Progress 10/01/01 to 09/30/06

Outputs
The response of trees to the gibberellin synthesis inhibitors paclobutrazol and flurprimidol were investigated. Both compounds are effective in reducing the growth in length of shoots by 40 to 60 percent. Research has also revealed that in addition to shoot growth suppression other benefits to tree health or tree responses valuable for tree care and maintenance occur. Both of these compounds reduce fungal disease infection and improve tolerance to drought and other adverse environmental conditions. Cambial growth also is reduced as in the growth of callus over wounds in the bark and those resulting from pruning branches. These growth inhibitors are known to bind to the protoheme iron of cytochrome P450 dependent enzymes in the isoprenoid pathway, inhibiting the production of gibberellin plant hormone, which controls the elongation of cells. We have shown that another mode of action for the growth reduction response in plants treated with paclobutrazol or flurprimidol could be an effect on electron transport in mitochondria. First mitochondria were isolated from plant cells and exposed to a range of concentrations of growth retardants in vitro. Reduction of electron transport at high concentrations and stimulation at low concentrations occurred. Subsequently, experiments were designed to determine if the same response would occur if the mitochondria were exposed to paclobutrazol and flurprimidol in vivo. Mature European black alder (Alnus glutinosa) and silver maple (Acer saccharinum) were treated with paclobutrazol and flurprimidol using standard methods in the spring before bud opening. Seeds produced by the silver maple trees were collected at the end of the first and second growing seasons and grown in the greenhouse. Mitochondria were isolated from the leaves of the mature trees and seedlings one and two growing seasons after treatment. Electron transport in the mitochondria as evident by NADH oxidation and cytochrome c reduction was determined. Paclobutrazol reduced whole chain electron transport in mitochondria of European black alder by reducing the oxidation of NADH and reduction of cytochrome c by 12 and 29 percent, respectively. Electron transport in mitochondria of seedlings grown from seeds collected from treated silver maple trees the first year following treatment was stimulated. The second year after treatment of the parent trees, electron transport was not affected This is the first report of a growth retardant affecting electron transport in plant mitochondria exposed to the compounds in vivo and of carryover of the response to the progeny of treated trees.

Impacts
Trees and shrubs often grow too large for the available space in urban areas. In the past, costly mechanical trimming was the sole method available to arborists and utility foresters to reduce tree and shrub size. Consequently, beginning in the 1950s, research on chemical growth retardants was initiated to develop an alternative approach to limiting size and growth rate of trees, particularly for trees under electric distribution wires. Today the electric industry is using the third generation of chemical substances and application methods to manage tree growth in utility rights-of-way. Satisfactory performance of the compound paclobutrazol as a growth retardant, as well as several benefits to tree health revealed through recent research, has spurred an active expansion of the market for this growth retardant to commercial landscape and general urban tree care. A mode of action for growth retardants involving the inhibition of gibberellin synthesis, which reduces the elongation of cells, has been known for a long time. Results of this research have demonstrated for the first time another mode of action involving interference with the so called electron transport chain in cell organelles called mitochondria. The production of metabolic energy was shown to be significantly reduced by concentrations of paclobutrazol that reduce growth.

Publications

• Chaney, W.R. 2005. Can trees get fat too. 2005. Arborist News 14(2):13-18.
• Cassens, D. and W. Chaney. 2005. Temporary wilting in Canaan fir, American Christmas Tree Journal 49(2):17-18
• Chaney, W.R. 2005. Top-of-hour break renews attention span. The Teaching Professor 19(6):1, 5. Chaney, W.R. 2003. Fantasy, Facts, and Fall Color, pp. 33-37. IN: Tree Biology A Collection of CEU Articles, International Society of Arboriculture, Champaign, IL
• Chaney, W.R. 2003. How Wind Affects Trees, pp. 45-51. IN: Tree Biology A Collection of CEU Articles, International Society of Arboriculture, Champaign, IL
• Dahle, G.A., H.A. Holt, W.R. Chaney, T.M. Whalen, D.L. Cassens, R. Gazo, and R.L. McKenzie. 2005. Implications of branch strength loss in silver maple trees converted from round-over to V-trims during electric line clearance operations, IN: Proceedings Environmental Concerns in Rights-of-Way Management 8th International Symposium, Saratoga Springs, N.Y., September 12, 2004.
• Chaney, W.R. 2005. A paclobutrazol treatment can leave a tree more stress tolerant. Golfdom, Turfgrass Trends, February, pp. 84-86.
• Chaney, W.R. 2005. The Legendary Baobab. Purdue University Cooperative Extension Service, Department Forestry and Natural Resources, FNR 259, 2p.
• Chaney, W.R., D.M. Mickey and H.A. Holt. 2005. Gibberellin Synthesis inhibitor affects annual xylem production and vessel element anatomy in some trees. IN: Proceedings Thirty-second Annual Meeting of the Plant Growth Regulation Society of America, Newport Beach, California, July 24-27, 2005.

