氮肥用量對雷公根養分、產量及有效成分濃度的影響

Abstract

摘要 雷公根特有的有效成分，是多種三萜類的化合物，可促進膠原蛋白的合成，可改善肌膚問題，或治療皮膚癌，也具有增強學習與記憶的效果，可做為癲癇症及中風後的治療藥物。雷公根為多年生的匍匐性草本植物，單位面積產量低，因此，如何增加其有效成分濃度與產量相當重要。本研究探討土耕與水耕氮肥用量對雷公根生長、養分吸收及有效成分產量與分布的影響，於臺灣大學農場溫室進行盆栽試驗，設計為完全逢機設計。土耕部分，以不打洞的藍色塑膠盆裝土13.5公斤，處理分為不施氮肥的對照組及化學肥料處理氮量分別為每平方公尺施用3 g、6 g、12 g、24 g氮，磷肥和鉀肥之用量均相同，每平方公尺施用磷和鉀分別為3 g和4.5 g，有機質肥料處理施用6 g氮，共六種處理，每處理四重複。植體於處理後70天採收地上部，112天採收全株並採集土壤。植體經洗淨後分根、莖與葉三部分，在70℃下烘乾，測定乾重、總氮、硝酸態氮、銨態氮、磷、鉀、鈣、鎂、鐵、錳、銅、鋅及有效成分濃度，土壤經風乾磨碎、過篩後，測定土壤pH值、EC值、有機質、總氮、硝酸態氮、銨態氮、Bray-1磷及Mehlich III可萃取性鉀、鈣、鎂、鐵、錳、銅、鋅濃度。水耕部分，試驗之水耕液以二分之一強度的Hoagland養液為基底，以硝酸銨用量調控氮濃度分別為105、161、217及329 mg L-1四種處理，每處理四重複。以二分之一強度的Hoagland養液培養14天後，以四種不同氮量處理，每14天更換養液，處理42天後採收，植體分析項目同上。土耕試驗結果顯示，化學氮肥處理會降低土壤pH值，提高EC值及硝酸態氮濃度，有機質肥料處理使土壤pH值上升；在每平方公尺施用24 g氮處理使雷公根植體Mehlich III可萃取性錳濃度上升，對雷公根的乾物產量及有效成分濃度影響並不顯著，土耕及水耕系統的有效成分皆主要分布於葉部。水耕試驗結果顯示，在氮肥處理42天後，氮濃度217 mg L-1處理有最高乾物產量，氮濃度329 mg L-1處理則最低；雷公根有效成分濃度受氮肥處理影響而降低，以莖最為敏感，葉次之，根受影響最少。四種主要有效成分中以羥基積雪草酸苷和積雪草酸苷為主要受氮肥影響的成分。雷公根全株有效成分產量以105、161及217 mg L-1處理較高，329 mg L-1處理有效成分產量最低。

Abstract Theactive metabolites of Centella asiatica, centelloside, could improve synthesis of collagen, treat some skin diseases and enhance learning and memory. It could be a drug used after brain attack and epilepsy. C. asiatica is a herbaceous annual plant, having creeping stolons with a low biomass yield. Therefore, high biomass yield and high concentration of centelloside are very important in order to use this plant. The study was conducted in the green house of National Taiwan University with two types of culture, i.e., soil culture and water culture. All treatments were arranged in a randomized complete design. In the soil culture, there were six treatments, including: five rates of nitrogen (N) fertilizer treatments (0, 3, 6, 12, 24 g N m-2) and an organic fertilizer treatment (6 g N m-2). The same amounts of phosphorous (P) (3 g P m-2) and potassium (K) (4.5 g K m-2) as potassium dihydrogen phosphate and potassium chloride, respectively, were applied to all treatments except for the organic one. The plants were harvested two times, 70 days and 112 days after planting (DAP). Only the shoot was sampled at 70 DAP and the whole plant was harvested at 112 DAP. The soils were also sampled at 112 DAP. In the water culture, 1/2 strength modified Hoagland’s solution was used. There were four rates of N fertilizer treatments (N 105, 161, 217, 329 mg L-1) by adding different amounts of ammonium nitrate. Treatments were initiated after preculturing for 14 days and the whole plant was harvested after treating for 42 days. The plants were separated into leaf, stem and root then oven drying at 70℃ for three days. The concentration of total N, nitrate-N, ammonium-N, P, K, calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), copper (Cu), zinc (Zn), madecassoside, asiaticoside, madecassic acid and asiatic acid were analyzed. The pH, electric conductivity of saturation extract and the concentrations of total N, nitrate-N, ammonium-N, Bray-1 P, organic matter, Mehlich III extractable K, Ca, Mg, Fe, Mn, Cu and Zn of soil were also determined. Nitrogen fertilizer application resulted in decrease soil pH, increase EC and nitrate-N concentration. However, organic fertilizer application resulted in increase soil pH. Treatment of 24 g N m-2 resulted in the highest Mn concentration in all parts of C. asiatica. The dry matter yield of N 217 mg L-1 treatment was the highest and that of N 329 mg L-1 treatment was the lowest in water culture. The concentrations of centelloside of different parts of C. asiatica were sensitive to the N concentration applied in the nutrient solution and decreased in the order: stem > leaf > root. Madecassoside and asiaticoside were most significant affected by N fertilizer treatment in the four chemicals studied. The centelloside yield was the lowest under N 329 mg L-1 treatment.