Effects of osmotic priming and ageing on onion seed germination

Onion seeds were osmotically primed in polyethylene glycol solution (342 g/kg water) either for 14 days before accelerated ageing at 40°C. 18% m.c. for 0, 24, 48, 72 or 96 h, or for 10, 14 or 17 days after ageing. Priming improved the rate of germination compared with non-primed seed. Priming before ageing delayed the loss of viability due to ageing, but priming after ageing had no effect on viability. Primed and dried onion seed was stored for 18 months at 10°C, 9% m.c. with no effect on viability; improvements in germination rate due to priming were maintained over the storage period. Conductivity measurements of seed leachates were not a consistently reliable indicator of germination performance.