Progress 10/01/03 to 09/29/04

Outputs
Paclobutrazol as a systemic fungicide for control of apple scab (Venturia inaequalis) was investigated in mature (cv. Hopa and Snow Drift) and young sapling (cv. Indian Magic) crabapples (Malus spp.). Treatments consisted of a control and paclobutrazol applied to mature trees at one or two times the recommended rate in April 2002 using the basal drench method. Saplings received both foliar and soil drench applications of paclobutrazol or propiconazole. Disease assessments of mature trees showed apple scab symptoms in treated trees were as severe as in untreated ones in the year of treatement, but were reduced slightly the second year in Hopa. Growth reduction occurred in all treated trees, suggesting that paclobutrazol levels needed for growth reduction were not sufficient to control apple scab in the year of treatment. In contrast, a one-time foliar application of paclobutrazol reduced apple scab incidence to levels found in saplings treated every two weeks with propiconazole, a fungicide and application method commonly recommended for apple scab control. Delayed uptake and transport of sufficient quantities of paclobutrazol to the crown of mature trees may account for the lack of apple scab control the year of treatment even though growth suppression occurred. The gibberellin synthesis inhibitor paclobutrazol, which causes growth reduction, is frequently used in ornamental plant production systems and in the maintenance of urban trees where growth space is limited. The compound is known to bind to the protoheme iron of cytochrome P450 dependent enzymes in the isoprenoid pathway, inhibiting the production of gibberellins, which control the elongation of cells and consequently growth in length. Because sterols necessary for synthesis of membranes in fungi also are produced via the isoprenoid pathway and their synthesis is inhibited by paclobutrazol, this study was conducted to determine if paclobutrazol could be effectively applied both as a contact and systemic fungicide.

Impacts
Tree growth regulators have become recognized as an important chemical tool for the care and maintenance of all trees and shrubs in the landscape. Demonstration of their ability to inhibit fungal disease infection and to improve tolerance to drought and other adverse environmental conditions has led to an expansion of their use solely by the electric utility industry to reduce regrowth of trees following trimming for clearance around electric wires. Today growth regulators also are used on ornamental trees and shrubs in urban landscape where size limitation and tree health are important concerns. Trees and shrubs often grow too large for the available space in urban areas. A mode of action for growth retardants has been known for a long time to be inhibition of the production in trees of the hormone gibberellin, which controls elongation of cells. Results of this research have demonstrated for the first time another mode of action for growth reduction by growth retardants compounds. The production of metabolic energy via the so called electron transport chain in cell organelles called mitochondria was shown to be significantly reduced by concentrations of the growth retardants paclobutrazol and flurprimidol that reduce growth.

Publications

• Blaedow, R.A., W.R. Chaney, P.C. Pecknold and H.A. Holt. 2003. Use of the tree growth regulator paclobutrazol to control apple scab, pp . 110-115 IN: Proceeding Thirtieth Annual Meeting Plant Growth Regulation Society of America, Vancouver, British Columbia, Canada, August 3-6, 2003.
• Bai, S., W.R. Chaney and Y. Qi. 2004. Response of cambial and shoot growth in trees treated with paclobutrazol, Journal of Arboriculture 30:137-145.
• Chaney, W.R. 2004. Here is how to stake newly planted trees. The Forestry Source 9(1):9.
• Chaney, W.R. 2004. Unexpected plant response to growth retardants: Anomaly or fact? pp. 15-21 IN: Proceedings Western Plant Growth Regulator Society 16th Annual Conference, Sacramento, California, January, 14-15, 2004.
• Chaney, W.R. 2004. Paclobutrazol: More than just a growth retardant. Illinois Nurserymen Growing Trends, April, pp. 25-27.
• Chaney, W.R. 2004. Are trees getting fat too? Purdue University Cooperative Extension Service, Department of Forestry and Natural Resources, FNR-250, 7p.
• Chaney, W.R. and S. Bai. 2004. Evidence of growth stimulation by low concentration of gibberellin synthesis inhibitors, IN: Proceedings Thirty-first Annual Meeting Plant Growth Regulation Society of America, Charleston, South Carolina, August 1-4, 2004

Progress 10/01/02 to 09/30/03

Outputs
Gibberellin synthesis inhibitors such as paclobutrazol and flurprimidol, which cause growth reduction, are frequently used in ornamental plant production systems and in the maintenance of urban trees where growth space is limited. These growth inhibitors are known to bind to the protoheme iron of cytochrome P450 dependent enzymes in the isoprenoid pathway, inhibiting the production of gibberellin plant hormone, which controls the elongation of cells. We have shown that another mode of action for the growth reduction response in plants treated with paclobutrazol or flurprimidol could be an effect on electron transport in mitochondria. However, the mitochondria were isolated from plant cells and exposed to the growth retardants in vitro. Experiments were designed to determine if the same response would occur if the mitochondria were exposed to paclobutrazol and flurprimidol in vivo. Mature European black alder (Alnus glutinosa) were treated with paclobutrazol by the soil injection method in the spring before bud opening. Silver maple (Acer saccharinum) were treated with flurprimidol by the trunk implantation method. Seeds produced by the silver maple trees were collected at the end of the first and second growing seasons and grown in the greenhouse. Mitochondria were isolated from the leaves of these trees and seedlings one and two growing seasons after treatment. Electron transport in the mitochondria as evident by NADH oxidation and cytochrome c reduction was determined. Paclobutrazol reduced whole chain electron transport in mitochondria of European black alder by reducing the oxidation of NADH and reduction of cytochrome c by 12 and 29%, respectively. Electron transport in mitochondria of seedlings grown from seeds collected from treated parent trees the first year following treatment was stimulated. The second year after treatment of the parent trees, electron transport was not affected This is the first report of a growth retardant affecting electron transport in plant mitochondria exposed to the compounds in vivo and of carryover of the response to the progeny of treated trees.

