臺灣博碩士論文加值系統

　　臺灣特有之臺灣水韭（Isoetes taiwanensis DeVol），不論生長在夢幻湖或溫室栽值，其葉片之萃取液中蘋果酸（malic acid）之含量，早晨及黃昏有明顯的差異：早晨含量約10-13mg/g鮮重，黃昏約1-3mg/g鮮重。pH（晨昏之變化在3-4及5-6之間）及可滴定酸（titrable acid）（晨昏之變化在220-20μeq/gfw之間）亦隨蘋果酸之變化而有變化。顯然臺灣水韭是一種具有景天酸代謝（Crassulacean Acid Metabolism）之植物。球莖（corm）之可滴定酸，晨昏間無明顯變化。暴露空氣中之葉片，其蘋果酸及可滴定酸晨昏之變化較低。
　　臺灣水韭之CAM現象，有利於其對夢幻湖之日照及湖水中白天缺乏二氧化碳之適應，且有利於拓展臺灣水韭在湖中之生存領域。
　　暴露空氣中之臺灣水韭葉片，其氣孔是張開的；而沈沒水中之臺灣水韭葉片，其氣孔是關閉的。氣孔暴露空氣中，2小時後氣孔張開率即達100%；而再度沈沒水中之氣孔，約10小時後，氣孔關閉率才達85%。氣孔快開慢閉之結果，有利於空氣中二氧化碳之吸收。
　　由掃瞄電子顯微鏡觀察葉表面之氣孔及石蠟切片法觀察橫切面中之氣孔，可看出氣孔之開關是由輔助細胞（subsidary cells）所控制。

　　In the leaves (but not corms) of the submerged aquatic plant Isoetes taiwanensis, both in the field and greenhouse, malic acid concentration fluctuates from 10-13mg/gfw in the morning to 1-3 mg/gfw in the evening. Associated with this is a change in pH (a. m. pH 3-4 vs. p. m. pH 5-6) and titrable acidity (220-20 ueq/gfw change in acidity between morning and evenign) of the plant extract, It is obvious that Isoetes taiwanensis is a CAM plant. The change of malic acid and titrable acidity are decreased when the leaves emerged.
　　It is suggested that CAM in Isoetes taiwanensis may be related to the lower availability of CO2 for photosynthesis during the day than during the night, and short time high intensity light.
　　The stomata are closed when the leaf submerged; and open when the leaf emerged. After 2 hours the leaf expose to air, the open ratio is 100%; but when the leaf submerged again, the closed ratio is only about 85% after 10 hours.
　　We find the movement of guard cells are controlled by the subsidary cells from the S. E. M. and paraffin method''s observations.