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James Robert Ault and Sandy S. Siqueira

appears to be only one previously published report on the tissue culture of this taxon ( Mori et al., 2005 ). Therefore, shoot, root, and callus induction were examined in L. michiganense in response to treatment with four auxin-type plant growth

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Anish Malladi and Jacqueline K. Burns

and to design practices to improve plant performance. Studies examining the nature of long-distance communication have shown that the common phytohormones, referred to within this article as plant growth regulators (PGRs), participate in such

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Bärbel Röck-Okuyucu, Meltem Bayraktar, Ismail Hakki Akgun, and Aynur Gurel

.71 µ m IAA) ( G ); Kn + NAA combinations (2.32 µ m Kn + 2.69 µ m NAA, 2.32 µ m Kn + 5.37 µ m NAA) ( H ). Scale bar = 1 cm. PGR = plant growth regulator; WPM = woody plant medium; BA = 6-benzyladenine; TDZ = thidiazuron; IAA = indoleacetic acid; NAA

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Jonathan Ebba, Ryan W. Dickson, Paul R. Fisher, Crysta N. Harris, Todd Guerdat, and Sofia Flores

, SPAD chlorophyll index, dry weight, and tissue nitrogen (N)] during a simulated consumer phase compared with plants that received only water-soluble fertilizer (WSF) during production. Plant growth regulators (PGRs) applied during production also have

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Leo G. Albrigo and Ed W. Stover

as they influenced preharvest fruit drop. Materials and methods Plant growth regulator trials to evaluate effects on HLB-related, preharvest fruit drop were started in Fall 2013. Additional tests were initiated with spray treatments in Jan.–Feb. 2014

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W. Rademacher and T. Bucci

Worldwide, plant growth regulators (PGRs) account for only 3% to 4% of the total sales of plant protection agents. This limited market potential, the rising costs of development and registration, and the demand for high profitability have created major constraints to the introduction of new PGRs. Conversely, PGRs have become an integral part of agricultural and horticultural practices and one might assume that the market is sufficiently lucrative to those companies active in this area. In the past decade, at least seven new PGR products have been introduced. In many cases, reduced requirements for registration have lowered the financial risks relative to expected profits.

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Jack D. Fry

A field study was conducted in southern Louisiana to screen several plant growth regulators (PGRs) for efficacy in suppressing centipedegrass [Eremochloa ophiuroides (Munro) Hack.] vegetative growth and seedhead production. PGRs were applied in three sequential treatments in 1988 and included ethephon, glyphosate, mefluidide, paclobutrazol, sethoxydim, and sulfometuron methyl. Ethephon (5.0 kg·ha-1) suppressed mean centipedegrass vegetative growth by 15% with no turf injury. Mefluidide (0.6 kg·ha-1) and ethephon reduced mean seedhead number by 55% and 61%, respectively. Glyphosate (0.6 kg·ha-1) suppressed vegetative and reproductive growth, but caused unacceptable phytotoxicity and reduced centipedegrass cover and quality during Spring 1989. Use of ethephon or mefluidide to reduce trimming requirements or mower operation in hazardous areas may be an effective means of inhibiting centipedegrass growth. Chemical names used: N -(phosphonomethyl) glycine (glyphosate); N -[2,4-dimethyl-5-[[(trifluromethyl) sulfonyl]amino] phenyl]acetimide (mefluidide); 2-[1-(ethoxyimino)butyl] -5[2-(ethylthio) propyl]-3-hydroxy-2-cycIohexen-l-one (sethoxy-dim); 2-[[[[(4,6-dimethyl-2 -pyrimidinyl) amino] carbonyl]amino] sulfonyl]benzoic acid (sulfometuron methyl); (2-chloroethyl) phosphoric acid (ethephon); (±)-(R*R*)β-[(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl) -1 H -l,2,4-triazole-l-ethanol (paclobutrazol).

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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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Brian A. Krug, Brian E. Whipker, Ingram McCall, and John M. Dole

Three experiments were conducted to determine the effectiveness of plant growth regulators (PGRs) on `Tete a Tete', `Dutch Master', and `Sweetness' narcissus (Narcissus pseudonarcissus). Ethephon foliar sprays (500 to 2500 mg·L-1) and substrate drenches of flurprimidol and paclobutrazol (0.25 to 4 mg/pot a.i.) did not control height during greenhouse forcing of `Tete a Tete' at any concentration trialed. Stem stretch was controlled during postharvest evaluation with ethephon foliar sprays ≥1000 mg·L-1, flurprimidol substrate drenches ≥0.5 mg/pot a.i., and paclobutrazol substrate drenches of 4 mg/pot a.i. A second experiment investigated preplant bulb soaks of flurprimidol (10 to 40 mg·L-1) applied to `Dutch Master' and `Tete a Tete' narcissus bulbs. Flurprimidol preplant bulb soaks controlled postharvest stretch on `Tete a Tete' and `Dutch Master' at concentrations ≥15 and ≥10 mg·L-1, respectively. A third experiment was conducted with paclobutrazol (75 to 375 mg·L-1) on `Tete a Tete' and `Dutch Master' and three concentrations of flurprimidol on `Sweetness' to determine optimal soak recommendations. Paclobutrazol preplant bulb soaks ≥75 mg·L-1 controlled postharvest stretch of `Tete a Tete' and `Dutch Master', while 37.5 mg·L-1 of flurprimidol controlled postharvest stretch of `Sweetness'. Based on the results of these experiments, growers can now select a PGR to help control excessive plant growth.

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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