細葉天仙果葉部泌水器的研究

Abstract

本文提供一種新的葉齡表示方法：葉測量間期指標值(LMI)，可替代之前所使用的葉生長間期指標值(LPI)方法；此葉齡表示法可用於有關植物葉片形態發育與其生理研究上。葉測量間期指標值的使用是建立於使用相同的測量時間間距為單位，此法不同於葉生長間期指標值是利用植物生長其連續葉片它生長間期的相等性作為單位指標。藉由相等的測量間期單位記錄每片葉子的生長資料，將各葉片的原始生長資料根據參考生長葉長，再藉由轉換公式進行對生長資料做時間軸的轉換。此法可以解決在葉生長間期指標值方法不能使用的情況下其葉齡的表示，例如；葉生長間期(plastochron)不相同、不穩定的生長情形，特別是植物生長於逆境環境下。葉測量間期指標值方法，基於下列三種假定：1. 葉片生長其早期生長為指數生長；2. 連續生長葉片的指數生長期的生長速率相似；3. 葉生長測量間期需一致而且小於指數生長期。 有關細葉天仙果葉部泌水器其外部形態與超顯微構造的研究結果。在形態上，細葉天仙果葉部泌水器屬於複雜末梢型泌水器；它是由許多水孔與表皮細胞、管胞末端、末梢組織細胞與束鞘細胞層所組成。水孔由兩個似保衛細胞所組成，孔口屬於永久開口不具調控功能，平時是靠外脊重疊造成關閉，等木質部內的靜水壓力達到臨界值才推開脊口進行泌溢；末梢組織是由一群具迂迴彎曲細胞壁的薄壁細胞組成。其超顯微構造特徵是，末梢細胞具有濃密細胞質、多數量的粒線體、發達內質網系統與許多衍生自高爾基氏體的小泡構造以及分佈隨著末梢細胞成熟度而增殖的過氧化小體。此外，末梢細胞彼此細胞壁間存在豐富的原生質連絡絲；並在末梢細胞其細胞膜內側發現許多具特別形態的細胞膜內凹體，這些細胞膜內凹體是由於不斷重複的細胞質離與去質離作用所造成細胞膜內噬作用而形成的構造。我們認為泌水器可作為日後研究植物細胞膜內噬作用的一個理想系統。 由於泌溢溶液內含有機及無機鹽類，再加上白天蒸散作用的濃縮效果，提高了泌水器內鹽類的濃度，容易對泌水器形成高鹽逆境而造成可能的鹽害。有關泌水作用其高鹽逆境對泌水器造成的鹽傷，從超微構造研究顯示主要的鹽害病徵是許多濃電子密度粒子分佈於細胞核與各種胞器內，造成細胞核仁濃縮、消失；細胞質內部胞器與內膜系崩解變成親過氧化鋨的物質存在，或隨著急速脫水作用使崩解的膜系呈玻璃化而形成類囊膜鞘構造。實驗中觀察不同的鹽害程度發現，末梢組織其耐高鹽的能力較鞘層細胞層高，顯示泌水器內末梢組織細胞似乎已演化出一些有效的調節機制，用來適應高鹽高滲透壓的逆境﹔除了生理代謝的調節適應外，其迂迴的細胞壁增加了表面與外界環境接觸面積，並配合大量增殖的過氧化小體、發達的內膜系統與內噬作用等形態構造上的改變，均可提高並增加對高鹽環境快速反應的能力。這些機制也可能提高了液胞功能的有效性，進而增加細胞對高鹽逆境的適應能力。 在泌水器形態發生研究上，我們將末梢組織的形態發生的發育過程區分定義成：I. 始原細胞期、II. 細胞分裂期、III. 細胞伸長與細胞分化期 與IV. 成熟期 等四個階段。葉片發育初期，泌水器的始原細胞開始出現於葉片上表面的巨大毛茸細胞附近；接著始原細胞進行細胞分裂，藉由表皮層細胞垂周分裂形成日後表皮細胞與水孔細胞，次表皮層進行不規則垂周與平周分裂形成一群細胞團，日後分別分化形成末梢組織、管胞與束鞘細胞層。待發育階段進入細胞生長與分化期，末梢組織的細胞因細胞內細胞質周圍特殊微小管體排列的影響以及細胞分泌的細胞壁分解酵素其作用並且配合細胞伸長作用產生的張力作用，這些因子交互作用使得末梢細胞生長形成特別的多裂形狀，並且擴大了細胞間的細胞間繫；同時細胞的多裂形狀增加了細胞與其外界環境的接觸面積。此時期的管胞亦進行分化，另外表皮水孔細胞的細胞數目增加速率達到最大。隨著發育階段進入成熟期，末梢組織中的管胞逐漸成熟且具有導水功能，加上末梢組織與水孔成熟的配合，使得管胞末端到水孔孔口的路徑得以暢通，使得泌溢作用更順利進行。有趣的事，是有關末梢組織的分化與成熟具有其方向性，是從表皮水孔下方區域逐漸向內近管胞末端區域成熟，所以等到近管胞末端的末梢細胞分化成熟時泌溢作用更明顯易見。 我們使用硝酸鑭當作胞外追蹤劑，探討末梢細胞其物質回收的機制為何? 由硝酸鑭的細胞化學定位實驗結果，推測包覆小泡型的內噬作用為末梢細胞中，除了幫浦氫離子並藉離子通道的主動吸收物質進入細胞的形式外，其它另外一種可在泌水作用中，用以從泌溢溶液中回收物質的方式。

