The effect of low water content on seed longevity

The effects of water content and temperature on the viability of seeds in storage were studied using four crop species: wheat (Triticum aestivum), rice (Oryza sativa, Japonica type), millet (Setaria italica) and peanut (Arachis hypogaea). Seeds were dried from about 10% to about 2% water content then packaged in airtight containers and stored at 45 degrees C, room temperature (22.5 +/- 7.5 degrees C) and 0 degrees C for 2.5-4 years. At 45 degrees C, there was a clear optimum water content at 2% for peanut, 4% for millet, 4.5% for rice and 5% for wheat. At lower storage temperatures, there was a detrimental effect on longevity when seeds were stored at extremely low water contents, but aging rates at higher water contents were negligible. Thus the presence of an optimum water content was less clear for seeds stored at room temperature and 0 degrees C. Observations of reduced longevity in extremely dry seeds suggest that genebank curators must be careful not to over-dry seeds.