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Zhongjie Ji, James J. Camberato, Cankui Zhang, and Yiwei Jiang

Salinity stress can severely inhibit plant growth and development. The adverse effects of salinity stress on plants are generally imposed through osmotic stress by limiting water uptake and excessive uptake of sodium (Na + ) ions ( Munns and Tester

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Mary Jane Clark and Youbin Zheng

fertility and pH ranges, plants can remain healthy ( Jones, 2012 ; Zheng and Clark, 2013 ). In conditions of low or high fertility, or when pH is outside an optimal range, stress conditions can contribute to minimal or excess plant growth, resulting in

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Yiwei Jiang, Yu Cui, Zhongyong Pei, Huifen Liu, and Shoujun Sun

the treatment ( Bian and Jiang, 2009 ; Jiang et al., 2010 ; Liu and Jiang, 2010 ; Xu et al., 2011 ; Zhou et al., 2014 ). Therefore, this experiment was designed to characterize plant growth, water status, and gene expression in response to DI and

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Gary W. Stutte and Greg Goins

In preparation for a spaceflight experiment to measure photosynthesis of wheat (PESTO), four solid media were evaluated for use in the rooting modules of the Biomass Production System (BPS), a new plant growth unit for microgravity. The media were commercial peat-vermiculite (PV) mixture, zeolite developed at Johnson Space (Z/JSC), commercial zeolite developed by Boulder Innovative Technologies (Z/BIT), and arcillite (AR) with slow-release fertilizer. Wheat (cv. USU Super Dwarf) was grown in the media at 1500 μmol/mol CO2, 350 μmol·m-2·s-1 PAR, 23 °C, and 75% relative humidity for 18 to 21 days. Water was delivered to the media through porous tubes imbedded in the media, and NDS pressures of -0.1 to -0.5 kPa were maintained with either a static or recirculating standpipe. Plant height, leaf area, and fresh mass were determined for each experiment. Results indicated that the AR and Z/BIT media resulted in larger and more uniform plants than Z/JSC or PV at the same NDS pressure. Additional experiments were conducted with AR to evaluate interactions between particle size and NDS pressure. At ≈14 days after planting, there was a loss of NDS prime in AR >2.0 mm when the NDS pressure was less than -0.3kPa. This resulted in drying of the media and poor plant growth. There was excess water in the media, which resulted in reduced plant size, in AR <1.0 mm at NDS pressures more than -0.3 kPa.

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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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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.

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Juan Carlos Díaz-Pérez and James E. Hook

excess) and calcium fertilization on plant growth, fruit yield, and fruit quality. Material and Methods Study site. Experiments were conducted at the Horticulture Farm, University of Georgia, Tifton, GA. The farm is located at an altitude of 108 m above

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B.J. Johnson

A field experiment was conducted over 2 years to determine the effects of treatment dates with plant growth regulators (PGRs) on performance of `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy] × [C. dactylon (L.) Pers.]. For flurprimidol at 0.84 kg·ha-1, the highest injury occurred from 16 or 28 June application in 1987 and from 17 May or June application in 1988. The injury was similar from treatment dates with flurprimidol + mefluidide or paclobutrazol + mefluidide. The PGRs were applied over a longer period in 1987 than 1988 without affecting vegetative suppression of `Tifway' bermudagrass. However, in 1988, the suppression from the 17 May treatment was equal to or better than that obtained when treatment dates were delayed until 1 June or later. Chemical names: α-(1 -methylethyl)- α -[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); N -[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide); (±)-(R*R*) β -[(4-chlorophenyl)-methyl]- α -(1,1-dimethylethyl)- 1H -1,2,4-triazole- 1-ethanol (paclobutrazol).

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D.A. Raworth and S.J. Clements

Red raspberry (Rubus idaeus L. cv. Willamette) primocanes were artificially defoliated to various degrees and at two dates in each of 2 years to simulate defoliation caused by the twospotted spider mite (Tetranychus urticae Koch). The effect on primocane diameter, lateral length, yield and four yield components was determined. When defoliation occurred evenly along the length of the primocanes, and all floricanes and excess primocanes were removed in early Aug. 1989, yield was reduced 26% at 25%, 50%, and 75% defoliation and 55% at 100% defoliation compared with nondefoliated controls. The number of canes per stool, number of fruit per lateral, and weight per fruit were reduced when defoliation occurred earlier, in August rather than September, but the number of laterals per cane increased with early defoliation. The effect of increasing defoliation on plant growth and yield was generally nonlinear. When defoliation occurred in sections along the lower 2 m of all primocanes, and all floricanes and excess primocanes were removed in Nov. 1992, no significant differences in yield or three yield components were detected. The effects of primocane defoliation are not necessarily predictable, so T. urticae should be controlled before mite-induced defoliation occurs.

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Amanda Wiberg, Richard Koenig, and Teresa Cerny-Koenig

There is extensive variability in physical and chemical properties among brands of retail potting media. The purpose of this study was to assess variability in seed germination and plant growth responses among and within brands. Twenty-four different brands of media, and multiple bags of five brands, were purchased at nine retail stores. Tomato (Lycopersicon esculentum) seeds were germinated in 11 different brands of media and in media from different bags of four of the same brands. Marigold (Tagetes erecta) and petunia (Petunia×hybrida) were grown to flowering in 10 brands of media. Germination varied significantly among media brands and among bags of one of the brands. Plant performance also varied significantly, with several of the brands producing plants with few flowers, long times to flowering, and low shoot and root dry weights even though all treatments received uniform applications of a complete fertilizer solution three times per week. Few relationships could be discerned between individual physical and chemical properties of the media and plant performance. Results indicate improvements in quality among brands and quality control within brands are needed in the retail potting media industry. Quality assessment tools emphasizing plant performance could improve overall media quality.