| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 96 === The Dendrobium species have been commonly used in traditional Chinese medicine, by fresh or by dried pseudobulb, as a tonic to nourish the stomach, replenish body fluid and reduce fever. However, the wild Dendrobium spp. are endangered for their slow growing and had been extensively taken off from their native land.
The orchid mychorrhiza fungi (OMF) belong to endomychorrizal fungi are generally found in the root cells of Orchid family. OMF normally inoculate and become symbiotic with orchid in the root cells by two ways: tolypophagy and ptyophagy. Growth improvement after inoculation of OMF had been found in several Orchid species. Plant growth substances (PGS) are synthetic compounds that have the same physiological effects as plant hormone and can be used to enhance plant growth. Moscatilin, a bibenzyl derivative originally purified from Dendrobium moscatum, is potentially efficacious against some kinds of cancer.
An attempt to increase the growth rate of herbal dendrobium and the content of moscatilin was carried out by the inoculation of OMF and application of PGS in this study. Thus the inoculation of OMF and application of PGS in seedlings of Dendrobium candidum and D. moniliforme results were conducted, and showed that amino acid powder (40 μg/ L), Lysine#24 (1000 μL/ L), Chitosan (500 μL/ L), and amino acid/organic fertilizer mixed solution (200 μL/ L) increased plant height, pseudobulb length, width or leaf numbers of both Dendrobium spp. The inoculation of Cylindrocarpon spp.(Cy) together with application of amino acid powder were highly recommended in practical use for enhancing the growth of both Dendrobium seedlings. An analysis of several common herbal and ornamental dendrobiums in Taiwan, the result showed that only two herbal dendrobium, D. tosaense and D. clavatum, contained moscatilin in the pseudobulbs. The amount of moscatilin stored in the pseudobulb of D. clavatum inoculated with Rhizoctonia spp., R01, are higher than those of the non-mycorrhizal ones. Also the inoculation of R04 significantly increased the amount of moscatilin in the pseudobulb of D. tosaense. Inoculation of Cylindrocarpon spp. enhanced the root growth of mature D. clavatum thus higher root dry weight of D. clavatum was found after 200 days. It was observed that the mycorrhizal structure of different dendrobiums by scanning electron microscopy. Results showed that two genera of OMFs, Rhizoctonia spp. and Cylindrocarpon spp., forming peletons in the roots of inoculated dendrobiums. The infection mode of these two OMFs belong to tolypophagy, in which mycorrhizal cortex cells, peletons could be observed.
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