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Trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3, 5-dioxocyclohexanecarboxylic acid ethyl ester] is a plant growth regulator registered for use in turfgrass. The objective of the research reported in this paper was to determine if TE could be used in the production of florist chrysanthemums (Dendranthema ×grandiflora) to produce more compact, higher value plants. Foliar applications of TE to non-pinched plants of the tall cultivar `Billings' reduced canopy height 8% to 40% as the amount of applied TE was increased from 6.25 × 10–5 to 2.0 × 10–3 g. The effects of TE varied among chrysanthemum cultivars. Growth inhibition of pinched plants among the various cultivars ranged from 7% (`White Viewtime') to 23% (`White Graceland') 28 days following a single application of 1.0 × 10–3 g TE. In most cultivars, the inhibitory action of TE was not observed after 28 days. In fact some cultivars exhibited a rebound effect during the post-suppression growth phase in which internode extension rates were greater in TE-treated plants than controls. Both the number and timing of the TE application affected efficacy. A second TE application 5 weeks after the first treatment, or application of TE at the appearance of flower buds produced the highest quality crop in terms of uniformity and compactness, with overall height reduction generally 15% to 20%. No differences in flower color, number, or mass per flower were observed due to TE application.

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Previous research on the potential of the gibberellin inhibiting growth regulator trinexapac-ethyl (TE) [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] to improve quality and density of shaded turfgrass has been conducted under neutral-density shade. However, some phytochrome-mediated growth responses of turfgrass, such as tillering, are different under deciduous shade versus neutral-density shade. The objectives of this study were to investigate 1) whether TE would result in improved stand density and quality of turfgrass grown under deciduous shade as has been observed under neutral-density shade and 2) the shade tolerance of sheep fescue (Festuca ovina L. `Quatro') compared to tall fescue (Festuca arundinacea Schreb. `Plantation'), and rough bluegrass (Poa trivialis L.). Trinexapac-ethyl at either 0 or 29 kg·ha–1 a.i. and nitrogen at 12 or 36 kg·ha–1 were applied on 23 May, 3 July, and 15 Aug. 2003 and 21 May 2004 to each species in a randomized complete block design under deciduous shade (about 9% of full sun). Clipping yield, color, and density data were collected for 6 weeks after the May applications in each year. Visual quality was assessed for 6 weeks after application in 2004 only. In 2003, TE significantly reduced clipping yields by 35% to 50% on sheep fescue, 58% to 76% on tall fescue and 55% to 80% on rough bluegrass. However, in 2004, yield reduction was 0% to 50% for all three species and there was no interaction between week, TE, and species. `Plantation' tall fescue had the highest overall visual quality and density. Sheep fescue also provided an acceptable quality turf stand. TE application did not significantly impact the quality of these species. Rough bluegrass performance was unacceptable, and high rate applications of TE to this species in shade resulted in significant (P < 0.05) losses in density. Trinexapac-ethyl application, based on the results of this study, may not enhance turf quality of cool season grasses grown under dense tree shade.

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Annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis palustris Huds. syn. A. stolonifera L.) coexist on golf greens as a dynamic ecosystem in the temperate regions of the United States. In a two year field study, the competitive ability of different populations of annual bluegrass was investigated both in and out of their native environment. In April 2000, at both The Country Club in Cleveland, Ohio, a temperate environment, and Camargo Club in Cincinnati, Ohio, a transition zone environment, 72 plugs of annual bluegrass were removed from golf greens and inserted into polyvinyl chloride pipe measuring 10.2 cm in diameter and 15 cm in length to eliminate root competition between species. Thirty-six plugs then were reestablished into one of three greens at the same golf course, and the remaining 36 plugs were transported to the opposite location and also established into one of three preselected greens. Each plug was centered in a 20.3-cm-diameter sward of `L-93' creeping bentgrass to provide an initial point of reference. Competitive ability was measured as the rate of increase or decrease in average diameter of each plug. Measurements initially were taken on a bimonthly basis and then on a monthly basis for the remainder of the study. Significant (P < 0.05) differences in the location × population interaction were seen in the first 2 months of the study and then not seen again until the last 2 months. The most frequent occurrence of significant (P < 0.05) differences was in the variability between greens within a particular location. At each location the native population of annual bluegrass outperformed the imported population. Differences at the beginning of the study are attributed to an additional acclimation period required by the exported population following transportation to the opposite location. From our study, annual bluegrass performance was similar across populations, suggesting that management recommendations can be made on a regional basis.

