Picky Partners: Why Our Native Orchids Grow Where They Do

Sponsoring Organization: US Botanic Garden

Speaker: Melissa McCormick, Ph.D, Ecologist, Smithsonian Environmental Research Center

The vast majority of plants require associations with mycorrhizal fungi to obtain nutrients and grow in natural environments. Orchids are no exception to this. However, while most mycorrhizal associations are beneficial to both partners, orchids generally parasitize their mycorrhizal fungi, actually digesting it to obtain nutrients. Most orchids can only form mycorrhizal associations with a few kinds of fungi, so they can only grow where these fungi are. However, it is not easy to figure out where particular fungi occur. DNA analysis helps map where host fungi grow in the soil and where they are abundant enough to support orchid growth. These techniques also determine what factors (such as soil and environmental conditions) affect orchid host fungi, where orchids can grow and how to improve growth conditions. Because they rely on only a few fungi, orchid mycorrhizal associations may be particularly sensitive to disruption by environmental changes.

Pre-registration required: Free. Program Code: LH041812. www.usbg.gov or by phone at (202) 225-1116.