Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: January 20, 2004
Publication Date: February 20, 2004
Citation: Towill, L.E. 2004. Pollen storage as a conservation tool. pp.180-188. In E. Guerrent, K. Havens and M. Maunder (eds) Ex Situ Plant Conservation: Supporting species survival in the wild. Island Press, Covela, CA. Interpretive Summary: Pollen preservation supplements seed and clonal preservation for conservation efforts. Although pollen is usually stored as a convenience in making crosses at desired times, it may be collected and used when seed is not available during collecting expeditions. Pollen preservation is very similar to seed preservation. Some pollens are desiccation tolerant and others quite sensitive. Longevity of the former is increased with desiccation and with storage at lower temperatures. The desiccation sensitive types often are more metabolically active and have quite short longevities at most storage temperatures. Cryogenic storage of the tolerant types is fairly easily accomplished; cryogenic storage of the sensitive types is possible, but requires more knowledge of the relationships between viability and moisture.
Technical Abstract: Pollen preservation may aid and supplement conservation efforts that traditionally involve seed or vegetative plant maintenance. As with seed, good quality pollen is desired and collection procedures should try to capture pollen with the best viability and vigor, and in sufficient amounts. Assays of viability include ability to set seed, pollen tube growth in the style or in vitro, and membrane permeability tests (fluorescein staining and tetrazolium staining). Vigor tests usually measure rate of pollen tube elongation or speed of germination. Pollen storage characteristics differ for desiccation-tolerant and -intolerant types. For the former lower moisture contents, within limits, and lower storage temperatures increase longevity. However, longevities differ considerably among species. Cryogenic storage is easily accomplished with pollen showing desiccation-tolerant behavior. Desiccation-sensitive pollen is problematic, often having very short lifetimes and high metabolic rates. Storage for some types can be days, but for others minutes. For some, cryogenic storage is possible if moisture levels are critically adjusted. When retrieved from storage either type of pollen must be used fairly quickly and may require humidification for optimum function.