本研究主要目的探討恆溫、變溫、水分潛勢、鹽分濃度、酸鹼度、光質與氧 氣對黃鵪菜（L. DC.)、兔兒菜（ixm+s cfe'we腦(Thunb.) Nakai ) 及長柄菊（L.)種子發芽能力之影響，試驗結果如下： 黃鵪菜及兔兒菜種子可發芽之恆溫範圍相同，在5〜30°C之間，長柄菊種子可發 芽溫度範圍較髙，在20〜40°C之間；變溫環境下之發芽能力較恆溫環境下為佳， 以黃鵪菜30/25C、兔兒菜25/20C、長柄菊35/30C之變溫環境下發芽率最髙， 分別為92.7%、88.0%及94.7%。黃鵪菜及兔兒菜種子可發芽的水分潛勢範圍在 0〜-0.4MPa間，長柄菊種子可發芽的水分潛勢範圍在0〜-0.2MPa間，以黃鵪菜 及兔兒菜較耐低水分潛勢。在鹽分濃度方面，黃鵪菜及兔兒菜種子於鹽分濃度0 〜0.8%間，長柄菊種子於鹽分濃度0〜0.4%間，種子皆有發芽能力，以長柄菊種 子對鹽分較為敏感。溶液酸鹼度方面，在pH 4〜10間三種種子皆可發芽，其中以 pH 6〜8處理下，有較髙的發芽率。光質對黃鵪菜及兔兒菜種子以白光、紅光之發 芽率逹74.7%以上最佳，長柄菊種子以白光、紅光、遠紅光、藍光之發芽率在 80.7%以上為最佳，而黑暗環境下兔兒菜及長柄菊種子之發芽率明顯受抑制。三 種種子在光照及有氧條件處理下發芽率最佳，而在無氧的情況下，無論光照或黑 暗，三種種子全無發芽。

The main purpose of this study was to investigate the effects of seed germination ability on Youngia japonica L. DC., Ixeris chinensis (Thunb.) Nakai and Tridax procumbens L., including constant temperature, alternate temperature, water potential, salt concentration, pH value, light quality and oxygen. The results were as follows: The seeds of Youngia japonica L. DC. and Ixeris chinensis (Thunb.) Nakaiat had same constant temperature for germinate from 5 to 300C, Tridax procumbens L. could germinate between 20 to 400C. Alternate temperature environments had better seed germination than constant temperature treatments. Youngia japonica L. DC., Ixeris chinensis (Thunb.) Nakai and Tridax procumbens L. with alternate temperature treatments had the highest germination percentage which were 30/250C(92.7%)、25/20 0C(88.0%) and 35/300C(94.7%). Youngia japonica L. DC. and Ixeris chinensis (Thunb.) Nakai at water potential treatments could germinate from 0 to -0.4MPa, Tridax procumbens L. could germinate from 0 to -0.2MPa, Youngia japonica L. DC. and Ixeris chinensis (Thunb.) Nakai had better resistant ability at low water potential. At salt concentration treatments, Youngia japonica L. DC. and Ixeris chinensis (Thunb.) Nakai could germinate from 0 to 0.8% and Tridax procumbens L. could germinate from 0 to 0.4%. Tridax procumbens L. was more sensitive to salt concentration. In terms of pH value, all species were able to germinate from pH 4 to pH 10 and had better germination percentage from pH 6 to pH 8. The light quality treatments of white and red light with Youngia japonica L. DC. and Ixeris ch~^^e^s^s (Thunb.) Nakai had better germination percentage which achieved over 74.7%. Tri^ax procum^ens L. had better germination percentage with white, red, far-red and blue light which achieved over 80.7%. However, dark environments obviously limited the germination percentage of Ixeris chinensis (Thunb.) Nakai and Tridax procumbens L.. All species had better germination percentage with light and oxygen. Without oxygen, all seeds could not germinate with light or without light.