Temperature Sensitivity of the Low-moisture-content Limit to Negative Seed Longevity–Moisture Content Relationships in Hermetic Storage

Background and Aims The negative logarithmic relationship between orthodox seed longevity and moisture content in hermetic storage is subject to a lowmoisture-content limit (mc), but is mc affected by temperatureMethods Red clover (Trifolium pratense) and alfalfa (Medicago sativa) seeds were stored hermetically at 12 moisture contents (2–15%) and five temperatures (–20, 30, 40, 50 and 65°C) for up to 14·5 years, and loss in viability was estimated.Key Results Viability did not change during 14·5 years hermetic storage at 20°C with moisture contents from 2·2 to 14·9% for red clover, or 2·0 to 12·0% for alfalfa. Negative logarithmic relationships between longevity and moisture contents >mc were detected at 30–65°C, with discontinuities at low moisture contents; mc varied between 4·0 and 5·4% (red clover) or 4·2 and 5·5% (alfalfa), depending upon storage temperature. Within the ranges investigated, a reduction in moisture content below mc at any one temperature had no effect on longevity. Estimates of mc were greater the cooler the temperature, the relationship (P < 0·01) being curvilinear. Above mc, the estimates of CH and CQ (i.e. the temperature term of the seed viability equation) did not differ (P > 0·10) between species, whereas those of KE and CW did (P < 0·001).Conclusions The low-moisture-content limit to negative logarithmic relationships between seed longevity and moisture content in hermetic storage increased the cooler the storage temperature, by approx. 1·5% over 35°C (4·0–4·2% at 65°C to 5·4–5·5% at 30–40°C) in these species. Further reduction in moisture content was not damaging. The variation in mc implies greater sensitivity of longevity to temperature above, compared with below, mc. This was confirmed (P < 0·005).