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Jack D. Fry and D. Wayne Wells

Field studies were conducted in south Louisiana to identify plant growth regulators that suppress carpetgrass (Axonopus affinis Chase.) seedhead development. In an initial study, best results were obtained with sethoxydim (0.11 kg·ha-1) and sulfometuron methyl (0.6 kg·ha-1), which reduced seedhead development by 88% and 86%, respectively, compared to untreated plots 21 days after treatment. Sulfometuron methyl caused unacceptable carpetgrass injury, however. Evaluation of seven sethoxydim application levels between 0 and 0.34 kg a.i./ha showed that carpetgrass seedhead number and elongation rate declined with increasing sethoxydim amount [SEEDHEAD NUMBER (m-2) = 515 – 1340 (kg), R 2 = 0.82; ELONGATION (cm) = 25.3 – 151 (kg) + 276 (kg2), R 2 = 0.77]. Carpetgrass seedhead production was restricted up to 6 weeks after sethoxydim (0.17 and 0.22 kg·ha-1) application. Chemical names used: (2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl)-3-hydroxy-2-cyclohexen-1-one) (seth-oxydim); (2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid) (sulfometuron methyl).

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Diane M. Camberato, James J. Camberato and Roberto G. Lopez

. Properties of the plant growth regulators used in the study as indicated on manufacturer label or material safety data sheet unless noted. Materials and Methods Initial carrier water characteristics. Because water is used as the carrier for the application of

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C.E. Wieland, J.E. Barrett, C.A. Bartuska, D.G. Clark and T.A. Nell

66 ORAL SESSION 15 (Abstr. 478–484) Plant Growth Regulators/Marketing–Floriculture/Foliage

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Modeste Kan Kouassi, Jane Kahia, Christophe N’guessan Kouame, Mathias Gnion Tahi and Edmond Kouablan Koffi

different cocoa genotypes react differently to different callus-inducing hormones ( Traore and Guiltinan, 2006 ). Plant growth regulators play a key role by intervening in the reactions that lead to a reorientation of the program of gene expression. This

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Edward W. Bush, Wayne C. Porter, Dennis P. Shepard and James N. McCrimmon

Field studies were performed on established carpetgrass (Axonopus affinis Chase) in 1994 and 1995 to evaluate plant growth regulators (PGRs) and application rates. Trinexapac-ethyl (0.48 kg·ha-1) improved turf quality and reduced cumulative vegetative growth (CVG) of unmowed and mowed plots by 38% and 46%, respectively, in 1995, and suppressed seedhead height in unmowed turf by >31% 6 weeks after treatment (WAT) both years. Mefluidide (0.14 and 0.28 kg·ha-1) had little effect on carpetgrass. Sulfometuron resulted in unacceptable phytotoxicity (>20%) 2 WAT in 1994 and 18% phytotoxicity in 1995. In 1995, sulfometuron reduced mowed carpetgrass CVG 21%, seedhead number 47%, seedhead height 36%, clipping yield 24%, and reduced the number of mowings required. It also improved unmowed carpetgrass quality at 6 WAT. Sethoxydim (0.11 kg·ha-1) suppressed seedhead formation by 60% and seedhead height by 20%, and caused moderate phytotoxicity (13%) in 1995. Sethoxydim (0.22 kg·ha-1) was unacceptably phytotoxic (38%) in 1994, but only slightly phytotoxic (7%) in 1995, reduced clipping yields (>24%), and increased quality of mowed carpetgrass both years. Fluazasulfuron (0.027 and 0.054 kg·ha-1) phytotoxicity ratings were unacceptable at 2 WAT in 1994, but not in 1995. Fluazasulfuron (0.054 kg·ha-1) reduced seedhead height by 23% to 26% in both years. Early seedhead formation was suppressed >70% when applied 2 WAT in 1994, and 43% when applied 6 WAT in 1995. The effects of the chemicals varied with mowing treatment and evaluation year. Chemical names used: 4-(cyclopropyl-x-hydroxy-methylene)-3,5 dioxo-cyclohexane-carboxylic acid ethyl ester (trinexapac-ethyl); N-2,4-dimethyl-5-[[(trifluoro-methyl)sulfonyl]amino]phenyl]acetamide] (mefluidide); [methyl 2-[[[[(4,6-dimethyl-2-pyrimidinyl) amino]carbonyl] amino] sulfonyl]benzoate)] (sulfometuron); (2-[1-(ethoxyimino)butyl-5-[(2-ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one) (sethoxydim); 1-(4,6-dimethoxypyrimidin-2yl)-3-[(3-trifluoromethyl-pyridin 2-yl) sulphonyl] urea (fluazasulfuron).

