無根萍的形態解剖與生理研究

Abstract

用FPA及Karnovsky二種不同的固定方法，在掃描電子顯微鏡(SEM)下觀察無根萍(Woffia arrhiza Winm.)之表面構造及其無性生殖方式。發現無根萍氣孔之平行排列確屬一般單子葉植物的特徵。而它的外形呈船形，下表面並具備trichomex，它的葉狀體只一端具生殖腔，此與其他二屬的浮萍葉狀體左右各具生殖腔不同。幼體由此生殖腔逐漸突出，脫落而成一獨立個體。以石蠟切片研究內部之分生組織，其分化情形與其他浮萍相似，幼體仍存在母體之生殖腔時，母體之分生組識已具有另二子代的芽體，幼體之分生組織也同樣具有至少下二代的芽體。 用5﹪ NaOCl消毒得到無菌種，有些無菌種在生態上發生變異，由漂浮液表面的生長而變為沈到液內的生長，形態上最大的差異是「沈萍」的上、下表面顏色相似，而漂浮液面者上表面顏色為深綠色。生長速度二者相同。 Modified Hoagland medium比Hoagland medium更適合於無根萍的生長。且無根萍的生長在缺鈣的情況下則完全不能繁殖下去。荷爾蒙處理中，GA及BA都能些微促進無根萍的生長。

The morphology and the vegetative reproduction of Wolffia arrhiza Winm. were observed under the scanning electron microscope. The vegetative body frond of W. arrhiza is boat-shaped, and has a flat surface, on which stomata are arranged in parallel rows. It has a reproductive pouch with an opening at one end. On the lining of the reproductive pouch distal to its opening is a group of cells whose meristematic activity gives rise to a new frond. The developing frond grows in size and finally is pushed out of the pouch, temporarily forming a dumb-bell-like structure. The daughter frond is still inside the rr reproductive pouch of mother frond, younger fronds are already in the making within the mother frond d as well as the daughter frond. The aseptic culture of W. arrhiza was obtained through sterilization with 5﹪ sodium hypochlorite for 1 to few minutes. As fronds are allowed to grow in flask aseptically, some tend to sink. The sunken fronds continue to grow at same rate as the floating ones, and are morphologically the same except they are pale-green, while the floating ones have dark-green upper surface. The modified Hoagland solution is more suitable; than the strait Hoagland solution for growing Wolffia, Gibberellic acid and benzyladenine have slight promotive effect on the growth of W. arrhiza is extremely sensitive to calcium deficiency; lack of calcium causes immediate death of the fronds.