyl and the radicle.