乾旱遮蔭及施氮量對青脆枝養分及喜樹鹼含量的影響

Abstract

喜樹鹼及其衍生物可抑制癌細胞之生長，已有兩種衍生物實際運用於癌症之治療。從植物中萃取是生產喜樹鹼的主要方法，青脆枝為能產生喜樹鹼的主要植物之一，而青脆枝栽培之研究甚少被關注。本研究探討缺水及遮蔭兩種環境因子及兩種施氮量對於青脆枝生長、養分吸收及喜樹鹼產量與分布之影響。本研究於臺灣大學農場溫室進行盆栽試驗，設計為逢機完全區集排列，材料為三年生之青脆枝，試驗前裁剪去所有枝條留下部份主幹，自2008年5月24日主幹開始抽芽，自此進行兩個月的培植與一個月的處理。培植期間每株以尿素為氮肥施入2 g氮，同時以過磷酸鈣與氯化鉀提供磷與鉀，每株施0.25 g的磷與鉀；之後進行一個月處理，少氮處理者 (2N) 不再施入氮肥，多氮 (3N)、缺水 (3ND) 及遮蔭處理者 (3NS) 皆再施入1 g氮，遮蔭處理者以黑色塑膠網遮去2/3日照，乾旱處理者以目視判斷，待葉片出現下垂徵狀一小時後澆水，重複缺水與供水，為期一個月。8月24日進行第一次採樣，留下一個枝條之葉提供後續生長所需能量，再次進行培植及處理，於12月20日採收土壤與所有植體。兩次採樣所有枝條從頂芽算起五公分之莖葉歸類為嫩莖及嫩葉，其餘者為成熟莖與成熟葉。結果顯示，所有處理之青脆枝地上部乾重無顯著差異，而乾旱可增加地下部乾重。各部位總氮、硝酸態氮與可溶性還原態氮濃度隨施氮量增加而升高，乾旱處理會減低根的錳濃度，遮蔭處理則增加全株的硝酸態氮濃度；施氮量不同對於喜樹鹼濃度無顯著差異之影響，乾旱處理可增加根部喜樹鹼濃度及產量，遮蔭處理可提高主幹的喜樹鹼濃度。青脆枝各器官喜樹鹼濃度的高低順序為根 > 主幹 > 莖 > 葉，嫩莖及嫩葉的喜樹鹼濃度較成熟部位低。

Camptothecin and its analogues are potent anticancer agents, and two of its semi-synthetic derivatives are now applied to clinical treatment for cancer. Most camptothecin was extracted from camptothecin-containing plants. High concentration of camptothecin alkaloids presents in Nothapodytes foetida, however, only few researches concentrated on the effects of cultivation on the camptothecin production in N. foetida. The objective of this study was to investigate the effect of nitrogen (N) application rate, water stress, and shading on the growth, nutrient uptake, and the production of camptothecin in N. foetida. The studied plants were three-year-old N. foetida, grown in the greenhouse of farm of National Taiwan University. The treatments contained low and high N application rates (2N & 3N), water stress (3ND) and shading (3NS). All treatments were replicated four times and were arranged in randomized complete block design. All shoots were cut off from the 37 cm in height above ground on May 9, 2008, and all plants sprouted on May 24, 2008. Two months of cultivation and one month of treatments were conducted after budding. Two grams of urea-N, 0.25 g superphosphate-P and 0.25 g KCl-K per plant were applied on May 24, 2004. Later one gram urea-N per plant was applied to each plant except the 2N treatment on July 8, 2004. For water stress treatment, the plants were withheld water until leaf wilting. After one jour of the leaf wilting, the plants were watered and a new drought cycle started. The shading treatment was processed with a black shade cloth that reduces 66% full sunlight. On October 24, all shoots were harvested with one shoot remaining. Then another treatment cycle was conducted. The whole plants were harvested after the second treatments. Five centimeter from the top of each shoot was defined as young leaves and young stems, and the remaining parts were mature leaves and mature stems. The results showed that treatments had no significant effect on the dry weight of the upper parts of plants; however, water stress treatment resulted in increase in the dry weight of root. The higher rate of N application resulted in increase in the concentration of total N, nitrate-N, and soluble reduced N of plants. There was no significant effect of treatment on the camptothecin concentration. Water stress resulted in decrease in the manganese concentration of the root, and increase in the amount and concentration of camptothecin of the root. Shading resulted in increase in the concentrations of the nitrate-N of all parts of plants and camptothecin of the trunk. The camptothecin concentration in different parts of plants decreased in following order: root > trunk > stem > leaf. The camptothecin concentrations were lower in young leaves and young stems than that in mature parts.