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Marco Volterrani, Nicola Grossi, Monica Gaetani, Lisa Caturegli, Aimila-Eleni Nikolopoulou, Filippo Lulli and Simone Magni

seeding is routinely adopted for several field crops. Properly sized sprigs could fit precision seeding machinery thus with the potential of being planted at a defined depth and spacing. Plant growth regulators (PGRs) are known for their ability to modify

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Patrick E. McCullough, Haibo Liu, Lambert B. McCarty and Ted Whitwell

Dwarf bermudagrass morphological characteristics following the use of plant growth regulators have not been reported. The objective of this greenhouse study was to determine short-term effects of seven plant growth regulators on clipping yield, chlorophyll concentration, and root mass of `TifEagle' bermudagrass. Growth regulators tested included ethephon, fenarimol, flurprimidol, maleic hydrazide, mefluidide, paclobutrazol, and trinexapac-ethyl. Two applications of each compound were made over a 6-week period. Root mass was reduced 39% by fenarimol and 43% by flurprimidol, while other PGRs had root mass similar to untreated turf. `TifEagle' bermudagrass treated with paclobutrazol, mefluidide, fenarimol, and flurprimidol averaged 45% less root mass than trinexapac-ethyl-treated turf. Trinexapac-ethyl was the only compound to reduce clippings and enhance turf quality without negative rooting effects. Chemical names used: [4-(cyclopropyl-[α]-hydroxymethylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (trinexapac-ethyl); {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl] 5-pyrimidine-methanol} (flurprimidol); (+/-)-(R*,R*)-β-[(4-chlorophenyl) methyl]-α-(1, 1-dimethyl)-1H-1,2,4,-triazole-1-ethanol (paclobutrazol); (N-[2,4-dimethyl-5 [[(trifluoro-methyl)-sulfonyl] amino]phenyl]acetamide) (mefluidide); [1,2-dihydro-3,6-pyridazine-dione] (maleic hydrazide); [(2-chloroethyl)phosphonic acid] (ethephon); and (2-(2-chlorophenyl)-2-(4-chlorophenyl)-5-pyrimidinemethanol) (fenarimol).

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L. Manivel, R. Raj Kumar, S. Marimuthu and V. Venkatesalu

146 ORAL SESSION 45 (Abstr. 338–343) Growth Regulators/Cross-commodity

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Fang Geng, Renae Moran, Michael Day, William Halteman and Donglin Zhang

of explant collection date, chilling nodal explants, and media concentration of the plant growth regulators GA 3 , EBR, BA, ZT, and TDZ on shoot growth of ‘G.30’ and ‘G.41’ apple during the initial proliferation stage of micropropagation. The focus of

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Martin J. Bukovac

The importance of spray application and the role of spray additives are reviewed in reference to increasing the effectiveness of plant growth regulators (PGR). The spray application process is composed of a number of interrelated components, from formulation of the active ingredient into a sprayable, bioactive solution (emulsion/suspension), to atomization, delivery, retention, and penetration into the plant tissue. Each of these events is critical to performance of the PGR. Also, each can be affected by spray additives, particularly adjuvants, which may be incorporated in the formulation of the active ingredient or added to the spray mixture. The role of the individual components and effects of spray adjuvants, particularly surfactants and fertilizer adjuvants, on the component processes are discussed.