全緣卷柏之葉部構造及葉舌之早期發育

Abstract

本文主要探討全緣卷柏 [Selaqinella delicatula (Desv.) Alston] 之葉片和葉舌的形態與解剖，以及葉舌組織之形成。 全緣卷柏有背、腹兩型營養葉，其枝梢的分生組織為單一細胞。背葉為披針形，腹葉為長橢圓形，二者幾乎全緣，均有葉舌。向軸面與背軸面的表皮細胞型、氣孔的分佈與副細胞的有無，均不相同。由解剖來看，葉肉細胞排列疏鬆，無柵狀組織與海綿組織之分化，葉脈單一，葉脈與葉舌之間有管胞相連。 葉舌組織由四種不同形態的薄壁細胞群所組成，從基部至末端分別為：舌鞘細胞、舌足細胞、基部細胞和頸部細胞。舌鞘細胞最扁平、細胞壁內凸，類似傳遞細胞；舌足細胞最大，液胞亦最大；基部細胞最為等徑形，原生質最濃；頸部細胞呈長條形，相互交錯排列。當完全展開葉的葉舌開始有萎縮現象時，頸部細胞最先瓦解。在幼期的葉舌組織中，顆粒體內有澱粉粒，較老期的葉舌則無。 葉舌起源於葉原原始表層的一群細胞，最先分化的是基部細胞，其次為舌足細胞、再次為舌鞘細胞，最後為頸部細胞。葉舌的外形變異很大，由單一指狀至雙叉或多裂的掌狀均有。推測葉舌為一具有分泌功能的構造。

The organography and anatomy of the leaf and ligule of Selaginella delicatula (Desv.) Alston were examined using both optical and electron microscopes. The initiation and development of ligule were also traced in the present work. The shoot bearing unisophyllous dorsal and ventral leaves was derived from the apical meristem with a single apical cell. Both dorsal arid ventral leaves are ligulate, single-veined and almost entire in outline, but the former is lanceolate and the latter oblong. The mesophyll in both kinds of leaves are quite similar, cells are loosely arranged and no differentiation of palisade and spongy tissues can be seen. However, the distribution pattern of stomata, the types of stomatal complexes, as well as the shapes of the ground epidermal cells are quite different. The ligules vary in form, from finger-like, bi-to multilobed palisade; acropetally as four regions basing on the cell morphology they are sheath glossopodium, basal cells region and neck. The sheath cells are flattened transfer cells; glosso-glossopodial cells are the largest and highly vacuolated; basal cells isodiametric and cytoplasmic; neck cells elongated and overlapped each other in arrangement. The first indication of the senescence of a ligule is the disintegration of neck cells. There are starch grains in the plastids of young ligules but none in that of older ones. Ligule is supposed to be a secretory structure. The ligule originated from a group of protodermal cells in leaf primordium. As it grows, the basal cells are the first tissue to be identified, followed by the glossopodial cells, sheath cells and the neck cells.