Root Collar Diameter Growth Research Articles

Growth response of loblolly pine ( Pinus taeda L.) seedlings to ozone fumigation

Twenty-two week-old Pinus taeda L. (loblolly pine) seedlings of 30 open-pollinated and five full-sib families, representing a wide range in geographic origin, were grown in charcoal-filtered (CF) air or CF-air supplemented with 160 or 320 nl liter −1 ozone for 8 h day −1, 4 days week −1, for 9 weeks. Visible foliar injury (banded chlorosis, tip burn and premature senescence) was apparent in many families after 3 weeks in 320 nl liter −1 and 6 weeks in 160 nl liter −1 ozone. Decreases in relative height and root collar diameter growth rates, total dry weight, root dry weight, shoot dry weight, and root/shoot ratios were evident after 9 weeks of treatment with both 160 and 320 nl liter −1 ozone. For relative height growth rates, family differences in response to ozone were observed. By the study's end, net photosynthesis rates were 15% less for the 320 nl liter −1 ozone treatment as compared to the CF-air treatment. Total soluble sugar and total starch content of roots were not changed after 9 weeks of ozone exposure.

Morphological Effects of Root Pruning and Wrenching White Spruce Transplants

Abstract The principal objective of this research was to evaluate the effect of root pruning followed by wrenching on the morphological quality of 2 + 2 white spruce transplant stock during the final year on the nursery. In 1984, white spruce transplants were root pruned: (1) before shoot elongation; (2) during elongation; and (3) after elongation, followed by root wrenching at 28-day intervals until September (4, 3, and 2 times, respectively). In 1985, similar stock was root pruned before shoot elongation and (1) root wrenched at 21-day intervals (4 times), and (2) root wrenched periodically (twice). In both years, height and root collar diameter growth were monitored throughout the season. In the fall, morphological quality was assessed and bud samples were collected to determine the effects of root conditioning on primordia development. Root conditioning modified the morphology of stock in both years by reducing height and root collar diameter and inducing the development of a compact fibrous root system. Early season root pruning followed by wrenching at regular intervals throughout the growing season had the most effect on shoot and root morphology. Differences in results between years were attributed to environment. North. J. Appl. For. 5:245-247, December 1988.