This study first proposed a new method for leaf age, the Leaf Measuring-Interval Index (LMI), to replace the Leaf Plastochron Index (LPI) method that often used in the leaf morphological and physiological studies. The LMI method is not dependent on plastochron and it is based on using a constant measuring interval (Mi) to record the leaf growth information. LMI of the leaves is obtained by transferring their growth data with formula, which is obtained according the reference leaf length λ. This method can solve the problem of using LPI when leaf plastochrons are variable especially when plants growing in stress environments. The LMI method depends on three assumptions. First, the early stage of leaf growth is exponential. Second, the exponential rates of successive leaves are the same. Final, the chose of Mi is less then the period of exponential growth of leaf. Morphological and ultrastructural features of hydathodes in Ficus formosana Maxim. f. Shimadai Hayata were studied in the second part of this dissertation. The laminar-hydathode is complex epithemal type, which consists of water pores and epidermis, tracheid-ends, epithem cells, and a sheath layer. Water pores are made up with two similar guard cells and the pore between them opens permanently. The epithem is consisted of a group of parenchyma cells with sinuous cell wall. On the ultrastructures, the epithem cell has a dense cytoplasm, numerous mitochondria, an extended ER, ER-derivative vesicles, many small vesicles derived from Golgi bodies, and proliferate peroxisomes. The numbers of peroxisomes were increased and coincided with the maturity of the epithem. In addition, abundant plasmodesmata were often observed on contacted cell wall between epithem cells. Multiple types of plasmalemmasome structures were also presented on the plasma membranes of the epithem that are results of endocytosis, which are performed during repeat cycles of plasmolysis and deplasmolysis. Hydathode is an idea system for studying endocytosis in plants was suggested. Ultrastructural studies on the salt injury of guttation on hydathodes show that the major symptoms of salt injury are as follows: many electron dense particles spread in the nucleus and organelles; the nucleolus is condensed and then disappeared, and the endomembrane system is collapsed then entirely formatted osmiphillic materials in the cytoplasm. Upon dehydration, the collapsed membranes become the myelin-like structures. According different degrees of salt injury on epithem, the abilities of different tissues’ salt-tolerance are variable and the salt tolerance of epithem is better than other tissues. It means that some special mechanisms in the epithem have been evolved to adapt high salt stress. In addition to physiological metabolism regulation, there are two suggestions that the sinuous cell wall increases the absorption surface of epithem with environment and that the abundant endomembrane system not only accelerates the cells’ response to salt stress, but also increases their salt-tolerance via fluid-phase endocytosis. These mechanisms may promote the tolerant efficiency of vacuoles in epithem cells under high salt stress. The morphogenesis of hydathodes in chapter three, the identified the processes of development into four stages: I, initial stage; II, cell division stage; III, cell elongation and cell differentiation stage; and IV, maturation stage. In the early stage of leaf development, the initial cells of hydathodeoccur near the region of a giant trichome cell base. Afterward in the cell division stage, epidermal initial cells are proceeding anticlinal division to form epidermal cells and water pores in the further, and subepidermal initial cells through anti- and periclinial divisions to produce a group of cells, which will be differentiated into epithem, tracheid and a sheath layer of hydathodes. During the cell elongation and differentiation stages, epithem cells grow becoming lobed shapes that are caused by some factors, which contain the special microtubules arrangement around the pericytoplasm, digesting enzymes secreted to cell wall acting, and the tension force causing by turgor of cell growth. These factors are not only causing the lobed cell formation, but also enlarging the intercellular spaces of epithem. The lobed shape’s epithem cells increase the contact surfaces between the cells and their environment. At the same time, tracheids are also starting differentiation and increasing rates in the numbers of water pores are reaching maximal on epidermis. In the maturation stage, tracheids within epithem are gradually matured, and associated with maturation of epithem cells and water pores, functioning as the passage between vein-ends and water process guttation. It is interesting that the way of epithem differentiation and maturation is starting from the regions under water pores to vein-end region. Since the epithem near the vein-ends are maturation, the guttation will be apparently. Finally, the lanthanum nitrate was used as an apoplastic tracer to study the retrieval mechanisms of epithem. Cytochemical data indicated that the epithem cell might also use the coated-vesicles endocytosis to retrieval nutrient from the guttated solution in addition to use proton pump.