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Decreased light quantity or quality affects the growth of turfgrass plants. Shade causes thinning of turfgrass stands and loss in surface quality. Plant changes include increased chlorophyll levels, lower soluble sugars, and loss of canopy cover. The objective of this research was to investigate if applications of foliar nitrogen and trinexapac-ethyl [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (TE) would result in beneficial biochemical changes in creeping bentgrass (Agrostis stolonifera L. cv. Penncross) grown in different shaded environments. Foliar applications of three nitrogen treatments, (NH2)2CO, Ca(NO3)2, or (NH4)2SO4, were made weekly at 0.43 g N/m2. Growth regulator treatments consisted of an untreated control or TE applied biweekly at an a.i. rate of 0.057 kg·ha−1. Plots were established in full sun (FS), neutral shade (NS), and deciduous shade (DS). Chlorophyll content, soluble carbohydrates, flavonoids, clipping yield, and color were measured. Nitrogen treatments caused some variation in levels of soluble carbohydrates in shaded conditions. Chlorophyll (Chl) levels varied between TE treatments, with increased levels of chlorophyll b (Chl b) found in TE-treated plots under FS. Application of TE resulted in higher flavonoid concentrations in leaf tissue in shaded conditions. Repeated applications of (NH2)2CO significantly improved color (P = 0.05). Turfgrass managers maintaining creeping bentgrass in shade may benefit from applications of TE and (NH2)2CO.

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Genetically transformed cultivars of creeping bentgrass (Agrostis stolonifera L. syn. Agrostis palustris Huds.) that are resistant to glyphosate have been developed by a collaboration of the Scotts and Monsanto companies. Prior to commercial release, we desired to determine if the transformed plants behave similarly to traditional creeping bentgrass except for the effects expected from the inserted gene, i.e., resistance to glyphosate. Therefore, studies were initiated on 23 June 2000 in Marysville, Ohio; 14 July 2000 in Middleton, N.J.; and 20 June 2000 in Gervais, Ore., to examine the relative lateral spread and competitive ability of several transformed lines of creeping bentgrass, non-transformed controls, and reference cultivars. Vegetative plugs of creeping bentgrass were transplanted into a mature stand of Kentucky bluegrass (Poa pratensis L.) or a uniform mixture of Kentucky bluegrass with perennial ryegrass (Lolium perenne L.). The plots were watered as needed to prevent moisture stress. Competitive ability of the transformed plants and reference cultivars were determined monthly by measuring the average diameter of the creeping bentgrass patch. On all observation dates, the transgenic lines, as a group, were smaller in average diameter (5.1-7.6 cm) compared to the reference cultivars (5.4-14.2 cm) and non-transformed control lines (5.9-10.2 cm). At the end of the observation period (Aug. 2001), no differences (P = 0.05) in lateral spread were observed between individual lines of transgenic bentgrass. Three lines of interest, ASR365, ASR368, and ASR333, had lateral spread rates that are similar to, or less than, that of their non-transformed parent and the conventional creeping bentgrass cultivars tested. Chemical names used: N-(phosphonomethyl) glycine (glyphosate).