Impacts
Trees and shrubs often grow too large for the available space in urban areas. To alleviate this problem these plants are frequently treated with growth retardants such as paclobutrazol or flurprimidol. The reduction in the rate of growth in response to these compounds is known to be caused by their inhibition of the production in plants of the hormone gibberellin, which controls elongation of cells. This has been considered as the only mode of action of these compounds and the sole explanation of their effects on plants. Results of this research have demonstrated for the first time another mode of action for growth reduction by growth retardants compounds. The production of metabolic energy via the so called electron transport chain in cell organelles called mitochondria is significantly reduced by concentrations of paclobutrazol and flurprimidol that reduce growth. The stimulation of metabolic energy at low concentrations of these growth retardants that was demonstrated in this research helps to explain the surprising growth stimulation often observed in plants exposed to low dose rates of paclobutrazol and flurprimidol.

Publications

• Bai, S. and W.R. Chaney. 2002. Treatment of mature trees and seedlings with gibberellin synthesis inhibitors affects electron transport in leaf mitochondria of parents and progeny. Plant Growth Regulation Society of America Quarterly 30:86-97. Chaney, W.R. 2003. Tree growth retardants: Arborists discovering new uses for an old tool. Tree CareIndustry 14(3):54-59.
• Chaney, W.R. 2003. How critters use bark and wood as food. Arborist News 12(4):35-40.
• Chaney, W.R. 2003. Plant growth regulator pathways and gibberellin inhibition. pp 2-10. IN: Proceedings Western Plant Growth Regulator Society Fifteenth Annual Conference, Santa Barbara, California, January, 2003.
• Chaney, W.R. 2003. Tree growth retardants: Arborists discovering new uses for an old tool. 2003. The Shade Tree. 76:36-43.
• Chaney, W.R. 2003. Why do animals eat the bark and wood of trees and shrubs? Purdue University Cooperative Extension Service, Department of Forestry and Natural Resources, FNR-203. 5p.

Progress 10/01/01 to 09/30/02

Outputs
Paclobutrazol and flurprimidol are growth retardants used in ornamental plant production systems and in the maintenance of urban landscape trees to control growth and size of plants. Growth reduction is known to arise from inhibition of three steps in the isoprenoid pathway leading to gibberellins, which regulate cell elongation. Paclobutrazol and flurprimidol are known to bind to the protoheme iron of cytochrome P450 dependent enzymes in the isoprenoid pathway to produce their effect. Experiments were designed to determine if these growth retardants also could bind with the iron moiety of cytochrome oxidase in mitochondria, thereby affecting the production of metabolic energy in the respiratory process. The specific objective was to determine the effects on NADH oxidation and cytochrome c reduction in mitochondria isolated from European black alder (Alnus glutinosa) and exposed to a range of concentrations of the growth retardants in vitro. NADH oxidation and cytochrome c reduction were enhanced by low concentrations of both compounds, whereas higher concentrations reduced electron transport. A mechanism for the stimulation of electron transport found in these studies is not apparent. No similar stimulation of electron transport by low concentrations of carbon monoxide, potassium cyanide, or sodium azide, known inhibitors of electron transport, has been reported. Graduate student = 1.

Impacts
Compounds such as paclobutrazol and flurprimidol are used to grow compact ornamental bedding plants and to reduce the rate of branch regrowth following pruning of trees growing under electric distribution lines. The growth reducing effects of these compounds is known to be caused by their inhibition of the production in plants of the hormone gibberellin, which is responsible for controlling the elongation of cells. This has been considered as the only mode of action of these compounds and the sole explanation of their effects on plants. This study has demonstrated for the first time another mode of action for growth reduction by these compounds. The stimulation of metabolic energy production at low concentrations that was found helps to explain the heretofore unexplained growth stimulation observed at low application rates of paclobutrazol and fluprimidol.

Publications

• Bai, S. and W.R. Chaney. 2002. Gibberellin Synthesis Inhibitors Affect Electron Transport in Plant Mitochondria. Plant Growth Regulation 35:262-2001.
• Bai, S. and W. R. Chaney. 2002. Treatment of Mature Trees and Seedlings with Gibberelllin Synthesis Inhibitors Affects Electron Transport in Leaf Mitochondria of Parents and Progeny. Plant Growth Regulation Society of America Quarterly 30:86-97.
• Chaney, W.R., H.A. Holt, R.A. Blaedow, G.A. Dahl and R.L. McKenzie. 2002. Soil Fertilization and Efficacy of Paclobutrazol. 29th Proceeding Plant Growth Regulation Society of America, Halifax, Nova Scotia, Canada, July, 2002.
• Qi, Y., T. Knighten and W. R. Chaney. 2002. Leaf Anatomy of Two Urban Tree Species as Affected by Paclobutrazol Tree Growth Regulator. 29th Proceeding Plant Growth Regulation Society of America, Halifax, Nova Scotia, Canada, July, 2002.

