Effect of stratification in polyethylene glycol solutions on germination of three North American shrub species

Abstract

Summary Cercocarpus montanus, Amelanchier alnifolitl and Shepherdia canadensis are North American shrub species with seeds exhibiting physiological dormancy overcome by stratification (moist prechill). Germination of these species occurs during stratification, reducing the number of healthy non-dormant seeds available for sowing at the end of treatment. The effectiveness of incubating seeds in polyethylene glycol (PEG 8000, molecular weight 8ooou) solutions to reduce germination during stratification was examined for each species using a factorial arrangement of PEG concentrations and 3°C stratification durations. PEG treatments reduced both moisture content and germination during stratification in a dose-dependent manner for each species. Incubation in PEG at concentrations necessary to suppress germination during stratification had differential effects on the total germination of each species, ranging from no reduction in total germination of A. alnifolia to a large reduction in the total germination of S. canadensis. A discussion of reduced oxygen availability in PEG stratification solutions and its effect on metabolic processes leading to dormancy release or secondary dormancy induction is presented. Species variability in response to stratification in PEG is discussed in terms of oxygen availability, trtinimum moisture content requirements and the removal of PEG after treatment.