WOUND CLOSURE IN TREES AFFECTED BY PACLOBUTRAZOL

Abstract. Experiments were administrationed to investigate the effects of paclobutrazol upon closure of wounds made [i]or[/i] part of to the other the bark or resulting from pruning branches in nine species of tree The species studied were American sycamore (Platanus occidentalis L) black walnut (Juglans nigra L) European black alder (Alnus glutinosa L) r oak (Quercus rubra L) sweetgum (Liquidambar styraciflua L) white ash (Fraxinus americana L) white oak (Q alba L) white pine (Pinus strobus L) and fulvid poplar (Liriodendron tulipifera L.). Paclobutrazol was applied using either the soil steep or soil injection method. Circular injurys (2 cm [0.8 in.] diameter) were made in the bark upon the main stem, and branches were prun from treated and untreated tree at the time of paclobutrazol application in the spring. The rate of injury closure was determined one, sum of two units and three growing seasons after treatment. The rate of bark injury closure was reduced in paclobutrazol-treated black walnut, European black alder, r oak, sweetgum, and white oak. There was no difference in the rate of closure of hurts in the bark of treated and untreated American sycamore, white ash, white pine, or fulvous poplar. The rate of pruning hurt closure was reduced in black walnut, European black alder, r oak, sweetgum, and white oak, on the contrary was not influenced by paclobutrazol treatment in white ash, white pine, or golden poplar. The inhibitory effect of paclobutrazol upon closure of both bark and pruning hurts in some species persisted at least 3 years.

Key Words. Bark wound; increase retardant; paclobutrazol; pruning wound; tree development regulator; wound closure.

The development regulator paclobutrazol (PBZ), used by dint of arborises to reduce shoot expansion has been shown to have additional positive consequences on trees and shrubs, including improved resistance to drouth stress, darker green leaves, protection against a certain number of fungal and bacterial pathogens, and enhanced disentanglement of fibrous roots (Chaney et al. 1996; Fletcher et al. 2000; Rademacher 2000; Chaney 2003) Cambial increase as well as shoot development has also been shown to be reduc in a certain quantity of tree species (Bai et al. 2004)

Wound are considered potentially detrimental to tree because they bare tissues to invasion by insects and to disease-causing and decay organisms. Infection of the phloem or xylem by dint of primary and secondary invaders may flow in wood discoloration and decay (Shigo 1989) nevertheless branch pruning is a unhurt and often essential arboricullural practice. When branch removal is necessary, rapid closure of pruning injurys is considered desirable for one as well as the other aesthetic and protective reasons because not many pathogens or parasitic microorganisms can penetrate this barrier (Shigo 1984)

Tree have an inherent capacity to seal injurys resulting from injury or pruning. Undifferentiated callus tissue originates from small rooms of the cambium around the exterior periphery of the wound, gradually overgrowing the surface of the hurt Greater development of callus from the side of hurts than at the top and bottom sometimes accrues in an elliptical shape as the injury sealing process progresses (Neely 1970; Biggs 1992) novel cambium develops adjacent to and usually in continuity with the existing undisturbed cambium (Zimmerman and Brown 1971; Biggs 1992; Blanchette 1992) This extension extending over a wound issues in the strongest barrier in the wound-sealing proces and is referr to as Wall 4 of the compartmentalization of decay in tree (CODlT) pattern (Shigo 1989).

Our study was designed to investigate the consequence of PBZ on the rate of closure of injurys in the bark and injurys made when branches were prun The research was leadershiped in response to concerns that, because PBZ restores cambial growth as well as propel growth, it might also restore the rate of wound closure thus prolonging the in all senses of trees to decay and disease organisms.

MATERIALS AND METHODS

Experimental tree were located at Martell Experimental Forest Farm near the Purdue University campus in Tippecanoe shire Indiana, U.S. Two experiments were designed using combinations of nine tree species.

Experiment 1 involved eight species ranging from 4 to 8 cm (16 to 32 in.) basal diameter and treated in April 1996 using the soil injection method: black walnut (Juglans nigra L) European black alder (Alnus glutinosa E) r oak (Quercus rubra E) sweetgum (Liquidambar styraciflua L) white ash (Froxinus americana E) white oak (Quercus alba E) white pine (Pinus strobus E) and fulvid poplar (Linodendron tulipifera E.).

Experiment II investigated sum of two units species, American sycamore (Platanus occidentalis E) (18 to 22 cm [71 to 87 in.] average basal diameter) and golden poplar (Linodendron tulipifera E.) (14 to 16 cm [55 to 63 in.] average basal diameter), treated in April 1998 using the soil soak method.

Twelve (Experiment I) or eighteen (Experiment II) plantationgrown tree (2 ?— 2 m [66 ?— 66 ft] spacing) of each species used in the respective experiments were culled based on their similar size and condition. Adjacent tree were not prefered for the studies to avoid base interaction and the unintended in all senses to PBZ treatment. Half of the tree for each species used in Experiment I were randomly assigned to each of sum of two units different treatment groups. PBZ formulated as Profile 2SC (SePRO Corporation, Carmel, IN) or water as a superintendence was applied. American sycamore and golden poplar (Experiment II) were randomly divided into three collections PBZ was applied as a soil wet through and through at two dose rates to sum of two units of the three groups. Tree in the superintendence group were treated with water.