WOUND CLOSURE IN TREES AFFECTED BY PACLOBUTRAZOL
Shuju Bai, William R. Chaney , and Yadong Qi
Abstract: Experiments were conducted to investigate the effects of paclobutrazol on closure of wounds made through the bark or resulting from pruning branches in nine species of trees. The species studied were American sycamore (Platanus occidentalis L.), black walnut (Juglans nigra L.), European black alder (Alnus glutinosa L.), red oak (Quercus rubra L.), sweetgum (Liquidambar styraciflua L.), white ash (Fraxinus americana L.), white oak (Q. alba L.), white pine (Pinus strobus L.), and yellow poplar (Liriodendron tulipifera L.). Paclobutrazol was applied using either the soil drench or soil injection method. Circular wounds (2 cm [0.8 in.] diameter) were made in the bark on the main stem, and branches were pruned from treated and untreated trees at the time of paclobutrazol application in the spring. The rate of wound closure was determined one, two, and three growing seasons after treatment. The rate of bark wound closure was reduced in paclobutrazol-treated black walnut, European black alder, red oak, sweetgum, and white oak. There was no difference in the rate of closure of wounds in the bark of treated and untreated American sycamore, white ash, white pine, or yellow poplar. The rate of pruning wound closure was reduced in black walnut, European black alder, red oak, sweetgum, and white oak, but was not influenced by paclobutrazol treatment in white ash, white pine, or yellow poplar. The inhibitory effect of paclobutrazol on closure of both bark and pruning wounds in some species persisted at least 3 years.
Keywords: Bark wound; growth retardant; paclobutrazol;
pruning wound; tree growth regulator; wound closure