Theoretical Basis of Protocols for Seed Storage III. Optimum Moisture Contents for Pea Seeds Stored at Different Temperatures

Abstract In previous work, we demonstrated that there was an optimum moisture level for seed storage at a given temperature (Vertucci and Roos, 1990), and suggested, using thermodynamic considerations, that the optimum moisture content increased as the storage temperature decreased (Vertucci and Roos, 1993 b ). In this paper, we present data from a two year study of aging rates in pea ( Pisum sativum ) seeds supporting the hypothesis that the optimum moisture content for storage varies with temperature. Seed viability and vigour were monitored during storage under dark or lighted conditions at relative humidities between 1 and 90%, and temperatures between -5 and 65°C. The optimum moisture content varied from 0·015 g H 2 O g -1 d.wt at 65°C to 0·101 g H 2 O g -1 d.wt at 15°C under dark conditions and from 0·057 at 35°C to 0·092 g H 2 O g -1 d.wt at -5°C under lighted conditions. Our results suggest that optimum moisture contents cannot be considered independently of temperature. This conclusion has important implications for 'ultra-dry' and cryopreservation technologies.