Overcoming Challenges of Conserving Seeds of Rare and Endangered Plants of North America.

Over 4400 plant species are considered at risk of extinction in the United States and Canada. Founded in 1984, the Center for Plant Conservation is a network of botanic institutions dedicated to preventing extinction and achieving recovery for imperiled native plants. CPC Participating Institutions directly protect over 1090 species in seed banks, tissue culture facilities, or botanical garden living collections. Rare plants pose unique challenges for collection and curation, as they often grow in remote locations in very small populations, bare seeds that may suffer low viability, and may not be easy to grow. We strive to maximize genetic diversity of our collections over spatial and ecological scales. Maintaining maternal lines separately enables us to estimate genetic diversity and maintain it during propagation and eventual repatriation to the wild. To increase options for future use, ideally we seek to store seeds long-term. Germination trials inform us about the storage capability of the rare species’ seeds. Viability tests before and after varying lengths of time in cold storage help us determine storage capability. In a comparison of 146 species from subtropical and tropical globally imperiled ecosystems in the US, most seeds (70.06%) tolerated dry and cold storage conditions at least for some period of time, while few (17.11%) were desiccation or freezing sensitive. Sensitive species include orchids and ferns, and many trees that are facing serious threats from pathogens require experimental cryogenic and tissue culture storage for preservation. Thus, multiple tools and devoted research are necessary to conserve endangered plant species.