The influence of aerated hydration seed treatment on seed longevity as assessed by the viability equations

Aerated hydration (AH) treatments of cauliflower seeds for 12 h (12AH) and 28 h (28AH) at 20 degreesC resulted in improved or reduced storage potentia l of low or high vigour seeds, respectively, Seeds were stored at their ini tial seed moisture content (mean 5.5% me) or at 12% me at 10 degreesC for 1 2 months and at 20 degreesC for 4 months. The improved longevity of low vig our seeds was associated with increased K-i (initial seed viability) and a reduced rate of deterioration (1/sigma) whereas the K-i of high vigour seed s fell after 28AH and the rate of deterioration increased such that the tim e to lose one probit of viability decreased from 28.7 to 5.3 months at 10 d egreesC and from 10.4 to 1.2 months at 20 "C. The improved K-i of low vigou r seeds could be explained by the reduction in the extent of deterioration after AH, as indicated by the increase in germination after cotrolled deter ioration (CD), and the possible activation of metabolic repair during treat ment. In contrast the reduced germination after CD of AH-treated high vigou r seeds was indicative of deterioration as a result of treatment. Both high and low vigour seeds contained constitutive levels of beta -tubulin which increased during AH treatment, the increase being greater in high vigour se eds. High vigour seeds also showed an increase in the proportion of nuclear DNA present as 4C DNA, from 3% (untreated seeds) to 26% (28AH), indicative of germination advancement from the G(1) to G(2) phase of the cell cycle d uring treatment. This higher proportion of 4C DNA is correlated with the in creased sensitivity of seeds to drying and/or storage after AH, leading to their reduced K-i and storage potential. In contrast, there was little chan ge in %4C in low vigour seeds. Priming in polyethylene glycol (PEG, -1.0 MP a) for 5 d or 13 d also improved the longevity of low vigour seeds stored a t their initial and 12% me at 10 degreesC for 8 months, as reflected in the ir laboratory and CD germination. In this case, however, the improved longe vity of the low vigour seeds following 13 d priming was associated with an increase in 4C DNA from 4% (dry control) to 56% after treatment. The germin ation of both untreated and primed high vigour seeds remained high througho ut the storage period. Increases in the rate of germination (decreased mean germination time) observed after all AH and PEG treatments were not consis tently associated with an increase in the proportion of nuclei containing 4 C DNA.