Pre-Severance Environmental Conditions Influence Rooting Response of Eastern White Pine Needle Fascicles
Abstract:Eastern white pine (Pinus strobus L.) needle fascicles collected from 40 otters, 10 seedlings at four locations, in each of 2 years varied greatly in rooting response. Correlations between percent rooting and foliar levels of carbohydrates and mineral nutrients were low and inconsistent within and between years, indicating factor(s) other than nutrition were responsible for the rooting response variation. The cause of within and among year variation in needle fascicle rooting response was explored in two additional experiments. In the first experiment, 20 otters were exposed to a constant 7°C temperature. Needle fascicles were collected after 0, 500, 1,000, and 1,500 hours exposure. Rooting response of needle fascicles from all 20 otters was greatest following 1,000 hours pre-severance chilling. In a second experiment, needle fascicles were collected at four times (Nov., Dec., Jan., and Feb. 15) from 26 ortets exposed to natural, fluctuating temperatures. In general, needle fascicles collected on Jan. 15 rooted best. Collection date, synonymous with accumulated chill units, accounted for the greatest proportion of the variation in rooting response. Several chill unit accumulation models were used to estimate chill unit accumulation under natural conditions. The best model accounted for 58 percent of the rooting response variation. The model-predicted accumulation of 1,166 chill units by the Jan. 15 collection date was in close agreement with the 1,000 hour optimum found at a constant 7°C. Fertilizer rates applied to ortets in the 1978 season affected needle fascicle rooting response in the 1979-80 season. Forest Sci. 30:343-354.
Document Type: Journal Article
Affiliations: Associate Professor, Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609
Publication date: June 1, 1984
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