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Traffic stress causes turfgrass injury and soil compaction but the underlying physiological mechanisms are not well documented. The objectives of this study were to investigate the physiological responses of kentucky bluegrass (Poa pratensis), tall fescue (Festuca arundinacea), and japanese zoysiagrass (Zoysia japonica) to three levels of traffic stress during the growing season under simulated soccer traffic conditions. Relative leaf water content (LWC), shoot density, leaf chlorophyll concentration (LCC), membrane permeability, and leaf antioxidant peroxidase (POD) activity were measured once per month. The traffic stress treatments caused a reduction in LWC, shoot density, LCC, and POD activity, and an increase in cell membrane permeability in all three species. Japanese zoysiagrass had less electrolyte leakage, and higher POD activity and shoot density than both kentucky bluegrass and tall fescue. The results suggest that turfgrass tolerance to traffic stress may be related to leaf antioxidant activity. Turfgrass species or cultivars with higher leaf antioxidant activity may be more tolerant to traffic stress than those with lower antioxidant activity. [ABSTRACT FROM AUTHOR]

Ultraviolet-B [UV-B (280-320 nm)] radiation is one of the major factors causing quality decline of transplanted sod. Pigments and antioxidants are associated with plant stress resistance, but their roles in turfgrass tolerance to UV-B damage are not well understood. The objectives of this study were to determine if kentucky bluegrass (Poa pratensis L) cultivars with darker green genetic leaf color possessed greater pigment and antioxidant defense capacities and if such characteristics were associated with greater resistance to UV-B. Two cultivars, 'Moonlight' (dark green) and 'Limerick' (light green), were selected and subjected to continuous, artificial UV-B radiation (70 µmol·m-2·s-1). UV-B irradiation reduced turf quality by 58% ('Moonlight') and 77% ('Limerick') relative to day 1 when measured 10 days after initiation of UV-B exposure. Higher canopy photochemical efficiency (PEc) was found in 'Moonlight' relative to 'Limerick' under UV-B stress and during recovery. 'Moonlight' contained greater levels of chlorophyll (1.5 to 1.6-fold), carotenoids (1.3-fold), superoxide dismutase [SOD (1.0-fold)] and catalase [CAT (1.5-fold)] than 'Limerick' when measured at 10 days after UV-B initiation. Turfgrass quality and PEc were positively correlated with pigments (chlorophyll and carotenoids) and antioxidant enzymes (SOD and CAT), and negatively correlated with lipid peroxidation. The results suggest that selecting dark-green cultivars with greater pigment content and antioxidant activity may be an effective approach for turfgrass breeders and sod producers to improve tolerance of newly transplanted sod to environments with higher UV-B radiation. [ABSTRACT FROM AUTHOR]

Creeping bentgrass (Agrostis stolonifera) is used extensively on temperate zone golf course greens, tees, and fairways, but often performs poorly in shade. Previous research has indicated that sequential applications of gibberellic acid (GA) inhibiting plant growth regulators (PGRs) such as trinexapac-ethyl (TE) increase cool-season turfgrass performance in 70-90% shade. This research was conducted to: 1) confirm appropriate TE application rates and frequencies for maintaining 'Penncross' creeping bentgrass in dense shade in the mid-Atlantic region of the U.S.; 2) determine the efficacy of other PGRs, biostimulants, and iron (Fe); and 3) assess whether the addition of a biostimulant with TE would have additive, synergistic, or negative effects. The other compounds tested against TE and the control were: propiconazole (PPC), iron sulfate, CPR (a seaweed and iron containing biostimulant), and a generic seaweed extract (SWE) (Ascophyllum nodosum) plus humic acid (HA) combination. These treatments were applied to 88% shaded bentgrass every 14 days from May or June through October in 2001 and 2002, with turf quality, leaf color, root strength, photochemical efficiency, and antioxidant enzyme superoxide dismutase (SOD) activity being determined. While the quality of control plots fell below a commercially acceptable level by the second month of the trial, repeated foliar TE application provided 33% to 44% better quality throughout the experiment. Propiconazole resulted in 13% to 17% better quality through September of each year. Trinexapac-ethyl and PPC resulted in darker leaf color and increased mid-trial root strength by 27% and 29%, respectively. Canopy photochemical efficiency and leaf SOD activity were also increased due to TE in August of both years. Treatment with Fe, CPIL, or SWE+HA did not have an effect on quality, root strength, SOD, or photochemical efficiency, but periodic increases in color were observed. The addition of CPR to TE in 2002 provided resul... [ABSTRACT FROM AUTHOR]

