石斛蘭與根節蘭頂端分生組織的研究

Abstract

中文摘要:石斛蘭與根節蘭的項端分生組織 ⑴石斛蘭與根節蘭頂端分生組織均具有外帶和內群的分化。外帶具有二層，細胞排列整齊，做罩狀。外帶細胞大部行垂周分裂，但第二層偶行平周分裂。內群細胞多呈等徑形。整個頂端分生組織常常染色很深，區域性分化不明顯。 ⑵髓部母細胞液胞化早，染色淡:細胞拉長，但排列不成束狀。石斛蘭屬具長莖者，在基本組織處多呈規則的細胞束。根節蘭具粗短的假球莖者，其成熟的基本組織，細胞排列不規則。 ⑶葉原來自周圍帶，平周分裂首先發生於第二層細胞。 ⑷腋芽原分化於葉子遠軸面，第一次平周分裂發生於第三層細胞上。腋芽分化早期尚有Shell zone的出現，Shell zone將整個腋芽原的分生組織包圍起來，其末端止於下一片葉子近軸面的基部上。在腋芽生長過程中Shell zone漸漸消失。根節蘭整個頂端分生組織的面積、體積均較石斛蘭者大得多。 ⑸根部頂端分生組織的始源細胞群由一個至四個都有，地生的根節蘭全為一個始源細胞群，耐附生的石斛蘭自一個至四個細胞群都有。多個始源細胞群的都具有根冠始源細胞群，上面的部份可為一個細胞群或分為根被和皮層一中柱始源細胞群。具有四個始源細胞群的植物，尚有皮層和中柱始源細胞群。 ⑹始源細胞群的染色與鄰近的衍生組織相似，並無顯著差異存在。在多個始源細胞群的植物，該始源細胞群的染色往往較臨近組織還濃，但是無論在具有一個或多個始源細胞群的植物始源細胞群處的細胞分裂都不易看見，而鄰近衍生組織常可看到有細胞分裂相的存在。 ⑺根冠多行平周分裂，外圍則堆積有澱粉粒。 ⑻根被為多層細胞，主要行垂周分裂，在石斛蘭，成熟的根被細胞較根節蘭要更為加厚，成假導管狀。根被的分化多少是呈離心方向的。 ⑼皮層液胞化早，澱粉粒很早即出現，外皮層為單層，細胞只行垂周分裂，到了某一高度，便開始行不均勻的細胞分裂。皮層靠內的細胞成熟方向是向心的，而皮層外圍部份細胞成熟方向是離心的，或不規則的，皮層的中間大部細胞則液胞化，且染色很淡。 ⑽針狀結晶束在每一種均有，同時多發生於自外皮層向內三至五層的距離上。 ?中柱由髓部和原始形成層構成，髓部佔了中往的絕大部份，液胞化早，細胞多行橫向分裂。原始形成層圍在中柱之外，細胞多行縱裂，細胞質濃，染色深。 ?根部內基木組織佔了絕大部份，其大小之差異為其他組織之冠。在根節蘭，根部始源細胞寬度，根冠高，根直徑和皮層寬度有正比的關係。在石斛蘭根直徑寬度，根被寬度和根冠高度亦約成正比關係。

1. Tunica-corpus organization commonly differentiates in the shoot apical meristern of both Dendrobium and Calanthe. Tunica with two layers of cells arranging in outermost layer looks like a semispherical mantle. Anticlinal division is dominant in the tunica layer, occasionally, periclinal division occurs in. the inner layer of tunica. Corpus consiats of isodiametric cells which are irregularly arranged. All the cells in the apical meristem are stained deeply and. zonation is obscure. 2. Pith mother cells vacuolize early, with lighter cytoplasm and longitudinally elongated, but are not arranged in a rib-like structure. In Dendrobium which usually develop long stem the cells in ground tissue are arranged in rib-like structure. This condition never occur in Calanthe which regularly bear short stem (pseudobulb). 3. The peripheral zone is commonly the region which possesses the cells with high mitotic activity in the apical meristem. It is the site of the leaf primordium. The first sign of leaf formation is a periclinal division of the second tunica layer which is followed by the division in various planes in its derivatives. During the development of leaf; the outer tunica divides antiolinally only. 4. Axillary bud primordium differentiates axilly at the base of the leaf primordium. The periclinal division in the third layer initiates the axillary bud. primordium then are followed by anticlinal divisions in the first and second layer. Shell zone appears in the developing axillary bud primordium, it gradually disappears during the development of axillary bud. In Calauthe both area and volume of the apical meristem are larger than that of Dendrobium. 5. The numbers of apical initial groups range from one to four All the terrestrial, species of Calanthe have only one initial groups, whereas epiphytic species have one to four groups. The presence of the calyptrogen is a common feature in the multi-initials. The differentiation of the initial group other than the calyptrogen varies according to the species. 6. The mitotic figure in the initial cells of root apical meristem which has either with one or multiple initials is not common. 7. The cells near the promeristem mainly divide periclimally. Many starch grains (amyloplast) are formed and always pile up peripherally in the cells of outer root cap. 8. Velamen is a multiple epidermis which divides mainly anticlinally in the region near the apical meristem. The secondary wall of the mature velamen cell in Dendrobium is always thicker than that in Celanthe. Differentiation of velamen in radial direction in centrifugal. 9 Cortex can constantly be divided into three regions, i.e. outermost uniseniete exodermis, middle multiseriate cortex proper and innermost uniseriate endodermis. Exodermis consists of two kinds of cells, i.e. short and long cells, which are formed by an unequal division at some distance behind the initial group. The differentiation of cortical cells in radial direction is bidirectional both centrifugally and centripetally from the middle part of the cortex. 10. Raphids are very common in every species and are distributed in the third to fifth layer from the exodermis. 11. The procambium which has denser cytoplasm occupies the peripheral part of the central stele and surrounds the central ground tissue (developing pith). The pith cells vacuolate almost at the same level as the vacuolation of cortical cells. 12. Ground tissue occupies the most. part. of the root, so that it plays an important role in determination of diameter as well as the size of the root, The width of the apical meristem in root closely correlate with the height of root cap, root diameter and width of root. The wider the apical meristem the more the root cap and diameter.