摘要或動機

槐葉蘋(Salvinia natnas)生長於台灣低海拔淡水濕地，目前已列為嚴重瀕臨滅絕的台灣原生物種，為不具有根的植物，是世界珍稀的漂浮型水生蕨類。本研究是探討槐葉蘋形態、生活史及生存環境因子，實驗發現可藉由成熟浮水葉外部形態特徵來區別槐葉蘋與外來種之人厭槐葉蘋(Salvinia molesta)；槐葉蘋成熟浮水葉呈橢圓形，葉上毛被物是叢生且分岔，人厭槐葉蘋成熟浮水葉呈雙耳形，葉上毛被物則像打蛋器。當兩物種共存於同一個環境空間時，人厭槐葉蘋以平均11.6 cm²/week 的生長率將槐葉蘋完全取而代之，顯示人厭槐葉蘋之入侵對槐葉蘋生存影響之深遠。經由兩年的槐葉蘋物候觀察，發現3~11 月為抽芽成長期、3~12 月為成熟繁殖期、12 月~隔年2 月為冬枯期及孢子囊果出現期，12 月~隔年5 月為孢子囊果成熟開裂期。其繁衍策略可分為無性繁殖（頂芽及側芽生長）及有性生殖（異配子體交配）。探討環境因子（光照度、氣溫、濕度、水質、水溫、pH 值）分析結果，適合槐葉蘋生存環境的條件為(1)陽光間接照射（半遮蔭，遮蔭度58.33%）、(2)乾淨未受污染的水質(pH 6.5~8)、(3)通風性良好。生長環境符合以上條件即可達到移地保育的目的。Salvinia natans, a floating fern without roots, grows in low elevation fresh water wetlands of Taiwan, and is a critically endangered precious Taiwanese native species. This research investigates the life form, life history, and living environment of Salvinia natans. Our experiments show that we can differentiate Salvinia natans and Salvinia molesta, two easily mixed up species. The shape of matured floating leaves of Salvinia natans is elliptical and smaller, while it is twin-ear shape and larger for Salvinia molesta. Also, they can be distinguished by their leaf hairs. The hairs of Salvinia natans are tufted and separated at the tips, while the hairs of Salvinia molesta form an ‘eggbeater’ shape at the tip. When these two species lived together, Salvinia molesta grew in a rate of 11.6 cm2/week and will replace all Salvinia natans eventually. This shows the profound impact of invasion of Salvinia molesta. From the data of 2-year phenology observation, we concluded that budding took place from Mar. to Nov., growing and reproducing from Mar. to Dec., decaying from Dec. to Feb. (sporocarps were born in this period), and sporocarps matured from Dec. to May. There are two reproduction strategies: sexual reproduction (intergametophytic mating), and asexual propagation (by terminal and axillary growth). After investigating the environment factors (illuminance, air temperature, water temperature, humidity, pH), we found that ex situ conservation for Salvinia natans requires 1) indirect sunshine, 2) unpolluted water (pH 6.5 ~8), and 3) good ventilation.