THEORETICAL BASIS OF PROTOCOLS FOR SEED STORAGE .3. OPTIMUM MOISTURE CONTENTS FOR PEA-SEEDS STORED AT DIFFERENT TEMPERATURES

In previous work, we demonstrated that there was an optimum moisture l evel 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 (Vertu cci 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 hypot hesis that the optimum moisture content for storage varies with temper ature. Seed viability and vigour were monitored during storage under d ark or lighted conditions at relative humidities between 1 and 90%, an d temperatures between -5 and 65 degrees C. The optimum moisture conte nt varied from 0.015 g H2O g(-1) d.wt at 65 degrees C to 0.101 g H2O g (-1) d.wt at 15 degrees C under dark conditions and from 0.057 at 35 d egrees C to 0.092 g H2O g(-1) d.wt at - 5 degrees C under lighted cond itions. Our results suggest that optimum moisture contents cannot be c onsidered independently of temperature. This conclusion has important implications for 'ultra-dry' and cryopreservation technologies.