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Anthocyanins are plant pigments that are in demand for medicinal and industrial uses. However, anthocyanin production is limited due to the harvest potential of the species currently used as anthocyanin sources. Rough bluegrass (Poa trivialis L.) is a perennial turfgrass known for accumulating anthocyanins, and may have the potential to serve as a source of anthocyanins through artificial light treatments. The objectives of this research were to determine optimal light conditions that favor anthocyanin synthesis in rough bluegrass, and to determine the suitability of rough bluegrass as a source of anthocyanins. When exposed to high-intensity white light, rough bluegrass increased anthocyanin content by 100-fold on average, and anthocyanin contents greater than 0.2% of dry tissue weight were observed in some samples. Blue light, at intensities between 150 and 250 μmol·m−2·s−1, was the only wavelength that increased anthocyanin content. However, when red light was applied with blue light at 30% or 50% of the total light intensity, anthocyanin content was increased compared with blue light alone. Further experiments demonstrated that these results may be potentially due to a combination of photosynthetic and photoreceptor-mediated regulation. Rough bluegrass is an attractive anthocyanin production system, since leaf tissue can be harvested while preserving meristematic tissues that allow new leaves to rapidly grow; thereby allowing multiple harvests in a single growing season and greater anthocyanin yields.

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Turf grown in shade exhibits increased stem elongation. Dwarfism could improve turfgrass quality by reducing elongation. The purpose of this study was to examine the effect of GA2-oxidase (GA2ox) overexpression on creeping bentgrass (Agrostis stolonifera L.) performance under restricted light conditions and low mowing heights. Greenhouse studies were conducted at The Ohio State University, Columbus, OH, from 1 Sept. to 31 Oct. in both 2008 and 2009. Two experimental lines, Ax6548 and Ax6549, transformed with CP4 EPSPS and PcGA2ox gene; and a nontransformed control (NTC) was subjected to four light environments: full sun, reduced red to far red light ratio (R:FR), neutral shade [reduced photosynthetic photon flux (PPF)], and canopy shade (reduced PPF and R:FR). Turf was evaluated every 10 days for color and percent coverage. GA2ox overexpression resulted in darker green color in both transgenic lines under all light treatments as compared with NTC plants. No differences in overall turfgrass coverage were noted in full sun conditions among the lines. A significant decrease in turf coverage occurred for all shade treatments regardless of line. However, Ax6549 decreased the least. Overall data indicated that GA2ox overexpression can improve quality of turfgrass under reduced light conditions.

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Ultraviolet (UV) radiation poses a potential stress for plant growth and development due to its effect on photosynthesis and plant productivity. In the northern hemisphere, peak UV radiation exposure is predicted to occur from 2010 to 2020, with reduced color from UV-related injury, a possibility for turfgrasses. The objective of this study was to investigate the effects of ultraviolet-B (UV-B) light on turfgrass growth and morphology in three cool-season grasses. Cultivars Barvado tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.], Penncross and L-93 creeping bentgrass (Agrostis stolonifera L.), and Barlenium perennial ryegrass (Lolium perenne L.), were selected because of limited information on their growth and development in elevated UV conditions at heights of cut above 10 cm. The impact of UV-B light treatment on color, relative growth rate, and tillering was measured over a 4-week period in repeated experiments. Ultraviolet-B radiation levels were measured at 16 kJ·m−2·d−1 biologically effective UV-B light in growth chambers programmed for a day/night regime of 14/10 hours. Chamber temperatures were maintained at 20 °C day/17 °C night. Ultraviolet-B light significantly inhibited tiller production in the first experiment in all grasses except PR, whereas no grasses were inhibited in the second experiment. Relative growth rates in all grasses were significantly lower in UV-B conditions 3 weeks after treatment initiation. Turfgrasses exposed to this level of UV-B light at typical lawn heights-of-cut had lower color ratings compared with the non-UV-B-treated control at 2 weeks after treatment initiation. The experiments demonstrated that exposure to UV-B resulted in a decline of growth rate and color in cool-season turfgrasses within a timeframe of 2 weeks. Coarse-textured turfgrasses [tall fescue (TF)/perennial ryegrass (PR)] may be more adapted to higher UV-B conditions due to morphological differences compared with the finer textured varieties [creeping bentgrass (CB)].

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