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Eleni M. Abraham, William A. Meyer, Stacy A. Bonos and Bingru Huang

turfgrasses has been associated with the maintenance of transpiration and photosynthesis among various other mechanisms ( Jiang and Huang, 2000 ). Kentucky bluegrass ( Poa pratensis L.) (KBG) is a commonly used cool-season turfgrass species for home lawns

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Joshua J. Skelton, William Sharp and Bruce E. Branham

time requiring the use of a postemergence herbicide application for eradication ( Branham et al., 2010 ). The selective control of ABG in cool-season turf, especially kentucky bluegrass ( Poa pratensis L.), can be challenging as a result of limited

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B. Shaun Bushman, Lijun Wang, Xin Dai, Alpana Joshi, Joseph G. Robins and Paul G. Johnson

. Pergamon Press, Oxford, UK Bushman, B.S. Amundsen, K.L. Warnke, S.E. Robins, J.G. Johnson, P.G. 2016 Transcriptome profiling of kentucky bluegrass ( Poa pratensis L.) accessions in response to salt stress BMC Genomics 17 1 12 Carrow, R.N. Duncan, R.R. 1998

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Masoud Arghavani, Mohsen Kafi, Mesbah Babalar, Roohangiz Naderi, Md. Anamul Hoque and Yoshiyoki Murata

( Gill and Rainville, 1994 ). NaCl is the principal soil salinity stress ( Yokoi et al., 2002 ). Kentucky bluegrass ( Poa pratensis L.) is a cool-season grass widely used for home lawns, sport fields, and commercial landscapes in temperate climates

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Matthew T. Elmore, James A. Murphy and Bradley S. Park

perenne L.), kentucky bluegrass ( Poa pratensis L.), and tall fescue. Research demonstrated consistently that sequential mesotrione applications provide more CBG control than single applications ( Branham et al., 2005 ; Dernoeden et al., 2008 ; Jones

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Rebecca Nelson Brown and Josef H. Gorres

( Table 1 ); these cultivars had been developed for salt tolerance, adaptation to low-input environments, or both. The cultivars represented seven species: red fescue, alkaligrass, kentucky bluegrass ( Poa pratensis L.), tufted hairgrass [ Deschampsia

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Zhongchun Jiang, W. Michael Sullivan and Richard J. Hull

Efficient utilization of fertilizer-nitrogen (N) by turfgrasses is probably related to N uptake efficiency of roots and metabolic efficiency of absorbed N in roots and shoots. This study evaluated Kentucky bluegrass (Poa pratensis L.) cultivars for potential differences in nitrate uptake rate (NUR), temporal variation in NUR, and the relationship between NUR and N use efficiency (NUE), defined as grams dry matter per gram N. Six cultivars were propagated from tillers of seeded plants, grown in silica sand, mowed weekly, and watered daily with a complete nutrient solution containing 1.0 mm nitrate. A nutrient depletion method from an initial nitrate concentration of 0.5 mm was used to determine NUR of 5-month-old plants. NUR (μmol·h-1 per plant) of the six cultivars ranked as follows: `Blacksburg' > `Conni' > `Dawn' > `Eclipse' = `Barzan' > `Gnome'. When NUR was based on root weight, `Conni' ranked highest; when NUR was based on root length, surface, or volume, `Eclipse' ranked highest. Averaged across cultivars, NUR on the second day was greater than NUR for the first day of nitrate exposure. Temporal variation was greatest in `Blacksburg', while none was noted in `Conni' or `Eclipse'. Cultivar differences in NUE were significant in fibrous roots, rhizomes, and leaf sheaths, but not in leaf blades and thatch. Total nitrate uptake was positively related to total N recovered and total plant dry matter, but NUR based on root weight was negatively correlated with NUE of the whole plant.