Discusses the secondary effects of applying the plant growth regulator Primo Maxx on turfgrass growth and development. Result of a radioactive tracing study on the foliage absorption of Primo Maxx application; Benefits of Primo application to the nonstructural carbohydrate content of creeping bentgrass; Findings of a laboratory test on the effect of Primo application to creeping bentgrass, Midnight Kentucky bluegrass and Tifway hybrid bermudagrass.

The article focuses on bermudagrass (Cynodon dactylon) as choice for golf course fairways & tees in the Transition Zone tolerating close mowing and forming durable, dense and persistent turf. Topics discussed include bermudagrass providing green color during winter and improving playability during slow-growth periods, overseeding with perennial ryegrass blending with carbohydrate content of rhizome and surface soil temperature, and negative effects of winter overseeding such as spring density.

Water deficit is a major limiting factor for grass culture in many regions with physiological mechanisms of tolerance not yet well understood. Antioxidant isozymes and hormones may play important roles in plant tolerance to water deficit. This study was designed to investigate antioxidant enzymes, isozymes, abscisic acid (ABA), and indole-3-acetic acid (IAA) responses to deficit irrigation in two perennial ryegrass (Lolium perenne L.) cultivars contrasting in drought tolerance. The plants were subjected to well-watered {100% container capacity, 34.4% ± 0.21% volumetric moisture content (VWC), or deficit irrigation [30% evapotranspiration (ET) replacement; 28.6% ± 0.15% to 7.5% ± 0.12% VWC]} conditions for up to 8 days and rewatering for 4 days for recovery in growth chambers. Deficit irrigation increased leaf malondialdehyde (MDA) content in both cultivars, but drought-tolerant Manhattan-5 exhibited lower levels relative to drought-sensitive Silver Dollar. Superoxide dismutase (SOD) activity declined and then increased during water-deficit treatment. 'Manhattan-5' had higher SOD activity and greater abundance of SOD1 isozyme than 'Silver Dollar' under water deficit. Deficit irrigation increased catalase (CAT) and ascorbate peroxidase (APX) activity in 'Manhattan-5', but not in 'Silver Dollar'. 'Manhattan-5' had higher CAT, APX, and peroxidase (POD) activity than 'Silver Dollar' during water limitation. Deficit irrigation increased mRNA accumulation of cytosolic cupper/zinc SOD (Cyt Cu/Zn SOD), whereas gene expression of manganese SOD (Mn SOD) and peroxisome APX (pAPX) were not significantly altered in response to deficit irrigation. No differences in Cyt Cu/Zn SOD, Mn SOD, and pAPX gene expression were found between the two cultivars under deficit irrigation. Water limitation increased leaf ABA and IAA contents in both cultivars, with Silver Dollar having a higher ABA content than Manhattan-5. Change in ABA level may regulate stomatal opening and oxidative stress, which may trigger antioxidant defense responses. These results indicate that accumulation of antioxidant enzymes and ABA are associated with perennial ryegrass drought tolerance. Activity and isozyme assays of key antioxidant enzymes under soil moisture limitation can be a practical screening approach to improve perennial ryegrass drought tolerance and quality. [ABSTRACT FROM AUTHOR]

The article discusses an integrated nutritional and chemical approach in controlling Poa annua in creeping bentgrass putting greens. It notes that a nutritional approach to Poa annua control is the use of sulfates of iron and ammonium to provide plant nutrition and gradual rootzone acidification. It adds that the ultimate goal of the approach is to provide a smooth transition to mostly creeping bentgrass, without sudden stand collapse.

