小花蔓澤蘭與蔓澤蘭發芽及營養生長之比較

Comparison of seed germination and vegetative growth of two Mikania species

小花蔓澤蘭和蔓澤蘭為台灣低海拔區常見的菊科植物，兩者的生長特性及棲地習性類似，近年來外來種小花蔓澤蘭已演變成嚴重的入侵植物。本試驗比較兩種蔓澤蘭植物的發芽及營養生長特性。小花蔓澤蘭的發芽溫度範圍介於8-32℃，比蔓澤蘭的12-28℃較為廣，兩者皆可於二週後達最高發芽率，20℃時兩者於播種後第6天開始發芽，於28-32℃間小花蔓澤蘭的發芽率比蔓澤蘭高。光照處理兩種蔓澤蘭可達68 %以上之發芽率；黑暗處理蔓澤蘭和小花蔓澤蘭只有25 %、3.5%的發芽率；pH5.5-7.5之間兩者發芽率差異不大；蔓澤蘭和小花蔓澤蘭的發芽率隨著水分的減少而明顯下降，當滲透壓為-0.8 MPa時，兩者皆不發芽；隨著覆土深度增加，萌芽率亦隨之降低，土深達2.5 cm時兩者幾乎不萌芽。兩種植物5-8月間在溫室的生長勢比較，小花蔓澤蘭的生長勢比蔓澤蘭快，於第4週時其蔓長、葉數、葉面積和乾重皆有顯著之差異，兩者之間又以葉面積的差異最大，至第11週時兩者之差異為蔓長1.8倍、葉片數2.1倍、葉面積7.9倍、鮮重13.1倍。

"Mikania cordata and M. micrantha of the Compositae are common in Taiwan at low elevations. These 2 Mikania species have similar vegetative characteristics and habitat preferences. In recent decades, the exotic M. micrantha has become a serious invasive plant in both natural and disturbed habitats. In this study, we compared the effects of temperature, pH, water potential, and planting depth on seed germination of the 2 Mikania species under controlled environments. Temperatures for seed germination ranged from 8 to 32 °C for M. micrantha and 12 to 28 °C for M. cordata. Initial germination was around 6 days after planting, and accumulated germination reached a plateau at about 60 % for both species 2 weeks after planting. Under an illuminated condition, more than 68 % of seeds of both species germinated. In darkness, only 3.5 % and 25 % of seeds of M. micrantha and M. cordata, respectively, germinated. More than 50 % of seeds of both species germinated between pH 5.5 and 7.5. Seed germination of M. cordata was higher than that of M. micrantha when the water potential was 0, -0.2, or -0.4 MPa. Seeds of both species failed to germinate when the water potential was at -0.8 MPa or lower. Seedling emergence sharply decreased with increased burial depth, and maximum depth for emergence was between 2 and 2.5 cm. In the greenhouse test, from June through August, results showed that vegetative growth of M. micrantha was much stronger than that of M. cordata under similar conditions. The invasive M. micrantha had longer vines (1.8 times), more leaves (2.1 times), a larger leaf area (7.9 times), and more biomass (13.1 times by fresh weight) than those of the indigenous M. cordata at 11 weeks after seedling emergence. Our data suggest that the invasive M. micrantha is capable of out-competing and displacing the indigenous M. cordata in natural habitats."