臺灣紅豆樹之胚胎學

Abstract

臺灣紅豆樹 (Ormosia formosana kanehira) 為臺灣之特有種，主要分布於臺灣的中部海拔300-1,000 m的常綠林，屬豆科，蝶形花亞科。常綠性喬木，兩性花，花萼具五枚裂片，花瓣五枚，由一枚旗瓣、兩枚翼瓣及兩枚龍骨瓣組成；雄蕊十枚，雌蕊單一。花期從三月初至五月中旬，莢果成熟於九至十月。 三月初，雄蕊原體形成。三月中旬至下旬，花藥壁層之構成，含表皮層、一層內壁層、二層中間層和一至二層營養層，發育類型屬基本型。營養層細胞為單核，極少數為二核，屬腺質性型。四月中旬至下旬，小孢子母細胞行減數分裂後，細胞質同時地分裂，產生四面體形及偶有十字形的小孢子四分體。五月上旬，成熟的花粉粒具二細胞，球形，徑幅約29-32 μm。五月中旬至下旬花藥縱向開裂，花粉粒散發。 雌蕊內具四至七枚胚珠，邊緣胎座。胚珠彎生，具雙珠被，厚珠心型。三月上旬至中旬，胚珠原體形成。四月中旬至下旬，大孢子母細胞行減數分裂，形成線形及T字形的大孢子四分體。胚囊發育類型為蓼型。兩極核於受精前融合，三只反足細胞於受精之前就已慢慢退化。胚乳發育形式為核型，於球形胚時期，發育為胚乳細胞；胚發育為柳葉菜型。

Ormosia formosana kanehira is an evergreen, endemic species to Taiwan, belongs to the Leguminosae, Papilionoideae. It is mainly distributed in the evergreen forests at the altitude of 300-1,000 m high over the central part of the island. Hermaphrodite flowers have 5-lobed calyx, 5 petals (consisting of one standard, two wings and two keels), 10 stamens (two whorls) and 1 pistil. The flowers are produced from the beginning of March to mid May, and the pods are mature from September to October. The stamen primordia are formed at the beginning of March. From mid to late March, the anther wall layers are composed of an epidermis, an endothecium, two middle layers and a tapetum. The development of anther wall layer belongs to Basic type. The tapetum is glandular type of characteristics and its cells are uninucleate but few of them are binucleate. The microspore mother cells undergo meiosis through simultaneous cytokinesis and give rise to tetrahedral or occasionally decussate-arranged tetrads of microspores. Mature pollen grains are 2-celled, globose and 29-32 μm in diameter. Anthers are longitudinally dehiscent and pollen grains shed by mid to late May. The pistil contains 4 to 7 ovules on a marginal placentation. Ovules are campylotropous, bitegmic and crassinucellate. The ovule primordia are formed in early to mid March. Megaspore mother cells give rise to linear or T-shaped tetrad of megaspores after meiosis. The embryo sac development is of Polygonum type. Two polar nuclei fuse before fertilization. Three antipodal cells are degenerated gradually before fertilization. Endosperm development is of Nuclear type. Endosperm nuclei begins to become cells when the embryo has developed a distinct globular embryo proper with a suspensor. Embryo development follows Onagrad type.