Progress 10/01/00 to 09/30/01

Outputs
Paclobutrazol is a tree growth regulator known to inhibit gibberellin synthesis and to reduce shoot growth of many tree species through its effects on cell elongation. A study was designed to investigate the effect of the growth retardant paclobutrazol on root and trunk cambial growth and fine root development of 12-20 cm diameter white oak (Quercus alba L.), red oak (Quercus rubrum L.), sweetgum (Liquidambar stryaciflua L.), and tuliptree (Liriodendron tulipifera L.) growing in plantations. Twenty white and red oak were selected and half were treated with paclobutrazol using the soil drench method. Twelve sweetgum and tuliptree were selected and half were treated with paclobutrazol using the soil injection method. Paclobutrazol formulated as Profile 2SC was applied at a dose of 9.5 gms paclobutrazol per tree in 500 ml of water. Four or five years after treatment two-inch-diameter soil cores taken near the base of trees to a depth of 9 inches showed increased fine root weight only in white oak. The root system was exposed for a 1.5 foot radius around each tree using an Air Spade. Cross-sections were cut from the roots for analysis of cambial growth. Cross-sections were also cut from the stem of trees 4.5 feet from the ground line for cambial analysis. Cambial growth in roots was reduced in both red oak and sweetgum, but was not influenced in either white oak or tuliptree. For red oak the reduction begin the second growing season after treatment and continued for three years. Cambial growth in roots of sweetgum was reduced in the year of treatment and continued for four years. Cambial growth in the trunk was reduced only in white oak and sweetgum, persisting for six years after treatment with paclobutrazol. Although the response to paclobutrazol was species dependent, the results suggest that treatment with paclobutrazol has potential to improve the health of some urban trees by increasing fine root development and to reduce problems associated with growth near sidewalks and curbs and other areas with restricted growing space through reduction in diameter growth of roots. Graduate Student = 1

Impacts
Results of these studies indicate that the growth retardant paclobutrazol could be used by urban tree managers as a tool to reduce diameter growth in roots of urban trees, which frequently damage sidewalks and curbs. It has been found that up to 30% of city trees cause sidewalk damage and that 25% of a city's annual budget goes to repair sidewalks damage caused by tree root growth. Another possible benefit of paclobutrazol treatment is an increase in fine root density. Fine roots play an essential role in tree health by absorbing water, oxygen , and nutrients and by maintaining the root-mycorrhizal association. Enhancement of fine root development is particularly important for trees growing in urban areas where soils are often infertile and compacted.

Publications

• Chaney, W.R. 2001. Effective Plant Growth Regulators for Rights-of-Ways and Potential Landscape Use. Proceedings Western Plant Growth Regulator Society Annual Conference, Monterey, California, January 10-11, 2001, 13:39-48.
• Sperry, C.E., W.R. Chaney, G. Shao and C.S. Sadof. 2001. Effects of Tree Density, Tree Species Diversity, and Percentage of Hardscape on Three Insect Pests of Honeylocust. Journal of Arboriculture 27:263-271.
• Chaney, W.R. 2001. Grand Finale. American Nurseryman 194(3):26-30.
• Mickey, D.M., W.R. Chaney and H.A. Holt. 2001. Cambial Growth and Fine Root Development in Several Tree Species in Response to Treatment with Paclobutrazol. Proceedings Plant Growth Regulation Society of America 28th Annual Conference, Miami Beach, Florida, July 1-4, 2001.
• Qi, Y., S. Bai, W.R. Chaney and J. Qin. 2001. Effects of Paclobutrazol on Leaf UV-B Absorbing Compounds, Chlorophyll Concentration and Leaf Anatomy of Sweetgum and Cherrybark Oak. Proceedings Plant Growth Regulation Society of America 28th Annual Conference, Miami Beach, Florida, July 1-4, 2001.
• Chaney, W.R. 2001. Tree Growth Retardants Provide Multiple Benefits. Under the Canopy. July, 9-11.

Progress 10/01/99 to 09/30/00

Outputs
The effect of a growth retardant, paclobutrazol, on cambial and shoot growth of white oak (Quercus alba L.) and northern red oak (Quercus rubra L.) was investigated. Twelve-year-old plantation-grown trees were used. An aqueous suspension of paclobutrazol, trade name Profile 2SC, was poured around the base of each treated tree, resulting in a dose of 9.6 grams active ingredient per tree. There were 10 replications of treated and untreated trees. Four growing seasons after treatment, the trees were harvested, shoot growth measured, and a trunk cross-section 50 cm above the ground line was removed. The cross-section was sanded and the annual ring width for four growing seasons after treatment was determined microscopically. Cambial growth, as well as annual shoot growth and total tree height, were reduced by treatment of trees with paclobutrazol. Treatment with paclobutrazol reduced the width of the xylem ring for four years after treatment by 80 percent in white oak and 60 percent in northern red oak. Annual shoot growth was not affected the first growing season after treatment in either species, but it was markedly reduced in white oak for the next three growing seasons. A significant reduction in annual shoot growth of northern red oak occurred only in the third year after growth retardant treatment. Nevertheless, total tree height after four growing seasons was less in both northern red oak and white oak treated with paclobutrazol than in untreated control trees.

