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

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Abstract

Background and Aims

The negative logarithmic relationship between orthodox seed longevity and moisture content in hermetic storage is subject to a low-moisture-content limit (mc), but is mc affected by temperature?

Methods

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).

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