| 摘要: | 虎杖（Polygonum cuspidatum Sieb. & Zucc.）屬於蓼科蓼屬植物，是一種中國傳統藥用植物。在台灣，虎杖廣泛分布於海拔2000~3800公尺之中央山脈地區，屬於常見的中高海拔物種。不少文獻指出，原生於亞洲的虎杖已經成為歐洲及北美洲之入侵物種，並造成當地生態某些程度上的危害。觀察合歡山地區虎杖的分布，推測它可能具相生相剋作用。為了解虎杖潛在的植物相生相剋作用，本研究針對合歡山地區之虎杖以及其兩種伴生植物，五月艾 (Artemisia indica)以及大扁雀麥 (Bromus catharticus)進行生物活性測試，並對上述3種植物做植物毒性的探討。
樣區植物調查的結果發現，虎杖為選定樣區中的優勢植物，且新生虎杖嫩芽有增加的趨勢，於第一次植物調查後3個月，虎杖相對覆蓋度增加20 %，其優勢性達70 %，此顯示虎杖具植物相生相剋潛能的作用。以小白菜、萵苣、小米、九層塔、小黃瓜及大花咸豐草為材料，對上述3種植物濃度1 %到5 %水溶萃取液進行生物分析，得知虎杖、五月艾及大扁雀麥之水溶萃取液都對大花咸豐草具有根長及發芽的抑制活性，在扣除滲透壓影響後，抑制活性強度由大到小分別為虎杖、五月艾及大扁雀麥。虎杖葉浸泡於蒸餾水中經過自然分解後其水溶萃取液之抑制活性呈現遞減現象，第一次濾液幾乎都具有最高的抑制活性，但和無分解的抑制活性相近，顯示第一次分解對活性影響不大。於虎杖葉中分離出3種化合物分別為槲皮素（quercetin）、扁蓄苷（avicularin）及兒茶素（catechin），其中兒茶素為已知的植物相生相剋物質，槲皮素在部份植物中亦被發現為植物毒物質。雖然虎杖在台灣屬於原生物種，但其族群分布及植物毒性或許有助於了解其可能的入侵機制。除了醫學應用外，希望本研究的結果能增加虎杖在生態上的了解及未來在生物農藥利用上之價值。
Polygonum cuspidatum Sieb. & Zucc., a traditional Chinese medicine, distributes widely from 2000 m to 3800 m in the central mountain ranges and is commonly found in area of middle to high-elevation in Taiwan. P. cuspidatum was reported as an invasive species in Europe and North America, and caused adverse effects on local plant community. In Hehuanshan, P. cuspidatum is often growing with two other species, Artemisia indica and Bromus catharticus, in the early growing stage but becomes a dominant species later. It revealed that the presence of the plant ranged from 50 % to 70 % in three experimental plots. The results of field study show that the dominance of P. cuspidatum might be due to an allelopathic effect, thus, bioassays of aqueous extracts of P. cuspidatum leaves in a series of concentrations, 1 % to 5 % ( 5 g of leaves in 95 ml distilled water), and the aqueous extract of decompositing leaves in different time intervals were conducted. Six test species, Brassica chinensis, Lactuca sativa, Setaria italica, Ocimum basilicum, Cucumis sativus and Bidens pilosa were bioassayed. The bioassay results showed a pronounced inhibition of radicle growth and germination against test species, such as B. pilosa, and other species as well. After eliminating the osmolarity effect of aqueous extract, inhibitory activity of descending order was P. cuspidatum, Artemisia indica and Bromus catharticus. In the decomposition experiments of P. cuspidatum leaves in water, most of the first extract showed the remarkably high inhibition of radicle growth of test plants regardless of the decomposition time interval. The responsible allelopathic compounds present in the aqueous extracts of P. cuspidatum levees were further isolated by mean of column, thin-layer, paper and high performance liquid chromatography. Three compounds, quercetin, avicularin, and catechin were structurally identified by NMR. Although P. cuspidatum is a native species in Taiwan, the study of plant population and allelopathy provides a better understanding the invasion mechanism of the plant. In addition to the medicine application, the result of this study is capable of enhancing the understanding the significance of P. cuspidatum in alpine plant community and its agroecological application of biological control. |