Impacts
Trees growing under electric wires are trimmed to maintain safe and reliable delivery of electric power to residential and commercial customers. Results of this research show that a tree growth retardant, paclobutrazol, has potential as a tool to reduce the growth of trees that are planted in space limiting situations such as under overhead electric distribution wires.

Publications

• Bai, S. and W.R. Chaney. 2000. Treatment of silver maple trees with gibberellin synthesis inhibitors influences growth of progeny seedlings. Plant Growth Regulation Society of America Quarterly 28(3):115-120
• Chaney, W.R. Biology of plant growth regulators used on ornamental plants, pp. 18-25, IN: Proceedings Western Plant Growth Regulator Society 12th Annual Conference. Sacramento, California, January 12-13, 2000.
• Bai, S. and W.R. Chaney. 2000. Paclobutrazol and flurprimidol affect electron transport in respiration. IN: Proceedings Plant Growth Regulation Society of America 27th Annual Conference, Kailua-Kona, Hawaii, July 30-August 3, 2000.
• Qi, Y. S. Bai and W.R. Chaney. 2000. Effects of paclobutrazol on leaf optical properties of sweetgum and cherrybark oak. IN: Proceedings Plant Growth Regulation Society of America 27th Annual Conference, Kailua-Kona, Hawaii, July 30-August 3, 2000.

Progress 10/01/98 to 09/30/99

Outputs
Trees growing under electric wires are trimmed to prevent the branches from contacting the wires and interrupting electrical service and creating hazards for people. To reduce the frequency of trimming, chemical tree growth retardants are often used to slow the regrowth of trees after trimming. The objective of the research reported was to determine the effect of growth retardants applied to parent trees on the progeny grown from seeds of the treated trees. Acer saccharinum trees growing under wires in northwestern Indiana were treated with paclobutrazol and flurprimidol using recommended methods. Seeds were collected from the trees for three consecutive growing seasons and the germination and growth of the seedlings determined. The growth retardants reduced growth of progeny of treated trees when the seeds were collected one-month after treatment. One year after treatment, growth of progeny seedings and chlorophyll a and b concentrations were stimulated. No effect on progeny occurred two years after treatment of parent trees. The concentration of TGR that stimulates seedling height growth is apparently very low since no stimulation in height growth or chlorophyll synthesis in Acer saccharinum seedlings was detected in a range of paclobutrazol or flurprimidol concentrations (0.0001 to 0.01 mg/L)applied to the soil of pots in which seedlings were grown in a greenhouse. However, 0.001 and 0.005 mg/L flurprimidol stimulated diameter growth of the seedlings.

Impacts
Carryover of tree growth retardants in chips derived from branches removed from treated trees has been demonstrated to affected the growth of plants to which the chips were applied as a mulch. However, this is the first report of a direct effect of growth retardants on progeny of treated trees. The stimulation of growth found is important because it indicates the necessity of timing retreatment of trees to prevent the natural degradation of the growth retardants over time with a consequent stimulation of growth, just the opposite of the desired effect.

Publications

• Bai, S. and W.R. Chaney. 1999. Response of cambial growth in red and white oak treated with paclobutrazol, pp. 34-41, In: Proceedings Western Plant Growth Regulator Society Eleventh Annual Conference, January 13-14, 1999.
• Bai, S. and W.R. Chaney. 1999. Closure of bark wounds affected by paclobutrazol, pp. 227-233, In: Proceedings Plant Growth Regulation Society of America, Costa Mesa, CA., July 11-14, 1999.
• Chaney, W.R. 1999. Water and chemical movement beneath the bark. Arbor Age 19(11):25-32
• Chaney, W.R. 1999. Eastern arborvitae-Thuja occidentalis, Arbor Age 19(12)32-33.
• Chaney, W.R. (editor). 1999. Proceedings Plant Growth Regulation Society of America, Costa Mesa, CA., July 11-14, 1999.

Progress 10/01/97 to 09/30/98

Outputs
Tree growth regulators (TGRs) are used as a tool by electric utility companies in electric line clearance operations to lengthen the time between tree trimming cycles and to reduce the amount of woody biomass produced. The objective of the research reported was to determine the influence of the growth retardant compounds on the rate of closure of wounds in the bark and wounds resulting from branch pruning. Nine species of trees, located in Indiana and Louisiana were investigated (Alnus glutinosa, Fraxinus americana, Juglans nigra, Liquidambar styraciflua, Liriodendron tulipifera, Quercus alba, Q. falcata var. pagodaefolia, Q. rubra, and Pinus strobus). Paclobutrazol was applied by soil injection or soil drench methods. Circular wounds (2-cm-dia.) were made in the bark and branches were pruned from treated and untreated trees. Wound closure was determined one, two or three growing seasons after treatment. The rate of closure of both types of wounds varied among species. For example, closure of bark wounds and branch pruning wounds was significantly less in treated than in control white ash, yellow poplar, and white pine. TGR treatment did not affect the closure of wounds on the other species. Although TGR treatment may delay the growth of callus tissue over the wound, the longer exposure of the wound to the air does not necessarily mean that the tree will be more susceptible to decay fungi and other organisms. Other barrier zones develop behind the wound that limited fungal invasion in spite of delayed callus closure of wounds. The reduced need for frequent pruning in TGR treated trees, which results in fewer wounds, is probably more important than the effect of TGRs on the rate of wound closure.

