| The orchid family is one of the famous ornamental and medical plants in the world. Many orchids require mycorrhizal symbioses with fungi for their survival and development. The purpose of this study was to find several orchid mycorrhizal fungi and optimize their growth in sterile culture and also study the condition of seed germination.The details of this paper included isolation and identification of mycorrhizal fungi of orchids; screening fungal elicitor which promoted growth of rhizome and differentiation of adventitious bud of Cymbidium goeringii; screening mycorrhizal fungi which promoted growth of tissue culture of Hybrid Cymbidium; observation of microstructure of mycorrhiza; condition of seed germination in situ of C. goeringii. The main results were as follows:1. Eight mycorrhizal fungal strains were isolated from the root of wild C. goeringii. Combination of traditional morphological observation and modern molecular technology isolated eight fungal strains and also nine fungal strains (kept in the lab) were identified. These strains belong to Fusarium, Ceratorhiza, Umbelopsis, Chaetomium, Papulospora, Aspergillus, Paecilomyces, Alternaria and Ozonium.2. Tissue cultures of C. goeringii were induced on culture medium with the fungal elicitor. The result showed that different fungal elicitor promoted the growth and differentiation of adventitious bud of tissue culture. Compared to the control, the inducing effects of CF3 and GH132 which were isolated from C. goeringii did the best in biomass increasing, and the fresh weight getting extremely. The inducing effects of CF3, GH132 and CF1 which were isolated from C. goeringii did the best in differentiation of adventitious bud. In addition, the fresh weight of tissue culture increased with adding fungal elicitor of CF1. The fresh weight had significant difference compared with those in control when the fungal elicitor added to concentration ofâ…¢. 3. Tissue culture seedlings of the Hybrid Cymbidium were inoculated with six different fungal strains. After inoculated with strains CF1, CF3 and GDB254 isolated from C. faberi for three months, the fresh weight of the seedings increased significantly and the new roots become stronger and larger compared to the control. In addition, the three strains were obtained by re-isolating. Pelotons, regarded as typical structures of orchid mycorrhizae, were also found in the inoculating roots under a microscope. It seemed that the strains of CF1, CF3 and GDB254 associated with the Hybrid Cymbidium well and supplied the orchid with nutrition. It could be confirmed that the three strains were beneficial for the seedlings of this hybrid.4. The observation of the mycorrhizal microstructure of Hybrid Cymbidium showed that it belonged to the typical mycorrhiza of orchids. The infection pathway started with the invasion of the fungi into the velamen and then entered the cortical tissue by breaking the velamen. The pelotons were irregularly distributed in the cortex, mainly in several of the outer cortical cells. In infected cortical cells, pelotons often occurred near the nucleus or twisted with them together which was the main existing way of pelotons. The hyphae penetrated through the wall of cortical cells and continuously spread inwards. Fresh pelotons and deformed pelotons in the cortical cells occurred simultaneously, and the hyphae provided nutrients to plants when they were digested and absorbed.5. The results of research on seed germination showed that the most of seeds of C. goeringii with sterile culture in dark could germinate after five months, and these seeds could differentiate rhizomes in light. Seed germination did not occurre in situ and ex situ , so the condition of germination needs further research. In addition, an innovative seed germination set made of lantern slide and nylon mesh was used; it was beneficial both to the observation of seed germination status and retrieve of germinated seeds. |
PDF Full Text Request