Author
|
Submitted to: Book Chapter
Publication Type: Book / Chapter Publication Acceptance Date: 12/1/2004 Publication Date: 11/1/2005 Citation: Walters, C. 2005. Water properties and cell longevity. In P. Buera, J. Welti-Chanes, P. Lillford and H. Corti (eds). Water Properties of Food, Pharmaceutical and Biological Materials. CRC Press, Boca Raton, FL. p. 191-204. Interpretive Summary: This paper provides a short primer on the current knowledge of seed longevity in genebanks and the factors that contribute to it. Factors are considered in a biophysical context which forms the basis for a mechanistic understanding of how factors interact. These interactions possibly explain why longevity of cryogenically stored seeds is shorter than expected. Technical Abstract: Most of the germplasm at NCGRP (~350,000 accessions) is stored as dried seeds. The innate desiccation tolerance of mature seeds from most agricultural crops allows them to be dried to very low water contents without damage. At NCGRP, seeds are dried to water contents between 0.04 and 0.08 g H2O/g dw which can be achieved in a relative humidity-controlled room set at 10 C and 25 to 30% RH. Once dried, seeds survive exposure to subfreezing temperatures and the bulk of the NCGRP collection is stored at -18 C. Cryogenically stored seeds are placed in the vapor phase above liquid nitrogen where temperatures range from -120 to -180 C. Viability of stored seeds is monitored on a 5 to 10 year cycle to ensure that the accession is flagged for regeneration before the seed becomes badly deteriorated. This paper reports results of longevity assays of seeds stored in conventional and cryogenic storage at NCGRP, showing that species vary widely in achieved longevity and that cryogenic storage does not provide the extensive increase in longevity once assumed. The status of water in stored seeds may explain the interaction of species, water content and temperature on aging kinetics. |