Impacts
(N/A)

Publications

• Premachandra, G.S., W.R. Chaney and H.A. Holt. 1997. Effect of mulch made from flurprimidol treated silver maple, white ash and zinnia on growth of zinnia. Journal of Environmental Horticulture 15:215-221.
• Bai, S., W.R. Chaney and Y. Qi. 1997. Wound closure in trees affected by paclobutrazol growth regulator, pp. 370-371, In: Proceedings Society of American Foresters Annual Conference, Memphis, Tennessee, October 4-8, 1997.
• Chaney, W.R. 1997. Austrian pine - Pinus nigra. Arbor Age 17(12):26-28.
• Bai, S. W.R. Chaney, Y. Qi and H.A. Holt. 1998. Effects of paclobutrazol on closure of wounds in trees pp. 12-18. In: Proceedings Western Plant Growth Regulator 10th Annual Conference, Monterey, California, January 14-15, 1998.
• Sperry, C.E. and W.R. Chaney. 1998. Tree growth regulator effect on phototropism - Its implication for utility forestry. Journal of Arboriculure 24:(In press)

Progress 10/01/96 to 09/30/97

Outputs
Plant growth regulators are used as a tool in electric line clearance operations to lengthen the time between tree trimming cycles and to reduce the amount of woody biomass produced. The objective of the research reported was to determine the rate of movement and pattern of distribution of flurprimidol implanted into the trunk of two tree species commonly found under electric distribution wires in urban areas. Silver maple (Acer saccharinum L.) and white ash (Fraxinus americana L.) trees were treated with Cutless Tree Implants at the recommended dosage rate (0.5 per diameter inch). All trees were drilled with a 3/8 inch brad point bit 70 cm above the ground line and a 1 g a.i. tablet was inserted into the holes of treated trees in early spring just before bud break. The trees were harvested 1, 6 and 18 months after treatment. A cross-section of the trunk was removed 50 cm below the implant site, 2 cm above the implant site, and at one meter intervals up the trunk to a height of six meters. Leaves and one-year-old twigs also were collected. The tissues were analyzed for flurprimidol using gas chromatography-mass spectrometry. Flurprimidol reached the leaves and terminal shoots within one month of application in both silver maple and white ash. Flurprimidol concentration in the xylem of the one-meter-long sections of trunk were lower than that in the leaves and twigs. The pattern of flurprimidol distribution within trees was similar 6 and 18 months after treatment, but the concentrations of the growth retardant were less than that measured one month after treatment. Relatively high concentrations of flurprimidol were detected 50 cm below the implant site, refuting the commonly held conviction that flurprimidol only moves upward in the xylem. Two graduate students were associated with this project.

Impacts
(N/A)

Publications

• PREMACHANDRA, G.S., CHANEY, W.R., and HOLT, H.A. 1997. Gas exchange and water relations of Fraxinus americana l. affected by flurprimidol. Tree Physiology 17:97-103.
• PREMACHANDRA, G.S., CHANEY, W.R., and HOLT, H.A. 1997. Effect of mulch made from flurprimidol treated silver maple, white ash and zinnia on growth of zinnia. Journal Environmental Horticulture (In Press).
• PREMACHANDRA, G.S., CHANEY, W.R., and HOLT, H.A. 1997. Rate and pattern of flurprimidol movement in mature trees, pp. 10-18. IN: Proceedings Western Plant Growth Regulator Society 9th Annual Conference, Santa Barbara, California, January 22-23, 1997.
• CHANEY, W.R. 1997. How wind affects trees, Arborists News 6(5): 31-38.
• CHANEY, W.R., JOHNSON, M., PREMACHANDRA, G.S., and HOLT, H.A. 1997. Carryover of flurprimidol in mulch made from treated trees. pp. 174-179, IN: Proceedings Plant Growth Regulation Society of America, August 9-12, 1997, Atlanta, GA.

Progress 10/01/95 to 09/30/96

Outputs
Although the dose rates for commercial application of the tree growth retardantsflurprimidol and paclobutrazol are known, there is little known about the effects of low concentrations or the quantity of these compounds necessary in meristems to affect shoot growth. Experiments were designed to investigate the response of cell and tissue cultures and whole plants to flurprimidol to determine the concentration of the growth retardant that affects growth in a system with active cell division. Initial studies have focused first on herbaceous plants because of their rapid growth compared to woody plants. For zinnia (Zinnia elegans), concentrations of flurprimidol of 0.2, 1 and 5 mg L-1 applied to the soil inhibited height growth and leaf area. However, at lower concentrations (0.04, 0.008 and 0.0016 mg L-1) growth stimulation was observed. In suspension cultures of tobacco cells, cell weights at 0.1, 0.5 and 1.0 mg L-1 flurprimidol were greater than the cell weights at 5 mg L-1 and higher, showing that inhibition as well as stimulation of growth may occur at different concentrations of flurprimidol. These results support conclusions from numerous studies of others that flurprimidol inhibits stem elongation and leaf area expansion. However, the stimulation of shoot elongation and leaf size in a plant by low concentrations of flurprimidol has not been reported before. These results could be important in commercial applications of flurprimidol to reduce growth if leaching, poor tissue penetration or g.