Salinity stress may involve the accumulation of glycine betaine (GB). The objective of this study was to examine whether exogenous GB would ameliorate the detrimental effect of salinity stress on perennial ryegrass (Lolium perenne). The grass was subjected to two salinity levels (0 and 250 mm NaCl) and three GB levels (0, 20, and 50 mm). Salinity resulted in a remarkable decrease in vertical shoot growth rate (VSGR), shoot and root fresh weight, relative water content (RWC), relative transpiration rate (Tr), and chlorophyll (Chl) content, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities. Plants subjected to salt exhibited an increase in leaf electrolyte leakage (EL), lipid peroxidation (MDA), and proline content. Application of GB reduced EL, MDA, and proline content in salt-stressed plants. Perennial ryegrass subjected to salt stress plus GB had a greater level of VSGR, RWC, relative Tr, Chl content, and activities of SOD, CAT, and APX when compared with salt-stressed without GB. Salt stress increased Na+ and decreased K+ content, which resulted in a higher Na+/K+ ratio in perennial ryegrass. Application of 20 mm GB suppressed Na+ accumulation, whereas the K+ content was significantly increased in shoot, which led to a higher K+/Na+ ratio under saline conditions. These results suggested that GB-enhanced salt tolerance in perennial ryegrass was mainly related to the elevated SOD, CAT, and APX activity and alleviation of cell membrane damage by reducing oxidation of membrane lipid and improving the ion homeostasis under salt stress. [ABSTRACT FROM AUTHOR]

Heat stress is a major limiting factor for growth of cool-season perennial grass species, and mechanisms of heat tolerance have not been well understood. This study was designed to investigate antioxidant enzyme and hormone metabolism responses to heat stress in two Kentucky bluegrass (Poa pratensis L.) cultivars contrasting in heat tolerance. The plants were subjected to 20/20 °C [day/night (control)] or 38/30 °C [day/night (heat stress)] for 28 days in growth chambers. Heat stress increased leaf electrolyte leakage (EL) and malondialdehyde (MDA) with heattolerant cultivar EverGlade exhibiting lower levels of EL and MDA relative to heat-sensitive cultivar Kenblue under heat stress. Superoxide dismutase (SOD) and catatase (CAT) activity increased and then declined during 28 days of heat stress. Peroxidase (POD) and ascorbate peroxidase (APX) activity declined and then increased during heat stress. 'EverGlade' had greater activities of SOD, CAT, POD, and APX relative to 'Kenblue' under heat stress. In addition, 'EverGlade' had two additional SOD isozymes and three additional POD isozymes relative to 'Kenblue' under heat stress. Leaf abscisic acid (ABA) increased in response to heat stress. Leaf indole-3-acetic acid (IAA) increased and then declined during heat stress. 'OverGlade' had higher ABA and IAA content relative to 'Kenblue'. At the end of heat stress, leaf IAA and ABA content were 27.8% and 73% higher in 'EverGlade' relative to 'Kenblue', respectively. The results indicated that antioxidant enzymes and the hormones (ABA and IAA) were associated with kentucky bluegrass heat tolerance. Selection and use of cultivars with higher IAA and ABA content and greater antioxidant enzyme activities may improve kentucky bluegrass growth and quality under heat stress. [ABSTRACT FROM AUTHOR]

The article focuses on a study which reveals that water deficit irrigation impacts antioxidant metabolism in creeping bentgrass. Topics discussed include reduction in freezing tolerance in drought stress condition of plants, accumulation of osmoprotectants during drought stress in winters, and increased level of leaf proline amino acid in plants with drought stress.