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Studies on the Original Plants identification, Mass Propagation and the Free Radical Scavenging Capacity of Three Taiwanese Dendrobium Species
|關鍵字:||櫻石斛;Dendrobium linawianum;石斛;黃花石斛;基原鑑定;大量繁殖;抗氧化作用;D. moniliforme;D. tosaense;Original Plants identification;Mass Propagation;Free Radical Scavenging Capacity||出版社:||農藝學系||摘要:||
為探討台灣藥用石斛包括櫻石斛(Dendrobium linawianum)、石斛(D. moniliforme)、黃花石斛(D. tosaense)等不同的基原植物之特性，本試驗於台灣山地採集三種石斛，進行植株外部形態調查及藥材的顯微鑑定，並利用組織培養大量繁殖實生苗後，移植於不同介質，再進行抗氧化作用評估及礦物元素濃度測定。研究結果摘要如下：
四、利用掃瞄電子顯微鏡 (SEM) 觀察種子外部形態，發現石斛及黃花石斛分別在授粉後5~8週及3~6週為大孢子細胞發育階段；分別在授粉後9週及7週時，種皮已完全形成並脫離胎座，種皮且開始逐漸乾縮。
五、使用石斛及黃花石斛授粉後12週的種子進行發芽試驗，結果以含1/2MS基本鹽類添加3% 蔗糖及0.9% Difco agar之培養基效果最佳。所產生的幼苗經培養於含全量MS基本鹽類並添加1.5% 蔗糖、8% 香蕉泥、8% 馬鈴薯汁液、8% 椰子汁液及0.9 % Difco agar之培養基，對於植株的生長最為有利。將石斛的組培苗移植到水苔或水苔與蛇木屑混合的栽培介質，植株的成活率最高。
六、移植後六個月的三種石斛移植苗經甲醇萃取，抽出物具有與α-tocopherol相近的抗氧化能力(DPPH radical scavenging activity)；另以黃花與石斛的甲醇抽出物經部份純化後，證實黃花石斛所含的quercetin及石斛的alkyl ferulates為植株具有抗氧化能力之主要成分。
Studies on the Morphology, Mass Propagation and the Free Radical Scavenging Capacity of Three Taiwanese Dendrobium Species
To understand the characteristics of native medicinal herb plants of Taiwanese Dendrobium, including D. linawianum, D. moniliforme and D. tosaense, field collection was conducted between 1999 and 2000. The collected plant materials were subjected to morphological studies by external observation and microscopic examination. Tissue culture experiments on seed germination were carried out followed by the screening of culture matrix of the transplanted seedlings. Chemical analysis of mineral concentrations and evaluation of anti-oxidizing ability of the 6-month old transplanted plants were then conducted to provide basic information related to their medicinal utilization. The results are abstracted as follows.
1. There were significant differences in external morphology among the three Dendrobium species. The mid-upper stem of D. linawianum is flat column in shape with elongated leaves containing 5 major veins per leaf. Its flower has light purple front ends on white petals and violet front end on lip petal. D. moniliforme has cylindrical stem and needle-shaped leaves with 3 major veins per leaf. The flower has white petals without any colored mark and a lip petal with a brown strip. D. tosaense has cylinder stem and shield-like leaves with 5-6 major veins per leaf. It has light green petals and a white lip petal with a red strip.
2. D. linawianum had the thickest leaf sheath and the widest vascular bundles than the other two species. Needle-shaped crystals were commonly observed in the leaf sheath cells of D. linawianum while only particle-shaped crystals were found sporadically in D. moniliforme. Tracheids of scalar form and net form existed in the three species, but those of spiral form were also observed in D. tosaense. Plants of D. linawianum had thicker cuticlular layer and slight lignification on stem surface. Lignification was not observed in the other two species. The stem cells of D. linawianum and D. moniliforme contained single-particle crystals but not for D. tosaense. Tracheids of net form and porous form were common in the stem of D. tosaense, and those of net form and scalar form were generally existed in the other two species.
3. Pollination experiments were conducted among different flowers within an individual species. Pollinating pollens collected 1-2 days after flowering for D. moniliforme and 1-4 days after flowering for D. tosaense to stigmas of the same age gave the highest fruiting rates (83% and 100%, respectively). The fruiting percentage was jointly affected by the vigor of pollen and stigma, as expressed (in days after flowering) by the pollen age and time of pollination. The capsules attained the maximum length at 6-7 weeks after pollination.
4. Examination by scanning electron microscopy revealed that the megaspore developmental staged occurred at 5-8 weeks after pollination for D. moniliforme and 3-6 weeks after D. tosaense. The seed coat was fully developed and the seed was separated from the placenta at 9 and 7 weeks after pollination for D. moniliforme and D. tosaense, respectively. The seed coat started to dry and showed wrinkled appearance thereafter..
5. Seeds of D. moniliforme and D. tosaense were germinated in vitro at 12 weeks after pollination. The culture medium containing 1/2 MS basic salt supplemented with 3% sucrose and 0.9% Difco agar showed the best results of germination rates. The young seedlings were then subcultured and the medium of MS basic salt with 1.5% sucrose, 8% each of banana homogenate, potato juice and coconut milk, and 0.9% Difco agar was superior in promoting plant growth to other medium treatments. When the seedlings were transplanted to the greenhouse, the best culture matrixes were sphagnum moss and the mixture of sphagnum moss and tree fern, judged by the performances of survival rates.
6. After 6-month culture in greenhouse, the plants were grounded and extracted with methanol. The extracts showed DPPH radical scavenging activities similar to that of α-tocopherol. Further tests on the partially purified extracts indicated that quercetin and alkyl ferulates were the major components of anti-oxidizing ability for D. tosaense and D. moniliforme, respectively.
7. The N, P and K concentrations in the in vitro cultured seedlings were high for both D. moniliforme and D. tosaense. After 1 year of culture in greenhouse, N, P, and K concentrations of the transplanted plants decreased significantly, and were similar to those of the field-collected plants in some cases. The transplanted plants had the highest concentrations of Ca and Mg. In addition, the in vitro cultured seedlings of D. tosaense tended to have higher concentrations of Fe, Mn, Cu, Zn, and B.
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