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Author: Dr. Fernando Camacho Source: Unknown - 1995 Please cite: Camacho, F. and Arron, G. (1995) Effects of the regulators paclobutrazol and flurprimidol on the growth of terminal sprouts formed on trimmed silver maple trees. Canadian Journal of Statistics 3(23). Data on tree growth used in the Case Study published in the September, 1995 issue of the Canadian Journal of Statistics. This data set was been provided by Dr. Fernando Camacho, Ontario Hydro Technologies, 800 Kipling Ave, Toronto Canada M3Z 5S4. It forms the basis of the Case Study in Data Analysis published in the Canadian Journal of Statistics, September 1995. It can be freely used for noncommercial purposes, as long as proper acknowledgement to the source and to the Canadian Journal of Statistics is made. Description The effects of the Growth Regulators Paclobutrazol (PP 333) and Flurprimidol (EL-500) on the Number and Length of Internodes in Terminal Sprouts Formed on Trimmed Silver Maple Trees. Introduction: The trimming of trees under distribution lines on city streets and in rural areas is a major problem and expense for electrical utilities. Such operations are routinely performed at intervals of one to eight years depending upon the individual species growth rate and the amount of clearance required. Ontario Hydro trims about 500,000 trees per year at a cost of about $25 per tree. Much effort has been spent in developing chemicals for the horticultural industry to retard the growth of woody and herbaceous plants. Recently, a group of new growth regulators was introduced which was shown to be effective in controlling the growth of trees without producing noticeable injury symptoms. In this group are PP 333 ( common name paclobutrazol) (2RS, 3RS - 1 -(4-chlorophenyl) - 4,4 - dimethyl - 2 - (1,2,4-triazol-l-yl) pentan - 3- ol and EL-500 (common name flurprimidol and composition alpha - (1-methylethyl) - alpha - [4-(trifluromethoxyl) phenyl] - 5- pyrimidine - methanol). Both EL-500 and PP-333 have been reported to control excessive sprout growth in a number of species when applied as a foliar spray, as a soil drench, or by trunk injection. Sprout length is a function of both the number of internodes and the length of the individual internodes in the sprout. While there have been many reports that both PP 333 and EL-500 cause a reduction in the length of internodes formed in sprouts on woody plants treated with the growth regulators, there has been but one report that EL-500 application to apple trees resulted in a reduction of the number of internodes formed per sprout. The purpose of the present study was to investigate the length of the terminal sprouts, the length of the individual internodes in those sprouts, and the number of internodes in trimmed silver maple trees following trunk injection with the growth regulators PP 333 and EL-500. Experimental Details. Multistemmed 12-year-old silver maple trees growing at Wesleyville, Ontario were trunk injected with methanolic solutions of EL-500 and PP-333 in May of 1985 using a third generation Asplundh tree injector. Two different application rates (20 g/L and 4 g/L) were used for each chemical. The volume of solution (and hence the amount of active ingredient) injected into each tree was determined from the diameter of the tree, using the formula: vol(mL) = (dbh)*(dbh)*.492 where dbh is the diameter at breast height. Two sets of control trees were included in the experiment. In one set, tree received no injection (control) and in a second set, the trees were injected with methanol, the carrier in the growth regulator solutions. Ten trees, chosen at random, were used in each of the control and experimental sets. Prior to injection, all the trees were trimmed by a forestry crew, with their heights being reduced by about one third. In January 1987, twenty months after the trees were injected, between six and eight limbs were removed at random from the bottom two-thirds of the canopy of each of the ten trees in each experimental and control set. The limbs were returned to the laboratory and the length of all the terminal sprouts, the lengths of the individual internodes, and the number of internodes recorded. Between one and 25 terminal sprouts were found on each limb collected. Sprouts which had a length of 1 cm or less were recorded as being 1 cm in length. In such spouts, the internode lengths were not measured, but were calculated from the total length of the sprout and the number of internodes counted. Internode lengths were then expressed to one decimal place. In two instances, one of the ten trees in a set could not be sampled because limb removal would have jeopardized the health of the tree over the long-term. Data set: Each of the records represents a terminal sprout and contains the following information: N the sprout number TR treatment 1 control 2 methanol control 3 PP 333 20g/L 4 PP 333 4g/L 5 EL 500 20g/L 6 EL 500 4g/L TREE tree id BR branch id TL total sprout length (cm) IN number of internodes on the sprout INTER a list of the lengths of the internodes in the sprout, starting from the base of the sprout (129 entries) Sprouts 1868 to 1879 do not have branch identification data.