蕁麻科植物葉部解剖構造的比較與咬人狗葉片表皮組織的形態形成

Abstract

本論文以蕁麻科9屬10種植物為材料，應用光學及電子顯微鏡技術觀察其葉片石胞的形態，並針對密花苧麻、水麻、糯米糰、霧水葛、小葉冷水麻和咬人狗六種蕁麻科植物葉部的毛茸做進一步的觀察。此外，另以咬人狗為材料，進一步觀察其葉部發育過程中，表皮組織之各種構造相對應的變化，以其瞭解各種細胞的起源與其周圍細胞間的相互關係。 蕁麻科植物成熟葉部的形態與解剖構造 於觀察的9屬10種蕁麻科植物的葉片中，其成熟葉表之石胞構造，可區分為線形、圓錐形、球形和乳頭狀石胞，其中盤花麻族的闊葉樓梯草和小葉冷水麻為線形石胞，蕁麻族的咬人狗為乳頭狀石胞，苧麻族中的水麻、糯米團、霧水葛為圓球形石胞，而密花苧麻則是圓錐形石胞（然而長梗紫麻、冷清草與咬人貓的石胞則尚不確定）。就深入觀察葉表構造的6種植物而言，由結果可知除了小葉冷水麻葉表面光滑無毛茸外，其餘種類上下表皮均有各式毛茸。涵蓋分泌型毛茸；腺毛和蟄毛；與非分泌型毛茸：勾狀、硬狀、表面瘤狀與長捲曲形毛茸。 咬人狗葉部生長與表皮組織的發育 咬人狗葉片與表皮組織發育過程可分為兩個階段共七個時期。第一階段A期（頂端分生組織至葉原0.75mm），此時頂端分生組織形成葉原，並以向尖發育的方式延伸中肋；第一階段B期（葉長0.75mm至1.85mm），此時一級脈形成，並於背軸面由葉尖向葉基方向逐漸形成毛茸；第一階段C期（葉長1.85mm至3.5mm），此時背軸面已密覆毛茸，向軸面由基部向葉尖端逐漸形成毛茸；第一階段D期（葉長3.5mm至1cm），此時背軸面與向軸面均已完全覆蓋各種毛茸，原始表層漸次分化石胞、泌水器以及氣孔；第二階段A期（葉長1cm至5cm），此時葉片已脫離托葉的包裹並且逐漸分化柵狀組織與海綿組織；第二階段B期（5cm至18cm），葉片進行平板生長，並增加葉片面積；第三階段C期，葉片已不再增長，各種細胞與組織皆已分化完全。 咬人狗葉片的原始表層分化成各種類型的細胞，有一般表皮細胞、毛茸、氣孔、泌水器和石胞。一般表皮細胞的細胞內有大型液胞以及各種胞器，但葉綠體並不發達。蟄毛由一個刺細胞與基部的一群蓮座細胞所組成，主要分佈於上表皮之一級脈之間的葉表面與下表皮之各級脈上。硬毛為單細胞毛茸，分佈於上下表皮。腺毛則由八個頭狀細胞，一個柄細胞以及一個基部細胞所組成，成熟時頭狀細胞堆積次級代謝物。氣孔複合體僅分佈於下表皮，其副細胞為一大兩小呈不等形排列。泌水器主要由一群水孔、末稍組織以及管胞等細胞組成，並在發育早期其周圍有一至二個腺毛，至泌水器成熟後腺毛萎縮並脫落。石胞為乳頭狀石胞，由細胞壁伸出基柄向內延長，最後於基柄末端形成圓形鐘乳體。葉肉之異形細胞包含針束狀草酸鈣結晶與特化之黏液細胞。

The morphology and distribution of lithocysts were studied in the mature leaves of ten species (eight genera) of Urticaceae by light and electron microscopy. In the leaves of Boehmerica densiflora Hook. & Am., Debregeasia orientalis C. J. Chen, Gonostegia hirta (Blume) Miq., Pouzolzia zeylanica (L.) Benn., Pilea microphylla (L.) Liebm, and Dendrocnide meyeniana (Walp.) Chew, the different kinds of trichomes and idioblasts in the mesophyllous tissue were anatomically investigated. Besides, the development and morphogenesis of the epidermis of D. meyeniana were studied in order to understand the relationship in between. The epidermis of mature leaves in some species of Urticaceae The lithocysts of these plant species are located in the epidermal tissue, and mostly in the adaxial side of the leaves. The shapes of lithocysts were classified into four types: (1) linear lithocysts: P. microphylla, and Elatostema platyphylloides Shih & Yang; (2) spherical lithocysts: G. hirta, D. orientalis, and P. zelanica; (3) conical lithocysts: B. densiflora; (4) papillate lithocysts: D. meyeniana. The results of the investigation on the trichomes in the mature leaves of six species (six genera) showed that except the leaves of P. microphylla there no trichome, and however different kinds of trichomes were observed in the leaves of the other species. Based on the types of trichomes, they were divided into two groups: (1) glandular trichomes: stinging and glandular trichome; (2) nonglandular trichomes: hispid, hooked, pustulate, and villous trichome. The leaf and epidermis development in D. meyeniana The leaf development in D. meyeniana were divided into seven periods: (1-A) the formation of leaf primodium in the apical meristem. (1-B) the abaxial epidermis differentiated trichomes. (1-c) the adaxial epidermis differentiated trichomes. (1-D) the differentiated of hydathode, stomata and lithocyst. (2-A) mesophyll tissue differentiated palisade tissue. (2-B) the spongy tissue appeared. (2-C) leaf matured. In D. meyeniana, the protoderm was differentiated into various kinds of epidermal cells including trichomes, guard cells, lithocysts and the hydathodes. Epidermis of leaves is only one cell layer. On the adaxial and abaxial side of mature leaves there were stinging, glandular, and hispid trichomes. The stinging trichome was composed of a central stinging cell and a group of pedestal cells. The hispid trichome was a single cell. The glandular trichome included a basal cell, stalk cell and eight head cells. The anisocytic stomatal complexes, which composed of two guard cells and the surrounding three subsidiary cells, were found only on the abaxial leaf surface. Nevertheless the hydathodes and papillate lithocysts were mostly distributed on the adaxial leaf surface. The hydathode included water pores, epithemal tissue and tracheids. The papillate lithocysts contained calcium carbornate crystal which was composed of a long stalk and the round body. In the mesophyll tissue, there were Ca oxalate crystal idioblasts, tannic cells and mucilage cells.