台灣產薯蕷屬植物之分類研究

Abstract

薯蕷屬(Dioscorea L.)植物約有六百種，主要分佈在熱帶及亞熱帶地區。本屬植物多具有經濟上的用途，其根莖或塊莖可供作食用及藥用。依本研究的處理，台灣產的薯蕷屬植物有十六個分類群，分佈自海拔0公尺至2000公尺。本研究觀察薯蕷屬植物之外部形態，並以掃描式電子顯微鏡觀察其葉表面及花部構造。觀察葉表面的氣孔(stomata)、毛狀體(trichomes)、蠟質(wax)之堆積方式，其中蠟質的堆積方式，不同種類間差異大，為一良好的分類特徵。本屬植物的氣孔型皆為不定型(anomocytic)，各種之間無明顯的特徵以資區分。毛狀體有數種不同形態：丁字形毛(biramous hair)，如刺薯蕷(D. esculenta (Lour.) Burkill var. spinosa R. Knuth)；長軟毛(villose)，如白薯榔(D. hispida Dennst.)、掌葉薯(D. codonopsidifolia Kamikoti)、蘭嶼田薯(D. cumingii Prain & Burkill)等；刺(spines)，如刺薯蕷、裡白葉薯榔(D. matsudae Hayata)，及普遍存於大多數種類葉表的多細胞毛狀體。本屬植物為雌雄異株，同一分類群間之雌雄花的差異主要在其雄花器及雌花器的發育程度不同；不同分類群間，花部的主要差異在其花被片的大小、形狀，及柱頭的特徵是否顯著。就已觀察種類的花粉來看，台灣產的薯蕷屬植物之花粉形態為二溝孔粒，細孔紋，這和美洲產的本屬植物為多屬單溝孔粒之特徵不同。

Plants of Yams, belonging to the genus Dioscorea L. in the family Dioscoreaceae, consist of more than 600 species, especially in the tropical and subtropical regions. In Taiwan, they distribute from sea level throughout 2000 m in elevation. Most of the members in this genus are economically important either for the edible tubers as crops or medicinal usage. In this study, based on the following method, fourteen species and three varieties are recognized. Besides the morphological observation, I have studied the stomatal complex, trichomes and the wax layers of leaves, as well as the floral parts intensively. Stomata are found randomly arranged only on the lower surface of the leaves. The pattern formed by guard cells and neighboring cells are anomocytic in Dioscorea. There are several types of trichomes: biramous hair and spines of D. esculenta (Lour.) Burkill var. spinosa R. Knuth; villose hairs of D. hispida Dennst. and D. codonopsidifolia Kamikoti, D. cumingii Prain & Burkill; and the multicellular trichomes in most of the species. The Dioscorea plants are dioecious. The sex determination in male and female flowers is due to the different development types in the stamens (staminodes) and pistils. When the staminal growth is inhibited in the early stage of floral development, the plants bear pistillate flowers, and stigmas will outgrow to trifid structures. On the contrary, when the pistils are depressed to be rudimentary and obscure morphologically, the plants bear staminate flowers. The pollens are bisulcate, with finely perforate exine in the species examined.