Impacts
(N/A)

Publications

• S., C. NAGASAKA, W.R. CHANEY and H.A. HOLT. 1996. Response of cells, callus, seeds and plants to a range of flurprimidol concentrations variesin zinnia, sunflower, green pepper, and tobacco. Plant Growth Regulation SocietyCHANEY, W.R. 1996. Yellow-poplar, Liriodendron tulipifera. Arbor Age 16(4):48-49.
• CHANEY, W.R. 1996. White ash, Fraxinus americana. Arbor Age 16(In press) CHANEY, W.R. 1996. How Trees Grow. Tree Care Industry 7(4):28-36.
• WHEELER, R.A., W.R. CHANEY, K. D., JOHNSON and L.G. BUTLER. 1996. Leucaena ForageAnalysis Using Near Infrared Reflectance Spectroscopy. Animal Feed Science and Technology (In press) PREMACHANDRA, G.
• S., W.R. CHANEY and H.A. HOLT. 1996. Gas exchange and water relations of Fraxinus americana L. affected by flurprimidol. Tree Physiology (InPress) PREMACHANDRA, G.

Progress 10/01/94 to 09/30/95

Outputs
Plant water relations, leaf gas exchange, and water use efficiency were determined in one-year-old white ash (Fraxinus americana L.) seedlings soil treated with flurprimidol (20 mg a.i./kg of soil) to evaluate the potential for enhanced tolerance to water stress. Flurprimidol is a plant growth regulator used commercially to suppress shoot growth in horticultural crops and urban trees. Two months after flurprimidol application, water was withheld from one-half of the seedlings and leaf water relations and gas exchange parameters were measured periodically for up to 22 days. Lower stomatal conductance reduced transpirational water loss and net CO2 assimilation in flurprimidol-treated seedlings under both irrigated and nonirrigated conditions. Flurprimidol treated seedlings had higher leaf water potential and relative water content. Greater turgor and sap osmolality and lower osmotic potential at full turgor observed in flurprimidol-treated, water stressed seedlings indicated that flurprimidol may increase osmotic adjustment. Water use efficiency was lower and gas exchange efficiency was higher in flurprimidol-treated than untreated seedlings exposed to water stress. Improved plant water status suggests that flurprimidol treatment may enhance survival of plants under water stress conditions. No graduate student worked on this project during the period.

Impacts
(N/A)

Publications

• PREMACHANDRA, G.S., W.R. CHANEY and H.A. HOLT. 1995. Flurprimidol improves tolerance of white ash seedlings to water stress. IN: Proceedings Plant Growth Regulator Society of America Annual Conference, Minneapolis, Minnesota, July 18._.
• ASHOKAN, P.K., W.R. CHANEY, AND G.S. PREMACHANDRA. 1995. Soil applied paclobutrazol affects leaf water relations and growth of American elm (Ulmus americana L.) seedlings. Plant Growth Regulator Society America Quarterly 23:1-12.
• CHANEY, W.R., P.E. POPE and W.R. BYRNES. 1995. Tree Survival and Growth After Twelve Years on Mined Land Reclaimed in Accord with the 1977 Surface Mining Control and Reclamation Act. Journal of Environmental Quality 24:630-634.
• MANN, M.P., H.A. HOLT, W.R. CHANEY, W.L. MILLS and R.L. MCKENZIE. 1995. Tree Growth Regulators Reduce Line Clearance Trimming Time. Journal of Arboriculture 21:209-212.
• CHANEY, W.R. 1995. Horsechestnut, Aesculus hippocastanum. Arbor Age 15(5):31-32.
• CHANEY, W.R. 1995. Norway maple, Acer platanoides. Arbor Age 15(10):22-23

Progress 10/01/93 to 09/30/94

Outputs
Effect on weeping and wound closure of plugs inserted into holes drilled for trunk injection of tree growth regulators was investigated. Four injection treatments (paclobutrazol, methanol, water or none) and four plugging treatments (wood dowel, rubber plug, silicone caulk or open) were applied to Liriodendron tuliperifera trees. Weeping was recorded weekly and the trees were harvested 1, 3, and 4 growing seasons after treatment and dissected to reveal the injection wounds and plugs. Wood dowels prolonged weeping for all injection treatments and generally extended the time for wound closure. The rubber plug varied from a minor obstacle to a complete obstruction to closure of injection holes. Both wood dowels and rubber plugs frequently were pulled outward from the point of original placement by callus and xylem growth. Silicone caulk reduced weeping and did not inhibit wound closure. The potential for residues of tree growth regulators in mulch made from plants treated with the growth retarding substances was investigated. Results showed the potential for growth reduction of zinnia plants by flurprimidol residues in Acer saccharinum leaves collected one month after treatment and in zinnia plants six weeks after treatment. No graduate student worked on this project during the period.

