Conifer seed germination is faster after membrane tube invigoration than after prechilling or osmotic priming

Two different pre-emergence treatments preventing radicle protrusion by limiting the extent of imbibition were tested on conifer seeds. Osmotic priming in solutions of polyethylene glycol (PEG) which prevented radicle protrusion during prolonged (3 weeks) treatment resulted in variable percentage germination, mean germination time, and coefficient of uniformity of germination among different seedlots when placed on water. All three germination parameters were either unchanged or inferior in seeds subjected to the various PEG concentrations, treatment temperatures and treatment durations when compared with prechilled controls. In contrast, white spruce and jack pine seeds invigorated at 30% moisture content and 15°C in Gore-Tex membrane tubes consistently germinated faster than prechilled control seeds when subsequently placed on water. Tube invigoration affected neither the ability of seeds to complete germination nor the uniformity of germination. The decrease in mean germination time as treatment duration progressed was always linear and plateaued at approximately 4 days after the tube-invigorated seeds were placed on water regardless of species or seed-lot On average, tube invigoration decreased white spruce mean germination time by 0 13 ± 0.02, and black spruce by 0.23 ± 0.03 day per day of invigoration for up to 20 days of treatment. Jack pine mean germination time decreased 0.2 ± 0.04 day per day of invigoration for up to 14 days of treatment.