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Weber, John C.; Sorensen, Frank C. 1990. Effects of stratification and temperature on seed germination speed and uniformity in central Oregon ponderosa pine (Pinus ponderosa Dougl. ex Laws.). Res. Pap. PNW-RP-429. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 13p. Effects of stratification period and incubation temperature on seed germination speed and uniformity were investigated in a bulked seed lot of 200 ponderosa pine trees (Pinus ponderosa Dougl. ex Laws.) sampled from 149 locations in central Oregon. Mean rate of embryo development towards germination (l/days to 50 percent germination) and standard deviation of rate were estimated in a replicated, factorial experiment with four stratification periods (15, 30, 60, and 120 days) and four incubation temperatures (10, 15, 20, and 25 °C). Higher mean rate and standard deviation of rate, respectively, indicate fewer days to 50 percent germination (greater average speed) and less spread around the day of 50 percent germination (greater uniformity) if interpreted on the day scale (reciprocal of rate). Nearly all seeds germinated during an 80-day incubation period. Germination was complete with 60 days of stratification. Percentage of germination showed a peak at 20 °C incubation. Germination speed and uniformity increased with longer stratification and higher incubation temperature. Effects of stratification were greater at lower incubation temperatures, and effects of temperature were greater after shorter stratification. Longer stratification seemed to lower the minimum temperature requirement for germination. Multiple-regression equations accounted for more than 95 percent of the variation in means and standard deviations of rate. The discussion emphasizes practical implications for nursery managers who handle genetically diverse seed lots of central Oregon ponderosa pine.

Effects of stratification and temperature on seed germination speed and uniformity in central Oregon ponderosa pine (Pinus ponderosa Dougl. ex Laws.) /