柳杉抽出成分對大花咸豐草種子發芽及生長抑制之研究

Abstract

本研究乃以針葉樹中之柳杉 (Cryptomeria japonica)，採取其過去較無用途的葉子與樹皮，製備精油、熱水抽出物、鹼萃抽出物等，並依序分離與進行生物活性分析，以分析其組成、篩選及評估各部抽出成分對雜草（大花咸豐草）之抑制活性。並將主要具生物活性物質予以分離、或區劃且加以鑑定之，以做為開發植物天然殺草劑用途之基本依據。 在精油對生長抑制方面，則以檸檬桉葉、赤桉葉及柳杉葉精油具明顯抑制效果，如於0.5%濃度時，對胚根分別有96.8%、88.5%及68.9%之抑制，對胚芽則為97.5%、93.9%及83.6%之抑制，尤檸檬桉精油於0.1%時，仍具90%之生長抑制。而實驗顯示精油成分Citral、Citronellol、Citronellal、（-）-Carveol、Cineole、D（+）-Camphor等含氧單萜化合物及Eugenol、Thymol等酚類化合物，在發芽及生長抑制試驗中均顯示高抑制效果。而會造成種子開裂死亡之精油化合物則有（-）-Carveol、Eugenol、Citral、Citronellol、Citronellal、Thymol。此外，柳杉樹皮分別含有高達46.45%的D（+）-Camphor與0.78%的 Cineole，故可作為柳杉未來應用於雜草管理之研究方向。 柳杉樹皮抽出成分中，由GC-MS圖譜可發現具抑制效果之分部，其成分多為酚類物質，包括了4-Hydroxybenzoic acid、Vanillic acid 、3,4-Dihydroxybenzoic等成分，而於單一成分之抑制試驗中，可發現2-Hydroxybenzoic acid及Phenol不論於發芽抑或是生長抑制均為適用，此兩者於濃度0.05%以上時，對發芽可達全抑制，而對胚根與胚芽亦均有90%以上之抑制率。而Ethyl 4-ethoxybenzoate則於胚芽抑制上具極佳之效果，即使於濃度0.01%下，亦可達60%以上之抑制率。 在盆栽試驗方面，未萃取之樹葉粉末，於4%添加量下雜草之種子階段可達到100%之萌芽抑制率，對於1星期幼苗亦有抑制生長之效果，而於5星期幼苗階段，亦能遠高於其他組別而達到36%之生長抑制率。樹葉粉末對於1星期幼苗之抑制效果，均較樹皮為佳，其已萃取及未萃取者對雜草之植株殘活率分別為24%及6%，因此於實地施用上應優先考量。此外，樹葉亦是一極易取得之原料，其並不需進行砍伐即可自林地中定期獲得，因此不論是從效果或來源考量，均是一極佳之除草劑原料。 此外，隨著雜草之成長，其對於外來物質之抵抗能力會逐步提高，而使的某些物質失去了其抑制之效果。不過由於各成分造成抑制之機制各不相同，且能產生抑制效果之時間長短與階段亦不相同，因此應慎選添加之物質及添加之時間點等條件，以期能對雜草進行良好之控制。

This study was to investigate the weed (Bidens pilosa L. var. radiate (BI.) Sherff) inhibition by using extractives from abandoned leaves and bark of a coniferous tree, Cryptomeria japonica. In order to develop the plant natural herbicide, the extractives including essential oils, hot water extractives, alkali extractives, etc., were separated to conduct the bioactivity experiment for screening and identifying the inhibition activity. The essential oils extracted from leave of E. citriodora, E. camaldulensis and Japanese cedar all showed the significant suppression effect on the growth of weed. At a concentration of 0.05%, they proformed 96.8%, 88.5% and 68.9% inhibition rate on radicle growth, respectively, and 97.5%, 93.9% and 83.6% inhibition rate on plunmle growth respectively. In particular, at a dosage of less than 0.1% of the leaf oil of E. citriodora achieved a high growth suppression rate of 90%. Oxygenated monoterpenes, such as 1, 8-Cineole, (-)-carveol, citral, citronellol, citronellal, and d(+)-camphor, and phenolics such as eugenol and thymol showed a higher inhibition capability for germination inhibition and growth suppression. The compounds led to bursting and death of weed seeds comprise (-)-carveol, eugenol, citral, Citronellol, citronellal and thymol. Because the Japanese cedar bark contains 46.45% d(+)-camphor and 0.78% 1,8-cineole, Cryptomeria japonica can be applied to the weed growth control in the future. The fraction with the inhibition effect in the extractives of the Japanese cedar bark was known as phenol compounds after analyzing by the GC-MS including 4-hydrox-ybenzoic acid, vanillic acid , 3,4-dihydroxybenzoic, etc. Among six test compounds, phenol and 2-hydroxybenzoic acid showed the higher capability for the germination inhibition and growth suppression. At a concentration of 0.05%, they can inhibit the seed germination completely, and showed more than 90% inhibition rate on radicle and plunmle growth. Ethyl 4-ethoxybenzoate performed good inhibition capability on plunmle growth. At a concentration of 0.01% below, it can display more than 60% inhibition rate. At the potting test, adding 4% of unextracted leaf powder can inhibit the seed germination completely and also the growth of one week-aged seedlings. For five week-aged seedlings, it also showed 36% growth inhibition which was much higher than other test groups. The inhibition effect of the powder from leaf was better than that from bark for one week-aged seedlings. The residua of seedlings were 24% and 6% for extracted and unextracted leaf powder respectively, so that leaf powder should be chosen at a high priority to applications. In addition, the leaf powder is easy to collect periodically without felling trees. Therefore, considering the source and inhibition effect, the leaf powder is a good herbicide. In addition, the weed can enhance the resistance capability to against the external substances following its growth. As a result, some substances lost their inhibition capability. Nevertheless, different compounds represent the different inhibition mechanism. The choice of substances and the timing for inhibition of weed growth should be very careful.