Abstract
High seed quality is a prerequisite for successful crop production,
making maintenance of seed viability and vigour during storage
important. The effects of temperature and humidity on seed ageing are
well known, while the negative effect of oxygen in the seed storage
environment has been studied less. Here we report on experiments to
study the quantitative effect of oxygen on the ageing of seeds. Primed
celery seeds were chosen as a model, because of their relatively short
shelf life. After equilibration at four relative humidity levels (16,
33, 43 and 60% RH), the seeds were stored at four temperatures (5, 13,
20 and 30°C) and six oxygen levels (1, 5.2, 10, 21, 50 and 99%) for a
period up to seven years. Germination tests after storage confirmed a
strong shelf life-extending effect of low oxygen conditions, at all four
temperatures and the three lower humidity levels. Modelling the
viability data revealed a linear double logarithmic relationship between
the oxygen concentration and the storage time till a 50% decline in
viability (p50), for seeds pe-equilibrated at 16, 33 or 43% RH. The
models also showed that each halving of the oxygen concentration
increased seed longevity by around 77%. This means that a reduction of
the environmental oxygen concentration to a level below 1% increased
the shelf life of the primed celery seeds by a factor of twelve. For
seeds pre-equilibrated at 60% RH, the effect of lowering the oxygen
concentration below 21% was much less or even absent at 30°C, likely
due to a different physical or physiological condition of the seeds at
this higher humidity level. The large and logarithmic effect of reducing
the oxygen level during the dry storage of seeds provides additional
opportunities to prolong the shelf life of seeds either for commercial
or genebank storage. To estimate the effect of these factors, a model is
provided describing the quantitative effect of all three factors,
temperature, equilibrium relative humidity and oxygen concentration.
Several options for practical application are discussed.