Factors affecting seed germination of the terrestrial orchid Goodyera repens var. ophioides Fernald and the in vitro culture of orchidaceous mycorrhizae.

摘要

Terrestrial orchids rely on a mycorrhizal association to grow and develop into adult plants. There are several aspects of this relationship about which little is known. The first area of study concentrated on developing a method of orchid symbiont identification. Results with orchid endophytes showed that exogenously applied polyamines (spermidine and spermine) induced clamp connections (in isolate UAMH 6440) and asexual reproductive structures in these fungi.; The second area of study concentrated on environmental factors (light; culture media; polyamine treatments; and fungal cell-wall filtrates) affecting development of the terrestrial orchid Goodyera repens var. ophioides Fernald. Light enhanced germination and root formation, but had no effect on seed mortality, rhizoid or large protocorm formation. Better germination and overall development was observed on a media rich in carbohydrates (Potato Dextrose Agar) compared to Murishage and Skoog's Minimal Organics. Germination occurred between 2 and 4 weeks. Light and media had somewhat additive effects on germination. Light triggered germination, but further development required a carbohydrate source which Murishage and Skoog's Minimal Organics media lacked. Spermidine and spermine inhibited germination and development of G. repens seeds. Light partially reversed the inhibition of germination and development by polyamines.; Red and fluorescent light treatments enhanced Goodyera repens seed germination to similar levels. Seed germination of cultures exposed to blue and ultraviolet light treatments were not significantly different from seeds germinated in continuous darkness. Far red light treatments decreased percent seed germination to a level below that of continuous darkness. These results support the idea that light enhanced germination of Goodyera repens seeds may be mediated through phytochrome.; Effects of conditioned media and fungal cell-free extracts (fungal elicitors/fungal cell-wall filtrates) on growth and development of G. repens were examined. The addition of distilled water and Potato Dextrose Broth had similar effects to the control. Conditioned media and cell-free extracts derived from Ceratorhiza goodyera-repentis (UAMH 6440) seemed to suppress germination and further development of G. repens seeds. Both fungal cell-free extracts and conditioned media derived from strain TN29-Pcil-154 promoted germination, but only the cell-free extracts enhanced further development.