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Zhimin Yang, Lixin Xu, Jingjin Yu, Michelle DaCosta and Bingru Huang

Carbohydrate metabolism is important for plant adaptation to drought stress. The objective of this study was to examine major forms of carbohydrates associated with superior drought tolerance and post-drought recovery in kentucky bluegrass (Poa pratensis) by comparing responses of different forms of carbohydrates with drought stress and re-watering in two cultivars contrasting in drought tolerance. Plants of drought-tolerant ‘Midnight’ and drought-sensitive ‘Brilliant’ were maintained well watered or subjected to drought stress for 10 days by withholding irrigation, and drought-stressed plants were re-watered for 3 days. Physiological analysis (turf quality, relative water content, and electrolyte leakage) confirmed the genetic variability of the two cultivars in drought tolerance. The two cultivars exhibited differential responses to drought stress and re-watering for the content of water-soluble sugars (sucrose, fructose, and glucose) and storage carbohydrates (starch and fructan), and ‘Midnight’ maintained higher sucrose content at 10 days of drought stress and more fructan at 3 days of re-watering. The greater accumulation of sucrose in ‘Midnight’ under drought stress corresponded with higher activities of two sucrose-synthesizing enzymes (sucrose phosphate synthase and sucrose synthase) but was not related to the sucrose-degrading enzyme activity (acid invertase). These results suggested that increased sucrose accumulation resulting from the maintenance of active sucrose synthesis could be associated with superior turf performance during drought stress, whereas increased fructan accumulation could contribute to rapid re-growth and post-drought recovery on re-watering in kentucky bluegrass.

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Zhimin Yang, Jingjin Yu, Emily Merewitz and Bingru Huang

Abscisic acid (ABA) and glycine betaine (GB) may regulate plant responses to drought or salinity stress. The objectives of this controlled-environment study were to determine whether foliar application of ABA or GB improves turf quality under drought or salinity and whether improved stress responses were associated changes in antioxidant metabolism in two C3 turfgrass species, creeping bentgrass (Agrostis stolonifera) and kentucky bluegrass (Poa pratensis). Physiological parameters evaluated included turf quality, leaf relative water content, membrane electrolyte leakage (EL), membrane lipid peroxidation [expressed as malondialdehyde (MDA) content], and activity of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Abscisic acid and GB were both effective in mitigating physiological damage resulting from drought or salinity for both grass species, but effects were more pronounced on kentucky bluegrass. The most notable effects of ABA or GB application were the suppression of EL and MDA accumulation and an increase in APX, POD, and SOD activities after prolonged periods of drought (21 days) or salinity stress (35 days). These results suggest foliar application of ABA or GB may alleviate physiological damage by drought or salinity stress in turfgrass and the maintenance of membrane stability and active antioxidant metabolism could contribute to the positive effects in the stress mitigation effects.

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Alexander R. Kowalewski, John N. Rogers III, James R. Crum and Jeffrey C. Dunne

Drain tile installation into a native-soil athletic field and subsequent sand topdressing applications are cost-effective alternatives to complete field renovation. However, if cumulative topdressing rates exceed root system development, surface stability may be compromised. The objective of this research was to evaluate the effects of cumulative topdressing, over a compacted sandy loam soil, on the fall wear tolerance and surface shear strength of a kentucky bluegrass (Poa pratensis)–perennial ryegrass (Lolium perenne) stand. Research was initiated in East Lansing, MI, on 10 Apr. 2007. A well-graded, high-sand-content root zone (90.0% sand, 7.0% silt, and 3.0% clay) was topdressed at a 0.25-inch depth [2.0 lb/ft2 (dry weight)] per application, providing cumulative topdressing depths of 0.0, 0.5, 1.0, 1.5, or 2.0 inches applied from 11 July to 15 Aug. 2007. Fall traffic was applied twice weekly to all treatments from 10 Oct. to 3 Nov. 2007. In 2008, topdressing applications and traffic, as described earlier, were repeated on the same experimental plots. Results obtained from this research suggest that the 0.5-inch topdressing depth applied over a 5-week period in the summer will provide improved shoot density and surface shear strength in the subsequent fall. Results also suggest that topdressing rates as thick as 4.0 inches accumulated over a 2-year period will provide increased shoot density, but diminished surface shear strength.