Studies On The Symbiotic Mechanism Between Anoectochilus Roxburghii And Its Endophytic Fungi

1. The effects of different combinations of cytokinin and auxin on tissue culture of Anoectochilus roxburghii (Wall) Lindl. was studied and the course of growth and development of buds and formation of complete plantlets was also observed. Shoot tips and nodal segments were used for axillary shoot proliferation on Murashige-and-Skoog-based medium supplemented with different combinations of cytokinin (1mg/1) and auxin(0.5mg/l). Different combinations of cytokinin and auxin have different effects on shoots induction,while cytokinin is a major factor. Combinations of BA+NAA and BA+IBA are the optimum media to micropropagation of A.roxburghii.2. A symbiotic system of Anoectochilus roxburghii and endophytic fungi was set up, so as to study the relationship between A. roxburghii and endophytic fungi and new cultural methods of A. roxburghii. The optimum composition of symbiotic medium is NH₄NO₃ 825mg/L , KNO₃950 mg/L , MgSO₄185 mg/L , inositol 100mg/L , other organic components are 2/3 times as much as that of MS medium , sugrose 15g/L , other components are the same as that of MS medium , agar 9g/L , pH 5.8 . Cultures were maintained at 24℃²5℃ under a 11-h photoperiod provided by cool white fluoresscent light (150Lx ) . A. roxburghii and endophytic fungi can grow together well and form endomycorrhiza in the symbiotic system. Moreover, endophytic fungi can stimulate the growth and developmemt of A. roxburghii.3. 17 strains of fungi isolated from orchids are cultured together with seedlings for one month, respectively. Two strains have been screened out. They could promote seedlings growth significantly and increase biomass production of seedlings. The two fungi provide a model organism for the study of beneficial plant-microbe interactions and a new tool for improving plant production systems. They belong to Epulorhiza sp.