Impacts
(N/A)

Publications

• BREEDLOVE, D.A., M.E. FOLEY, H.A. HOLT and W.R. CHANEY. 1994 Diffusion of (superscript 14)C-flurprimidol in various carriers through excised silver maple bark. Journal of Arboriculture 10:104-107.
• WHEELER, R.A., W.R. CHANEY, L.G. BUTLER, and J.L. BREWBAKER. 1994. Condensed tannins in Leucaena and their relation to psyllid resistance. Agroforestry Systems 26:139-146.
• CHANEY, W.R. 1994. Pin Oak, Quercus Palustris. Arbor Age 14(9):31-32.
• WHEELER, R.A., W.R. CHANEY and M.J. CECAVA. 1994. Forage analysis of leucaena species and hybrids adapted to cool upland conditions. IN: Proceedings Third North American Agroforestry Conference, Iowa State University. Ames, IA. August.
• PREMACHANDRA, G.S., C. NAGASAKA, W.R. CHANEY and H.A. HOLT. 1994. Flurprimidol affects seed germination and growth of seedlings callus tissue and cell cultures of zinnia, sunflower, green pepper and tobacco. Proceedings Plant Growth Reg.

Progress 10/01/92 to 09/30/93

Outputs
Distribution of the plant growth regulator, flurprimidol, over time in seedlingsof Acer saccharinum (silver maple) and Fraxinus pennsylvanica (green ash) was investigated. A dose of 500 ug flurprimidol in 50 ul of isopropanol was injected into each seedling with a microinjector. Untreated seedlings served as a control. The seedlings were harvested 2 days, 2 weeks and 12 weeks after treatment, partitioned into stem sections and leaves, and analyzed for flurprimidol by gas chromatography. In both species, the apical section of stems contained less flurprimidol than the leaves. The highest concentration remained near the site of injection. After 12 weeks only 34% and 13% of flurprimidol was recovered from tissues of green ash and silver maple, respectively. These results reflect either movement to the roots or degradation of the compound in the plant tissue. Field studies of distribution of flurprimidol in larger trees have been initiated. Trees were implanted with tablets of flurprimidol at a dose of 0.5 g/diameter inch. The treated trees are to be harvested 1, 6, 12 and 18 months after treatment. The harvest at 1 and 6 months after treatment have been made and samples prepared for residue analysis. The samples were taken at one-meter intervals up the trunk and from leaves and one-year-old twigs. One graduate student worked on this project.

Impacts
(N/A)

Publications

• WASNIEWSKI, T.A., W.R. CHANEY and H.A. HOLT. 1993. Hole angle for trunk injection of tree growth regulators and its effect on weeping, wound closure and wood discoloration. Journal of Arboriculture 19:131-137.
• WASNIEWSKI, T.A., W.R. CHANEY, H.A. HOLT and J.F. SENFT. 1993. Strength properties of wood related to trunk injection of tree growth regulators. Journal of Arboriculture 19:220-225.
• BORGES, R.G. and W.R. CHANEY. 1993. Solar irradiance and the development of endomycorrhizal green ash seedlings. Tree Physiology 13:227-238.
• CHANEY, W.R., H.A. HOLT and M.V. CARLUCCI. 1993. Anatomie und Physiologie in Abhangigkeit von Translokation und Effizienz von Stamm-injierten (Anatomy and Physiology Related to Translocation and Efficacy of Trunk Injected Growth Regulators.

Progress 10/01/91 to 09/30/92

Outputs
Effects of gibberellin synthesis inhibitors injected into tree trunks on wound exudation, wound closure and wood discoloration were determined at various times up to 23 months after treatment. Plantation grown Liriodendron tulipifera trees located in Tippecanoe County, Indiana received four treatments: injection of the tree growth regulators Cutless TP or Clipper 20UL in holes drilled at an angle (45 degrees) or straight into the tree using standard volumes and pressure. Injection holes drilled at 45 degrees began weeping sooner and tended to have a higher percentage of weeping during non-dormancy periods than those drilled straight into trees. Holes injected with Cutless began weeping sooner and a higher percentage wept than holes injected with Clipper. Less than one percent of the total volume of wood in tree trunks was discolored by injection treatment. The amount of wood discolored was not influenced by the north, south, east or west orientation of the injection hole and was the same for treatment with either Clipper or Cutless. No difference was found in wound closure rates due to the different tree growth regulators or the angle of injection. The only benefit of making injection wounds straight into trees was a slight reduction in weeping. There was one graduate student associated with this project.

Impacts
(N/A)

Publications

• BUERGER, T.A., W.R. CHANEY, H.A. HOLT AND J.F. SENFT. 1992. Strength properties of yellow poplar wood related to trunk injection of tree growth regulators. Journal of Arboriculture 18:331 (Abstract).
• JORGE, P.E., R.J. GREEN, JR. AND W.R. CHANEY. 1992. Inoculation with Fusarium and Verticillium to increase resistance in Fusarium-resistant tomato. Plant Disease 76:340-343.
• JORGE, P.E., R.J. GREEN, JR. AND W.R. CHANEY. 1992. Effect of inoculum concentration of Verticillium dahliae or Fusarium oxysporum f. sp. lycopersici on disease severity of susceptible tomato cultivars. Phytopathology 82:608.
• WASNIEWSKI, T.A., W.R. CHANEY AND H.A. HOLT. 1993. Hole angle for trunk injection of tree growth regulators and its effect on weeping, wound closure and wood discoloration. Journal of Arboriculture 19: (in-press).
• CHANEY, W.R. AND W.R. BYRNES. 1993. Effect of seedling age and taproot length on performance of oak. Northern Journal of Applied Forestry (in press).